Implement Cast Streaming mirroring, DLNA casting, daemon+GUI, and breadd integration

Builds out the full v1 scope: a vendored+patched openscreen subset for
low-latency Cast Streaming (Mirroring receiver 0F5096E8) alongside the
existing Cast V2/HLS and new DLNA/AVTransport casting paths, breadcastd's
Idle/Casting state machine with a private IPC socket, the breadcast GTK4
popup as a thin IPC client, and bread.cast.*/bread.command.cast.* breadd
integration (device discovery, start/stop, mirroring lifecycle events).
Also adds bakery/systemd/Forgejo CI packaging.

Validated end-to-end against a real Chromecast/Google TV: negotiated
Cast Streaming session, live pipeline playback, and daemon+GUI click-to-cast/
stop through the actual popup.

.forgejo/workflows/beta-release.yml

@@ -0,0 +1,79 @@
+name: beta release
+
+# Publishes a beta-track build on every push to `beta` — a frozen
+# stabilization branch cut from `dev` when ready to stabilize; only
+# fix/<issue> branches merged into `beta` should land here afterward.
+# See bread-ecosystem's docs/release-channels.md for the three-track policy.
+on:
+  push:
+    branches: ['beta']
+
+jobs:
+  build:
+    runs-on: [self-hosted, hestia]
+    steps:
+      - name: checkout
+        run: |
+          set -euo pipefail
+          rm -rf src && mkdir src
+          git clone --branch beta --depth 1 \
+            "https://git.breadway.dev/${GITHUB_REPOSITORY}.git" src
+
+      - name: build
+        run: cd src && cargo build --release --locked
+
+      - name: compute beta version
+        run: |
+          set -euo pipefail
+          cd src
+          # Base the beta version off the latest published stable tag,
+          # not Cargo.toml — Cargo.toml can go stale relative to the last
+          # real release (seen in practice: breadbox/breadpad/breadcrumbs/
+          # breadpaper), which would make a beta build sort as OLDER than
+          # what's already installed and bakery would correctly refuse it.
+          LATEST_TAG="$(git ls-remote --tags --refs \
+            "https://git.breadway.dev/${GITHUB_REPOSITORY}.git" 'v*' \
+            | awk -F/ '{print $NF}' | sed 's/^v//' | sort -V | tail -1)"
+          if [ -n "${LATEST_TAG}" ]; then
+            CUR="${LATEST_TAG}"
+          else
+            CUR="$(grep -m1 '^version' breadcast/Cargo.toml | sed -E 's/.*"(.*)".*/\1/')"
+          fi
+          IFS='.' read -r MA MI PA <<< "${CUR}"
+          SHA="$(git rev-parse --short HEAD)"
+          TS="$(date -u +%Y%m%d%H%M%S)"
+          echo "VERSION=${MA}.${MI}.$((PA + 1))-beta.${TS}+${SHA}" >> "$GITHUB_ENV"
+
+      - name: prepare artifacts
+        run: |
+          set -euo pipefail
+          PKG_DIR="/srv/breadway-dl/beta/breadcast/${VERSION}"
+          mkdir -p "${PKG_DIR}"
+          for bin in breadcast breadcastd; do
+            cp "src/target/release/${bin}" "${PKG_DIR}/${bin}-x86_64"
+            strip "${PKG_DIR}/${bin}-x86_64"
+            sha256sum "${PKG_DIR}/${bin}-x86_64" | awk '{print $1}' \
+              > "${PKG_DIR}/${bin}-x86_64.sha256"
+          done
+          cp src/contrib/breadcastd.service "${PKG_DIR}/"
+          cp src/bakery.toml "${PKG_DIR}/bakery.toml"
+          ln -sfn "${VERSION}" "/srv/breadway-dl/beta/breadcast/latest"
+
+      # No GitHub Release upload — beta, like dev, is only distributed via
+      # dl.breadway.dev/beta/.
+      - name: regenerate beta index.json
+        env:
+          MINISIGN_SEC_KEY: ${{ secrets.BAKERY_MINISIGN_SEC_KEY_PATH }}
+        run: |
+          set -euo pipefail
+          if [ -z "${MINISIGN_SEC_KEY:-}" ]; then
+            echo "::error::BAKERY_MINISIGN_SEC_KEY_PATH secret not set — refusing to regenerate beta index.json unsigned (would leave a stale signature mismatched against fresh content and break bakery for everyone on the beta track)"
+            exit 1
+          fi
+          rm -rf /tmp/bread-ecosystem-ci-* 2>/dev/null || true
+          # mktemp: a fixed clone path races when multiple repos' dev/beta
+          # workflows run close together on the same self-hosted runner.
+          ECOSYSTEM_CI_DIR="$(mktemp -d /tmp/bread-ecosystem-ci-XXXXXX)"
+          git clone https://git.breadway.dev/Breadway/bread-ecosystem.git "${ECOSYSTEM_CI_DIR}"
+          TRACK=beta bash "${ECOSYSTEM_CI_DIR}/scripts/gen-index.sh"
+          rm -rf "${ECOSYSTEM_CI_DIR}"

.forgejo/workflows/dev-release.yml

@@ -0,0 +1,79 @@
+name: dev release
+
+# Publishes a dev-track build on every push to `dev` —
+# separate from release.yml's tag-triggered stable releases. See
+# bread-ecosystem's docs/release-channels.md for the three-track policy
+# this is part of.
+on:
+  push:
+    branches: ['dev']
+
+jobs:
+  build:
+    runs-on: [self-hosted, hestia]
+    steps:
+      - name: checkout
+        run: |
+          set -euo pipefail
+          rm -rf src && mkdir src
+          git clone --branch dev --depth 1 \
+            "https://git.breadway.dev/${GITHUB_REPOSITORY}.git" src
+
+      - name: build
+        run: cd src && cargo build --release --locked
+
+      - name: compute dev version
+        run: |
+          set -euo pipefail
+          cd src
+          # Base the dev version off the latest published stable tag,
+          # not Cargo.toml — Cargo.toml can go stale relative to the last
+          # real release (seen in practice: breadbox/breadpad/breadcrumbs/
+          # breadpaper), which would make a dev build sort as OLDER than
+          # what's already installed and bakery would correctly refuse it.
+          LATEST_TAG="$(git ls-remote --tags --refs \
+            "https://git.breadway.dev/${GITHUB_REPOSITORY}.git" 'v*' \
+            | awk -F/ '{print $NF}' | sed 's/^v//' | sort -V | tail -1)"
+          if [ -n "${LATEST_TAG}" ]; then
+            CUR="${LATEST_TAG}"
+          else
+            CUR="$(grep -m1 '^version' breadcast/Cargo.toml | sed -E 's/.*"(.*)".*/\1/')"
+          fi
+          IFS='.' read -r MA MI PA <<< "${CUR}"
+          SHA="$(git rev-parse --short HEAD)"
+          TS="$(date -u +%Y%m%d%H%M%S)"
+          echo "VERSION=${MA}.${MI}.$((PA + 1))-dev.${TS}+${SHA}" >> "$GITHUB_ENV"
+
+      - name: prepare artifacts
+        run: |
+          set -euo pipefail
+          PKG_DIR="/srv/breadway-dl/dev/breadcast/${VERSION}"
+          mkdir -p "${PKG_DIR}"
+          for bin in breadcast breadcastd; do
+            cp "src/target/release/${bin}" "${PKG_DIR}/${bin}-x86_64"
+            strip "${PKG_DIR}/${bin}-x86_64"
+            sha256sum "${PKG_DIR}/${bin}-x86_64" | awk '{print $1}' \
+              > "${PKG_DIR}/${bin}-x86_64.sha256"
+          done
+          cp src/contrib/breadcastd.service "${PKG_DIR}/"
+          cp src/bakery.toml "${PKG_DIR}/bakery.toml"
+          ln -sfn "${VERSION}" "/srv/breadway-dl/dev/breadcast/latest"
+
+      # No GitHub Release upload — dev, like the other non-stable track,
+      # is only distributed via dl.breadway.dev/dev/.
+      - name: regenerate dev index.json
+        env:
+          MINISIGN_SEC_KEY: ${{ secrets.BAKERY_MINISIGN_SEC_KEY_PATH }}
+        run: |
+          set -euo pipefail
+          if [ -z "${MINISIGN_SEC_KEY:-}" ]; then
+            echo "::error::BAKERY_MINISIGN_SEC_KEY_PATH secret not set — refusing to regenerate dev index.json unsigned (would leave a stale signature mismatched against fresh content and break bakery for everyone on the dev track)"
+            exit 1
+          fi
+          rm -rf /tmp/bread-ecosystem-ci-* 2>/dev/null || true
+          # mktemp: a fixed clone path races when multiple repos' dev/beta
+          # workflows run close together on the same self-hosted runner.
+          ECOSYSTEM_CI_DIR="$(mktemp -d /tmp/bread-ecosystem-ci-XXXXXX)"
+          git clone --branch dev https://git.breadway.dev/Breadway/bread-ecosystem.git "${ECOSYSTEM_CI_DIR}"
+          TRACK=dev bash "${ECOSYSTEM_CI_DIR}/scripts/gen-index.sh"
+          rm -rf "${ECOSYSTEM_CI_DIR}"

.forgejo/workflows/release.yml

@@ -0,0 +1,58 @@
+name: release
+
+on:
+  push:
+    tags: ["v*"]
+
+jobs:
+  build:
+    runs-on: [self-hosted, hestia]
+    steps:
+      - name: checkout
+        run: |
+          set -euo pipefail
+          rm -rf src && mkdir src
+          git clone --branch "${GITHUB_REF_NAME}" --depth 1 \
+            "https://git.breadway.dev/${GITHUB_REPOSITORY}.git" src
+
+      - name: build
+        run: cd src && cargo build --release --locked
+
+      - name: prepare artifacts
+        run: |
+          set -euo pipefail
+          VERSION="${GITHUB_REF_NAME#v}"
+          PKG_DIR="/srv/breadway-dl/breadcast/${VERSION}"
+          mkdir -p "${PKG_DIR}"
+          for bin in breadcast breadcastd; do
+            cp "src/target/release/${bin}" "${PKG_DIR}/${bin}-x86_64"
+            strip "${PKG_DIR}/${bin}-x86_64"
+            sha256sum "${PKG_DIR}/${bin}-x86_64" | awk '{print $1}' \
+              > "${PKG_DIR}/${bin}-x86_64.sha256"
+          done
+          cp src/contrib/breadcastd.service "${PKG_DIR}/"
+          cp src/bakery.toml "${PKG_DIR}/bakery.toml"
+          ln -sfn "${VERSION}" "/srv/breadway-dl/breadcast/latest"
+
+      - name: regenerate index.json
+        run: |
+          set -euo pipefail
+          rm -rf /tmp/bread-ecosystem-ci
+          git clone https://git.breadway.dev/Breadway/bread-ecosystem.git /tmp/bread-ecosystem-ci
+          bash /tmp/bread-ecosystem-ci/scripts/gen-index.sh
+
+      - name: upload to GitHub Release
+        env:
+          GH_TOKEN: ${{ secrets.GH_RELEASE_TOKEN }}
+        run: |
+          set -euo pipefail
+          VERSION="${GITHUB_REF_NAME#v}"
+          PKG_DIR="/srv/breadway-dl/breadcast/${VERSION}"
+          gh release create "${GITHUB_REF_NAME}" --repo Breadway/breadcast \
+            --title "breadcast v${VERSION}" --generate-notes 2>/dev/null || true
+          gh release upload "${GITHUB_REF_NAME}" --repo Breadway/breadcast \
+            "${PKG_DIR}/breadcast-x86_64" \
+            "${PKG_DIR}/breadcastd-x86_64" \
+            "${PKG_DIR}/breadcast-x86_64.sha256" \
+            "${PKG_DIR}/breadcastd-x86_64.sha256" \
+            --clobber

.gitignore

@@ -0,0 +1,34 @@
+# Rust build artifacts
+target/
+
+# Editor and IDE files
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS artifacts
+.DS_Store
+Thumbs.db
+desktop.ini
+
+# Environment and secrets
+.env
+.env.*
+*.env
+*.pem
+*.key
+*.p12
+secrets/
+
+# Log files
+*.log
+logs/
+
+# Runtime files
+*.sock
+*.pid
+
+# Local hygiene notes (not for commit)
+CLAUDE.md

CONTRIBUTING.md

@@ -0,0 +1,91 @@
+# Contributing
+
+`breadcast` — cast your screen to any Chromecast/Google TV, for Hyprland
+(daemon + GTK4 popup).
+
+Part of the bread ecosystem; this repo follows the same branch/release
+workflow as every other ecosystem product.
+
+## Branches
+
+- **`main`** — release branch, always tag-ready. Nothing is committed to it
+  directly; it only moves forward via a `beta` merge (see below).
+- **`dev`** — integration branch. All day-to-day work lands here first.
+  Every push to `dev` automatically builds and publishes a **dev-track**
+  build (see Tracks below) — use this to test your change in a real install
+  before it goes any further.
+- **`beta`** — a frozen stabilization branch, cut from `dev` periodically.
+  Every push to `beta` automatically builds and publishes a **beta-track**
+  build. While a freeze is active, only fixes for issues found *in that
+  freeze* should land on `beta`.
+
+New work — features and bug fixes alike — goes on a short-lived branch:
+
+```
+feature/<short-name>
+fix/<issue-number-or-short-name>
+```
+
+Branch off `dev`, open a PR/push back into `dev` when ready. If you're fixing
+something reported against an active `beta` freeze, branch off `beta`
+instead, merge the fix there to unblock testers, and also forward the same
+fix into `dev` so it doesn't quietly reappear next cycle.
+
+## The release cycle
+
+1. Work accumulates on `dev` via `feature/x` / `fix/x` branches. Each push
+   auto-publishes a dev build — install it with `bakery track set dev` and
+   `bakery update --all`, then report or fix anything broken with another
+   push to `dev`.
+2. Once `dev` has gone roughly **a week** without new issues, `beta` is cut
+   fresh from `dev`'s current tip. This freezes it as the stabilization
+   target — `dev` keeps moving independently starting the next cycle.
+3. `beta` is open for anyone to test: `bakery track set beta` and
+   `bakery update --all`. **File issues against anything you find on this
+   repo's Forgejo issue tracker.** Fixes land via `fix/<issue>` branches
+   merged into `beta`.
+4. Once `beta` has gone roughly **a month** without new issues, it's merged
+   into `main` and tagged `vX.Y.Z` — that tag is what actually triggers the
+   stable release build. `beta` is then reset from `dev` to start the next
+   cycle.
+
+## Tracks, from a user's perspective
+
+```
+bakery track show              # what you're currently on (defaults to stable)
+bakery track set dev           # or beta, or stable
+bakery update --all            # pull the latest build on your current track
+```
+
+| Track  | What it is | Published from |
+|--------|-----------|-----------------|
+| `stable` | The last tagged release | `main`, on a `vX.Y.Z` tag push |
+| `beta` | Current stabilization freeze | `beta`, on every push |
+| `dev` | Bleeding edge | `dev`, on every push |
+
+Dev/beta versions are auto-computed (`X.Y.Z-dev.<timestamp>+<sha>` /
+`-beta.…`) from the latest published stable tag, so they always sort as
+newer than what you have installed — no manual version bumping needed when
+pushing to `dev` or `beta`.
+
+## Local development
+
+```sh
+cargo build --release --workspace
+cargo test --release --workspace
+```
+
+## CI
+
+- `dev-release.yml` — triggered on push to `dev`.
+- `beta-release.yml` — triggered on push to `beta`.
+- `release.yml` — triggered on a `v*` tag push, cuts the actual stable release.
+
+All CI runs on a self-hosted runner; nothing runs automatically on plain
+commits or PRs beyond the track builds above. See
+[bread-ecosystem's docs/release-channels.md](https://git.breadway.dev/Breadway/bread-ecosystem/src/branch/main/docs/release-channels.md)
+for the full policy, including how a new product gets wired onto these tracks.
+
+## Questions
+
+Open an issue on this repo's Forgejo tracker.

Cargo.toml

@@ -0,0 +1,28 @@
+[workspace]
+members = ["breadcast-core", "breadcastd", "breadcast", "breadcast-caststream-sys"]
+resolver = "2"
+
+[workspace.package]
+version = "0.1.0"
+edition = "2021"
+license = "MIT"
+authors = ["Breadway <plasticbread849@gmail.com>"]
+
+[workspace.dependencies]
+anyhow = "1"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+tracing = "0.1"
+tracing-subscriber = "0.3"
+tokio = { version = "1", features = ["rt-multi-thread", "net", "sync", "time", "macros", "io-util"] }
+
+[profile.release]
+lto = "thin"
+codegen-units = 1
+strip = "symbols"
+
+# Adds CastDevice::send_message() -- a point-to-point send on an arbitrary
+# namespace, needed for the Cast Streaming OFFER/ANSWER exchange. See
+# vendor/rust_cast-0.21.0/PATCHES.md.
+[patch.crates-io]
+rust_cast = { path = "vendor/rust_cast-0.21.0" }

EVENTS.md

@@ -0,0 +1,44 @@
+# breadcast — bread event integration
+
+breadcast is a standalone screen-mirroring app: it works exactly the same
+with or without `breadd` running. When breadd *is* present, `breadcastd`
+publishes events into the shared bread automation fabric and listens for a
+small set of commands. See the parent `bread` repo's `Documentation.md` —
+specifically its "Namespaces" and "Integrating a bread\* app" sections — for
+the general convention this follows.
+
+App id: **`cast`**. Transport: `bread-utils`'s `bread_client` module
+(feature `bread-client`) — `breadcastd` links it directly, since it's a
+long-running process for both the command-subscription half and the
+discovery-driven emit half.
+
+## Events published (`bread.cast.*`)
+
+| Event | Data | When |
+|-------|------|------|
+| `bread.cast.device_found` | `{ "id": "<mdns id or DLNA description URL>", "name": "<friendly name>", "model": "<model>", "protocol": "cast" \| "dlna" }` | A Chromecast/Google TV (mDNS) or DLNA/UPnP media renderer (SSDP) is discovered (or re-resolved) on the LAN. Fires on every re-resolution, not just the first sighting — treat it as an upsert keyed by `id`, not an append-only log. `id` is protocol-specific and only unique *within* a protocol — a Cast device's mDNS id and a DLNA device's description URL share no namespace. |
+| `bread.cast.mirroring_started` | `{ "device_id": "<id>", "device_name": "<name>", "protocol": "cast" \| "dlna" }` | A mirroring session successfully started, whether triggered by `bread.command.cast.start`, the `breadcast` GTK popup, or (once wired) any other IPC client. |
+| `bread.cast.mirroring_stopped` | `{}` | A mirroring session ended, whether via an explicit stop (command, IPC, or GTK popup) or unprompted (the portal picker's "stop sharing", the receiver dropping the connection, a DLNA renderer stopping playback from its own remote). There is no separate "stopped by whom" distinction in this event — `breadcastd`'s own logs have that detail if needed. |
+| `bread.cast.mirroring_failed` | `{ "device_id": "<id>", "error": "<message>" }` | A `start_cast`/`bread.command.cast.start` attempt failed before a session was established (device unreachable, portal capture denied, negotiation timeout, renderer rejected the stream, etc). |
+
+## Commands honored (`bread.command.cast.*`)
+
+| Command | Data | Effect |
+|---------|------|--------|
+| `bread.command.cast.start` | `{ "device_id": "<id>" }` | Starts mirroring to the given device (looked up across both the Cast and DLNA device lists — same `device_id` a `list_devices`/`device_list_changed` payload reports). Fire-and-forget: the outcome shows up as `bread.cast.mirroring_started`/`.failed`, not a reply to this command. No-ops (logged) if already casting. |
+| `bread.command.cast.stop` | none | Stops the active mirroring session, if any. No-ops if already idle. |
+
+Both commands are handled identically regardless of whether the session was
+started from here, the `breadcast` GTK popup, or the IPC socket directly —
+`breadcastd`'s daemon actor has exactly one notion of "the active session"
+(see `breadcastd/src/daemon.rs`), not one per control surface.
+
+## Fail-safe behavior
+
+- If breadd isn't installed or isn't running, `emit` is a silent no-op
+  (`BreadClient::emit` never blocks or errors the caller) and the
+  command subscription simply never receives anything — breadcastd's actual
+  discovery functionality is entirely unaffected either way.
+- If breadd restarts, the command subscription reconnects automatically
+  (`BreadClient::subscribe`'s background thread has its own backoff loop);
+  no restart of breadcastd is needed.

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Breadway
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -0,0 +1,97 @@
+# breadcast
+
+Cast your screen to any Chromecast/Google TV, for Hyprland. It consists of
+two binaries:
+
+- **`breadcastd`** — a background daemon that discovers Cast devices on the
+  LAN and (once built — see Status) owns the screen-capture/encode/serve
+  pipeline and the live Cast V2 session.
+- **`breadcast`** — a GTK4 Layer Shell popup for picking a device and
+  starting/stopping a cast.
+
+## Status
+
+This is early: device discovery (mDNS) and the Cast V2 sender (real device
+control — connect, launch the receiver, load media) are built and validated
+against real Chromecast/Google TV hardware. The actual screen-mirroring
+pipeline (portal-based screen capture → GPU-accelerated encode → HLS →
+local HTTP server) and the GTK4 device-picker UI are not built yet.
+`breadcastd` today only does discovery and optional breadd event
+publishing; `breadcast` is a stub binary. See `CLAUDE.md`'s Status section
+for more detail.
+
+## Requirements
+
+- Rust toolchain (edition 2021)
+- GTK 4.12+ and `gtk4-layer-shell` (once the UI lands)
+- GStreamer + `gst-plugin-pipewire`, `gst-plugins-bad` (VA-API `va` plugin),
+  `gst-plugin-hlssink3` (once the capture pipeline lands)
+- Hyprland (or any Wayland compositor with Layer Shell and the
+  `xdg-desktop-portal` ScreenCast interface)
+
+## Build
+
+```sh
+git clone https://git.breadway.dev/breadway/breadcast
+cd breadcast
+cargo build --release
+```
+
+The compiled binaries are at `target/release/breadcast` and
+`target/release/breadcastd`.
+
+## Try device discovery today
+
+```sh
+cargo run -p breadcast-core --example discover
+```
+
+Prints Chromecast/Google TV devices as they appear/disappear on the LAN.
+
+## Install
+
+Copy the binaries to somewhere on your `$PATH`, e.g.:
+
+```sh
+cp target/release/breadcast target/release/breadcastd ~/.local/bin/
+```
+
+### systemd user service
+
+A unit file is provided in `contrib/`:
+
+```sh
+cp contrib/breadcastd.service ~/.config/systemd/user/
+systemctl --user daemon-reload
+systemctl --user enable --now breadcastd
+```
+
+### Hyprland keybind
+
+For stock Hyprland, add the contents of `contrib/hyprland.conf` to your
+`hyprland.conf`:
+
+```
+layerrule = blur, breadcast
+layerrule = ignorezero, breadcast
+
+bind = $mainMod, C, exec, breadcast
+```
+
+On BOS, Hyprland config is Lua+JSON-driven instead — see
+`contrib/binds.json` for the equivalent keybind entry to merge into your
+`binds.json` by hand (there's no per-app self-registration mechanism yet).
+There is currently no BOS-native equivalent for the `layerrule` blur lines.
+
+## bread event integration
+
+`breadcastd` optionally publishes into the shared bread automation fabric
+(`bread.cast.*`) when `breadd` is running, and works identically without
+it. See `EVENTS.md` for the full, honest-about-scope contract — most of the
+eventually-planned events (mirroring start/stop) aren't implemented yet,
+since the mirroring pipeline itself isn't built yet.
+
+## Theming
+
+`breadcast` will inherit its colour palette from `bread-theme`, matching
+the rest of the ecosystem, once its GTK4 UI is built.

bakery.toml

@@ -0,0 +1,34 @@
+name = "breadcast"
+description = "Cast your screen to any Chromecast/Google TV or DLNA renderer — daemon + GTK4 popup"
+binaries = ["breadcast", "breadcastd"]
+# gst-plugin-va: the `vah264enc` element both encode pipelines use (see
+# breadcast-core/src/pipeline/mod.rs) -- a separate Arch package from
+# gst-plugins-bad itself, not bundled into it. jsoncpp/openssl: runtime
+# shared-library deps of breadcastd itself (not just a build dep of
+# breadcast-caststream-sys), confirmed via `ldd target/release/breadcastd`
+# showing libjsoncpp.so/libcrypto.so -- the vendored openscreen Cast
+# Streaming code (see breadcast-caststream-sys/vendor/openscreen) links
+# dynamically against the system's jsoncpp/libcrypto rather than vendoring
+# them too.
+system_deps = [
+    "gtk4",
+    "gtk4-layer-shell",
+    "gstreamer",
+    "gst-plugin-pipewire",
+    "gst-plugins-bad",
+    "gst-plugin-hlssink3",
+    "gst-plugin-va",
+    "jsoncpp",
+    "openssl",
+]
+optional_system_deps = ["hyprland", "xdg-desktop-portal-hyprland"]
+bread_deps = []
+
+[[service]]
+unit = "breadcastd.service"
+enable = true
+
+[install]
+post_install = [
+    "systemctl --user is-active --quiet breadcastd || systemctl --user start breadcastd",
+]

breadcast-caststream-sys/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "breadcast-caststream-sys"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+description = "Low-level FFI bindings to a pruned, vendored openscreen Cast Streaming sender (see vendor/openscreen/PATCHES.md)"
+links = "breadcast_caststream"
+build = "build.rs"
+
+[build-dependencies]
+cc = "1"
+pkg-config = "0.3"
+
+[dev-dependencies]
+tracing-subscriber = { workspace = true }

breadcast-caststream-sys/build.rs

@@ -0,0 +1,60 @@
+use std::path::{Path, PathBuf};
+
+fn collect_cc_files(dir: &Path, out: &mut Vec<PathBuf>) {
+    for entry in std::fs::read_dir(dir).unwrap_or_else(|e| {
+        panic!("failed to read {}: {e}", dir.display());
+    }) {
+        let entry = entry.unwrap();
+        let path = entry.path();
+        if path.is_dir() {
+            collect_cc_files(&path, out);
+        } else if path.extension().is_some_and(|ext| ext == "cc") {
+            out.push(path);
+        }
+    }
+}
+
+fn main() {
+    let vendor = Path::new("vendor/openscreen");
+    let jsoncpp = pkg_config::probe_library("jsoncpp")
+        .expect("jsoncpp not found (pacman: jsoncpp / apt: libjsoncpp-dev)");
+    // Just libcrypto, not the full "openssl" .pc -- this vendored subset of
+    // openscreen never touches libssl (no TLS; see vendor/openscreen/PATCHES.md).
+    let libcrypto = pkg_config::probe_library("libcrypto").expect("libcrypto not found");
+
+    let mut sources = Vec::new();
+    collect_cc_files(vendor, &mut sources);
+    sources.push(PathBuf::from("src/message_port_bridge.cc"));
+    sources.push(PathBuf::from("src/session.cc"));
+    sources.push(PathBuf::from("src/facade.cc"));
+
+    let mut build = cc::Build::new();
+    build
+        .cpp(true)
+        .std("c++20")
+        .include(vendor)
+        .include("src")
+        // Force-included into every translation unit -- see
+        // vendor/openscreen/patches/compat_shims.h for what this papers over
+        // (a couple of missing includes and BoringSSL-only APIs system
+        // OpenSSL doesn't expose).
+        .flag(format!("-include{}", vendor.join("patches/compat_shims.h").display()))
+        // This is a vendored, pruned third-party subset (see
+        // vendor/openscreen/PATCHES.md) -- warnings in it aren't
+        // breadcast's to fix, and upstream builds it with -w itself for the
+        // same reason (see BoringSSL's "internal_config" in its own BUILD.gn).
+        .warnings(false);
+
+    for path in jsoncpp.include_paths.iter().chain(libcrypto.include_paths.iter()) {
+        build.include(path);
+    }
+
+    for source in &sources {
+        println!("cargo:rerun-if-changed={}", source.display());
+        build.file(source);
+    }
+    println!("cargo:rerun-if-changed=src/facade.h");
+    println!("cargo:rerun-if-changed=vendor/openscreen/PATCHES.md");
+
+    build.compile("breadcast_caststream");
+}

breadcast-caststream-sys/src/facade.cc

@@ -0,0 +1,297 @@
+#include "facade.h"
+
+#include <atomic>
+#include <future>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "cast/streaming/public/encoded_frame.h"
+#include "cast/streaming/public/environment.h"
+#include "cast/streaming/rtp_time.h"
+#include "message_port_bridge.h"
+#include "platform/api/time.h"
+#include "platform/base/ip_address.h"
+#include "platform/impl/platform_client_posix.h"
+#include "platform/impl/task_runner.h"
+#include "session.h"
+
+namespace {
+
+// How often to refresh the atomics polled by
+// breadcast_caststream_sender_{needs_key_frame,estimated_bandwidth_bps}.
+// These are advisory (encoder bitrate/keyframe hints), so a small amount of
+// staleness is fine -- this just needs to be fast enough not to be the
+// bottleneck in reacting to network conditions.
+constexpr std::chrono::milliseconds kPollInterval(100);
+
+// Used as the pre-negotiation default so the very first frames (sent before
+// any RTCP feedback exists to compute a real estimate from) aren't wildly
+// over-encoded. Conservative middle-of-the-road value; real estimates from
+// BandwidthEstimator::ComputeNetworkBandwidth() take over once available.
+constexpr int32_t kDefaultBandwidthEstimateBps = 2 * 1000 * 1000;
+
+}  // namespace
+
+struct CastStreamSender {
+  std::unique_ptr<openscreen::cast::Environment> environment;
+  std::unique_ptr<breadcast_caststream::MessagePortBridge> message_port;
+  std::unique_ptr<breadcast_caststream::MirroringSenderSession> session;
+
+  // Set once, the first time a frame is enqueued after negotiation
+  // completes; used to compute monotonically-increasing RTP timestamps
+  // relative to session start.
+  bool have_origin = false;
+  int64_t origin_capture_time_us = 0;
+
+  // negotiated uses acquire/release so that once
+  // breadcast_caststream_sender_enqueue_frame observes it true (from an
+  // arbitrary caller thread), `session->video_sender()` is guaranteed
+  // already set -- see OnNegotiatedTrampoline below.
+  std::atomic<bool> negotiated{false};
+  std::atomic<bool> needs_key_frame{true};
+  std::atomic<int32_t> estimated_bandwidth_bps{kDefaultBandwidthEstimateBps};
+
+  // The caller's own user_data + callbacks, as passed to `_create`. Not
+  // called directly -- session.h/message_port_bridge.h are instead given
+  // trampolines below (with `this` as their user_data) so this struct can
+  // update its own bookkeeping (e.g. `negotiated`) before forwarding.
+  void* rust_user_data = nullptr;
+  BreadcastOnNegotiatedFn rust_on_negotiated = nullptr;
+  BreadcastOnErrorFn rust_on_error = nullptr;
+  BreadcastOnPictureLostFn rust_on_picture_lost = nullptr;
+
+  void SchedulePoll() {
+    environment->task_runner().PostTaskWithDelay(
+        [this] {
+          if (session && session->video_sender()) {
+            needs_key_frame.store(session->video_sender()->NeedsKeyFrame(),
+                                  std::memory_order_relaxed);
+            const int bps = session->GetEstimatedBandwidthBps();
+            if (bps > 0) {
+              estimated_bandwidth_bps.store(bps, std::memory_order_relaxed);
+            }
+          }
+          SchedulePoll();
+        },
+        kPollInterval);
+  }
+};
+
+namespace {
+
+void OnNegotiatedTrampoline(void* user_data) {
+  auto* sender = static_cast<CastStreamSender*>(user_data);
+  sender->negotiated.store(true, std::memory_order_release);
+  if (sender->rust_on_negotiated) {
+    sender->rust_on_negotiated(sender->rust_user_data);
+  }
+}
+
+void OnErrorTrampoline(void* user_data, const char* message, size_t message_len) {
+  auto* sender = static_cast<CastStreamSender*>(user_data);
+  if (sender->rust_on_error) {
+    sender->rust_on_error(sender->rust_user_data, message, message_len);
+  }
+}
+
+void OnPictureLostTrampoline(void* user_data) {
+  auto* sender = static_cast<CastStreamSender*>(user_data);
+  if (sender->rust_on_picture_lost) {
+    sender->rust_on_picture_lost(sender->rust_user_data);
+  }
+}
+
+}  // namespace
+
+extern "C" {
+
+CastStreamSender* breadcast_caststream_sender_create(
+    const char* remote_ip,
+    size_t remote_ip_len,
+    const char* local_source_id,
+    size_t local_source_id_len,
+    const char* receiver_id,
+    size_t receiver_id_len,
+    int32_t width,
+    int32_t height,
+    int32_t max_bitrate_bps,
+    int32_t max_frame_rate_numerator,
+    int32_t max_frame_rate_denominator,
+    void* user_data,
+    BreadcastPostMessageFn post_message,
+    BreadcastOnNegotiatedFn on_negotiated,
+    BreadcastOnErrorFn on_error,
+    BreadcastOnPictureLostFn on_picture_lost) {
+  auto address_result =
+      openscreen::IPAddress::Parse(std::string(remote_ip, remote_ip_len));
+  if (!address_result) {
+    return nullptr;
+  }
+
+  auto handle = std::make_unique<CastStreamSender>();
+  handle->rust_user_data = user_data;
+  handle->rust_on_negotiated = on_negotiated;
+  handle->rust_on_error = on_error;
+  handle->rust_on_picture_lost = on_picture_lost;
+
+  // Spins up openscreen's TaskRunner + networking threads. Safe to call more
+  // than once process-wide only if ShutDown() was called first -- breadcast
+  // only ever has one active cast-streaming session at a time, so this
+  // assumption (baked into PlatformClientPosix's own singleton design) holds.
+  openscreen::PlatformClientPosix::Create(std::chrono::milliseconds(50));
+  openscreen::TaskRunner& task_runner =
+      openscreen::PlatformClientPosix::GetInstance()->GetTaskRunner();
+
+  breadcast_caststream::VideoParams params;
+  params.width = width;
+  params.height = height;
+  params.max_bit_rate = max_bitrate_bps;
+  params.max_frame_rate_numerator = max_frame_rate_numerator;
+  params.max_frame_rate_denominator = max_frame_rate_denominator;
+
+  breadcast_caststream::SessionCallbacks callbacks;
+  callbacks.user_data = handle.get();
+  callbacks.on_negotiated = &OnNegotiatedTrampoline;
+  callbacks.on_error = &OnErrorTrampoline;
+  callbacks.on_picture_lost = &OnPictureLostTrampoline;
+
+  const openscreen::IPAddress remote_address = address_result.value();
+  std::string local_source_id_str(local_source_id, local_source_id_len);
+  std::string receiver_id_str(receiver_id, receiver_id_len);
+
+  // Environment's constructor synchronously creates and binds a UdpSocket,
+  // whose posix implementation asserts it's only ever touched from the
+  // TaskRunner thread (see udp_socket_posix.cc) -- so construction has to
+  // happen there too, not on this (arbitrary caller's) thread.
+  CastStreamSender* handle_ptr = handle.get();
+  std::promise<void> constructed;
+  std::future<void> constructed_future = constructed.get_future();
+  task_runner.PostTask([handle_ptr, &task_runner, &params, &callbacks, remote_address,
+                        local_source_id_str, receiver_id_str, post_message, user_data,
+                        &constructed] {
+    handle_ptr->environment =
+        std::make_unique<openscreen::cast::Environment>(&openscreen::Clock::now, task_runner);
+    handle_ptr->message_port =
+        std::make_unique<breadcast_caststream::MessagePortBridge>(user_data, post_message);
+    handle_ptr->session = std::make_unique<breadcast_caststream::MirroringSenderSession>(
+        *handle_ptr->environment, *handle_ptr->message_port, remote_address,
+        local_source_id_str, receiver_id_str, params, callbacks);
+    constructed.set_value();
+  });
+  constructed_future.wait();
+
+  return handle.release();
+}
+
+void breadcast_caststream_sender_negotiate(CastStreamSender* sender) {
+  sender->environment->task_runner().PostTask([sender] {
+    sender->session->Negotiate();
+    sender->SchedulePoll();
+  });
+}
+
+void breadcast_caststream_sender_on_message(CastStreamSender* sender,
+                                            const char* source_id,
+                                            size_t source_id_len,
+                                            const char* message_namespace,
+                                            size_t message_namespace_len,
+                                            const char* message,
+                                            size_t message_len) {
+  auto source = std::make_shared<std::string>(source_id, source_id_len);
+  auto ns = std::make_shared<std::string>(message_namespace, message_namespace_len);
+  auto body = std::make_shared<std::string>(message, message_len);
+  sender->environment->task_runner().PostTask([sender, source, ns, body] {
+    sender->message_port->DeliverMessage(*source, *ns, *body);
+  });
+}
+
+int32_t breadcast_caststream_sender_enqueue_frame(CastStreamSender* sender,
+                                                  const uint8_t* data,
+                                                  size_t data_len,
+                                                  int32_t is_key_frame,
+                                                  int64_t capture_time_us) {
+  if (!sender->negotiated.load(std::memory_order_acquire)) {
+    return -1;
+  }
+
+  // Copied here (not captured as a borrowed span) because PostTask defers
+  // execution -- `data` is only guaranteed valid for the duration of this
+  // call, per facade.h's documented contract.
+  auto owned_data = std::make_shared<std::vector<uint8_t>>(data, data + data_len);
+  const bool is_key = is_key_frame != 0;
+
+  sender->environment->task_runner().PostTask([sender, owned_data, is_key, capture_time_us] {
+    using namespace openscreen;
+    using namespace openscreen::cast;
+
+    Sender* video_sender = sender->session->video_sender();
+    if (!video_sender) {
+      return;
+    }
+
+    if (!sender->have_origin) {
+      sender->have_origin = true;
+      sender->origin_capture_time_us = capture_time_us;
+    }
+
+    const FrameId frame_id = video_sender->GetNextFrameId();
+    const FrameId referenced_frame_id =
+        is_key || frame_id == FrameId::first() ? frame_id : frame_id - 1;
+
+    // breadcast's encoder (vah264enc via GStreamer) is assumed to produce a
+    // simple linear IPPP GOP structure (no B-frames / no multi-reference),
+    // so "depends on the immediately preceding frame" is a correct
+    // reference, not just an approximation.
+    const int64_t elapsed_us = capture_time_us - sender->origin_capture_time_us;
+    const RtpTimeTicks rtp_timestamp = RtpTimeTicks::FromTimeSinceOrigin(
+        std::chrono::microseconds(elapsed_us), video_sender->config().rtp_timebase);
+
+    const EncodedFrame::Dependency dependency =
+        is_key ? EncodedFrame::Dependency::kKeyFrame : EncodedFrame::Dependency::kDependent;
+    EncodedFrame frame(dependency, frame_id, referenced_frame_id, rtp_timestamp, Clock::now(),
+                       /*new_playout_delay=*/std::chrono::milliseconds::zero(),
+                       ByteView(owned_data->data(), owned_data->size()));
+
+    // EnqueueFrame()'s result (e.g. MAX_DURATION_IN_FLIGHT under backpressure)
+    // isn't propagated to the caller: by the time this runs, enqueue_frame()
+    // has already returned 0 synchronously (this call is posted, not
+    // immediate -- see facade.h's threading contract). Backpressure here just
+    // means this one frame is dropped; the encoder finds out indirectly via
+    // needs_key_frame()/estimated_bandwidth_bps() polling.
+    (void)video_sender->EnqueueFrame(frame);
+  });
+
+  return 0;
+}
+
+int32_t breadcast_caststream_sender_needs_key_frame(CastStreamSender* sender) {
+  return sender->needs_key_frame.load(std::memory_order_relaxed) ? 1 : 0;
+}
+
+int32_t breadcast_caststream_sender_estimated_bandwidth_bps(CastStreamSender* sender) {
+  return sender->estimated_bandwidth_bps.load(std::memory_order_relaxed);
+}
+
+void breadcast_caststream_sender_destroy(CastStreamSender* sender) {
+  if (!sender) {
+    return;
+  }
+  // These must be torn down on the TaskRunner thread (they hold raw
+  // references into it and into `environment`), so hop over there and block
+  // until it's done before shutting the TaskRunner itself down.
+  std::promise<void> done;
+  std::future<void> done_future = done.get_future();
+  sender->environment->task_runner().PostTask([sender, &done] {
+    sender->session.reset();
+    sender->message_port.reset();
+    sender->environment.reset();
+    done.set_value();
+  });
+  done_future.wait();
+
+  openscreen::PlatformClientPosix::ShutDown();
+  delete sender;
+}
+
+}  // extern "C"

breadcast-caststream-sys/src/facade.h

@@ -0,0 +1,123 @@
+// The extern "C" surface breadcast-caststream-sys's build.rs compiles and
+// the Rust side (src/lib.rs) declares `extern "C"` bindings for.
+//
+// Threading contract: `breadcast_caststream_sender_create` spins up
+// openscreen's own TaskRunner + networking threads internally (via
+// PlatformClientPosix) -- callers don't manage those. All
+// `breadcast_caststream_sender_*` functions taking a `CastStreamSender*` are
+// safe to call from any single thread (they internally marshal onto the
+// TaskRunner thread via TaskRunner::PostTask, which is documented
+// thread-safe) -- but the *callbacks* passed to `_create` fire FROM that
+// TaskRunner thread, not the caller's thread. This mirrors the existing
+// single-io-thread actor pattern breadcast-core's CastSession already uses
+// for CASTV2: the Rust wrapper is expected to run one dedicated thread that
+// owns the CastStreamSender and treats callback invocations as arriving from
+// a foreign thread (e.g. hands them off over an mpsc channel), exactly like
+// CastSession's io loop already does for rust_cast's own callbacks.
+#ifndef BREADCAST_CASTSTREAM_FACADE_H_
+#define BREADCAST_CASTSTREAM_FACADE_H_
+
+#include <cstddef>
+#include <cstdint>
+
+extern "C" {
+
+typedef struct CastStreamSender CastStreamSender;
+
+// Forwards an outbound OFFER/ANSWER-exchange message to Rust for sending
+// over the existing CASTV2 urn:x-cast:com.google.cast.webrtc channel. All
+// buffers are borrowed for the duration of the call only.
+typedef void (*BreadcastPostMessageFn)(void* user_data,
+                                       const char* destination_id,
+                                       size_t destination_id_len,
+                                       const char* message_namespace,
+                                       size_t message_namespace_len,
+                                       const char* message,
+                                       size_t message_len);
+
+// Fired once OFFER/ANSWER negotiation succeeds and the video sender is
+// ready to accept frames.
+typedef void (*BreadcastOnNegotiatedFn)(void* user_data);
+
+// Fired on a negotiation or session error. `message` is borrowed for the
+// duration of the call only.
+typedef void (*BreadcastOnErrorFn)(void* user_data,
+                                   const char* message,
+                                   size_t message_len);
+
+// Fired when the receiver reports picture loss and wants a key frame ASAP
+// (a push notification; see also breadcast_caststream_sender_needs_key_frame
+// for the pull-style equivalent, which also catches this condition).
+typedef void (*BreadcastOnPictureLostFn)(void* user_data);
+
+// Creates a session and starts openscreen's TaskRunner/networking threads.
+// `remote_ip` is the receiver's IP address (the same one rust_cast already
+// connected to for the CASTV2 control channel); `local_source_id`/
+// `receiver_id` are the CASTV2 source/destination IDs to use when sending
+// messages over the webrtc namespace (already known to the Rust caller from
+// its existing CASTV2 session). Returns null on failure (e.g. invalid IP or
+// failure to bind the local UDP socket).
+CastStreamSender* breadcast_caststream_sender_create(
+    const char* remote_ip,
+    size_t remote_ip_len,
+    const char* local_source_id,
+    size_t local_source_id_len,
+    const char* receiver_id,
+    size_t receiver_id_len,
+    int32_t width,
+    int32_t height,
+    int32_t max_bitrate_bps,
+    int32_t max_frame_rate_numerator,
+    int32_t max_frame_rate_denominator,
+    void* user_data,
+    BreadcastPostMessageFn post_message,
+    BreadcastOnNegotiatedFn on_negotiated,
+    BreadcastOnErrorFn on_error,
+    BreadcastOnPictureLostFn on_picture_lost);
+
+// Sends the OFFER and begins waiting for an ANSWER.
+void breadcast_caststream_sender_negotiate(CastStreamSender* sender);
+
+// Delivers a message received on the webrtc namespace (e.g. the ANSWER)
+// into the session. All buffers are copied before this returns.
+void breadcast_caststream_sender_on_message(CastStreamSender* sender,
+                                            const char* source_id,
+                                            size_t source_id_len,
+                                            const char* message_namespace,
+                                            size_t message_namespace_len,
+                                            const char* message,
+                                            size_t message_len);
+
+// Enqueues one encoded video access unit (Annex-B H.264) for sending.
+// `data` is copied before this returns, so the caller may reuse/free its
+// buffer immediately after. `capture_time_us` is only used to derive the
+// RTP timestamp's relative spacing between frames (it does not need to be
+// wall-clock-accurate, just monotonically increasing and proportional to
+// real elapsed time between frames). Returns 0 if queued, nonzero if the
+// session isn't negotiated yet or the frame was rejected (e.g. too large,
+// or the in-flight queue is full -- the caller should back off encoding
+// when this happens rather than treating it as fatal).
+int32_t breadcast_caststream_sender_enqueue_frame(CastStreamSender* sender,
+                                                  const uint8_t* data,
+                                                  size_t data_len,
+                                                  int32_t is_key_frame,
+                                                  int64_t capture_time_us);
+
+// True (nonzero) if the receiver wants a key frame as soon as possible.
+// Safe to poll frequently; cheap, non-blocking, lock-free.
+int32_t breadcast_caststream_sender_needs_key_frame(CastStreamSender* sender);
+
+// Best-effort current bandwidth estimate in bits per second. Safe to poll
+// frequently; cheap, non-blocking, lock-free. Intended to drive the video
+// encoder's target bitrate (this vendored subset of openscreen only does
+// flow control, not congestion control -- see Sender's class comment in
+// vendor/openscreen/cast/streaming/public/sender.h).
+int32_t breadcast_caststream_sender_estimated_bandwidth_bps(CastStreamSender* sender);
+
+// Tears down the session and stops openscreen's internal threads. Blocks
+// until shutdown completes.
+void breadcast_caststream_sender_destroy(CastStreamSender* sender);
+
+}  // extern "C"
+
+#endif  // BREADCAST_CASTSTREAM_FACADE_H_

breadcast-caststream-sys/src/lib.rs

@@ -0,0 +1,133 @@
+//! Raw FFI bindings to `src/facade.h`/`src/facade.cc`, which wrap a pruned,
+//! vendored subset of `chromium/openscreen`'s Cast Streaming sender (see
+//! `vendor/openscreen/PATCHES.md`). This crate is intentionally low-level and
+//! unsafe -- see `breadcast-caststream` (not this crate) for the ergonomic,
+//! thread-safe wrapper most callers should use instead.
+//!
+//! # Threading contract
+//!
+//! `sender_create` spins up openscreen's own TaskRunner + networking threads
+//! internally; callers don't manage those. Every `sender_*` function taking
+//! a `*mut CastStreamSender` is safe to call from any thread (calls are
+//! internally marshaled onto the TaskRunner thread). The callbacks passed to
+//! `sender_create`, however, fire FROM that TaskRunner thread, not the
+//! caller's thread -- see `facade.h`'s doc comment for the full contract,
+//! which mirrors the single-io-thread actor pattern breadcast-core's
+//! `CastSession` already uses for CASTV2.
+
+use std::ffi::{c_char, c_void};
+
+#[repr(C)]
+pub struct CastStreamSender {
+    _private: [u8; 0],
+}
+
+// Safety: every function below is documented (facade.h) as safe to call
+// from any thread; only the callbacks fire cross-thread, and those are
+// plain `extern "C" fn` pointers rather than captured state, so there is no
+// non-Send/Sync data hanging off `*mut CastStreamSender` itself.
+unsafe impl Send for CastStreamSender {}
+
+pub type PostMessageFn = extern "C" fn(
+    user_data: *mut c_void,
+    destination_id: *const c_char,
+    destination_id_len: usize,
+    message_namespace: *const c_char,
+    message_namespace_len: usize,
+    message: *const c_char,
+    message_len: usize,
+);
+
+pub type OnNegotiatedFn = extern "C" fn(user_data: *mut c_void);
+
+pub type OnErrorFn =
+    extern "C" fn(user_data: *mut c_void, message: *const c_char, message_len: usize);
+
+pub type OnPictureLostFn = extern "C" fn(user_data: *mut c_void);
+
+unsafe extern "C" {
+    /// Returns null on failure (e.g. an unparseable `remote_ip`, or the
+    /// local UDP socket failed to bind).
+    ///
+    /// # Safety
+    /// `remote_ip`/`local_source_id`/`receiver_id` must each point to
+    /// `_len` valid, readable bytes for the duration of this call.
+    /// `post_message`/`on_negotiated`/`on_error`/`on_picture_lost` must be
+    /// valid to call for as long as the returned sender is alive (i.e.
+    /// until `sender_destroy` returns). `user_data` is passed back
+    /// unmodified to every callback and may be null.
+    pub fn breadcast_caststream_sender_create(
+        remote_ip: *const c_char,
+        remote_ip_len: usize,
+        local_source_id: *const c_char,
+        local_source_id_len: usize,
+        receiver_id: *const c_char,
+        receiver_id_len: usize,
+        width: i32,
+        height: i32,
+        max_bitrate_bps: i32,
+        max_frame_rate_numerator: i32,
+        max_frame_rate_denominator: i32,
+        user_data: *mut c_void,
+        post_message: PostMessageFn,
+        on_negotiated: OnNegotiatedFn,
+        on_error: OnErrorFn,
+        on_picture_lost: OnPictureLostFn,
+    ) -> *mut CastStreamSender;
+
+    /// # Safety
+    /// `sender` must be a live pointer returned by `sender_create` and not
+    /// yet passed to `sender_destroy`.
+    pub fn breadcast_caststream_sender_negotiate(sender: *mut CastStreamSender);
+
+    /// Delivers an inbound message (e.g. the receiver's ANSWER) received on
+    /// the CASTV2 `urn:x-cast:com.google.cast.webrtc` namespace into the
+    /// session. All buffers are copied before this returns.
+    ///
+    /// # Safety
+    /// `sender` must be live. `source_id`/`message_namespace`/`message` must
+    /// each point to `_len` valid, readable bytes for the duration of this
+    /// call only.
+    pub fn breadcast_caststream_sender_on_message(
+        sender: *mut CastStreamSender,
+        source_id: *const c_char,
+        source_id_len: usize,
+        message_namespace: *const c_char,
+        message_namespace_len: usize,
+        message: *const c_char,
+        message_len: usize,
+    );
+
+    /// Enqueues one encoded video access unit (Annex-B H.264) for sending.
+    /// Returns 0 if queued, nonzero if not negotiated yet.
+    ///
+    /// # Safety
+    /// `sender` must be live. `data` must point to `data_len` valid,
+    /// readable bytes for the duration of this call only (it is copied
+    /// before this returns).
+    pub fn breadcast_caststream_sender_enqueue_frame(
+        sender: *mut CastStreamSender,
+        data: *const u8,
+        data_len: usize,
+        is_key_frame: i32,
+        capture_time_us: i64,
+    ) -> i32;
+
+    /// # Safety
+    /// `sender` must be live.
+    pub fn breadcast_caststream_sender_needs_key_frame(sender: *mut CastStreamSender) -> i32;
+
+    /// # Safety
+    /// `sender` must be live.
+    pub fn breadcast_caststream_sender_estimated_bandwidth_bps(
+        sender: *mut CastStreamSender,
+    ) -> i32;
+
+    /// Tears down the session and blocks until openscreen's internal
+    /// threads stop. `sender` must not be used again after this call.
+    ///
+    /// # Safety
+    /// `sender` must be a live pointer returned by `sender_create`, not
+    /// already passed to this function.
+    pub fn breadcast_caststream_sender_destroy(sender: *mut CastStreamSender);
+}

breadcast-caststream-sys/src/message_port_bridge.cc

@@ -0,0 +1,35 @@
+#include "message_port_bridge.h"
+
+namespace breadcast_caststream {
+
+MessagePortBridge::MessagePortBridge(void* user_data,
+                                     PostMessageCallback post_message)
+    : user_data_(user_data), post_message_(post_message) {}
+
+MessagePortBridge::~MessagePortBridge() = default;
+
+void MessagePortBridge::DeliverMessage(const std::string& source_id,
+                                       const std::string& message_namespace,
+                                       const std::string& message) {
+  if (client_) {
+    client_->OnMessage(source_id, message_namespace, message);
+  }
+}
+
+void MessagePortBridge::SetClient(Client& client) {
+  client_ = &client;
+}
+
+void MessagePortBridge::ResetClient() {
+  client_ = nullptr;
+}
+
+void MessagePortBridge::PostMessage(const std::string& destination_id,
+                                    const std::string& message_namespace,
+                                    const std::string& message) {
+  post_message_(user_data_, destination_id.data(), destination_id.size(),
+               message_namespace.data(), message_namespace.size(),
+               message.data(), message.size());
+}
+
+}  // namespace breadcast_caststream

breadcast-caststream-sys/src/message_port_bridge.h

@@ -0,0 +1,58 @@
+// A openscreen::cast::MessagePort implementation that forwards outbound
+// messages to a Rust-provided callback (which sends them over the existing
+// rust_cast-managed CASTV2 TLS channel, in the
+// urn:x-cast:com.google.cast.webrtc namespace) and accepts inbound messages
+// via DeliverMessage(), called by Rust when a reply arrives on that
+// channel. This is what lets openscreen's own SenderSessionMessenger/
+// SenderPacketRouter run OFFER/ANSWER negotiation without this crate
+// needing its own TLS stack -- see ../vendor/openscreen/PATCHES.md.
+#ifndef BREADCAST_CASTSTREAM_MESSAGE_PORT_BRIDGE_H_
+#define BREADCAST_CASTSTREAM_MESSAGE_PORT_BRIDGE_H_
+
+#include <cstddef>
+#include <cstdint>
+#include <string>
+
+#include "cast/common/public/message_port.h"
+
+namespace breadcast_caststream {
+
+// Matches the PostMessageFn typedef in facade.h.
+using PostMessageCallback = void (*)(void* user_data,
+                                     const char* destination_id,
+                                     size_t destination_id_len,
+                                     const char* message_namespace,
+                                     size_t message_namespace_len,
+                                     const char* message,
+                                     size_t message_len);
+
+class MessagePortBridge final : public openscreen::cast::MessagePort {
+ public:
+  MessagePortBridge(void* user_data, PostMessageCallback post_message);
+  ~MessagePortBridge() override;
+
+  // Called by facade.cc's FFI entry point when Rust has received a message
+  // on the webrtc namespace for us. Safe to call from any thread; the
+  // caller is responsible for making sure this only actually touches
+  // `client_` while running on the Environment's TaskRunner thread (facade.cc
+  // marshals this via TaskRunner::PostTask before calling here).
+  void DeliverMessage(const std::string& source_id,
+                      const std::string& message_namespace,
+                      const std::string& message);
+
+  // openscreen::cast::MessagePort implementation.
+  void SetClient(Client& client) override;
+  void ResetClient() override;
+  void PostMessage(const std::string& destination_id,
+                   const std::string& message_namespace,
+                   const std::string& message) override;
+
+ private:
+  void* const user_data_;
+  const PostMessageCallback post_message_;
+  Client* client_ = nullptr;
+};
+
+}  // namespace breadcast_caststream
+
+#endif  // BREADCAST_CASTSTREAM_MESSAGE_PORT_BRIDGE_H_

breadcast-caststream-sys/src/session.cc

@@ -0,0 +1,181 @@
+#include "session.h"
+
+#include <utility>
+
+#include "cast/streaming/impl/rtp_defines.h"
+#include "cast/streaming/message_fields.h"
+#include "cast/streaming/public/constants.h"
+#include "cast/streaming/public/session_config.h"
+#include "cast/streaming/sender_message.h"
+#include "util/crypto/random_bytes.h"
+
+namespace breadcast_caststream {
+
+namespace {
+
+using openscreen::Error;
+using openscreen::ErrorOr;
+using openscreen::GenerateRandomBytes16;
+using openscreen::cast::AudioStream;
+using openscreen::cast::CastMode;
+using openscreen::cast::GenerateSsrc;
+using openscreen::cast::GetPayloadType;
+using openscreen::cast::kMinVideoHeight;
+using openscreen::cast::kMinVideoWidth;
+using openscreen::cast::kRtpVideoTimebase;
+using openscreen::cast::Offer;
+using openscreen::cast::ReceiverMessage;
+using openscreen::cast::Resolution;
+using openscreen::cast::SenderMessage;
+using openscreen::cast::SessionConfig;
+using openscreen::cast::Stream;
+using openscreen::cast::ToStreamType;
+using openscreen::cast::VideoCodec;
+using openscreen::cast::VideoStream;
+
+// breadcast always mirrors exactly one video stream at index 0 -- there is
+// no audio stream in this integration (breadcast's capture pipeline is
+// video-only), so the index scheme sender_session.cc uses for interleaving
+// audio-then-video streams collapses to just "index 0 is the video stream."
+constexpr int kVideoStreamIndex = 0;
+
+VideoStream BuildVideoStream(const VideoParams& params,
+                             bool use_android_rtp_hack) {
+  Stream stream;
+  stream.index = kVideoStreamIndex;
+  stream.type = Stream::Type::kVideoSource;
+  stream.channels = 1;
+  stream.rtp_payload_type = GetPayloadType(VideoCodec::kH264, use_android_rtp_hack);
+  stream.ssrc = GenerateSsrc(/*higher_priority=*/false);
+  stream.target_delay = openscreen::cast::kDefaultTargetPlayoutDelay;
+  stream.aes_key = GenerateRandomBytes16();
+  stream.aes_iv_mask = GenerateRandomBytes16();
+  stream.receiver_rtcp_event_log = true;
+  stream.rtp_timebase = kRtpVideoTimebase;
+
+  VideoStream video_stream;
+  video_stream.stream = std::move(stream);
+  video_stream.codec = VideoCodec::kH264;
+  video_stream.max_frame_rate = openscreen::SimpleFraction{
+      params.max_frame_rate_numerator, params.max_frame_rate_denominator};
+  video_stream.max_bit_rate = (params.max_bit_rate >= openscreen::cast::kDefaultVideoMinBitRate)
+                                  ? params.max_bit_rate
+                                  : openscreen::cast::kDefaultVideoMaxBitRate;
+  video_stream.resolutions.push_back(Resolution{
+      std::max(params.width, kMinVideoWidth), std::max(params.height, kMinVideoHeight)});
+  return video_stream;
+}
+
+}  // namespace
+
+MirroringSenderSession::MirroringSenderSession(
+    openscreen::cast::Environment& environment,
+    openscreen::cast::MessagePort& message_port,
+    openscreen::IPAddress remote_address,
+    std::string local_source_id,
+    std::string receiver_id,
+    VideoParams params,
+    SessionCallbacks callbacks)
+    : environment_(environment),
+      remote_address_(remote_address),
+      receiver_id_(std::move(receiver_id)),
+      params_(params),
+      callbacks_(callbacks),
+      messenger_(
+          message_port,
+          std::move(local_source_id),
+          receiver_id_,
+          [this](Error error) { ReportError(error.message()); },
+          environment.task_runner()),
+      packet_router_(environment) {}
+
+MirroringSenderSession::~MirroringSenderSession() {
+  if (video_sender_) {
+    video_sender_->SetObserver(nullptr);
+  }
+}
+
+void MirroringSenderSession::Negotiate() {
+  // use_android_rtp_hack defaults on upstream too (crbug.com/631828) --
+  // Google TV devices are Android TV under the hood, so this is left on.
+  constexpr bool kUseAndroidRtpHack = true;
+
+  Offer offer;
+  offer.cast_mode = CastMode::kMirroring;
+  offer.video_streams.push_back(BuildVideoStream(params_, kUseAndroidRtpHack));
+  pending_offer_ = offer;
+
+  const Error result = messenger_.SendRequest(
+      SenderMessage{SenderMessage::Type::kOffer, ++sequence_number_,
+                    /*valid=*/true, std::move(offer)},
+      ReceiverMessage::Type::kAnswer,
+      [this](ErrorOr<ReceiverMessage> message) { OnAnswer(std::move(message)); });
+  if (!result.ok()) {
+    ReportError(result.message());
+  }
+}
+
+void MirroringSenderSession::OnAnswer(ErrorOr<ReceiverMessage> message) {
+  if (!message) {
+    ReportError(message.error().message());
+    return;
+  }
+  if (!message.value().valid || message.value().type != ReceiverMessage::Type::kAnswer) {
+    ReportError("Receiver sent an invalid or unexpected ANSWER response");
+    return;
+  }
+
+  const auto& answer = std::get<openscreen::cast::Answer>(message.value().body);
+  if (answer.send_indexes.empty() || answer.ssrcs.empty()) {
+    ReportError("ANSWER selected no streams");
+    return;
+  }
+
+  environment_.set_remote_endpoint(
+      openscreen::IPEndpoint{remote_address_, static_cast<uint16_t>(answer.udp_port)});
+
+  const openscreen::cast::VideoStream& stream = pending_offer_.video_streams[0];
+  const openscreen::cast::RtpPayloadType payload_type = stream.stream.rtp_payload_type;
+
+  SessionConfig config{stream.stream.ssrc,
+                       answer.ssrcs[0],
+                       stream.stream.rtp_timebase,
+                       stream.stream.channels,
+                       stream.stream.target_delay,
+                       stream.stream.aes_key,
+                       stream.stream.aes_iv_mask,
+                       /*is_pli_enabled=*/true,
+                       ToStreamType(payload_type, /*use_android_rtp_hack=*/true)};
+  if (!config.IsValid()) {
+    ReportError("Derived an invalid SessionConfig from the ANSWER");
+    return;
+  }
+
+  video_sender_ = std::make_unique<openscreen::cast::SenderImpl>(
+      environment_, packet_router_, std::move(config), payload_type);
+  video_sender_->SetObserver(this);
+
+  if (callbacks_.on_negotiated) {
+    callbacks_.on_negotiated(callbacks_.user_data);
+  }
+}
+
+int MirroringSenderSession::GetEstimatedBandwidthBps() const {
+  return packet_router_.ComputeNetworkBandwidth();
+}
+
+void MirroringSenderSession::OnFrameCanceled(openscreen::cast::FrameId) {}
+
+void MirroringSenderSession::OnPictureLost() {
+  if (callbacks_.on_picture_lost) {
+    callbacks_.on_picture_lost(callbacks_.user_data);
+  }
+}
+
+void MirroringSenderSession::ReportError(const std::string& message) {
+  if (callbacks_.on_error) {
+    callbacks_.on_error(callbacks_.user_data, message.data(), message.size());
+  }
+}
+
+}  // namespace breadcast_caststream

breadcast-caststream-sys/src/session.h

@@ -0,0 +1,102 @@
+// A minimal, video-only Cast Streaming sender negotiation driver.
+//
+// This deliberately does NOT use openscreen's own
+// cast::SenderSession -- that class bundles mirroring negotiation together
+// with RPC/remoting/input support, which pulls in protobuf
+// (input.pb.h/remoting.pb.h) for no benefit here (breadcast only ever does
+// one-way video mirroring). Instead, this reimplements just the
+// OFFER-building and ANSWER-handling logic SenderSession itself uses
+// internally (see CreateMirroringOffer/StartNegotiation/SelectSenders in
+// upstream's public/sender_session.cc), built directly on
+// SenderSessionMessenger + Offer/Answer/SessionConfig + SenderImpl. See
+// ../vendor/openscreen/PATCHES.md.
+#ifndef BREADCAST_CASTSTREAM_SESSION_H_
+#define BREADCAST_CASTSTREAM_SESSION_H_
+
+#include <cstddef>
+#include <memory>
+#include <string>
+
+#include "cast/streaming/impl/sender_impl.h"
+#include "cast/streaming/public/environment.h"
+#include "cast/streaming/public/offer_messages.h"
+#include "cast/streaming/public/receiver_message.h"
+#include "cast/streaming/public/sender.h"
+#include "cast/streaming/public/session_messenger.h"
+#include "cast/streaming/sender_packet_router.h"
+#include "platform/base/ip_address.h"
+
+namespace breadcast_caststream {
+
+struct VideoParams {
+  int width = 1920;
+  int height = 1080;
+  int max_bit_rate = 8 * 1000 * 1000;
+  int max_frame_rate_numerator = 30;
+  int max_frame_rate_denominator = 1;
+};
+
+struct SessionCallbacks {
+  void* user_data = nullptr;
+  void (*on_negotiated)(void* user_data) = nullptr;
+  void (*on_error)(void* user_data, const char* message, size_t message_len) =
+      nullptr;
+  void (*on_picture_lost)(void* user_data) = nullptr;
+};
+
+// Owns the OFFER/ANSWER exchange and, once negotiated, the resulting video
+// Sender. All methods (other than the constructor) must be called on
+// `environment`'s TaskRunner thread -- facade.cc is responsible for
+// marshaling calls onto it via TaskRunner::PostTask, matching the threading
+// contract the rest of openscreen's Environment/SenderPacketRouter/Sender
+// classes already assume.
+class MirroringSenderSession final : public openscreen::cast::Sender::Observer {
+ public:
+  MirroringSenderSession(openscreen::cast::Environment& environment,
+                         openscreen::cast::MessagePort& message_port,
+                         openscreen::IPAddress remote_address,
+                         std::string local_source_id,
+                         std::string receiver_id,
+                         VideoParams params,
+                         SessionCallbacks callbacks);
+  ~MirroringSenderSession() override;
+
+  MirroringSenderSession(const MirroringSenderSession&) = delete;
+  MirroringSenderSession& operator=(const MirroringSenderSession&) = delete;
+
+  // Sends the OFFER and begins waiting for an ANSWER. `callbacks.on_negotiated`
+  // or `callbacks.on_error` will be called once the exchange completes.
+  void Negotiate();
+
+  // Valid only after `on_negotiated` has fired.
+  openscreen::cast::Sender* video_sender() { return video_sender_.get(); }
+
+  // Best-effort current bandwidth estimate in bits per second, or a
+  // conservative default before enough RTCP feedback has arrived.
+  int GetEstimatedBandwidthBps() const;
+
+  // Sender::Observer implementation.
+  void OnFrameCanceled(openscreen::cast::FrameId frame_id) override;
+  void OnPictureLost() override;
+
+ private:
+  void OnAnswer(openscreen::ErrorOr<openscreen::cast::ReceiverMessage> message);
+  void ReportError(const std::string& message);
+
+  openscreen::cast::Environment& environment_;
+  const openscreen::IPAddress remote_address_;
+  const std::string receiver_id_;
+  const VideoParams params_;
+  const SessionCallbacks callbacks_;
+
+  openscreen::cast::SenderSessionMessenger messenger_;
+  openscreen::cast::SenderPacketRouter packet_router_;
+
+  int sequence_number_ = 0;
+  openscreen::cast::Offer pending_offer_;
+  std::unique_ptr<openscreen::cast::SenderImpl> video_sender_;
+};
+
+}  // namespace breadcast_caststream
+
+#endif  // BREADCAST_CASTSTREAM_SESSION_H_

breadcast-caststream-sys/tests/smoke.rs

@@ -0,0 +1,91 @@
+//! Exercises the raw FFI end-to-end from Rust: create a sender, kick off
+//! negotiation, and confirm the C++ side calls back out through
+//! `post_message` with a real Cast Streaming OFFER -- without needing an
+//! actual receiver on the network (nothing here waits for an ANSWER).
+
+use std::ffi::c_void;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Mutex;
+use std::time::{Duration, Instant};
+
+use breadcast_caststream_sys::{
+    breadcast_caststream_sender_create, breadcast_caststream_sender_destroy,
+    breadcast_caststream_sender_estimated_bandwidth_bps,
+    breadcast_caststream_sender_needs_key_frame, breadcast_caststream_sender_negotiate,
+};
+
+static GOT_OFFER: AtomicBool = AtomicBool::new(false);
+static LAST_OFFER: Mutex<Vec<u8>> = Mutex::new(Vec::new());
+
+extern "C" fn post_message(
+    _user_data: *mut c_void,
+    _destination_id: *const std::ffi::c_char,
+    _destination_id_len: usize,
+    _message_namespace: *const std::ffi::c_char,
+    _message_namespace_len: usize,
+    message: *const std::ffi::c_char,
+    message_len: usize,
+) {
+    let bytes = unsafe { std::slice::from_raw_parts(message as *const u8, message_len) };
+    *LAST_OFFER.lock().unwrap() = bytes.to_vec();
+    GOT_OFFER.store(true, Ordering::Release);
+}
+
+extern "C" fn on_negotiated(_user_data: *mut c_void) {}
+
+extern "C" fn on_error(_user_data: *mut c_void, message: *const std::ffi::c_char, message_len: usize) {
+    let bytes = unsafe { std::slice::from_raw_parts(message as *const u8, message_len) };
+    panic!("session error: {}", String::from_utf8_lossy(bytes));
+}
+
+extern "C" fn on_picture_lost(_user_data: *mut c_void) {}
+
+#[test]
+fn create_negotiate_sends_offer_and_tears_down_cleanly() {
+    let remote_ip = "192.0.2.1";
+    let local_source_id = "sender-0";
+    let receiver_id = "receiver-0";
+
+    let sender = unsafe {
+        breadcast_caststream_sender_create(
+            remote_ip.as_ptr() as *const _,
+            remote_ip.len(),
+            local_source_id.as_ptr() as *const _,
+            local_source_id.len(),
+            receiver_id.as_ptr() as *const _,
+            receiver_id.len(),
+            1920,
+            1080,
+            8_000_000,
+            30,
+            1,
+            std::ptr::null_mut(),
+            post_message,
+            on_negotiated,
+            on_error,
+            on_picture_lost,
+        )
+    };
+    assert!(!sender.is_null(), "sender_create returned null");
+
+    unsafe { breadcast_caststream_sender_negotiate(sender) };
+
+    let deadline = Instant::now() + Duration::from_secs(2);
+    while !GOT_OFFER.load(Ordering::Acquire) && Instant::now() < deadline {
+        std::thread::sleep(Duration::from_millis(10));
+    }
+    assert!(GOT_OFFER.load(Ordering::Acquire), "never received OFFER via post_message");
+
+    let offer = String::from_utf8(LAST_OFFER.lock().unwrap().clone()).unwrap();
+    assert!(offer.contains("\"type\":\"OFFER\""), "unexpected payload: {offer}");
+    assert!(offer.contains("\"codecName\":\"h264\""), "unexpected payload: {offer}");
+
+    // Before negotiation with a real receiver completes, these should still
+    // return sane defaults rather than garbage/crashing.
+    let needs_key = unsafe { breadcast_caststream_sender_needs_key_frame(sender) };
+    let bandwidth = unsafe { breadcast_caststream_sender_estimated_bandwidth_bps(sender) };
+    assert_eq!(needs_key, 1);
+    assert!(bandwidth > 0);
+
+    unsafe { breadcast_caststream_sender_destroy(sender) };
+}

breadcast-caststream-sys/vendor/openscreen/LICENSE

@@ -0,0 +1,27 @@
+// Copyright 2018 The Chromium Authors
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google LLC nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

breadcast-caststream-sys/vendor/openscreen/PATCHES.md

@@ -0,0 +1,64 @@
+# Vendoring notes
+
+This directory is a **pruned subset** of [chromium/openscreen](https://chromium.googlesource.com/openscreen),
+pinned at the commit in `PINNED_COMMIT`, licensed BSD-3-Clause (see `LICENSE`).
+It contains only the files needed for the Cast Streaming *sender* data path
+(RTP/RTCP send, OFFER/ANSWER message types, AES frame encryption) plus the
+POSIX platform/util plumbing that path needs — not the receiver, not OSP
+discovery, not remoting/RPC, not TLS (breadcast's TLS CASTV2 control channel
+is handled by the existing `rust_cast`-based Rust code; this vendored code
+only drives the UDP RTP/RTCP data path once `rust_cast` has already
+negotiated OFFER/ANSWER and we know where to send packets).
+
+It is compiled directly via the `cc` crate in `../build.rs`, not GN/Ninja —
+there is no build system here to regenerate anything from.
+
+## Rolling the pin
+
+There are no release/API-stability guarantees upstream. To update:
+1. Re-run the file selection against the new commit's `cast/streaming/BUILD.gn`
+   (`:common` + `:sender` targets, minus `public/sender_session.*` and
+   `public/rpc_messenger.*` — see "What's excluded" below) plus
+   `platform/BUILD.gn`'s `:base`/`:api`/`:standalone_impl` targets.
+2. Re-apply the patches below (they're small; check if upstream has since
+   fixed the same problem and the patch can be dropped).
+3. Update `PINNED_COMMIT` and rebuild.
+
+## What's excluded and why
+
+- **`public/sender_session.{h,cc}`, `public/rpc_messenger.{h,cc}`,
+  `public/receiver_session.*`, receiver-side files, `remoting.proto`/
+  `input.proto`** — `SenderSession` bundles mirroring negotiation together
+  with RPC/remoting/input support, which pulls in protobuf
+  (`input.pb.h`/`remoting.pb.h`) for no benefit here (breadcast only ever
+  does one-way video mirroring). Instead, `../src/session.cc` drives
+  `Offer`/`Answer`/`SessionConfig` directly — logic adapted from
+  `sender_session.cc`'s `CreateMirroringOffer`/`StartNegotiation`/
+  `SelectSenders`, minus everything RPC/remoting/audio/input-related.
+- **All TLS support** (`platform/impl/tls_*`, `platform/impl/stream_socket*`) —
+  unused; see above.
+- **`util/crypto/{certificate_utils,digest_sign,pem_helpers,rsa_private_key,
+  secure_hash,sha2}.*`** — only needed for OSP discovery / X.509 certificate
+  handling, not the RTP data path.
+- **`util/scoped_wake_lock_mac.cc`** — macOS-only.
+
+## Local patches (not upstream)
+
+1. **`build/build_config.h`, `build/buildflag.h`** — stand-ins for Chromium's
+   GN-generated versions of these headers. Only define what the 3 callers
+   here actually check (`IS_POSIX`, `IS_LINUX`, `IS_APPLE`, `IS_ANDROID`),
+   hardcoded for Linux.
+2. **`patches/aes_ctr128_compat.cc`** — `frame_crypto.cc` calls
+   `AES_ctr128_encrypt()`, a BoringSSL convenience wrapper not in system
+   OpenSSL's public headers. Reimplemented from scratch (standard CTR mode
+   over `AES_encrypt()`, which OpenSSL does still expose).
+3. **`platform/impl/platform_client_posix.{h,cc}`** — stripped the
+   `TlsDataRouterPosix` member/accessor (see "All TLS support" above).
+4. **`util/crypto/openssl_util.{h,cc}`** — dropped `SSLErrorCodeToError()`/
+   `GetSSLError()`, which reference BoringSSL's `SSL_error_description()`
+   (not in system OpenSSL). Unused for the same reason as (3).
+5. **`util/base64.cc`** — upstream implements this on
+   `third_party/modp_b64`, which isn't fetched by a plain shallow clone
+   (pulled in separately via gclient/DEPS in a full Chromium checkout).
+   Reimplemented on `EVP_EncodeBlock`/`EVP_DecodeBlock` from system OpenSSL
+   instead, same public interface.

breadcast-caststream-sys/vendor/openscreen/PINNED_COMMIT

@@ -0,0 +1 @@
+920129874c16365415a8a52fdbbc492d7623dc11

breadcast-caststream-sys/vendor/openscreen/build/build_config.h

@@ -0,0 +1,19 @@
+// Minimal stand-in for Chromium's build/build_config.h, providing just the
+// BUILDFLAG(IS_*) values this vendored subset of openscreen actually checks
+// (see ip_address.cc, logging_posix.cc, udp_socket_posix.cc). breadcast only
+// ever builds this for Linux, so everything else is hardcoded off. Not part
+// of upstream openscreen.
+#ifndef BUILD_BUILD_CONFIG_H_
+#define BUILD_BUILD_CONFIG_H_
+
+#include "build/buildflag.h"
+
+#define BUILDFLAG_IS_LINUX() (1)
+#define BUILDFLAG_IS_POSIX() (1)
+#define BUILDFLAG_IS_APPLE() (0)
+#define BUILDFLAG_IS_ANDROID() (0)
+#define BUILDFLAG_IS_WIN() (0)
+#define BUILDFLAG_IS_CHROMEOS() (0)
+#define BUILDFLAG_IS_IOS() (0)
+
+#endif  // BUILD_BUILD_CONFIG_H_

breadcast-caststream-sys/vendor/openscreen/build/buildflag.h

@@ -0,0 +1,17 @@
+// Minimal stand-in for Chromium's generated build/buildflag.h.
+//
+// The real header is produced per-target by GN's buildflag_header() rule,
+// which generates a `BUILDFLAG_<FLAG>()` macro per flag; BUILDFLAG(flag)
+// then token-pastes "BUILDFLAG_" with the flag name and calls it. Since this
+// vendored subset is compiled directly with the `cc` crate rather than
+// GN/Ninja, build_config.h defines those BUILDFLAG_<FLAG>() macros directly
+// for the Linux target breadcast always builds for. Not part of upstream
+// openscreen.
+#ifndef BUILD_BUILDFLAG_H_
+#define BUILD_BUILDFLAG_H_
+
+#define BUILDFLAG_CAT_INDIRECT(a, b) a##b
+#define BUILDFLAG_CAT(a, b) BUILDFLAG_CAT_INDIRECT(a, b)
+#define BUILDFLAG(flag) (BUILDFLAG_CAT(BUILDFLAG_, flag)())
+
+#endif  // BUILD_BUILDFLAG_H_

breadcast-caststream-sys/vendor/openscreen/cast/common/public/message_port.h

@@ -0,0 +1,52 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_COMMON_PUBLIC_MESSAGE_PORT_H_
+#define CAST_COMMON_PUBLIC_MESSAGE_PORT_H_
+
+#include <string>
+
+#include "platform/base/error.h"
+
+namespace openscreen::cast {
+
+// This interface is intended to provide an abstraction for communicating
+// cast messages across a pipe with guaranteed delivery. This is used to
+// decouple the cast streaming receiver and sender sessions from the
+// network implementation.
+class MessagePort {
+ public:
+  class Client {
+   public:
+    // Called whenever a message arrives on the message port.
+    virtual void OnMessage(const std::string& source_id,
+                           const std::string& message_namespace,
+                           const std::string& message) = 0;
+
+    // Called whenever an error occurs on the message port.
+    virtual void OnError(const Error& error) = 0;
+
+    // Clients should expose a unique identifier used as the "source" of
+    // all messages sent on this message port.
+    virtual const std::string& source_id() = 0;
+
+   protected:
+    virtual ~Client() = default;
+  };
+
+  virtual ~MessagePort() = default;
+
+  // Set or reset the `MessagePort::Client` for this instance.
+  virtual void SetClient(Client& client) = 0;
+  virtual void ResetClient() = 0;
+
+  // Sends a message to a given `destination_id`.
+  virtual void PostMessage(const std::string& destination_id,
+                           const std::string& message_namespace,
+                           const std::string& message) = 0;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_COMMON_PUBLIC_MESSAGE_PORT_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/capture_configs.h

@@ -0,0 +1,81 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_CAPTURE_CONFIGS_H_
+#define CAST_STREAMING_CAPTURE_CONFIGS_H_
+
+#include <string>
+#include <vector>
+
+#include "cast/streaming/public/constants.h"
+#include "cast/streaming/resolution.h"
+#include "util/simple_fraction.h"
+
+namespace openscreen::cast {
+
+// A configuration set that can be used by the sender to capture audio, and the
+// receiver to playback audio. Used by Cast Streaming to provide an offer to the
+// receiver.
+struct AudioCaptureConfig {
+  // Audio codec represented by this configuration.
+  AudioCodec codec = AudioCodec::kOpus;
+
+  // Number of channels used by this configuration.
+  int channels = kDefaultAudioChannels;
+
+  // Average bit rate in bits per second used by this configuration. A value
+  // of "zero" suggests that the bitrate should be automatically selected by
+  // the sender.
+  int bit_rate = 0;
+
+  // Sample rate for audio RTP timebase.
+  int sample_rate = kDefaultAudioSampleRate;
+
+  // Target playout delay in milliseconds.
+  std::chrono::milliseconds target_playout_delay = kDefaultTargetPlayoutDelay;
+
+  // The codec parameter for this configuration. Honors the format laid out
+  // in RFC 6381: https://datatracker.ietf.org/doc/html/rfc6381
+  // NOTE: the "profiles" parameter is not supported in our implementation.
+  std::string codec_parameter;
+};
+
+// A configuration set that can be used by the sender to capture video, as
+// well as the receiver to playback video. Used by Cast Streaming to provide an
+// offer to the receiver.
+struct VideoCaptureConfig {
+  // Video codec represented by this configuration.
+  VideoCodec codec = VideoCodec::kVp8;
+
+  // Maximum frame rate in frames per second.
+  // For simple cases, the frame rate may be provided by simply setting the
+  // number to the desired value, e.g. 30 or 60FPS. Some common frame rates like
+  // 23.98 FPS (for NTSC compatibility) are represented as fractions, in this
+  // case 24000/1001.
+  SimpleFraction max_frame_rate{kDefaultFrameRate, 1};
+
+  // Number specifying the maximum bit rate for this stream. A value of
+  // zero means that the maximum bit rate should be automatically selected by
+  // the sender.
+  int max_bit_rate = 0;
+
+  // Resolutions to be offered to the receiver. At least one resolution
+  // must be provided.
+  std::vector<Resolution> resolutions;
+
+  // Target playout delay in milliseconds.
+  std::chrono::milliseconds target_playout_delay = kDefaultTargetPlayoutDelay;
+
+  // The codec parameter for this configuration. Honors the format laid out
+  // in RFC 6381: https://datatracker.ietf.org/doc/html/rfc6381.
+  // VP8 and VP9 codec parameter versions are defined here:
+  // https://developer.mozilla.org/en-US/docs/Web/Media/Formats/codecs_parameter#webm
+  // https://www.webmproject.org/vp9/mp4/#codecs-parameter-string
+  // NOTE: the "profiles" parameter is not supported in our implementation.
+  std::string codec_parameter;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_CAPTURE_CONFIGS_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/bandwidth_estimator.cc

@@ -0,0 +1,155 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/bandwidth_estimator.h"
+
+#include <algorithm>
+
+#include "util/osp_logging.h"
+#include "util/saturate_cast.h"
+
+namespace openscreen::cast {
+
+using clock_operators::operator<<;
+
+namespace {
+
+// Converts units from `bytes` per `time_window` number of Clock ticks into
+// bits-per-second.
+int ToClampedBitsPerSecond(int32_t bytes, Clock::duration time_window) {
+  OSP_CHECK_GT(time_window, Clock::duration::zero());
+
+  // Divide `bytes` by `time_window` and scale the units to bits per second.
+  constexpr int64_t kBitsPerByte = 8;
+  constexpr int64_t kClockTicksPerSecond =
+      Clock::to_duration(std::chrono::seconds(1)).count();
+  const int64_t bits = bytes * kBitsPerByte;
+  const int64_t bits_per_second =
+      (bits * kClockTicksPerSecond) / time_window.count();
+  return saturate_cast<int>(bits_per_second);
+}
+
+}  // namespace
+
+BandwidthEstimator::BandwidthEstimator(int max_packets_per_timeslice,
+                                       Clock::duration timeslice_duration,
+                                       Clock::time_point start_time)
+    : max_packets_per_history_window_(max_packets_per_timeslice *
+                                      kNumTimeslices),
+      history_window_(timeslice_duration * kNumTimeslices),
+      burst_history_(timeslice_duration, start_time),
+      feedback_history_(timeslice_duration, start_time) {
+  OSP_CHECK_GT(max_packets_per_timeslice, 0);
+  OSP_CHECK_GT(timeslice_duration, Clock::duration::zero());
+}
+
+BandwidthEstimator::~BandwidthEstimator() = default;
+
+void BandwidthEstimator::OnBurstComplete(int num_packets_sent,
+                                         Clock::time_point when) {
+  OSP_CHECK_GE(num_packets_sent, 0);
+  burst_history_.Accumulate(num_packets_sent, when);
+}
+
+void BandwidthEstimator::OnRtcpReceived(
+    Clock::time_point arrival_time,
+    Clock::duration estimated_round_trip_time) {
+  OSP_CHECK_GE(estimated_round_trip_time, Clock::duration::zero());
+  // Move forward the feedback history tracking timeline to include the latest
+  // moment a packet could have left the Sender.
+  feedback_history_.AdvanceToIncludeTime(arrival_time -
+                                         estimated_round_trip_time);
+}
+
+void BandwidthEstimator::OnPayloadReceived(
+    int payload_bytes_acknowledged,
+    Clock::time_point ack_arrival_time,
+    Clock::duration estimated_round_trip_time) {
+  OSP_CHECK_GE(payload_bytes_acknowledged, 0);
+  OSP_CHECK_LT(ack_arrival_time, Clock::time_point::max());
+  OSP_CHECK_GE(estimated_round_trip_time, Clock::duration::zero());
+  // Track the bytes in terms of when the last packet was sent.
+  feedback_history_.Accumulate(payload_bytes_acknowledged,
+                               ack_arrival_time - estimated_round_trip_time);
+}
+
+int BandwidthEstimator::ComputeNetworkBandwidth() const {
+  // Determine whether the `burst_history_` time window overlaps with the
+  // `feedback_history_` time window by at least half. The time windows don't
+  // have to overlap entirely because the calculations are averaging all the
+  // measurements (i.e., recent typical behavior). Though, they should overlap
+  // by "enough" so that the measurements correlate "enough."
+  const Clock::time_point overlap_begin =
+      std::max(burst_history_.begin_time(), feedback_history_.begin_time());
+  const Clock::time_point overlap_end =
+      std::min(burst_history_.end_time(), feedback_history_.end_time());
+  if ((overlap_end - overlap_begin) < (history_window_ / 2)) {
+    return 0;
+  }
+
+  const int32_t num_packets_transmitted = burst_history_.Sum();
+  if (num_packets_transmitted <= 0) {
+    // Cannot estimate because there have been no transmissions recently.
+    return 0;
+  }
+  const Clock::duration transmit_duration = history_window_ *
+                                            num_packets_transmitted /
+                                            max_packets_per_history_window_;
+  const int32_t num_bytes_received = feedback_history_.Sum();
+  return ToClampedBitsPerSecond(num_bytes_received, transmit_duration);
+}
+
+// static
+constexpr int BandwidthEstimator::kNumTimeslices;
+
+BandwidthEstimator::FlowTracker::FlowTracker(Clock::duration timeslice_duration,
+                                             Clock::time_point begin_time)
+    : timeslice_duration_(timeslice_duration), begin_time_(begin_time) {}
+
+BandwidthEstimator::FlowTracker::~FlowTracker() = default;
+
+void BandwidthEstimator::FlowTracker::AdvanceToIncludeTime(
+    Clock::time_point until) {
+  if (until < end_time()) {
+    return;  // Not advancing.
+  }
+
+  // Step forward in time, at timeslice granularity.
+  const int64_t num_periods = 1 + (until - end_time()) / timeslice_duration_;
+  begin_time_ += num_periods * timeslice_duration_;
+
+  // Shift the ring elements, discarding N oldest timeslices, and creating N new
+  // ones initialized to zero.
+  const int shift_count = std::min<int64_t>(num_periods, kNumTimeslices);
+  for (int i = 0; i < shift_count; ++i) {
+    history_ring_[tail_++] = 0;
+  }
+}
+
+void BandwidthEstimator::FlowTracker::Accumulate(int32_t amount,
+                                                 Clock::time_point when) {
+  if (when < begin_time_) {
+    return;  // Ignore a data point that is already too old.
+  }
+
+  AdvanceToIncludeTime(when);
+
+  // Because of the AdvanceToIncludeTime() call just made, the offset/index
+  // calculations here are guaranteed to point to a valid element in the
+  // `history_ring_`.
+  const int64_t offset_from_first = (when - begin_time_) / timeslice_duration_;
+  const index_mod_256_t ring_index = tail_ + offset_from_first;
+  int32_t& timeslice = history_ring_[ring_index];
+  timeslice = saturate_cast<int32_t>(int64_t{timeslice} + amount);
+}
+
+int32_t BandwidthEstimator::FlowTracker::Sum() const {
+  int64_t result = 0;
+  for (int32_t amount : history_ring_) {
+    result += amount;
+  }
+  return saturate_cast<int32_t>(result);
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/bandwidth_estimator.h

@@ -0,0 +1,168 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_BANDWIDTH_ESTIMATOR_H_
+#define CAST_STREAMING_IMPL_BANDWIDTH_ESTIMATOR_H_
+
+#include <stdint.h>
+
+#include <limits>
+
+#include "platform/api/time.h"
+
+namespace openscreen::cast {
+
+// Tracks send attempts and successful receives, and then computes a total
+// network bandwith estimate.
+//
+// Two metrics are tracked by the BandwidthEstimator, over a "recent history"
+// time window:
+//
+//   1. The number of packets sent during bursts (see SenderPacketRouter for
+//      explanation of what a "burst" is). These track when the network was
+//      actually in-use for transmission and the magnitude of each burst. When
+//      computing bandwidth, the estimator assumes the timeslices where the
+//      network was not in-use could have been used to send even more bytes at
+//      the same rate.
+//
+//   2. Successful receipt of payload bytes over time, or a lack thereof.
+//      Packets that include acknowledgements from the Receivers are providing
+//      proof of the successful receipt of payload bytes. All other packets
+//      provide proof of network connectivity over time, and are used to
+//      identify periods of time where nothing was received.
+//
+// The BandwidthEstimator assumes a simplified model for streaming over the
+// network. The model does not include any detailed knowledge about things like
+// protocol overhead, packet re-transmits, parasitic bufferring, network
+// reliability, etc. Instead, it automatically accounts for all such things by
+// looking at what's actually leaving the Senders and what's actually making it
+// to the Receivers.
+//
+// This simplified model does produce some known inaccuracies in the resulting
+// estimations. If no data has recently been transmitted (or been received),
+// estimations cannot be provided. If the transmission rate is near (or
+// exceeding) the network's capacity, the estimations will be very accurate. In
+// between those two extremes, the logic will tend to under-estimate the
+// network's capacity. However, those under-estimates will still be far larger
+// than the current transmission rate.
+//
+// Thus, these estimates can be used effectively as a control signal for
+// congestion control in upstream code modules. The logic computing the media's
+// encoding target bitrate should be adjusted in realtime using a TCP-like
+// congestion control algorithm:
+//
+//   1. When the estimated bitrate is less than the current encoding target
+//      bitrate, aggressively and immediately decrease the encoding bitrate.
+//
+//   2. When the estimated bitrate is more than the current encoding target
+//      bitrate, gradually increase the encoding bitrate (up to the maximum
+//      that is reasonable for the application).
+class BandwidthEstimator {
+ public:
+  // `max_packets_per_timeslice` and `timeslice_duration` should match the burst
+  // configuration in SenderPacketRouter. `start_time` should be a recent
+  // point-in-time before the first packet is sent.
+  BandwidthEstimator(int max_packets_per_timeslice,
+                     Clock::duration timeslice_duration,
+                     Clock::time_point start_time);
+
+  ~BandwidthEstimator();
+
+  // Returns the duration of the fixed, recent-history time window over which
+  // data flows are being tracked.
+  Clock::duration history_window() const { return history_window_; }
+
+  // Records `when` burst-sending was active or inactive. For the active case,
+  // `num_packets_sent` should include all network packets sent, including
+  // non-payload packets (since both affect the modeled utilization/capacity).
+  // For the inactive case, this method should be called with zero for
+  // `num_packets_sent`.
+  void OnBurstComplete(int num_packets_sent, Clock::time_point when);
+
+  // Records when a RTCP packet was received. It's important for Senders to call
+  // this any time a packet comes in from the Receivers, even if no payload is
+  // being acknowledged, since the time windows of "nothing successfully
+  // received" is also important information to track.
+  void OnRtcpReceived(Clock::time_point arrival_time,
+                      Clock::duration estimated_round_trip_time);
+
+  // Records that some number of payload bytes has been acknowledged (i.e.,
+  // successfully received).
+  void OnPayloadReceived(int payload_bytes_acknowledged,
+                         Clock::time_point ack_arrival_time,
+                         Clock::duration estimated_round_trip_time);
+
+  // Computes the current network bandwith estimate. Returns 0 if this cannot be
+  // determined due to a lack of sufficiently-recent data.
+  int ComputeNetworkBandwidth() const;
+
+ private:
+  // FlowTracker (below) manages a ring buffer of size 256. It simplifies the
+  // index calculations to use an integer data type where all arithmetic is mod
+  // 256.
+  using index_mod_256_t = uint8_t;
+  static constexpr int kNumTimeslices =
+      static_cast<int>(std::numeric_limits<index_mod_256_t>::max()) + 1;
+
+  // Tracks volume (e.g., the total number of payload bytes) over a fixed
+  // recent-history time window. The time window is divided up into a number of
+  // identical timeslices, each of which represents the total number of bytes
+  // that flowed during a certain period of time. The data is accumulated in
+  // ring buffer elements so that old data points drop-off as newer ones (that
+  // move the history window forward) are added.
+  class FlowTracker {
+   public:
+    FlowTracker(Clock::duration timeslice_duration,
+                Clock::time_point begin_time);
+    ~FlowTracker();
+
+    Clock::time_point begin_time() const { return begin_time_; }
+    Clock::time_point end_time() const {
+      return begin_time_ + timeslice_duration_ * kNumTimeslices;
+    }
+
+    // Advance the end of the time window being tracked such that the
+    // most-recent timeslice includes `until`. Too-old timeslices are dropped
+    // and new ones are initialized to a zero amount.
+    void AdvanceToIncludeTime(Clock::time_point until);
+
+    // Accumulate the given `amount` into the timeslice that includes `when`.
+    void Accumulate(int32_t amount, Clock::time_point when);
+
+    // Return the sum of all the amounts in recent history. This clamps to the
+    // valid range of int32_t, if necessary.
+    int32_t Sum() const;
+
+   private:
+    const Clock::duration timeslice_duration_;
+
+    // The beginning of the oldest timeslice in the recent-history time window,
+    // the one pointed to by `tail_`.
+    Clock::time_point begin_time_;
+
+    // A ring buffer tracking the accumulated amount for each timeslice.
+    int32_t history_ring_[kNumTimeslices]{};
+
+    // The index of the oldest timeslice in the `history_ring_`. This can also
+    // be thought of, equivalently, as the index just after the most-recent
+    // timeslice.
+    index_mod_256_t tail_ = 0;
+  };
+
+  // The maximum number of packet sends that could possibly be attempted during
+  // the recent-history time window.
+  const int max_packets_per_history_window_;
+
+  // The range of time being tracked.
+  const Clock::duration history_window_;
+
+  // History tracking for send attempts, and success feeback. These timeseries
+  // are in terms of when packets have left the Senders.
+  FlowTracker burst_history_;
+  FlowTracker feedback_history_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_BANDWIDTH_ESTIMATOR_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/clock_drift_smoother.cc

@@ -0,0 +1,79 @@
+// Copyright 2014 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/clock_drift_smoother.h"
+
+#include <cmath>
+
+#include "util/chrono_helpers.h"
+#include "util/osp_logging.h"
+#include "util/saturate_cast.h"
+
+namespace openscreen::cast {
+namespace {
+
+constexpr Clock::time_point kNullTime = Clock::time_point::min();
+}
+
+using clock_operators::operator<<;
+
+ClockDriftSmoother::ClockDriftSmoother(Clock::duration time_constant)
+    : time_constant_(time_constant),
+      last_update_time_(kNullTime),
+      estimated_tick_offset_(0.0) {
+  OSP_CHECK(time_constant_ > decltype(time_constant_)::zero());
+}
+
+ClockDriftSmoother::~ClockDriftSmoother() = default;
+
+std::optional<Clock::duration> ClockDriftSmoother::Current() const {
+  if (last_update_time_ == kNullTime) {
+    return std::nullopt;
+  }
+  return Clock::duration(
+      rounded_saturate_cast<Clock::duration::rep>(estimated_tick_offset_));
+}
+
+void ClockDriftSmoother::Reset(Clock::time_point now,
+                               Clock::duration measured_offset) {
+  OSP_CHECK_NE(now, kNullTime);
+  last_update_time_ = now;
+  estimated_tick_offset_ = static_cast<double>(measured_offset.count());
+}
+
+void ClockDriftSmoother::Update(Clock::time_point now,
+                                Clock::duration measured_offset) {
+  OSP_CHECK_NE(now, kNullTime);
+  if (last_update_time_ == kNullTime) {
+    Reset(now, measured_offset);
+    return;
+  }
+
+  if (now < last_update_time_) {
+    // `now` is not monotonically non-decreasing.
+    OSP_NOTREACHED();
+  }
+
+  const double elapsed_ticks =
+      static_cast<double>((now - last_update_time_).count());
+  last_update_time_ = now;
+
+  // This is a standard exponential moving average (EMA) filter.
+  // The alpha value is calculated such that the filter has the desired time
+  // constant.
+  const double alpha = 1.0 - std::exp(-elapsed_ticks / time_constant_.count());
+  estimated_tick_offset_ =
+      alpha * static_cast<double>(measured_offset.count()) +
+      (1.0 - alpha) * estimated_tick_offset_;
+
+  const auto current = Current();
+  OSP_VLOG << "Local clock is ahead of the remote clock by: measured = "
+           << measured_offset << ", "
+           << "filtered = " << (current ? ToString(*current) : "null") << ".";
+}
+
+// static
+constexpr std::chrono::seconds ClockDriftSmoother::kDefaultTimeConstant;
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/clock_drift_smoother.h

@@ -0,0 +1,58 @@
+// Copyright 2014 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_CLOCK_DRIFT_SMOOTHER_H_
+#define CAST_STREAMING_IMPL_CLOCK_DRIFT_SMOOTHER_H_
+
+#include <chrono>
+#include <optional>
+
+#include "platform/api/time.h"
+
+namespace openscreen::cast {
+
+// Tracks the jitter and drift between clocks, providing a smoothed offset.
+// Internally, a Simple IIR filter is used to maintain a running average that
+// moves at a rate based on the passage of time.
+class ClockDriftSmoother {
+ public:
+  // `time_constant` is the amount of time an impulse signal takes to decay by
+  // ~62.6%.  Interpretation: If the value passed to several Update() calls is
+  // held constant for T seconds, then the running average will have moved
+  // towards the value by ~62.6% from where it started.
+  explicit ClockDriftSmoother(Clock::duration time_constant);
+  ~ClockDriftSmoother();
+
+  // Returns the current offset. Will be std::nullopt if no values have been
+  // set yet (via Reset() or Update()).
+  std::optional<Clock::duration> Current() const;
+
+  // Discard all history and reset to exactly `offset`, measured `now`.
+  void Reset(Clock::time_point now, Clock::duration offset);
+
+  // Update the current offset, which was measured `now`.  The weighting that
+  // `measured_offset` will have on the running average is influenced by how
+  // much time has passed since the last call to this method (or Reset()).
+  // `now` should be monotonically non-decreasing over successive calls of this
+  // method.
+  void Update(Clock::time_point now, Clock::duration measured_offset);
+
+  // A time constant suitable for most use cases, where the clocks are expected
+  // to drift very little with respect to each other, and the jitter caused by
+  // clock imprecision is effectively canceled out.
+  static constexpr std::chrono::seconds kDefaultTimeConstant{30};
+
+ private:
+  const std::chrono::duration<double, Clock::duration::period> time_constant_;
+
+  // The time at which `estimated_tick_offset_` was last updated.
+  Clock::time_point last_update_time_;
+
+  // The current estimated offset, as number of Clock::duration ticks.
+  double estimated_tick_offset_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_CLOCK_DRIFT_SMOOTHER_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/clock_offset_estimator.h

@@ -0,0 +1,71 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_CLOCK_OFFSET_ESTIMATOR_H_
+#define CAST_STREAMING_IMPL_CLOCK_OFFSET_ESTIMATOR_H_
+
+#include <memory>
+#include <optional>
+
+#include "cast/streaming/impl/statistics_common.h"
+#include "cast/streaming/public/statistics.h"
+#include "platform/base/trivial_clock_traits.h"
+
+namespace openscreen::cast {
+
+// Used to estimate the offset between the Sender and Receiver clocks.
+class ClockOffsetEstimator {
+ public:
+  static std::unique_ptr<ClockOffsetEstimator> Create();
+
+  virtual ~ClockOffsetEstimator() {}
+
+  // TODO(issuetracker.google.com/298085631): these should be in a separate
+  // header, like Chrome's raw event subscriber pattern.
+  // See: //media/cast/logging/raw_event_subscriber.h
+  virtual void OnFrameEvent(const FrameEvent& frame_event) = 0;
+  virtual void OnPacketEvent(const PacketEvent& packet_event) = 0;
+
+  // Estimates the clock offset between the sender and the receiver.
+  //
+  // This is calculated by solving a system of two linear equations with two
+  // unknowns: the clock offset and the network latency. The two equations are
+  // derived from two round-trip time measurements.
+  //
+  // Let's define:
+  //   - latency: the one-way network latency.
+  //   - offset: the clock offset, where Clock_Receiver(t) = Clock_Sender(t) +
+  //   offset.
+  //
+  // The estimator measures two bounds:
+  //
+  // 1. packet_bound (sender -> receiver):
+  //    delta = TS_receiver - TS_sender
+  //          = (TS_sender + latency + offset) - TS_sender
+  //          = latency + offset
+  //
+  // 2. frame_bound (receiver -> sender):
+  //    delta = TS_sender - TS_receiver
+  //          = (TS_receiver + latency - offset) - TS_receiver
+  //          = latency - offset
+  //
+  // The offset is then isolated by the formula:
+  //    (packet_bound - frame_bound) / 2 =
+  //     ( (latency + offset) - (latency - offset) ) / 2 =
+  //     (2 * offset) / 2 = offset
+  virtual std::optional<Clock::duration> GetEstimatedOffset() const = 0;
+
+  // Estimates the one-way network latency.
+  // This uses the same bounds as GetEstimatedOffset().
+  //
+  // The latency is isolated by the formula:
+  //   (packet_bound + frame_bound) / 2 =
+  //   ( (latency + offset) + (latency - offset) ) / 2 = (2 * latency) / 2 =
+  //   latency
+  virtual std::optional<Clock::duration> GetEstimatedLatency() const = 0;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_CLOCK_OFFSET_ESTIMATOR_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/clock_offset_estimator_impl.cc

@@ -0,0 +1,222 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/clock_offset_estimator_impl.h"
+
+#include <algorithm>
+#include <chrono>
+#include <memory>
+#include <utility>
+
+#include "platform/base/trivial_clock_traits.h"
+#include "util/chrono_helpers.h"
+
+namespace openscreen::cast {
+namespace {
+
+// This should be large enough so that we can collect all 3 events before
+// the entry gets removed from the map.
+constexpr size_t kMaxEventTimesMapSize = 500;
+
+// Bitwise merging of values to produce an ordered key for entries in the
+// BoundCalculator::events_ map. Since std::map is sorted by key value, we
+// ensure that the Packet ID is first (since the RTP timestamp may roll over
+// eventually).
+//
+//  0         1         2         3         4         5         6
+//  0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4 6 8 0 2 4
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |   Packet ID   |               RTP Timestamp                 |*| (is_audio)
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+uint64_t MakeEventKey(RtpTimeTicks rtp, uint16_t packet_id, bool audio) {
+  return (static_cast<uint64_t>(packet_id) << 48) |
+         (static_cast<uint64_t>(rtp.lower_32_bits()) << 1) |
+         static_cast<uint64_t>(audio ? 1 : 0);
+}
+
+}  // namespace
+
+std::unique_ptr<ClockOffsetEstimator> ClockOffsetEstimator::Create() {
+  return std::make_unique<ClockOffsetEstimatorImpl>();
+}
+
+ClockOffsetEstimatorImpl::ClockOffsetEstimatorImpl() = default;
+ClockOffsetEstimatorImpl::ClockOffsetEstimatorImpl(
+    ClockOffsetEstimatorImpl&&) noexcept = default;
+ClockOffsetEstimatorImpl& ClockOffsetEstimatorImpl::operator=(
+    ClockOffsetEstimatorImpl&&) = default;
+ClockOffsetEstimatorImpl::~ClockOffsetEstimatorImpl() = default;
+
+void ClockOffsetEstimatorImpl::OnFrameEvent(const FrameEvent& frame_event) {
+  switch (frame_event.type) {
+    case StatisticsEvent::Type::kFrameAckSent:
+      frame_bound_.SetSent(
+          frame_event.rtp_timestamp, 0,
+          frame_event.media_type == StatisticsEvent::MediaType::kAudio,
+          frame_event.timestamp);
+      break;
+    case StatisticsEvent::Type::kFrameAckReceived:
+      frame_bound_.SetReceived(
+          frame_event.rtp_timestamp, 0,
+          frame_event.media_type == StatisticsEvent::MediaType::kAudio,
+          frame_event.timestamp);
+      break;
+    default:
+      // Ignored
+      break;
+  }
+}
+
+void ClockOffsetEstimatorImpl::OnPacketEvent(const PacketEvent& packet_event) {
+  switch (packet_event.type) {
+    case StatisticsEvent::Type::kPacketSentToNetwork:
+      packet_bound_.SetSent(
+          packet_event.rtp_timestamp, packet_event.packet_id,
+          packet_event.media_type == StatisticsEvent::MediaType::kAudio,
+          packet_event.timestamp);
+      break;
+    case StatisticsEvent::Type::kPacketReceived:
+      packet_bound_.SetReceived(
+          packet_event.rtp_timestamp, packet_event.packet_id,
+          packet_event.media_type == StatisticsEvent::MediaType::kAudio,
+          packet_event.timestamp);
+      break;
+    default:
+      // Ignored
+      break;
+  }
+}
+
+bool ClockOffsetEstimatorImpl::GetReceiverOffsetBounds(
+    Clock::duration& frame_bound,
+    Clock::duration& packet_bound) const {
+  if (!frame_bound_.has_bound() || !packet_bound_.has_bound()) {
+    return false;
+  }
+
+  frame_bound = -frame_bound_.bound();
+  packet_bound = packet_bound_.bound();
+
+  return true;
+}
+
+std::optional<Clock::duration> ClockOffsetEstimatorImpl::GetEstimatedOffset()
+    const {
+  Clock::duration frame_bound;
+  Clock::duration packet_bound;
+  if (!GetReceiverOffsetBounds(frame_bound, packet_bound)) {
+    return {};
+  }
+  return (packet_bound + frame_bound) / 2;
+}
+
+std::optional<Clock::duration> ClockOffsetEstimatorImpl::GetEstimatedLatency()
+    const {
+  Clock::duration frame_bound;
+  Clock::duration packet_bound;
+  if (!GetReceiverOffsetBounds(frame_bound, packet_bound)) {
+    return {};
+  }
+  return (packet_bound - frame_bound) / 2;
+}
+
+ClockOffsetEstimatorImpl::KalmanFilter::KalmanFilter(
+    Clock::duration process_noise,
+    Clock::duration measurement_noise)
+    : q_nanos_squared_(
+          static_cast<double>(std::chrono::nanoseconds(process_noise).count()) *
+          std::chrono::nanoseconds(process_noise).count()),
+      r_nanos_squared_(
+          static_cast<double>(
+              std::chrono::nanoseconds(measurement_noise).count()) *
+          std::chrono::nanoseconds(measurement_noise).count()) {}
+
+void ClockOffsetEstimatorImpl::KalmanFilter::Update(
+    Clock::duration measurement) {
+  if (!has_estimate_) {
+    // First measurement, initialize the state.
+    estimated_latency_ = measurement;
+    error_covariance_nanos_squared_ = r_nanos_squared_;
+    has_estimate_ = true;
+    return;
+  }
+
+  // --- 1. PREDICT ---
+  // The predicted state is the same as the previous state.
+  // The uncertainty (covariance) increases by the process noise.
+  const double predicted_error_covariance =
+      error_covariance_nanos_squared_ + q_nanos_squared_;
+
+  // --- 2. UPDATE ---
+  // Calculate Kalman Gain.
+  const double kalman_gain = predicted_error_covariance /
+                             (predicted_error_covariance + r_nanos_squared_);
+
+  // Update the estimate with the new measurement.
+  const double measurement_nanos =
+      static_cast<double>(std::chrono::nanoseconds(measurement).count());
+  const double estimate_nanos =
+      static_cast<double>(std::chrono::nanoseconds(estimated_latency_).count());
+  const double new_estimate_nanos =
+      estimate_nanos + kalman_gain * (measurement_nanos - estimate_nanos);
+  estimated_latency_ =
+      std::chrono::duration_cast<Clock::duration>(std::chrono::nanoseconds(
+          static_cast<Clock::duration::rep>(new_estimate_nanos)));
+
+  // Update the error covariance.
+  error_covariance_nanos_squared_ =
+      (1.0 - kalman_gain) * predicted_error_covariance;
+}
+
+ClockOffsetEstimatorImpl::BoundCalculator::BoundCalculator()
+    : filter_(kProcessNoise, kMeasurementNoise) {}
+
+ClockOffsetEstimatorImpl::BoundCalculator::BoundCalculator(
+    BoundCalculator&&) noexcept = default;
+ClockOffsetEstimatorImpl::BoundCalculator&
+ClockOffsetEstimatorImpl::BoundCalculator::operator=(BoundCalculator&&) =
+    default;
+ClockOffsetEstimatorImpl::BoundCalculator::~BoundCalculator() = default;
+
+void ClockOffsetEstimatorImpl::BoundCalculator::SetSent(RtpTimeTicks rtp,
+                                                        uint16_t packet_id,
+                                                        bool audio,
+                                                        Clock::time_point t) {
+  const uint64_t key = MakeEventKey(rtp, packet_id, audio);
+  events_[key].first = t;
+  CheckUpdate(key);
+}
+
+void ClockOffsetEstimatorImpl::BoundCalculator::SetReceived(
+    RtpTimeTicks rtp,
+    uint16_t packet_id,
+    bool audio,
+    Clock::time_point t) {
+  const uint64_t key = MakeEventKey(rtp, packet_id, audio);
+  events_[key].second = t;
+  CheckUpdate(key);
+}
+
+void ClockOffsetEstimatorImpl::BoundCalculator::UpdateBound(
+    Clock::time_point sent,
+    Clock::time_point received) {
+  filter_.Update(received - sent);
+}
+
+void ClockOffsetEstimatorImpl::BoundCalculator::CheckUpdate(uint64_t key) {
+  const TimeTickPair& ticks = events_[key];
+  if (ticks.first && ticks.second) {
+    UpdateBound(ticks.first.value(), ticks.second.value());
+    events_.erase(key);
+    return;
+  }
+
+  if (events_.size() > kMaxEventTimesMapSize) {
+    // We can make use of the fact that std::map sorts by key and just erase
+    // the first entry.
+    events_.erase(events_.begin());
+  }
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/clock_offset_estimator_impl.h

@@ -0,0 +1,136 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_CLOCK_OFFSET_ESTIMATOR_IMPL_H_
+#define CAST_STREAMING_IMPL_CLOCK_OFFSET_ESTIMATOR_IMPL_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <map>
+#include <optional>
+#include <utility>
+
+#include "cast/streaming/impl/clock_offset_estimator.h"
+#include "cast/streaming/impl/statistics_common.h"
+#include "cast/streaming/rtp_time.h"
+#include "platform/base/trivial_clock_traits.h"
+#include "util/chrono_helpers.h"
+
+namespace openscreen::cast {
+
+// This implementation listens to two pairs of events:
+//     1. FrameAckSent / FrameAckReceived (receiver->sender)
+//     2. PacketSentToNetwork / PacketReceived (sender->receiver)
+//
+// There is a causal relationship between these events in that these events
+// must happen in order. This class obtains the lower and upper bounds for
+// the offset by taking the difference of timestamps.
+class ClockOffsetEstimatorImpl final : public ClockOffsetEstimator {
+ public:
+  ClockOffsetEstimatorImpl();
+  ClockOffsetEstimatorImpl(ClockOffsetEstimatorImpl&&) noexcept;
+  ClockOffsetEstimatorImpl(const ClockOffsetEstimatorImpl&) = delete;
+  ClockOffsetEstimatorImpl& operator=(ClockOffsetEstimatorImpl&&);
+  ClockOffsetEstimatorImpl& operator=(const ClockOffsetEstimatorImpl&) = delete;
+  ~ClockOffsetEstimatorImpl() final;
+
+  void OnFrameEvent(const FrameEvent& frame_event) final;
+  void OnPacketEvent(const PacketEvent& packet_event) final;
+
+  bool GetReceiverOffsetBounds(Clock::duration& frame_bound,
+                               Clock::duration& packet_bound) const;
+
+  // ClockOffsetEstimator overrides.
+  std::optional<Clock::duration> GetEstimatedOffset() const final;
+  std::optional<Clock::duration> GetEstimatedLatency() const final;
+
+ private:
+  // These values are chosen based on common network conditions.
+  //
+  // Q (process_noise): We expect latency to drift by up to 5ms between
+  // measurements.
+  static constexpr Clock::duration kProcessNoise = milliseconds(5);
+  //
+  // R (measurement_noise): We expect jitter of up to 30ms.
+  static constexpr Clock::duration kMeasurementNoise = milliseconds(30);
+
+  // Simplified 1D Kalman Filter for latency estimation.
+  class KalmanFilter {
+   public:
+    // Q: process_noise - Represents the expected variance of the latency
+    //    itself between time steps. A higher value makes the filter adapt
+    //    more quickly to real changes in latency.
+    // R: measurement_noise - Represents the variance of the measurement
+    //    noise (jitter). A higher value makes the filter trust its own
+    //    prediction more and smooth out noisy measurements.
+    KalmanFilter(Clock::duration process_noise,
+                 Clock::duration measurement_noise);
+    KalmanFilter(KalmanFilter&&) noexcept = default;
+    KalmanFilter& operator=(KalmanFilter&&) = default;
+
+    Clock::duration GetEstimate() const { return estimated_latency_; }
+    bool HasEstimate() const { return has_estimate_; }
+    void Update(Clock::duration measurement);
+
+   private:
+    double q_nanos_squared_;
+    double r_nanos_squared_;
+
+    bool has_estimate_ = false;
+    Clock::duration estimated_latency_{};
+    double error_covariance_nanos_squared_ = 0.0;
+  };
+
+  // This helper uses the difference between sent and received event
+  // to calculate an upper bound on the difference between the clocks
+  // on the sender and receiver. Note that this difference can take
+  // very large positive or negative values, but the smaller value is
+  // always the better estimate, since a receive event cannot possibly
+  // happen before a send event.  Note that we use this to calculate
+  // both upper and lower bounds by reversing the sender/receiver
+  // relationship.
+  class BoundCalculator {
+   public:
+    typedef std::pair<std::optional<Clock::time_point>,
+                      std::optional<Clock::time_point>>
+        TimeTickPair;
+    typedef std::map<uint64_t, TimeTickPair> EventMap;
+
+    BoundCalculator();
+    BoundCalculator(BoundCalculator&&) noexcept;
+    BoundCalculator(const BoundCalculator&) = delete;
+    BoundCalculator& operator=(BoundCalculator&&);
+    BoundCalculator& operator=(const BoundCalculator&) = delete;
+    ~BoundCalculator();
+    bool has_bound() const { return filter_.HasEstimate(); }
+    Clock::duration bound() const { return filter_.GetEstimate(); }
+
+    void SetSent(RtpTimeTicks rtp,
+                 uint16_t packet_id,
+                 bool audio,
+                 Clock::time_point t);
+
+    void SetReceived(RtpTimeTicks rtp,
+                     uint16_t packet_id,
+                     bool audio,
+                     Clock::time_point t);
+
+   private:
+    void UpdateBound(Clock::time_point a, Clock::time_point b);
+    void CheckUpdate(uint64_t key);
+
+   private:
+    EventMap events_;
+    KalmanFilter filter_;
+  };
+
+  // Fixed size storage to store event times for recent frames and packets.
+  BoundCalculator packet_bound_;
+  BoundCalculator frame_bound_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_CLOCK_OFFSET_ESTIMATOR_IMPL_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/compound_rtcp_parser.cc

@@ -0,0 +1,479 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/compound_rtcp_parser.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "cast/streaming/impl/packet_util.h"
+#include "cast/streaming/impl/rtcp_session.h"
+#include "cast/streaming/impl/statistics_common.h"
+#include "util/chrono_helpers.h"
+#include "util/osp_logging.h"
+#include "util/std_util.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+// Use the Clock's minimum time value (an impossible value, waaaaay before epoch
+// time) to represent unset time_point values.
+constexpr auto kNullTimePoint = Clock::time_point::min();
+
+// Some receivers send time sync requests (that we ignore).
+constexpr uint32_t kTimeSyncRequestName =
+    ('T' << 24) + ('I' << 16) + ('M' << 8) + 'E';
+
+// Canonicalizes the just-parsed list of packet-specific NACKs so that the
+// CompoundRtcpParser::Client can make several simplifying assumptions when
+// processing the results.
+void CanonicalizePacketNackVector(std::vector<PacketNack>* packets) {
+  // First, sort all elements. The sort order is the normal lexicographical
+  // ordering, with one exception: The special kAllPacketsLost packet_id value
+  // should be treated as coming before all others. This special sort order
+  // allows the filtering algorithm below to be simpler, and only require one
+  // pass; and the final result will be the normal lexicographically-sorted
+  // output the CompoundRtcpParser::Client expects.
+  std::sort(packets->begin(), packets->end(),
+            [](const PacketNack& a, const PacketNack& b) {
+              // Since the comparator is a hot code path, use a simple modular
+              // arithmetic trick in lieu of extra branching: When comparing the
+              // tuples, map all packet_id values to packet_id + 1, mod 0x10000.
+              // This results in the desired sorting behavior since
+              // kAllPacketsLost (0xffff) wraps-around to 0x0000, and all other
+              // values become N + 1.
+              static_assert(static_cast<FramePacketId>(kAllPacketsLost + 1) <
+                                FramePacketId{0x0000 + 1},
+                            "comparison requires integer wrap-around");
+              return PacketNack{a.frame_id,
+                                static_cast<FramePacketId>(a.packet_id + 1)} <
+                     PacketNack{b.frame_id,
+                                static_cast<FramePacketId>(b.packet_id + 1)};
+            });
+
+  // De-duplicate elements. Two possible cases:
+  //
+  //   1. Identical elements (same FrameId+FramePacketId).
+  //   2. If there are any elements with kAllPacketsLost as the packet ID,
+  //      prune-out all other elements having the same frame ID, as they are
+  //      redundant.
+  //
+  // This is done by walking forwards over the sorted vector and deciding which
+  // elements to keep. Those that are kept are stacked-up at the front of the
+  // vector. After the "to-keep" pass, the vector is truncated to remove the
+  // left-over garbage at the end.
+  auto have_it = packets->begin();
+  if (have_it != packets->end()) {
+    auto kept_it = have_it;  // Always keep the first element.
+    for (++have_it; have_it != packets->end(); ++have_it) {
+      if (have_it->frame_id != kept_it->frame_id ||
+          (kept_it->packet_id != kAllPacketsLost &&
+           have_it->packet_id != kept_it->packet_id)) {  // Keep it.
+        ++kept_it;
+        *kept_it = *have_it;
+      }
+    }
+    packets->erase(++kept_it, packets->end());
+  }
+}
+
+}  // namespace
+
+CompoundRtcpParser::CompoundRtcpParser(RtcpSession& session,
+                                       CompoundRtcpParser::Client& client)
+    : session_(session),
+      client_(client),
+      latest_receiver_timestamp_(kNullTimePoint) {}
+
+CompoundRtcpParser::~CompoundRtcpParser() = default;
+
+bool CompoundRtcpParser::Parse(ByteView buffer, FrameId max_feedback_frame_id) {
+  // These will contain the results from the various ParseXYZ() methods. None of
+  // the results will be dispatched to the Client until the entire parse
+  // succeeds.
+  Clock::time_point receiver_reference_time = kNullTimePoint;
+  std::optional<RtcpReportBlock> receiver_report;
+  std::vector<RtcpReceiverFrameLogMessage> log_messages;
+  FrameId checkpoint_frame_id;
+  milliseconds target_playout_delay{};
+  std::vector<FrameId> received_frames;
+  std::vector<PacketNack> packet_nacks;
+  bool picture_loss_indicator = false;
+
+  // The data contained in `buffer` can be a "compound packet," which means that
+  // it can be the concatenation of multiple RTCP packets. The loop here
+  // processes each one-by-one.
+  while (!buffer.empty()) {
+    const auto header = RtcpCommonHeader::Parse(buffer);
+    if (!header) {
+      return false;
+    }
+    buffer = buffer.subspan(kRtcpCommonHeaderSize);
+    if (static_cast<int>(buffer.size()) < header->payload_size) {
+      return false;
+    }
+    ByteView payload = buffer.subspan(0, header->payload_size);
+    buffer = buffer.subspan(header->payload_size);
+
+    switch (header->packet_type) {
+      case RtcpPacketType::kReceiverReport:
+        if (!ParseReceiverReport(payload, header->with.report_count,
+                                 receiver_report)) {
+          return false;
+        }
+        break;
+
+      case RtcpPacketType::kApplicationDefined:
+        if (!ParseApplicationDefined(header->with.subtype, payload,
+                                     log_messages)) {
+          return false;
+        }
+        break;
+
+      case RtcpPacketType::kPayloadSpecific:
+        switch (header->with.subtype) {
+          case RtcpSubtype::kPictureLossIndicator:
+            if (!ParsePictureLossIndicator(payload, picture_loss_indicator)) {
+              return false;
+            }
+            break;
+          case RtcpSubtype::kFeedback:
+            if (!ParseFeedback(payload, max_feedback_frame_id,
+                               &checkpoint_frame_id, &target_playout_delay,
+                               &received_frames, packet_nacks)) {
+              return false;
+            }
+            break;
+          default:
+            // Ignore: Unimplemented or not part of the Cast Streaming spec.
+            break;
+        }
+        break;
+
+      case RtcpPacketType::kExtendedReports:
+        if (!ParseExtendedReports(payload, receiver_reference_time)) {
+          return false;
+        }
+        break;
+
+      default:
+        // Ignored, unimplemented or not part of the Cast Streaming spec.
+        break;
+    }
+  }
+
+  // A well-behaved Cast Streaming Receiver will always include a reference time
+  // report. This essentially "timestamps" the RTCP packets just parsed.
+  // However, the spec does not explicitly require this be included. When it is
+  // present, improve the stability of the system by ignoring stale/out-of-order
+  // RTCP packets.
+  if (receiver_reference_time != kNullTimePoint) {
+    // If the packet is out-of-order (e.g., it got delayed/shuffled when going
+    // through the network), just ignore it. Since RTCP packets always include
+    // all the necessary current state from the peer, dropping them does not
+    // mean important signals will be lost. In fact, it can actually be harmful
+    // to process compound RTCP packets out-of-order.
+    if (latest_receiver_timestamp_ != kNullTimePoint &&
+        receiver_reference_time < latest_receiver_timestamp_) {
+      return true;
+    }
+    latest_receiver_timestamp_ = receiver_reference_time;
+    client_->OnReceiverReferenceTimeAdvanced(latest_receiver_timestamp_);
+  }
+
+  // At this point, the packet is known to be well-formed. Dispatch events of
+  // interest to the Client.
+  if (receiver_report) {
+    client_->OnReceiverReport(*receiver_report);
+  }
+  if (!log_messages.empty()) {
+    client_->OnCastReceiverFrameLogMessages(std::move(log_messages));
+  }
+  if (!checkpoint_frame_id.is_null()) {
+    client_->OnReceiverCheckpoint(checkpoint_frame_id, target_playout_delay);
+  }
+  if (!received_frames.empty()) {
+    OSP_DCHECK(AreElementsSortedAndUnique(received_frames));
+    client_->OnReceiverHasFrames(std::move(received_frames));
+  }
+  CanonicalizePacketNackVector(&packet_nacks);
+  if (!packet_nacks.empty()) {
+    client_->OnReceiverIsMissingPackets(std::move(packet_nacks));
+  }
+  if (picture_loss_indicator) {
+    client_->OnReceiverIndicatesPictureLoss();
+  }
+
+  return true;
+}
+
+bool CompoundRtcpParser::ParseReceiverReport(
+    ByteView in,
+    int num_report_blocks,
+    std::optional<RtcpReportBlock>& receiver_report) {
+  if (in.size() < kRtcpReceiverReportSize) {
+    return false;
+  }
+  if (ConsumeField<uint32_t>(in) == session_->receiver_ssrc()) {
+    receiver_report = RtcpReportBlock::ParseOne(in, num_report_blocks,
+                                                session_->sender_ssrc());
+  }
+  return true;
+}
+
+bool CompoundRtcpParser::ParseApplicationDefined(
+    RtcpSubtype subtype,
+    ByteView in,
+    std::vector<RtcpReceiverFrameLogMessage>& messages) {
+  if (in.size() < 2 * sizeof(uint32_t)) {
+    return false;
+  }
+
+  const uint32_t sender_ssrc = ConsumeField<uint32_t>(in);
+  const uint32_t name = ConsumeField<uint32_t>(in);
+
+  // Just ignore events that aren't intended for us.
+  if (sender_ssrc != session_->receiver_ssrc()) {
+    return true;
+  }
+  if (name != kCastName) {
+    // We ignore time sync requests but don't throw an error for them.
+    return name == kTimeSyncRequestName;
+  }
+  if (subtype == RtcpSubtype::kReceiverLog) {
+    return ParseFrameLogMessages(in, messages);
+  }
+  return true;
+}
+
+bool CompoundRtcpParser::ParseFrameLogMessages(
+    ByteView in,
+    std::vector<RtcpReceiverFrameLogMessage>& messages) {
+  while (!in.empty()) {
+    if (in.size() < kRtcpReceiverFrameLogMessageHeaderSize) {
+      messages.clear();
+      return false;
+    }
+    const uint32_t truncated_rtp_timestamp = ConsumeField<uint32_t>(in);
+    const uint32_t data = ConsumeField<uint32_t>(in);
+
+    // The 24 least significant bits contain the event timestamp, which is
+    // offset from when the first packet was sent.
+    const uint32_t raw_timestamp = data & 0xFFFFFF;
+    const Clock::time_point event_timestamp_base =
+        session_->start_time() + milliseconds(raw_timestamp);
+
+    // The 8 most significant bits contain the number of events.
+    // NOTE: at least one event is required, so a value of "0" over the wire
+    // actually means there is one event.
+    const size_t num_events = 1u + static_cast<uint8_t>(data >> 24);
+
+    const RtpTimeTicks frame_log_rtp_timestamp =
+        latest_frame_log_rtp_timestamp_.Expand(truncated_rtp_timestamp);
+    RtcpReceiverFrameLogMessage frame_log_message{.rtp_timestamp =
+                                                      frame_log_rtp_timestamp};
+
+    for (size_t event = 0; event < num_events; ++event) {
+      if (in.size() < kRtcpReceiverFrameLogMessageBlockSize) {
+        messages.clear();
+        return false;
+      }
+
+      const uint16_t delay_delta_or_packet_id = ConsumeField<uint16_t>(in);
+      const uint16_t event_type_and_timestamp_delta =
+          ConsumeField<uint16_t>(in);
+
+      // Skip unknown event types, they are not useful.
+      const auto event_type =
+          StatisticsEvent::FromWireType(static_cast<StatisticsEvent::WireType>(
+              event_type_and_timestamp_delta >> 12));
+      if (event_type == StatisticsEvent::Type::kUnknown) {
+        continue;
+      }
+
+      RtcpReceiverEventLogMessage event_log{
+          .type = event_type,
+          .timestamp = event_timestamp_base +
+                       milliseconds(event_type_and_timestamp_delta & 0xFFF)};
+      if (event_type == StatisticsEvent::Type::kPacketReceived) {
+        event_log.packet_id = delay_delta_or_packet_id;
+      } else {
+        event_log.delay =
+            milliseconds(static_cast<int16_t>(delay_delta_or_packet_id));
+      }
+      frame_log_message.messages.emplace_back(std::move(event_log));
+    }
+    latest_frame_log_rtp_timestamp_ = frame_log_rtp_timestamp;
+    messages.emplace_back(std::move(frame_log_message));
+  }
+
+  return true;
+}
+
+bool CompoundRtcpParser::ParseFeedback(ByteView in,
+                                       FrameId max_feedback_frame_id,
+                                       FrameId* checkpoint_frame_id,
+                                       milliseconds* target_playout_delay,
+                                       std::vector<FrameId>* received_frames,
+                                       std::vector<PacketNack>& packet_nacks) {
+  OSP_CHECK(!max_feedback_frame_id.is_null());
+
+  if (static_cast<int>(in.size()) < kRtcpFeedbackHeaderSize) {
+    return false;
+  }
+  if (ConsumeField<uint32_t>(in) != session_->receiver_ssrc() ||
+      ConsumeField<uint32_t>(in) != session_->sender_ssrc()) {
+    return true;  // Ignore report from mismatched SSRC(s).
+  }
+  if (ConsumeField<uint32_t>(in) != kRtcpCastIdentifierWord) {
+    return false;
+  }
+
+  const FrameId feedback_frame_id =
+      max_feedback_frame_id.ExpandLessThanOrEqual(ConsumeField<uint8_t>(in));
+  const int loss_field_count = ConsumeField<uint8_t>(in);
+  const auto playout_delay = milliseconds(ConsumeField<uint16_t>(in));
+  // Don't process feedback that would move the checkpoint backwards. The Client
+  // makes assumptions about what frame data and other tracking state can be
+  // discarded based on a monotonically non-decreasing checkpoint FrameId.
+  if (!checkpoint_frame_id->is_null() &&
+      *checkpoint_frame_id > feedback_frame_id) {
+    return true;
+  }
+  *checkpoint_frame_id = feedback_frame_id;
+  *target_playout_delay = playout_delay;
+  received_frames->clear();
+  packet_nacks.clear();
+  if (static_cast<int>(in.size()) <
+      (kRtcpFeedbackLossFieldSize * loss_field_count)) {
+    return false;
+  }
+
+  // Parse the NACKs.
+  for (int i = 0; i < loss_field_count; ++i) {
+    const FrameId frame_id =
+        feedback_frame_id.ExpandGreaterThan(ConsumeField<uint8_t>(in));
+    FramePacketId packet_id = ConsumeField<uint16_t>(in);
+    uint8_t bits = ConsumeField<uint8_t>(in);
+    packet_nacks.push_back(PacketNack{frame_id, packet_id});
+
+    if (packet_id != kAllPacketsLost) {
+      // Translate each set bit in the bit vector into another missing
+      // FramePacketId.
+      while (bits) {
+        ++packet_id;
+        if (bits & 1) {
+          packet_nacks.push_back(PacketNack{frame_id, packet_id});
+        }
+        bits >>= 1;
+      }
+    }
+  }
+
+  // Parse the optional CST2 feedback (frame-level ACKs).
+  if (static_cast<int>(in.size()) < kRtcpFeedbackAckHeaderSize ||
+      ConsumeField<uint32_t>(in) != kRtcpCst2IdentifierWord) {
+    // Optional CST2 extended feedback is not present. For backwards-
+    // compatibility reasons, do not consider any extra "garbage" in the packet
+    // that doesn't match 'CST2' as corrupted input.
+    return true;
+  }
+  // Skip over the "Feedback Count" field. It's currently unused, though it
+  // might be useful for event tracing later...
+  in = in.subspan(sizeof(uint8_t));
+  const int ack_bitvector_octet_count = ConsumeField<uint8_t>(in);
+  if (static_cast<int>(in.size()) < ack_bitvector_octet_count) {
+    return false;
+  }
+  // Translate each set bit in the bit vector into a FrameId. See the
+  // explanation of this wire format in rtp_defines.h for where the "plus two"
+  // comes from.
+  FrameId starting_frame_id = feedback_frame_id + 2;
+  for (int i = 0; i < ack_bitvector_octet_count; ++i) {
+    uint8_t bits = ConsumeField<uint8_t>(in);
+    FrameId frame_id = starting_frame_id;
+    while (bits) {
+      if (bits & 1) {
+        received_frames->push_back(frame_id);
+      }
+      ++frame_id;
+      bits >>= 1;
+    }
+    constexpr int kBitsPerOctet = 8;
+    starting_frame_id += kBitsPerOctet;
+  }
+
+  return true;
+}
+
+bool CompoundRtcpParser::ParseExtendedReports(
+    ByteView in,
+    Clock::time_point& receiver_reference_time) {
+  if (static_cast<int>(in.size()) < kRtcpExtendedReportHeaderSize) {
+    return false;
+  }
+  if (ConsumeField<uint32_t>(in) != session_->receiver_ssrc()) {
+    return true;  // Ignore report from unknown receiver.
+  }
+
+  while (!in.empty()) {
+    // All extended report types have the same 4-byte subheader.
+    if (static_cast<int>(in.size()) < kRtcpExtendedReportBlockHeaderSize) {
+      return false;
+    }
+    const uint8_t block_type = ConsumeField<uint8_t>(in);
+    in = in.subspan(sizeof(uint8_t));  // Skip the "reserved" byte.
+    const int block_data_size =
+        static_cast<int>(ConsumeField<uint16_t>(in)) * 4;
+    if (static_cast<int>(in.size()) < block_data_size) {
+      return false;
+    }
+    if (block_type == kRtcpReceiverReferenceTimeReportBlockType) {
+      if (block_data_size != sizeof(uint64_t)) {
+        return false;  // Length field must always be 2 words.
+      }
+      receiver_reference_time = session_->ntp_converter().ToLocalTime(
+          ReadBigEndian<uint64_t>(in.data()));
+    } else {
+      // Ignore any other type of extended report.
+    }
+    in = in.subspan(block_data_size);
+  }
+
+  return true;
+}
+
+bool CompoundRtcpParser::ParsePictureLossIndicator(
+    ByteView in,
+    bool& picture_loss_indicator) {
+  if (static_cast<int>(in.size()) < kRtcpPictureLossIndicatorHeaderSize) {
+    return false;
+  }
+  // Only set the flag if the PLI is from the Receiver and to this Sender.
+  if (ConsumeField<uint32_t>(in) == session_->receiver_ssrc() &&
+      ConsumeField<uint32_t>(in) == session_->sender_ssrc()) {
+    picture_loss_indicator = true;
+  }
+  return true;
+}
+
+CompoundRtcpParser::Client::Client() = default;
+CompoundRtcpParser::Client::~Client() = default;
+void CompoundRtcpParser::Client::OnReceiverReferenceTimeAdvanced(
+    Clock::time_point reference_time) {}
+void CompoundRtcpParser::Client::OnReceiverReport(
+    const RtcpReportBlock& receiver_report) {}
+void CompoundRtcpParser::Client::OnCastReceiverFrameLogMessages(
+    std::vector<RtcpReceiverFrameLogMessage> messages) {}
+void CompoundRtcpParser::Client::OnReceiverIndicatesPictureLoss() {}
+void CompoundRtcpParser::Client::OnReceiverCheckpoint(
+    FrameId frame_id,
+    milliseconds playout_delay) {}
+void CompoundRtcpParser::Client::OnReceiverHasFrames(
+    std::vector<FrameId> acks) {}
+void CompoundRtcpParser::Client::OnReceiverIsMissingPackets(
+    std::vector<PacketNack> nacks) {}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/compound_rtcp_parser.h

@@ -0,0 +1,135 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_COMPOUND_RTCP_PARSER_H_
+#define CAST_STREAMING_IMPL_COMPOUND_RTCP_PARSER_H_
+
+#include <chrono>
+#include <optional>
+#include <vector>
+
+#include "cast/streaming/impl/rtcp_common.h"
+#include "cast/streaming/impl/rtp_defines.h"
+#include "cast/streaming/public/frame_id.h"
+#include "platform/base/span.h"
+#include "util/raw_ref.h"
+
+namespace openscreen::cast {
+
+class RtcpSession;
+
+// Parses compound RTCP packets from a Receiver, invoking client callbacks when
+// information of interest to a Sender (in the current process) is encountered.
+class CompoundRtcpParser {
+ public:
+  // Callback interface used while parsing RTCP packets of interest to a Sender.
+  // The implementation must take into account:
+  //
+  //   1. Some/All of the data could be stale, as it only reflects the state of
+  //      the Receiver at the time the packet was generated. A significant
+  //      amount of time may have passed, depending on how long it took the
+  //      packet to reach this local instance over the network.
+  //   2. The data shouldn't necessarily be trusted blindly: Some may be
+  //      inconsistent (e.g., the same frame being ACKed and NACKed; or a frame
+  //      that has not been sent yet is being NACKed). While that would indicate
+  //      a badly-behaving Receiver, the Sender should be robust to such things.
+  class Client {
+   public:
+    Client();
+
+    // Called when a Receiver Reference Time Report has been parsed.
+    virtual void OnReceiverReferenceTimeAdvanced(
+        Clock::time_point reference_time);
+
+    // Called when a Receiver Report with a Report Block has been parsed.
+    virtual void OnReceiverReport(const RtcpReportBlock& receiver_report);
+
+    // Called when a group of Cast Receiver frame log messages has been parsed.
+    virtual void OnCastReceiverFrameLogMessages(
+        std::vector<RtcpReceiverFrameLogMessage> messages);
+
+    // Called when the Receiver has encountered an unrecoverable error in
+    // decoding the data. The Sender should provide a key frame as soon as
+    // possible.
+    virtual void OnReceiverIndicatesPictureLoss();
+
+    // Called when the Receiver indicates that all of the packets for all frames
+    // up to and including `frame_id` have been successfully received (or
+    // otherwise do not need to be re-transmitted). The `playout_delay` is the
+    // Receiver's current end-to-end target playout delay setting, which should
+    // reflect any changes the Sender has made by using the "Cast Adaptive
+    // Latency Extension" in RTP packets.
+    virtual void OnReceiverCheckpoint(FrameId frame_id,
+                                      std::chrono::milliseconds playout_delay);
+
+    // Called to indicate the Receiver has successfully received all of the
+    // packets for each of the given `acks`. The argument's elements are in
+    // monotonically increasing order.
+    virtual void OnReceiverHasFrames(std::vector<FrameId> acks);
+
+    // Called to indicate the Receiver is missing certain specific packets for
+    // certain specific frames. Any elements where the packet_id is
+    // kAllPacketsLost indicates that all the packets are missing for a frame.
+    // The argument's elements are in monotonically increasing order.
+    virtual void OnReceiverIsMissingPackets(std::vector<PacketNack> nacks);
+
+   protected:
+    virtual ~Client();
+  };
+
+  // `session` and `client` must be non-null and must outlive the
+  // CompoundRtcpParser instance.
+  CompoundRtcpParser(RtcpSession& session, Client& client);
+  ~CompoundRtcpParser();
+
+  // Parses the packet, invoking the Client callback methods when appropriate.
+  // Returns true if the `packet` was well-formed, or false if it was corrupt.
+  // Note that none of the Client callback methods will be invoked until a
+  // packet is known to be well-formed.
+  //
+  // `max_feedback_frame_id` is the maximum-valued FrameId that could possibly
+  // be ACKnowledged by the Receiver, if there is Cast Feedback in the `packet`.
+  // This is needed for expanding truncated frame IDs correctly.
+  bool Parse(ByteView packet, FrameId max_feedback_frame_id);
+
+ private:
+  // These return true if the input was well-formed, and false if it was
+  // invalid/corrupt. The true/false value does NOT indicate whether the data
+  // contained within was ignored. Output arguments are only modified if the
+  // input contained the relevant field(s).
+  bool ParseReceiverReport(ByteView in,
+                           int num_report_blocks,
+                           std::optional<RtcpReportBlock>& receiver_report);
+  bool ParseApplicationDefined(
+      RtcpSubtype subtype,
+      ByteView in,
+      std::vector<RtcpReceiverFrameLogMessage>& messages);
+  bool ParseFrameLogMessages(
+      ByteView in,
+      std::vector<RtcpReceiverFrameLogMessage>& messages);
+  bool ParseFeedback(ByteView in,
+                     FrameId max_feedback_frame_id,
+                     FrameId* checkpoint_frame_id,
+                     std::chrono::milliseconds* target_playout_delay,
+                     std::vector<FrameId>* received_frames,
+                     std::vector<PacketNack>& packet_nacks);
+  bool ParseExtendedReports(ByteView in,
+                            Clock::time_point& receiver_reference_time);
+  bool ParsePictureLossIndicator(ByteView in, bool& picture_loss_indicator);
+
+  const raw_ref<RtcpSession> session_;
+  const raw_ref<Client> client_;
+
+  // Tracks the latest timestamp seen from any Receiver Reference Time Report,
+  // and uses this to ignore stale RTCP packets that arrived out-of-order and/or
+  // late from the network.
+  Clock::time_point latest_receiver_timestamp_;
+
+  // Tracks the last parsed RTP timestamp seen from any Cast receiver frame log.
+  RtpTimeTicks latest_frame_log_rtp_timestamp_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_COMPOUND_RTCP_PARSER_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/expanded_value_base.h

@@ -0,0 +1,174 @@
+// Copyright 2015 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_EXPANDED_VALUE_BASE_H_
+#define CAST_STREAMING_IMPL_EXPANDED_VALUE_BASE_H_
+
+#include <stdint.h>
+
+#include <limits>
+
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+// Abstract base template class for common "sequence value" data types such as
+// RtpTimeTicks, FrameId, or PacketId which generally increment/decrement in
+// predictable amounts as media is streamed, and which often need to be reliably
+// truncated and re-expanded for over-the-wire transmission.
+//
+// FullWidthInteger should be a signed integer POD type that is of sufficiently
+// high width (in bits) such that it is never expected to under/overflow during
+// the longest reasonable length of continuous system operation.  Subclass is
+// the class inheriting the common functionality provided in this template, and
+// is used to provide operator overloads.  The Subclass must friend this class
+// to enable these operator overloads.
+//
+// Please see RtpTimeTicks and unit test code for examples of how to define
+// Subclasses and add features specific to their concrete data type, and how to
+// use data types derived from ExpandedValueBase.  For example, a RtpTimeTicks
+// adds math operators consisting of the meaningful and valid set of operations
+// allowed for doing "time math."  On the other hand, FrameId only adds math
+// operators for incrementing/decrementing since multiplication and division are
+// meaningless.
+template <typename FullWidthInteger, class Subclass>
+class ExpandedValueBase {
+  static_assert(std::numeric_limits<FullWidthInteger>::is_signed,
+                "FullWidthInteger must be a signed integer.");
+  static_assert(std::numeric_limits<FullWidthInteger>::is_integer,
+                "FullWidthInteger must be a signed integer.");
+
+ public:
+  // Methods that return the lower bits of this value.  This should only be used
+  // for serializing/wire-formatting, and not to subvert the restricted set of
+  // operators allowed on this data type.
+  constexpr uint8_t lower_8_bits() const {
+    return static_cast<uint8_t>(value_);
+  }
+  constexpr uint16_t lower_16_bits() const {
+    return static_cast<uint16_t>(value_);
+  }
+  constexpr uint32_t lower_32_bits() const {
+    return static_cast<uint32_t>(value_);
+  }
+
+  // Compute the greatest value less than or equal to `this` value whose lower
+  // bits are those of `x`.  The purpose of this method is to re-instantiate an
+  // original value from its truncated form, usually when deserializing
+  // off-the-wire, when `this` value is known to be the greatest possible valid
+  // value.
+  //
+  // Use case example: Start with an original 32-bit value of 0x000001fe (510
+  // decimal) and truncate, throwing away its upper 24 bits: 0xfe.  Now, send
+  // this truncated value over-the-wire to a peer who needs to expand it back to
+  // the original 32-bit value.  The peer knows that the greatest possible valid
+  // value is 0x00000202 (514 decimal).  This method will initially attempt to
+  // just concatenate the upper 24 bits of |this->value_| with |x| (the 8-bit
+  // value), and get a result of 0x000002fe (766 decimal).  However, this is
+  // greater than |this->value_|, so the upper 24 bits are subtracted by one to
+  // get 0x000001fe, which is the original value.
+  template <typename ShortUnsigned>
+  Subclass ExpandLessThanOrEqual(ShortUnsigned x) const {
+    static_assert(!std::numeric_limits<ShortUnsigned>::is_signed,
+                  "`x` must be an unsigned integer.");
+    static_assert(std::numeric_limits<ShortUnsigned>::is_integer,
+                  "`x` must be an unsigned integer.");
+    static_assert(sizeof(ShortUnsigned) <= sizeof(FullWidthInteger),
+                  "`x` must fit within the FullWidthInteger.");
+
+    if (sizeof(ShortUnsigned) < sizeof(FullWidthInteger)) {
+      // Initially, the `result` is composed of upper bits from `value_` and
+      // lower bits from `x`.
+      const FullWidthInteger short_max =
+          std::numeric_limits<ShortUnsigned>::max();
+      FullWidthInteger result = (value_ & ~short_max) | x;
+
+      // If the `result` is larger than `value_`, decrement the upper bits by
+      // one.  In other words, `x` must always be interpreted as a truncated
+      // version of a value less than or equal to `value_`.
+      if (result > value_)
+        result -= short_max + 1;
+
+      return Subclass(result);
+    } else {
+      // Debug builds: Ensure the highest bit is not set (which would cause
+      // overflow when casting to the signed integer).
+      OSP_CHECK_EQ(
+          static_cast<ShortUnsigned>(0),
+          x & (static_cast<ShortUnsigned>(1) << ((sizeof(x) * 8) - 1)));
+      return Subclass(x);
+    }
+  }
+
+  // Compute the smallest value greater than `this` value whose lower bits are
+  // those of `x`.
+  template <typename ShortUnsigned>
+  Subclass ExpandGreaterThan(ShortUnsigned x) const {
+    const Subclass maximum_possible_result(
+        value_ + std::numeric_limits<ShortUnsigned>::max() + 1);
+    return maximum_possible_result.ExpandLessThanOrEqual(x);
+  }
+
+  // Compute the value closest to `this` value whose lower bits are those of
+  // `x`.  The result is always within `max_distance_for_expansion()` of `this`
+  // value.  The purpose of this method is to re-instantiate an original value
+  // from its truncated form, usually when deserializing off-the-wire.  See
+  // comments for ExpandLessThanOrEqual() above for further explanation.
+  template <typename ShortUnsigned>
+  Subclass Expand(ShortUnsigned x) const {
+    const Subclass maximum_possible_result(
+        value_ + max_distance_for_expansion<ShortUnsigned>());
+    return maximum_possible_result.ExpandLessThanOrEqual(x);
+  }
+
+  // Comparison operators.
+  constexpr bool operator==(const ExpandedValueBase& rhs) const {
+    return value_ == rhs.value_;
+  }
+  constexpr bool operator!=(const ExpandedValueBase& rhs) const {
+    return value_ != rhs.value_;
+  }
+  constexpr bool operator<(const ExpandedValueBase& rhs) const {
+    return value_ < rhs.value_;
+  }
+  constexpr bool operator>(const ExpandedValueBase& rhs) const {
+    return value_ > rhs.value_;
+  }
+  constexpr bool operator<=(const ExpandedValueBase& rhs) const {
+    return value_ <= rhs.value_;
+  }
+  constexpr bool operator>=(const ExpandedValueBase& rhs) const {
+    return value_ >= rhs.value_;
+  }
+
+  // (De)Serialize for transmission over IPC.  Do not use these to subvert the
+  // valid set of operators allowed by this class or its Subclass.
+  uint64_t SerializeForIPC() const {
+    static_assert(sizeof(uint64_t) >= sizeof(FullWidthInteger),
+                  "Cannot serialize FullWidthInteger into an uint64_t.");
+    return static_cast<uint64_t>(value_);
+  }
+  static Subclass DeserializeForIPC(uint64_t serialized) {
+    return Subclass(static_cast<FullWidthInteger>(serialized));
+  }
+
+  // Design limit: Values that are truncated to the ShortUnsigned type must be
+  // no more than this maximum distance from each other in order to ensure the
+  // original value can be determined correctly.
+  template <typename ShortUnsigned>
+  static constexpr FullWidthInteger max_distance_for_expansion() {
+    return std::numeric_limits<ShortUnsigned>::max() / 2;
+  }
+
+ protected:
+  // Only subclasses are permitted to instantiate directly.
+  constexpr explicit ExpandedValueBase(FullWidthInteger value)
+      : value_(value) {}
+
+  FullWidthInteger value_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_EXPANDED_VALUE_BASE_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/frame_crypto.cc

@@ -0,0 +1,106 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/frame_crypto.h"
+
+#include <random>
+#include <utility>
+
+#include "openssl/crypto.h"
+#include "openssl/err.h"
+#include "openssl/rand.h"
+#include "platform/base/span.h"
+#include "util/big_endian.h"
+#include "util/crypto/openssl_util.h"
+#include "util/crypto/random_bytes.h"
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+EncryptedFrame::EncryptedFrame() {
+  data = owned_data_;
+}
+
+EncryptedFrame::~EncryptedFrame() = default;
+
+EncryptedFrame::EncryptedFrame(EncryptedFrame&& other) noexcept
+    : EncodedFrame(static_cast<EncodedFrame&&>(other)),
+      owned_data_(std::move(other.owned_data_)) {
+  data = owned_data_;
+  other.data = ByteView();
+}
+
+EncryptedFrame& EncryptedFrame::operator=(EncryptedFrame&& other) {
+  this->EncodedFrame::operator=(static_cast<EncodedFrame&&>(other));
+  owned_data_ = std::move(other.owned_data_);
+  data = owned_data_;
+  other.data = ByteView();
+  return *this;
+}
+
+FrameCrypto::FrameCrypto(const std::array<uint8_t, 16>& aes_key,
+                         const std::array<uint8_t, 16>& cast_iv_mask)
+    : aes_key_{}, cast_iv_mask_(cast_iv_mask) {
+  // Ensure that the library has been initialized. CRYPTO_library_init() may be
+  // safely called multiple times during the life of a process.
+  CRYPTO_library_init();
+
+  // Initialize the 244-byte AES_KEY struct once, here at construction time. The
+  // const_cast<> is reasonable as this is a one-time-ctor-initialized value
+  // that will remain constant from here onward.
+  const int return_code = AES_set_encrypt_key(
+      aes_key.data(), aes_key.size() * 8, const_cast<AES_KEY*>(&aes_key_));
+  if (return_code != 0) {
+    ClearOpenSSLERRStack(CURRENT_LOCATION);
+    OSP_LOG_FATAL << "Failure when setting encryption key; unsafe to continue.";
+    OSP_NOTREACHED();
+  }
+}
+
+FrameCrypto::~FrameCrypto() = default;
+
+EncryptedFrame FrameCrypto::Encrypt(const EncodedFrame& encoded_frame) const {
+  EncryptedFrame result;
+  encoded_frame.CopyMetadataTo(&result);
+  result.owned_data_.resize(encoded_frame.data.size());
+  result.data = result.owned_data_;
+  Crypt(encoded_frame.frame_id, {&encoded_frame.data, 1}, result.owned_data_);
+  return result;
+}
+
+void FrameCrypto::Decrypt(FrameId frame_id,
+                          ChunkList chunks,
+                          ByteBuffer out) const {
+  Crypt(frame_id, chunks, out);
+}
+
+void FrameCrypto::Crypt(FrameId frame_id,
+                        ChunkList chunks,
+                        ByteBuffer out) const {
+  OSP_CHECK(!frame_id.is_null());
+
+  // Compute the AES nonce for Cast Streaming payload encryption, which is based
+  // on the `frame_id`.
+  std::array<uint8_t, 16> aes_nonce{};
+  static_assert(AES_BLOCK_SIZE == sizeof(aes_nonce),
+                "AES_BLOCK_SIZE is not 16 bytes.");
+  WriteBigEndian<uint32_t>(frame_id.lower_32_bits(), aes_nonce.data() + 8);
+  for (size_t i = 0; i < aes_nonce.size(); ++i) {
+    aes_nonce[i] ^= cast_iv_mask_[i];
+  }
+
+  std::array<uint8_t, 16> ecount_buf{};
+  unsigned int block_offset = 0;
+  size_t out_offset = 0;
+  for (ByteView chunk : chunks) {
+    OSP_CHECK_LE(out_offset + chunk.size(), out.size());
+    AES_ctr128_encrypt(chunk.data(), out.data() + out_offset, chunk.size(),
+                       &aes_key_, aes_nonce.data(), ecount_buf.data(),
+                       &block_offset);
+    out_offset += chunk.size();
+  }
+  OSP_CHECK_EQ(out_offset, out.size());
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/frame_crypto.h

@@ -0,0 +1,78 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_FRAME_CRYPTO_H_
+#define CAST_STREAMING_IMPL_FRAME_CRYPTO_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <array>
+#include <vector>
+
+#include "cast/streaming/public/encoded_frame.h"
+#include "openssl/aes.h"
+#include "platform/base/span.h"
+
+namespace openscreen::cast {
+
+class FrameCrypto;
+
+// A subclass of EncodedFrame that represents an EncodedFrame with encrypted
+// payload data, and owns the buffer storing the encrypted payload data. Use
+// FrameCrypto (below) to explicitly convert between EncryptedFrames and
+// EncodedFrames.
+struct EncryptedFrame : public EncodedFrame {
+  EncryptedFrame();
+  ~EncryptedFrame();
+  EncryptedFrame(EncryptedFrame&&) noexcept;
+  EncryptedFrame& operator=(EncryptedFrame&&);
+
+ protected:
+  // Since only FrameCrypto is trusted to generate the
+  // payload data, it is allowed direct access to the storage.
+  friend class FrameCrypto;
+
+  // Note: EncodedFrame::data must be updated whenever any mutations are
+  // performed on this member!
+  std::vector<uint8_t> owned_data_;
+};
+
+// Encrypts EncodedFrames before sending, or decrypts EncryptedFrames that have
+// been received.
+class FrameCrypto {
+ public:
+  using ChunkList = std::span<const ByteView>;
+
+  // Construct with the given 16-bytes AES key and IV mask. Both arguments
+  // should be randomly-generated for each new streaming session.
+  // GenerateRandomBytes() can be used to create them.
+  FrameCrypto(const std::array<uint8_t, 16>& aes_key,
+              const std::array<uint8_t, 16>& cast_iv_mask);
+
+  ~FrameCrypto();
+
+  EncryptedFrame Encrypt(const EncodedFrame& encoded_frame) const;
+
+  // Decrypts `chunks` into `out`. `out` must have a sufficiently-sized
+  // data buffer.
+  void Decrypt(FrameId frame_id, ChunkList chunks, ByteBuffer out) const;
+
+ private:
+  // The 244-byte AES_KEY struct, derived from the `aes_key` passed to the ctor,
+  // and initialized by boringssl's AES_set_encrypt_key() function.
+  const AES_KEY aes_key_;
+
+  // Random bytes used in the custom heuristic to generate a different
+  // initialization vector for each frame.
+  const std::array<uint8_t, 16> cast_iv_mask_;
+
+  // AES-CTR is symmetric. Thus, the "meat" of both Encrypt() and Decrypt() is
+  // the same.
+  void Crypt(FrameId frame_id, ChunkList chunks, ByteBuffer out) const;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_FRAME_CRYPTO_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/message_constants.h

@@ -0,0 +1,15 @@
+// Copyright 2026 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_MESSAGE_CONSTANTS_H_
+#define CAST_STREAMING_IMPL_MESSAGE_CONSTANTS_H_
+
+namespace openscreen::cast {
+
+// RTP extension strings.
+inline constexpr char kInputEventsRtpExtension[] = "input_events";
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_MESSAGE_CONSTANTS_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/ntp_time.cc

@@ -0,0 +1,54 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/ntp_time.h"
+
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+// The number of seconds between 1 January 1900 and 1 January 1970.
+constexpr NtpSeconds kTimeBetweenNtpEpochAndUnixEpoch(2208988800);
+
+}  // namespace
+
+NtpTimeConverter::NtpTimeConverter(Clock::time_point now,
+                                   std::chrono::seconds since_unix_epoch)
+    : start_time_(now),
+      since_ntp_epoch_(
+          std::chrono::duration_cast<NtpSeconds>(since_unix_epoch) +
+          kTimeBetweenNtpEpochAndUnixEpoch) {}
+
+NtpTimeConverter::~NtpTimeConverter() = default;
+
+NtpTimestamp NtpTimeConverter::ToNtpTimestamp(
+    Clock::time_point time_point) const {
+  const Clock::duration time_since_start = time_point - start_time_;
+  const auto whole_seconds =
+      std::chrono::duration_cast<NtpSeconds>(time_since_start);
+  const auto remainder =
+      std::chrono::duration_cast<NtpFraction>(time_since_start - whole_seconds);
+  return AssembleNtpTimestamp(since_ntp_epoch_ + whole_seconds, remainder);
+}
+
+Clock::time_point NtpTimeConverter::ToLocalTime(NtpTimestamp timestamp) const {
+  auto ntp_seconds = NtpSecondsPart(timestamp);
+  // Year 2036 wrap-around check: If the NTP timestamp appears to be a
+  // point-in-time before 1970, assume the 2036 wrap-around has occurred, and
+  // adjust to compensate.
+  if (ntp_seconds <= kTimeBetweenNtpEpochAndUnixEpoch) {
+    constexpr NtpSeconds kNtpSecondsPerEra{INT64_C(1) << 32};
+    ntp_seconds += kNtpSecondsPerEra;
+  }
+
+  const auto whole_seconds = ntp_seconds - since_ntp_epoch_;
+  const auto seconds_since_start =
+      Clock::to_duration(whole_seconds) + start_time_;
+  const auto remainder = Clock::to_duration(NtpFractionPart(timestamp));
+  return seconds_since_start + remainder;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/ntp_time.h

@@ -0,0 +1,73 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_NTP_TIME_H_
+#define CAST_STREAMING_IMPL_NTP_TIME_H_
+
+#include <stdint.h>
+
+#include "platform/api/time.h"
+
+namespace openscreen::cast {
+
+// NTP timestamps are 64-bit timestamps that consist of two 32-bit parts: 1) The
+// number of seconds since 1 January 1900; and 2) The fraction of the second,
+// where 0 maps to 0x00000000 and each unit increment represents another 2^-32
+// seconds.
+//
+// Note that it is part of the design of NTP for the seconds part to roll around
+// on 7 February 2036.
+using NtpTimestamp = uint64_t;
+
+// NTP fixed-point time math: Declare two std::chrono::duration types with the
+// bit-width necessary to reliably perform all conversions to/from NTP format.
+using NtpSeconds = std::chrono::duration<int64_t, std::chrono::seconds::period>;
+using NtpFraction =
+    std::chrono::duration<int64_t, std::ratio<1, INT64_C(0x100000000)>>;
+
+constexpr NtpSeconds NtpSecondsPart(NtpTimestamp timestamp) {
+  return NtpSeconds(timestamp >> 32);
+}
+
+constexpr NtpFraction NtpFractionPart(NtpTimestamp timestamp) {
+  return NtpFraction(timestamp & 0xffffffff);
+}
+
+constexpr NtpTimestamp AssembleNtpTimestamp(NtpSeconds seconds,
+                                            NtpFraction fraction) {
+  return (static_cast<uint64_t>(seconds.count()) << 32) |
+         static_cast<uint32_t>(fraction.count());
+}
+
+// Converts between Clock::time_points and NtpTimestamps. The class is
+// instantiated with the current Clock time and the current wall clock time, and
+// these are used to determine a fixed origin reference point for all
+// conversions. Thus, to avoid introducing unintended timing-related behaviors,
+// only one NtpTimeConverter instance should be used for converting all the NTP
+// timestamps in the same streaming session.
+class NtpTimeConverter {
+ public:
+  NtpTimeConverter(
+      Clock::time_point now,
+      std::chrono::seconds since_unix_epoch = GetWallTimeSinceUnixEpoch());
+  ~NtpTimeConverter();
+
+  NtpTimestamp ToNtpTimestamp(Clock::time_point time_point) const;
+  Clock::time_point ToLocalTime(NtpTimestamp timestamp) const;
+
+ private:
+  // The time point on the platform clock's timeline that corresponds to
+  // approximately the same time point on the NTP timeline. Note that it is
+  // acceptable for the granularity of the NTP seconds value to be whole seconds
+  // here: Both a Cast Streaming Sender and Receiver will assume their clocks
+  // can be off (with respect to each other) by even a large amount; and all
+  // that matters is that time ticks forward at a reasonable pace from some
+  // initial point.
+  const Clock::time_point start_time_;
+  const NtpSeconds since_ntp_epoch_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_NTP_TIME_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/packet_util.cc

@@ -0,0 +1,39 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/packet_util.h"
+
+#include "cast/streaming/impl/rtcp_common.h"
+#include "cast/streaming/impl/rtp_defines.h"
+
+namespace openscreen::cast {
+
+std::pair<ApparentPacketType, Ssrc> InspectPacketForRouting(ByteView packet) {
+  // Check for RTP packets first, since they are more frequent.
+  if (packet.size() >= kRtpPacketMinValidSize &&
+      packet[0] == kRtpRequiredFirstByte &&
+      IsRtpPayloadType(packet[1] & kRtpPayloadTypeMask)) {
+    constexpr int kOffsetToSsrcField = 8;
+    return std::make_pair(
+        ApparentPacketType::RTP,
+        Ssrc{ReadBigEndian<uint32_t>(packet.data() + kOffsetToSsrcField)});
+  }
+
+  // While RTCP packets are valid if they consist of just the RTCP Common
+  // Header, all the RTCP packet types processed by this implementation will
+  // also have a SSRC field immediately following the header. This is important
+  // for routing the packet to the correct parser instance.
+  constexpr int kRtcpPacketMinAcceptableSize =
+      kRtcpCommonHeaderSize + sizeof(uint32_t);
+  if (packet.size() >= kRtcpPacketMinAcceptableSize &&
+      RtcpCommonHeader::Parse(packet).has_value()) {
+    return std::make_pair(
+        ApparentPacketType::RTCP,
+        Ssrc{ReadBigEndian<uint32_t>(packet.data() + kRtcpCommonHeaderSize)});
+  }
+
+  return std::make_pair(ApparentPacketType::UNKNOWN, Ssrc{0});
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/packet_util.h

@@ -0,0 +1,60 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_PACKET_UTIL_H_
+#define CAST_STREAMING_IMPL_PACKET_UTIL_H_
+
+#include <utility>
+
+#include "cast/streaming/ssrc.h"
+#include "platform/base/span.h"
+#include "util/big_endian.h"
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+// Reads a field from the start of the given span and advances the span to point
+// just after the field.
+template <typename Integer>
+inline Integer ConsumeField(ByteView& in) {
+  OSP_CHECK_GE(in.size(), sizeof(Integer));
+  const Integer result = ReadBigEndian<Integer>(in.data());
+  in = in.subspan(sizeof(Integer));
+  return result;
+}
+
+// Writes a field at the start of the given span and advances the span to point
+// just after the field.
+template <typename Integer>
+inline void AppendField(Integer value, ByteBuffer& out) {
+  WriteBigEndian<Integer>(value, out.data());
+  out = out.subspan(sizeof(Integer));
+}
+
+// Returns a bitmask for a field having the given number of bits. For example,
+// FieldBitmask<uint8_t>(5) returns 0b00011111.
+template <typename Integer>
+constexpr Integer FieldBitmask(unsigned field_size_in_bits) {
+  return (Integer{1} << field_size_in_bits) - 1;
+}
+
+// Reserves `num_bytes` from the beginning of the given span, returning the
+// reserved space.
+inline ByteBuffer ReserveSpace(int num_bytes, ByteBuffer& out) {
+  const ByteBuffer reserved = out.subspan(0, num_bytes);
+  out = out.subspan(num_bytes);
+  return reserved;
+}
+
+// Performs a quick-scan of the packet data for the purposes of routing it to an
+// appropriate parser. Identifies whether the packet is a RTP packet, RTCP
+// packet, or unknown; and provides the originator's SSRC. This only performs a
+// very quick scan of the packet data, and does not guarantee that a full parse
+// will later succeed.
+enum class ApparentPacketType { UNKNOWN, RTP, RTCP };
+std::pair<ApparentPacketType, Ssrc> InspectPacketForRouting(ByteView packet);
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_PACKET_UTIL_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/rtcp_common.cc

@@ -0,0 +1,241 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/rtcp_common.h"
+
+#include <algorithm>
+#include <limits>
+
+#include "cast/streaming/impl/packet_util.h"
+#include "util/saturate_cast.h"
+
+namespace openscreen::cast {
+
+RtcpCommonHeader::RtcpCommonHeader() = default;
+RtcpCommonHeader::~RtcpCommonHeader() = default;
+
+void RtcpCommonHeader::AppendFields(ByteBuffer& buffer) const {
+  OSP_CHECK_GE(buffer.size(), kRtcpCommonHeaderSize);
+
+  uint8_t byte0 = kRtcpRequiredVersionAndPaddingBits
+                  << kRtcpReportCountFieldNumBits;
+  switch (packet_type) {
+    case RtcpPacketType::kSenderReport:
+    case RtcpPacketType::kReceiverReport:
+      OSP_CHECK_LE(with.report_count,
+                   FieldBitmask<int>(kRtcpReportCountFieldNumBits));
+      byte0 |= with.report_count;
+      break;
+    case RtcpPacketType::kSourceDescription:
+      OSP_UNIMPLEMENTED();
+      break;
+    case RtcpPacketType::kApplicationDefined:
+    case RtcpPacketType::kPayloadSpecific:
+      switch (with.subtype) {
+        case RtcpSubtype::kPictureLossIndicator:
+        case RtcpSubtype::kFeedback:
+        case RtcpSubtype::kReceiverLog:
+          byte0 |= static_cast<uint8_t>(with.subtype);
+          break;
+
+        // We should not be creating application or payload specific packets
+        // with an unknown or null subtype -- they will just be ignored.
+        case RtcpSubtype::kNull:
+          OSP_NOTREACHED();
+      }
+      break;
+    case RtcpPacketType::kExtendedReports:
+      break;
+    case RtcpPacketType::kNull:
+      OSP_NOTREACHED();
+  }
+  AppendField<uint8_t>(byte0, buffer);
+
+  AppendField<uint8_t>(static_cast<uint8_t>(packet_type), buffer);
+
+  // The size of the packet must be evenly divisible by the 32-bit word size.
+  OSP_CHECK_EQ(0, payload_size % sizeof(uint32_t));
+  AppendField<uint16_t>(payload_size / sizeof(uint32_t), buffer);
+}
+
+// static
+std::optional<RtcpCommonHeader> RtcpCommonHeader::Parse(ByteView buffer) {
+  if (buffer.size() < kRtcpCommonHeaderSize) {
+    return std::nullopt;
+  }
+
+  const uint8_t byte0 = ConsumeField<uint8_t>(buffer);
+  if ((byte0 >> kRtcpReportCountFieldNumBits) !=
+      kRtcpRequiredVersionAndPaddingBits) {
+    return std::nullopt;
+  }
+  const uint8_t report_count_or_subtype =
+      byte0 & FieldBitmask<uint8_t>(kRtcpReportCountFieldNumBits);
+
+  const uint8_t byte1 = ConsumeField<uint8_t>(buffer);
+  if (!IsRtcpPacketType(byte1)) {
+    return std::nullopt;
+  }
+
+  // Optionally set `header.with.report_count` or `header.with.subtype`,
+  // depending on the packet type.
+  RtcpCommonHeader header;
+  header.packet_type = static_cast<RtcpPacketType>(byte1);
+  switch (header.packet_type) {
+    case RtcpPacketType::kSenderReport:
+    case RtcpPacketType::kReceiverReport:
+      header.with.report_count = report_count_or_subtype;
+      break;
+    case RtcpPacketType::kApplicationDefined:
+    case RtcpPacketType::kPayloadSpecific:
+      switch (static_cast<RtcpSubtype>(report_count_or_subtype)) {
+        case RtcpSubtype::kPictureLossIndicator:
+        case RtcpSubtype::kReceiverLog:
+        case RtcpSubtype::kFeedback:
+          header.with.subtype =
+              static_cast<RtcpSubtype>(report_count_or_subtype);
+          break;
+        default:  // Unknown subtype.
+          header.with.subtype = RtcpSubtype::kNull;
+          break;
+      }
+      break;
+    default:
+      // Neither `header.with.report_count` nor `header.with.subtype` are used.
+      break;
+  }
+
+  header.payload_size =
+      static_cast<int>(ConsumeField<uint16_t>(buffer)) * sizeof(uint32_t);
+
+  return header;
+}
+
+RtcpReportBlock::RtcpReportBlock() = default;
+RtcpReportBlock::~RtcpReportBlock() = default;
+
+void RtcpReportBlock::AppendFields(ByteBuffer& buffer) const {
+  OSP_CHECK_GE(buffer.size(), kRtcpReportBlockSize);
+
+  AppendField<uint32_t>(ssrc, buffer);
+  OSP_CHECK_GE(packet_fraction_lost_numerator,
+               std::numeric_limits<uint8_t>::min());
+  OSP_CHECK_LE(packet_fraction_lost_numerator,
+               std::numeric_limits<uint8_t>::max());
+  OSP_CHECK_GE(cumulative_packets_lost, 0);
+  OSP_CHECK_LE(cumulative_packets_lost,
+               FieldBitmask<int>(kRtcpCumulativePacketsFieldNumBits));
+  AppendField<uint32_t>(
+      (static_cast<int>(packet_fraction_lost_numerator)
+       << kRtcpCumulativePacketsFieldNumBits) |
+          (static_cast<int>(cumulative_packets_lost) &
+           FieldBitmask<uint32_t>(kRtcpCumulativePacketsFieldNumBits)),
+      buffer);
+  AppendField<uint32_t>(extended_high_sequence_number, buffer);
+  const int64_t jitter_ticks = jitter / RtpTimeDelta::FromTicks(1);
+  OSP_CHECK_GE(jitter_ticks, 0);
+  OSP_CHECK_LE(jitter_ticks, int64_t{std::numeric_limits<uint32_t>::max()});
+  AppendField<uint32_t>(jitter_ticks, buffer);
+  AppendField<uint32_t>(last_status_report_id, buffer);
+  const int64_t delay_ticks = delay_since_last_report.count();
+  OSP_CHECK_GE(delay_ticks, 0);
+  OSP_CHECK_LE(delay_ticks, int64_t{std::numeric_limits<uint32_t>::max()});
+  AppendField<uint32_t>(delay_ticks, buffer);
+}
+
+void RtcpReportBlock::SetPacketFractionLostNumerator(
+    int64_t num_apparently_sent,
+    int64_t num_received) {
+  if (num_apparently_sent <= 0) {
+    packet_fraction_lost_numerator = 0;
+    return;
+  }
+  // The following computes the fraction of packets lost as "one minus
+  // `num_received` divided by `num_apparently_sent`" and scales by 256 (the
+  // kPacketFractionLostDenominator). It's valid for `num_received` to be
+  // greater than `num_apparently_sent` in some cases (e.g., if duplicate
+  // packets were received from the network).
+  const int64_t numerator =
+      ((num_apparently_sent - num_received) * kPacketFractionLostDenominator) /
+      num_apparently_sent;
+  // Since the value must be in the range [0,255], just do a saturate_cast
+  // to the uint8_t type to clamp.
+  packet_fraction_lost_numerator = saturate_cast<uint8_t>(numerator);
+}
+
+void RtcpReportBlock::SetCumulativePacketsLost(int64_t num_apparently_sent,
+                                               int64_t num_received) {
+  const int64_t num_lost = num_apparently_sent - num_received;
+  // Clamp to valid range supported by the wire format (and RTP spec).
+  //
+  // Note that `num_lost` can be negative if duplicate packets were received.
+  // The RFC spec (https://tools.ietf.org/html/rfc3550#section-6.4.1) states
+  // this should result in a clamped, "zero loss" value.
+  cumulative_packets_lost = static_cast<int>(
+      std::min(std::max<int64_t>(num_lost, 0),
+               FieldBitmask<int64_t>(kRtcpCumulativePacketsFieldNumBits)));
+}
+
+void RtcpReportBlock::SetDelaySinceLastReport(
+    Clock::duration local_clock_delay) {
+  // Clamp to valid range supported by the wire format (and RTP spec). The
+  // bounds checking is done in terms of Clock::duration, since doing the checks
+  // after the duration_cast may allow overflow to occur in the duration_cast
+  // math (well, only for unusually large inputs).
+  constexpr Delay kMaxValidReportedDelay(std::numeric_limits<uint32_t>::max());
+  constexpr auto kMaxValidLocalClockDelay =
+      Clock::to_duration(kMaxValidReportedDelay);
+  if (local_clock_delay > kMaxValidLocalClockDelay) {
+    delay_since_last_report = kMaxValidReportedDelay;
+    return;
+  }
+  if (local_clock_delay <= Clock::duration::zero()) {
+    delay_since_last_report = Delay::zero();
+    return;
+  }
+
+  // If this point is reached, then the `local_clock_delay` is representable as
+  // a Delay within the valid range.
+  delay_since_last_report =
+      std::chrono::duration_cast<Delay>(local_clock_delay);
+}
+
+// static
+std::optional<RtcpReportBlock> RtcpReportBlock::ParseOne(ByteView buffer,
+                                                         int report_count,
+                                                         Ssrc ssrc) {
+  if (static_cast<int>(buffer.size()) < (kRtcpReportBlockSize * report_count)) {
+    return std::nullopt;
+  }
+
+  std::optional<RtcpReportBlock> result;
+  for (int block = 0; block < report_count; ++block) {
+    if (ConsumeField<uint32_t>(buffer) != ssrc) {
+      // Skip-over report block meant for some other recipient.
+      buffer = buffer.subspan(kRtcpReportBlockSize - sizeof(uint32_t));
+      continue;
+    }
+
+    RtcpReportBlock& report_block = result.emplace();
+    report_block.ssrc = ssrc;
+    const auto second_word = ConsumeField<uint32_t>(buffer);
+    report_block.packet_fraction_lost_numerator =
+        second_word >> kRtcpCumulativePacketsFieldNumBits;
+    report_block.cumulative_packets_lost =
+        second_word &
+        FieldBitmask<uint32_t>(kRtcpCumulativePacketsFieldNumBits);
+    report_block.extended_high_sequence_number = ConsumeField<uint32_t>(buffer);
+    report_block.jitter =
+        RtpTimeDelta::FromTicks(ConsumeField<uint32_t>(buffer));
+    report_block.last_status_report_id = ConsumeField<uint32_t>(buffer);
+    report_block.delay_since_last_report =
+        RtcpReportBlock::Delay(ConsumeField<uint32_t>(buffer));
+  }
+  return result;
+}
+
+RtcpSenderReport::RtcpSenderReport() = default;
+RtcpSenderReport::~RtcpSenderReport() = default;
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/rtcp_common.h

@@ -0,0 +1,203 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_RTCP_COMMON_H_
+#define CAST_STREAMING_IMPL_RTCP_COMMON_H_
+
+#include <stdint.h>
+
+#include <optional>
+#include <tuple>
+#include <vector>
+
+#include "cast/streaming/impl/ntp_time.h"
+#include "cast/streaming/impl/rtp_defines.h"
+#include "cast/streaming/impl/statistics_common.h"
+#include "cast/streaming/public/frame_id.h"
+#include "cast/streaming/rtp_time.h"
+#include "cast/streaming/ssrc.h"
+#include "platform/base/span.h"
+
+namespace openscreen::cast {
+
+struct RtcpCommonHeader {
+  RtcpCommonHeader();
+  ~RtcpCommonHeader();
+
+  RtcpPacketType packet_type = RtcpPacketType::kNull;
+
+  union {
+    // The number of report blocks if `packet_type` is kSenderReport or
+    // kReceiverReport.
+    int report_count;
+
+    // Indicates the type of an application-defined message if `packet_type` is
+    // kApplicationDefined or kPayloadSpecific.
+    RtcpSubtype subtype;
+
+    // Otherwise, not used.
+  } with{0};
+
+  // The size (in bytes) of the RTCP packet, not including the header.
+  int payload_size = 0;
+
+  // Serializes this header into the first `kRtcpCommonHeaderSize` bytes of the
+  // given `buffer` and adjusts `buffer` to point to the first byte after it.
+  void AppendFields(ByteBuffer& buffer) const;
+
+  // Parse from the 4-byte wire format in `buffer`. Returns nullopt if the data
+  // is corrupt.
+  static std::optional<RtcpCommonHeader> Parse(ByteView buffer);
+};
+
+// The middle 32-bits of the 64-bit NtpTimestamp field from the Sender Reports.
+// This is used as an opaque identifier that the Receiver will use in its
+// reports to refer to specific previous Sender Reports.
+using StatusReportId = uint32_t;
+constexpr StatusReportId ToStatusReportId(NtpTimestamp ntp_timestamp) {
+  return static_cast<uint32_t>(ntp_timestamp >> 16);
+}
+
+// One of these is optionally included with a Sender Report or a Receiver
+// Report. See: https://tools.ietf.org/html/rfc3550#section-6.4.1
+struct RtcpReportBlock {
+  RtcpReportBlock();
+  ~RtcpReportBlock();
+
+  // The intended recipient of this report block.
+  Ssrc ssrc = 0;
+
+  // The fraction of RTP packets lost since the last report, specified as a
+  // variable numerator and fixed denominator. The numerator will always be in
+  // the range [0,255] since, semantically:
+  //
+  //   a. Negative values are impossible.
+  //   b. Values greater than 255 would indicate 100% packet loss, and so a
+  //      report block would not be generated in the first place.
+  int packet_fraction_lost_numerator = 0;
+  static constexpr int kPacketFractionLostDenominator = 256;
+
+  // The total number of RTP packets lost since the start of the session. This
+  // value will always be in the range [0,2^24-1], as the wire format only
+  // provides 24 bits; so, wrap-around is possible.
+  int cumulative_packets_lost = 0;
+
+  // The highest sequence number received in any RTP packet. Wrap-around is
+  // possible.
+  uint32_t extended_high_sequence_number = 0;
+
+  // An estimate of the recent variance in RTP packet arrival times.
+  RtpTimeDelta jitter;
+
+  // The last Status Report received.
+  StatusReportId last_status_report_id{};
+
+  // The delay between when the peer received the most-recent Status Report and
+  // when this report was sent. The timebase is 65536 ticks per second and,
+  // because of the wire format, this value will always be in the range
+  // [0,65536) seconds.
+  using Delay = std::chrono::duration<int64_t, std::ratio<1, 65536>>;
+  Delay delay_since_last_report{};
+
+  // Convenience helper to compute/assign the `packet_fraction_lost_numerator`,
+  // based on the `num_apparently_sent` and `num_received` packet counts since
+  // the last report was sent.
+  void SetPacketFractionLostNumerator(int64_t num_apparently_sent,
+                                      int64_t num_received);
+
+  // Convenience helper to compute/assign the `cumulative_packets_lost`, based
+  // on the `num_apparently_sent` and `num_received` packet counts since the
+  // start of the entire session.
+  void SetCumulativePacketsLost(int64_t num_apparently_sent,
+                                int64_t num_received);
+
+  // Convenience helper to convert the given `local_clock_delay` to the
+  // RtcpReportBlock::Delay timebase, then clamp and assign it to
+  // `delay_since_last_report`.
+  void SetDelaySinceLastReport(Clock::duration local_clock_delay);
+
+  // Serializes this report block in the first `kRtcpReportBlockSize` bytes of
+  // the given `buffer` and adjusts `buffer` to point to the first byte after
+  // it.
+  void AppendFields(ByteBuffer& buffer) const;
+
+  // Scans the wire-format report blocks in `buffer`, searching for one with the
+  // matching `ssrc` and, if found, returns the parse result. Returns nullopt if
+  // the data is corrupt or no report block with the matching SSRC was found.
+  static std::optional<RtcpReportBlock> ParseOne(ByteView buffer,
+                                                 int report_count,
+                                                 Ssrc ssrc);
+};
+
+struct RtcpSenderReport {
+  RtcpSenderReport();
+  ~RtcpSenderReport();
+
+  // The point-in-time at which this report was sent, according to both: 1) the
+  // common reference clock shared by all RTP streams; 2) the RTP timestamp on
+  // the media capture/playout timeline. Together, these are used by a Receiver
+  // to achieve A/V synchronization across RTP streams for playout.
+  Clock::time_point reference_time{};
+  RtpTimeTicks rtp_timestamp;
+
+  // The total number of RTP packets transmitted since the start of the session
+  // (wrap-around is possible).
+  uint32_t send_packet_count = 0;
+
+  // The total number of payload bytes transmitted in RTP packets since the
+  // start of the session (wrap-around is possible).
+  uint32_t send_octet_count = 0;
+
+  // The report block, if present. While the RTCP spec allows for zero or
+  // multiple reports, Cast Streaming only uses zero or one.
+  std::optional<RtcpReportBlock> report_block;
+};
+
+// A pair of IDs that refers to a specific missing packet within a frame. If
+// `packet_id` is kAllPacketsLost, then it represents all the packets of a
+// frame.
+struct PacketNack {
+  FrameId frame_id;
+  FramePacketId packet_id;
+
+  constexpr bool operator==(const PacketNack& other) const {
+    return frame_id == other.frame_id && packet_id == other.packet_id;
+  }
+  constexpr bool operator!=(const PacketNack& other) const {
+    return frame_id != other.frame_id || packet_id != other.packet_id;
+  }
+  constexpr bool operator<(const PacketNack& other) const {
+    return (frame_id < other.frame_id) ||
+           (frame_id == other.frame_id && packet_id < other.packet_id);
+  }
+};
+
+// Statistics events sent from the receiver over RTCP.
+struct RtcpReceiverEventLogMessage {
+  // The statistics event type, may be either a receiver side frame event or
+  // packet event.
+  StatisticsEvent::Type type;
+
+  // The time at which this event occurred.
+  Clock::time_point timestamp;
+
+  // Only set for frame played out events.
+  // If this value is zero the frame is rendered on time.
+  // If this value is positive it means the frame is rendered late.
+  // If this value is negative it means the frame is rendered early.
+  Clock::duration delay;
+
+  // Only set for packet events.
+  // The ID of the packet associated with this event.
+  FramePacketId packet_id;
+};
+
+struct RtcpReceiverFrameLogMessage {
+  RtpTimeTicks rtp_timestamp;
+  std::vector<RtcpReceiverEventLogMessage> messages;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_RTCP_COMMON_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/rtcp_session.cc

@@ -0,0 +1,25 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/rtcp_session.h"
+
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+RtcpSession::RtcpSession(Ssrc sender_ssrc,
+                         Ssrc receiver_ssrc,
+                         Clock::time_point start_time)
+    : sender_ssrc_(sender_ssrc),
+      receiver_ssrc_(receiver_ssrc),
+      start_time_(start_time),
+      ntp_converter_(start_time) {
+  OSP_CHECK_NE(sender_ssrc_, kNullSsrc);
+  OSP_CHECK_NE(receiver_ssrc_, kNullSsrc);
+  OSP_CHECK_NE(sender_ssrc_, receiver_ssrc_);
+}
+
+RtcpSession::~RtcpSession() = default;
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/rtcp_session.h

@@ -0,0 +1,43 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_RTCP_SESSION_H_
+#define CAST_STREAMING_IMPL_RTCP_SESSION_H_
+
+#include "cast/streaming/impl/ntp_time.h"
+#include "cast/streaming/ssrc.h"
+
+namespace openscreen::cast {
+
+// Session-level configuration and shared components for the RTCP messaging
+// associated with a single Cast RTP stream. Multiple packet serialization and
+// parsing components share a single RtcpSession instance for data consistency.
+class RtcpSession {
+ public:
+  // `start_time` should be the current time, as it is used by NtpTimeConverter
+  // to set a fixed reference point between the local Clock and current "real
+  // world" wall time.
+  RtcpSession(Ssrc sender_ssrc,
+              Ssrc receiver_ssrc,
+              Clock::time_point start_time);
+  ~RtcpSession();
+
+  Ssrc sender_ssrc() const { return sender_ssrc_; }
+  Ssrc receiver_ssrc() const { return receiver_ssrc_; }
+  const NtpTimeConverter& ntp_converter() const { return ntp_converter_; }
+  Clock::time_point start_time() const { return start_time_; }
+
+ private:
+  const Ssrc sender_ssrc_;
+  const Ssrc receiver_ssrc_;
+
+  Clock::time_point start_time_;
+
+  // Translates between system time (internal format) and NTP (wire format).
+  NtpTimeConverter ntp_converter_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_RTCP_SESSION_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/rtp_defines.cc

@@ -0,0 +1,113 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/rtp_defines.h"
+
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+RtpPayloadType GetPayloadType(AudioCodec codec, bool use_android_rtp_hack) {
+  if (use_android_rtp_hack) {
+    return RtpPayloadType::kAudioHackForAndroidTV;
+  }
+
+  switch (codec) {
+    case AudioCodec::kAac:
+      return RtpPayloadType::kAudioAac;
+    case AudioCodec::kOpus:
+      return RtpPayloadType::kAudioOpus;
+    case AudioCodec::kNotSpecified:
+      return RtpPayloadType::kAudioVarious;
+    default:
+      OSP_NOTREACHED();
+  }
+}
+
+RtpPayloadType GetPayloadType(VideoCodec codec, bool use_android_rtp_hack) {
+  if (use_android_rtp_hack) {
+    return RtpPayloadType::kVideoHackForAndroidTV;
+  }
+  switch (codec) {
+    // VP8 and VP9 share the same payload type.
+    case VideoCodec::kVp9:
+    case VideoCodec::kVp8:
+      return RtpPayloadType::kVideoVp8;
+
+    // H264 and HEVC/H265 share the same payload type.
+    case VideoCodec::kHevc:  // fallthrough
+    case VideoCodec::kH264:
+      return RtpPayloadType::kVideoH264;
+
+    case VideoCodec::kAv1:
+      return RtpPayloadType::kVideoAv1;
+
+    case VideoCodec::kNotSpecified:
+      return RtpPayloadType::kVideoVarious;
+
+    default:
+      OSP_NOTREACHED();
+  }
+}
+
+StreamType ToStreamType(RtpPayloadType type, bool use_android_rtp_hack) {
+  if (use_android_rtp_hack) {
+    if (type == RtpPayloadType::kAudioHackForAndroidTV) {
+      return StreamType::kAudio;
+    }
+    if (type == RtpPayloadType::kVideoHackForAndroidTV) {
+      return StreamType::kVideo;
+    }
+  }
+
+  if (RtpPayloadType::kAudioFirst <= type &&
+      type <= RtpPayloadType::kAudioLast) {
+    return StreamType::kAudio;
+  }
+  if (RtpPayloadType::kVideoFirst <= type &&
+      type <= RtpPayloadType::kVideoLast) {
+    return StreamType::kVideo;
+  }
+  return StreamType::kUnknown;
+}
+
+bool IsRtpPayloadType(uint8_t raw_byte) {
+  switch (static_cast<RtpPayloadType>(raw_byte)) {
+    case RtpPayloadType::kAudioOpus:
+    case RtpPayloadType::kAudioAac:
+    case RtpPayloadType::kAudioPcm16:
+    case RtpPayloadType::kAudioVarious:
+    case RtpPayloadType::kVideoVp8:
+    case RtpPayloadType::kVideoH264:
+    case RtpPayloadType::kVideoVp9:
+    case RtpPayloadType::kVideoAv1:
+    case RtpPayloadType::kVideoVarious:
+    case RtpPayloadType::kAudioHackForAndroidTV:
+      // Note: RtpPayloadType::kVideoHackForAndroidTV has the same value as
+      // kAudioOpus.
+      return true;
+
+    case RtpPayloadType::kNull:
+      break;
+  }
+  return false;
+}
+
+bool IsRtcpPacketType(uint8_t raw_byte) {
+  switch (static_cast<RtcpPacketType>(raw_byte)) {
+    case RtcpPacketType::kSenderReport:
+    case RtcpPacketType::kReceiverReport:
+    case RtcpPacketType::kSourceDescription:
+    case RtcpPacketType::kApplicationDefined:
+    case RtcpPacketType::kPayloadSpecific:
+    case RtcpPacketType::kExtendedReports:
+      return true;
+
+    case RtcpPacketType::kNull:
+      break;
+  }
+  return false;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/rtp_defines.h

@@ -0,0 +1,382 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_RTP_DEFINES_H_
+#define CAST_STREAMING_IMPL_RTP_DEFINES_H_
+
+#include <stdint.h>
+
+#include "cast/streaming/public/constants.h"
+
+namespace openscreen::cast {
+
+// Note: Cast Streaming uses a subset of the messages in the RTP/RTCP
+// specification, but also adds some of its own extensions. See:
+// https://tools.ietf.org/html/rfc3550
+
+// Uniquely identifies one packet within a frame. These are sequence numbers,
+// starting at 0. Each Cast RTP packet also includes the "last ID" so that a
+// receiver always knows the range of valid FramePacketIds for a given frame.
+using FramePacketId = uint16_t;
+
+// A special FramePacketId value meant to represent "all packets lost" in Cast
+// RTCP Feedback messages.
+inline constexpr FramePacketId kAllPacketsLost = 0xffff;
+inline constexpr FramePacketId kMaxAllowedFramePacketId = kAllPacketsLost - 1;
+
+// The maximum size of any RTP or RTCP packet, in bytes. The calculation below
+// is: Standard Ethernet MTU bytes minus IP header bytes minus UDP header bytes.
+// The remainder is available for RTP/RTCP packet data (header + payload).
+//
+// A nice explanation of this: https://jvns.ca/blog/2017/02/07/mtu/
+//
+// Constants are provided here for UDP over IPv4 and IPv6 on Ethernet. Other
+// transports and network mediums will need additional consideration, alternate
+// calculations. Note that MTU is dynamic, depending on the path the packets
+// take between two endpoints (the 1500 here is just a commonly-used value for
+// LAN Ethernet).
+inline constexpr int kMaxRtpPacketSizeForIpv4UdpOnEthernet = 1500 - 20 - 8;
+inline constexpr int kMaxRtpPacketSizeForIpv6UdpOnEthernet = 1500 - 40 - 8;
+
+// The Cast RTP packet header:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ^
+// |V=2|P|X| CC=0  |M|      PT     |      sequence number          | |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+RTP
+// +                         RTP timestamp                         |Spec
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
+// +         synchronization source (SSRC) identifier              | v
+// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+// |K|R| EXT count |  FID          |              PID              | ^
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+Cast
+// |             Max PID           |  optional fields, extensions,  Spec
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  then payload...                v
+//
+// Byte 0:  Version 2, no padding, no RTP extensions, no CSRCs.
+// Byte 1:  Marker bit indicates whether this is the last packet, followed by a
+//          7-bit payload type.
+// Byte 12: Key Frame bit, followed by "RFID will be provided" bit, followed by
+//          6 bits specifying the number of extensions that will be provided.
+
+// The minimum-possible valid size of a Cast RTP packet (i.e., no optional
+// fields, extensions, nor payload).
+inline constexpr int kRtpPacketMinValidSize = 18;
+
+// All Cast RTP packets must carry the version 2 flag, not use padding, not use
+// RTP extensions, and have zero CSRCs.
+inline constexpr uint8_t kRtpRequiredFirstByte = 0b10000000;
+
+// Bitmasks to isolate fields within byte 2 of the Cast RTP header.
+inline constexpr uint8_t kRtpMarkerBitMask = 0b10000000;
+inline constexpr uint8_t kRtpPayloadTypeMask = 0b01111111;
+
+// Describes the content being transported over RTP streams. These are Cast
+// Streaming specific assignments, within the "dynamic" range provided by
+// IANA. Note that this Cast Streaming implementation does not manipulate
+// already-encoded data, and so these payload types are only "informative" in
+// purpose and can be used to check for corruption while parsing packets.
+enum class RtpPayloadType : uint8_t {
+  kNull = 0,
+
+  kAudioFirst = 96,
+  kAudioOpus = 96,
+  kAudioAac = 97,
+  kAudioPcm16 = 98,
+  kAudioVarious = 99,  // Codec being used is not fixed.
+  kAudioLast = kAudioVarious,
+
+  kVideoFirst = 100,
+  kVideoVp8 = 100,
+  kVideoH264 = 101,
+  kVideoVarious = 102,  // Codec being used is not fixed.
+  kVideoVp9 = 103,
+  kVideoAv1 = 104,
+  kVideoLast = kVideoAv1,
+
+  // Some AndroidTV receivers require the payload type for audio to be 127, and
+  // video to be 96; regardless of the codecs actually being used. This is
+  // definitely out-of-spec, and inconsistent with the audio versus video range
+  // of values, but must be taken into account for backwards-compatibility.
+  kAudioHackForAndroidTV = 127,
+  kVideoHackForAndroidTV = 96,
+};
+
+// Returns the stream type associated with the RTP payload type.
+StreamType ToStreamType(RtpPayloadType type, bool use_android_rtp_hack);
+
+// Setting `use_android_rtp_hack` to true means that we match the legacy Chrome
+// sender's behavior of always sending the audio and video hacks for AndroidTV,
+// as some legacy android receivers require these.
+// TODO(issuetracker.google.com/184438154): we need to figure out what receivers
+// need this still, if any. The hack should be removed when possible.
+RtpPayloadType GetPayloadType(AudioCodec codec, bool use_android_rtp_hack);
+RtpPayloadType GetPayloadType(VideoCodec codec, bool use_android_rtp_hack);
+
+// Returns true if the `raw_byte` can be type-casted to a RtpPayloadType, and is
+// also not RtpPayloadType::kNull. The caller should mask the byte, to select
+// the lower 7 bits, if applicable.
+bool IsRtpPayloadType(uint8_t raw_byte);
+
+// Bitmasks to isolate fields within byte 12 of the Cast RTP header.
+inline constexpr uint8_t kRtpKeyFrameBitMask = 0b10000000;
+inline constexpr uint8_t kRtpHasReferenceFrameIdBitMask = 0b01000000;
+inline constexpr uint8_t kRtpExtensionCountMask = 0b00111111;
+
+// Cast extensions. This implementation supports only the Adaptive Latency
+// extension, and ignores all others:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |  TYPE = 1 | Ext data SIZE = 2 |Playout Delay (unsigned millis)|
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//
+// The Adaptive Latency extension permits changing the fixed end-to-end playout
+// delay of a single RTP stream.
+inline constexpr uint8_t kAdaptiveLatencyRtpExtensionType = 1;
+inline constexpr int kNumExtensionDataSizeFieldBits = 10;
+
+// RTCP Common Header:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |V=2|P|RC/Subtyp|  Packet Type  |            Length             |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+inline constexpr int kRtcpCommonHeaderSize = 4;
+// All RTCP packets must carry the version 2 flag and not use padding.
+inline constexpr uint8_t kRtcpRequiredVersionAndPaddingBits = 0b100;
+inline constexpr int kRtcpReportCountFieldNumBits = 5;
+
+// https://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml
+enum class RtcpPacketType : uint8_t {
+  kNull = 0,
+
+  kSenderReport = 200,
+  kReceiverReport = 201,
+  kSourceDescription = 202,
+  kApplicationDefined = 204,
+  kPayloadSpecific = 206,
+  kExtendedReports = 207,
+};
+
+// Returns true if the `raw_byte` can be type-casted to a RtcpPacketType, and is
+// also not RtcpPacketType::kNull.
+bool IsRtcpPacketType(uint8_t raw_byte);
+
+// Supported subtype values in the RTCP Common Header when the packet type is
+// kApplicationDefined or kPayloadSpecific.
+enum class RtcpSubtype : uint8_t {
+  kNull = 0,
+
+  kPictureLossIndicator = 1,
+  kReceiverLog = 2,
+  kFeedback = 15,
+};
+
+// RTCP Sender Report:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                        SSRC of Sender                         |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                                                               |
+// |                         NTP Timestamp                         |
+// |                                                               |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                         RTP Timestamp                         |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                     Sender's Packet Count                     |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                     Sender's Octet Count                      |
+// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+//        ...Followed by zero or more "Report Blocks"...
+inline constexpr int kRtcpSenderReportSize = 24;
+
+// RTCP Receiver Report:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                       SSRC of Receiver                        |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//        ...Followed by zero or more "Report Blocks"...
+inline constexpr int kRtcpReceiverReportSize = 4;
+
+// RTCP Report Block. For Cast Streaming, zero or one of these accompanies a
+// Sender or Receiver Report, which is different than the RTCP spec (which
+// allows zero or more).
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                           "To" SSRC                           |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Fraction Lost |       Cumulative Number of Packets Lost       |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |      [32-bit extended] Highest Sequence Number Received       |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Interarrival Jitter Mean Absolute Deviation (in RTP Timebase) |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |    Middle 32-bits of NTP Timestamp from last Sender Report    |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |     Delay since last Sender Report (1/65536 sec timebase)     |
+// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+inline constexpr int kRtcpReportBlockSize = 24;
+inline constexpr int kRtcpCumulativePacketsFieldNumBits = 24;
+
+// Cast Feedback Message:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                       SSRC of Receiver                        |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                        SSRC of Sender                         |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |               Unique identifier 'C' 'A' 'S' 'T'               |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | CkPt Frame ID | # Loss Fields | Current Playout Delay (msec)  |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+inline constexpr int kRtcpFeedbackHeaderSize = 16;
+inline constexpr uint32_t kRtcpCastIdentifierWord =
+    (uint32_t{'C'} << 24) | (uint32_t{'A'} << 16) | (uint32_t{'S'} << 8) |
+    uint32_t{'T'};
+//
+// "Checkpoint Frame ID" indicates that all frames prior to and including this
+// one have been fully received. Unfortunately, the Frame ID is truncated to its
+// lower 8 bits in the packet, and 8 bits is not really enough: If a RTCP packet
+// is received very late (e.g., more than 1.2 seconds late for 100 FPS audio),
+// the Checkpoint Frame ID here will be mis-interpreted as representing a
+// higher-numbered frame than what was intended. This could make the sender's
+// tracking of "completely received" frames inconsistent, and Cast Streaming
+// would live-lock. However, this design issue has been baked into the spec and
+// millions of deployments over several years, and so there's no changing it
+// now. See kMaxUnackedFrames in constants.h.
+//
+// "# Loss fields" indicates the number of packet-level NACK words, 0 to 255:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | w/in Frame ID | Lost Frame Packet ID          | PID BitVector |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+inline constexpr int kRtcpFeedbackLossFieldSize = 4;
+//
+// "Within Frame ID" is a truncated-to-8-bits frame ID field and, when
+// bit-expanded should always be interpreted to represent a value greater than
+// the Checkpoint Frame ID. "Lost Frame Packet ID" is either a specific packet
+// (within the frame) that has not been received, or kAllPacketsLost to indicate
+// none the packets for the frame have been received yet. In the former case,
+// "PID Bit Vector" then represents which of the next 8 packets are also
+// missing.
+//
+// Finally, all of the above is optionally followed by a frame-level ACK bit
+// vector:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |               Unique identifier 'C' 'S' 'T' '2'               |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |Feedback Count | # BVectOctets | ACK BitVect (2 to 254 bytes)...
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ → zero-padded to word boundary
+inline constexpr int kRtcpFeedbackAckHeaderSize = 6;
+inline constexpr uint32_t kRtcpCst2IdentifierWord =
+    (uint32_t{'C'} << 24) | (uint32_t{'S'} << 16) | (uint32_t{'T'} << 8) |
+    uint32_t{'2'};
+inline constexpr int kRtcpMinAckBitVectorOctets = 2;
+inline constexpr int kRtcpMaxAckBitVectorOctets = 254;
+//
+// "Feedback Count" is a wrap-around counter indicating the number of Cast
+// Feedbacks that have been sent before this one. "# Bit Vector Octets"
+// indicates the number of bytes of ACK bit vector following. Cast RTCP
+// alignment/padding requirements (to 4-byte boundaries) dictates the following
+// rules for generating the ACK bit vector:
+//
+//   1. There must be at least 2 bytes of ACK bit vector, if only to pad the 6
+//      byte header with two more bytes.
+//   2. If more than 2 bytes are needed, they must be added 4 at a time to
+//      maintain the 4-byte alignment of the overall RTCP packet.
+//   3. The total number of octets may not exceed 255; but, because of #2, 254
+//      is effectively the limit.
+//   4. The first bit in the first octet represents "Checkpoint Frame ID" plus
+//      two. "Plus two" and not "plus one" because otherwise the "Checkpoint
+//      Frame ID" should have been a greater value!
+
+// RTCP Extended Report:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                     SSRC of Report Author                     |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+inline constexpr int kRtcpExtendedReportHeaderSize = 4;
+//
+// ...followed by zero or more Blocks:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |  Block Type   | Reserved = 0  |       Block Length            |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |           ..."Block Length" words of report data...           |
+// +                                                               +
+// +                                                               +
+inline constexpr int kRtcpExtendedReportBlockHeaderSize = 4;
+//
+// Cast Streaming only uses Receiver Reference Time Reports:
+// https://tools.ietf.org/html/rfc3611#section-4.4. So, the entire block would
+// be:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Block Type=4  | Reserved = 0  |       Block Length = 2        |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                         NTP Timestamp                         |
+// |                                                               |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+inline constexpr uint8_t kRtcpReceiverReferenceTimeReportBlockType = 4;
+inline constexpr int kRtcpReceiverReferenceTimeReportBlockSize = 8;
+
+// Cast Picture Loss Indicator Message:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                       SSRC of Receiver                        |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                        SSRC of Sender                         |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+inline constexpr int kRtcpPictureLossIndicatorHeaderSize = 8;
+
+// The Cast Receiver RTCP frame log message is an application specific
+// extension that contains receiver side statistics about the Receiver Session.
+// The message format is:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                         RTP Timestamp                         |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Event Count   |                 Event Timestamp               |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+inline constexpr int kRtcpReceiverFrameLogMessageHeaderSize = 8;
+//
+// Followed by a list of zero or more event blocks:
+//
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Delay Delta or Packet ID      | Type  | Event Timestamp       |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+inline constexpr int kRtcpReceiverFrameLogMessageBlockSize = 4;
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_RTP_DEFINES_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/rtp_packetizer.cc

@@ -0,0 +1,133 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/rtp_packetizer.h"
+
+#include <algorithm>
+#include <limits>
+#include <random>
+
+#include "cast/streaming/impl/packet_util.h"
+#include "platform/api/time.h"
+#include "util/big_endian.h"
+#include "util/integer_division.h"
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+// Returns a random sequence number to start with. The reason for using a random
+// number instead of zero is unclear, but this has existed both in several
+// versions of the Cast Streaming spec and in other implementations for many
+// years.
+uint16_t GenerateRandomSequenceNumberStart() {
+  // Use a statically-allocated generator, instantiated upon first use, and
+  // seeded with the current time tick count. This generator was chosen because
+  // it is light-weight and does not need to produce unguessable (nor
+  // crypto-secure) values.
+  static std::minstd_rand generator(static_cast<std::minstd_rand::result_type>(
+      Clock::now().time_since_epoch().count()));
+
+  return std::uniform_int_distribution<uint16_t>()(generator);
+}
+
+}  // namespace
+
+RtpPacketizer::RtpPacketizer(RtpPayloadType payload_type,
+                             Ssrc sender_ssrc,
+                             int max_packet_size)
+    : payload_type_7bits_(static_cast<uint8_t>(payload_type)),
+      sender_ssrc_(sender_ssrc),
+      max_packet_size_(max_packet_size),
+      sequence_number_(GenerateRandomSequenceNumberStart()) {
+  OSP_CHECK(IsRtpPayloadType(payload_type_7bits_));
+  OSP_CHECK_GT(max_packet_size_, kMaxRtpHeaderSize);
+}
+
+RtpPacketizer::~RtpPacketizer() = default;
+
+ByteBuffer RtpPacketizer::GeneratePacket(const EncryptedFrame& frame,
+                                         FramePacketId packet_id,
+                                         ByteBuffer buffer) {
+  OSP_CHECK_GE(static_cast<int>(buffer.size()), max_packet_size_);
+
+  const int num_packets = ComputeNumberOfPackets(frame);
+  OSP_CHECK_GT(num_packets, 0);
+  OSP_CHECK_LT(int{packet_id}, num_packets);
+  const bool is_last_packet = int{packet_id} == (num_packets - 1);
+
+  // Compute the size of this packet, which is the number of bytes of header
+  // plus the number of bytes of payload. Note that the optional Adaptive
+  // Latency information is only added to the first packet.
+  int packet_size = kBaseRtpHeaderSize;
+  const bool include_adaptive_latency_change =
+      (packet_id == 0 &&
+       frame.new_playout_delay > std::chrono::milliseconds(0));
+  if (include_adaptive_latency_change) {
+    OSP_CHECK_LE(frame.new_playout_delay.count(),
+                 int{std::numeric_limits<uint16_t>::max()});
+    packet_size += kAdaptiveLatencyHeaderSize;
+  }
+  int data_chunk_size = max_payload_size();
+  const int data_chunk_start = data_chunk_size * int{packet_id};
+  if (is_last_packet) {
+    data_chunk_size = static_cast<int>(frame.data.size()) - data_chunk_start;
+  }
+  packet_size += data_chunk_size;
+  OSP_CHECK_LE(packet_size, max_packet_size_);
+  const ByteBuffer packet(buffer.data(), packet_size);
+
+  // RTP Header.
+  AppendField<uint8_t>(kRtpRequiredFirstByte, buffer);
+  AppendField<uint8_t>(
+      (is_last_packet ? kRtpMarkerBitMask : 0) | payload_type_7bits_, buffer);
+  AppendField<uint16_t>(sequence_number_++, buffer);
+  AppendField<uint32_t>(frame.rtp_timestamp.lower_32_bits(), buffer);
+  AppendField<uint32_t>(sender_ssrc_, buffer);
+
+  // Cast Header.
+  AppendField<uint8_t>(
+      ((frame.dependency == EncodedFrame::Dependency::kKeyFrame)
+           ? kRtpKeyFrameBitMask
+           : 0) |
+          kRtpHasReferenceFrameIdBitMask |
+          (include_adaptive_latency_change ? 1 : 0),
+      buffer);
+  AppendField<uint8_t>(frame.frame_id.lower_8_bits(), buffer);
+  AppendField<uint16_t>(packet_id, buffer);
+  AppendField<uint16_t>(num_packets - 1, buffer);
+  AppendField<uint8_t>(frame.referenced_frame_id.lower_8_bits(), buffer);
+
+  // Extension of Cast Header for Adaptive Latency change.
+  if (include_adaptive_latency_change) {
+    AppendField<uint16_t>(
+        (kAdaptiveLatencyRtpExtensionType << kNumExtensionDataSizeFieldBits) |
+            sizeof(uint16_t),
+        buffer);
+    AppendField<uint16_t>(frame.new_playout_delay.count(), buffer);
+  }
+
+  // Copy the encrypted payload data into the packet.
+  auto data_chunk = frame.data.subspan(data_chunk_start, data_chunk_size);
+  std::copy(data_chunk.begin(), data_chunk.end(), buffer.data());
+
+  return packet;
+}
+
+int RtpPacketizer::ComputeNumberOfPackets(const EncryptedFrame& frame) const {
+  // The total number of packets is computed by assuming the payload will be
+  // split-up across as few packets as possible.
+  int num_packets = DividePositivesRoundingUp(
+      static_cast<int>(frame.data.size()), max_payload_size());
+  // Edge case: There must always be at least one packet, even when there are no
+  // payload bytes. Some audio codecs, for example, use zero bytes to represent
+  // a period of silence.
+  num_packets = std::max(1, num_packets);
+
+  // Ensure that the entire range of FramePacketIds can be represented.
+  return num_packets <= int{kMaxAllowedFramePacketId} ? num_packets : -1;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/rtp_packetizer.h

@@ -0,0 +1,79 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_RTP_PACKETIZER_H_
+#define CAST_STREAMING_IMPL_RTP_PACKETIZER_H_
+
+#include <stdint.h>
+
+#include "cast/streaming/impl/frame_crypto.h"
+#include "cast/streaming/impl/rtp_defines.h"
+#include "cast/streaming/ssrc.h"
+#include "platform/base/span.h"
+
+namespace openscreen::cast {
+
+// Transforms a logical sequence of EncryptedFrames into RTP packets for
+// transmission. A single instance of RtpPacketizer should be used for all the
+// frames in a Cast RTP stream having the same SSRC.
+class RtpPacketizer {
+ public:
+  // `payload_type` describes the type of the media content for the RTP stream
+  // from the sender having the given `sender_ssrc`.
+  //
+  // The `max_packet_size` argument depends on the optimal over-the-wire size of
+  // packets for the network medium being used. See discussion in rtp_defines.h
+  // for further info.
+  RtpPacketizer(RtpPayloadType payload_type,
+                Ssrc sender_ssrc,
+                int max_packet_size);
+
+  ~RtpPacketizer();
+
+  // Wire-format one of the RTP packets for the given frame, which must only be
+  // transmitted once. This method should be called in the same sequence that
+  // packets will be transmitted. This also means that, if a packet needs to be
+  // re-transmitted, this method should be called to generate it again. Returns
+  // the subspan of `buffer` that contains the packet. `buffer` must be at least
+  // as large as the `max_packet_size` passed to the constructor.
+  ByteBuffer GeneratePacket(const EncryptedFrame& frame,
+                            FramePacketId packet_id,
+                            ByteBuffer buffer);
+
+  // Given `frame`, compute the total number of packets over which the whole
+  // frame will be split-up. Returns -1 if the frame is too large and cannot be
+  // packetized.
+  int ComputeNumberOfPackets(const EncryptedFrame& frame) const;
+
+  // See rtp_defines.h for wire-format diagram.
+  static constexpr int kBaseRtpHeaderSize =
+      // Plus one byte, because this implementation always includes the 8-bit
+      // Reference Frame ID field.
+      kRtpPacketMinValidSize + 1;
+  static constexpr int kAdaptiveLatencyHeaderSize = 4;
+  static constexpr int kMaxRtpHeaderSize =
+      kBaseRtpHeaderSize + kAdaptiveLatencyHeaderSize;
+
+ private:
+  int max_payload_size() const {
+    // Start with the configured max packet size, then subtract reserved space
+    // for packet header fields. The rest can be allocated to the payload.
+    return max_packet_size_ - kMaxRtpHeaderSize;
+  }
+
+  // The validated ctor RtpPayloadType arg, in wire-format form.
+  const uint8_t payload_type_7bits_;
+
+  const Ssrc sender_ssrc_;
+  const int max_packet_size_;
+
+  // Incremented each time GeneratePacket() is called. Every packet, even those
+  // re-transmitted, must have different sequence numbers (within wrap-around
+  // concerns) per the RTP spec.
+  uint16_t sequence_number_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_RTP_PACKETIZER_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/sender_impl.cc

@@ -0,0 +1,686 @@
+// Copyright 2026 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/sender_impl.h"
+
+#include <algorithm>
+#include <chrono>
+#include <ratio>
+#include <utility>
+
+#include "cast/streaming/impl/rtp_defines.h"
+#include "cast/streaming/impl/statistics_common.h"
+#include "cast/streaming/public/session_config.h"
+#include "platform/base/trivial_clock_traits.h"
+#include "util/chrono_helpers.h"
+#include "util/osp_logging.h"
+#include "util/std_util.h"
+#include "util/string_util.h"
+#include "util/trace_logging.h"
+
+namespace openscreen::cast {
+namespace {
+
+// The minimum amount of media the Sender keeps in-flight, regardless of the
+// measured network round-trip time. This keeps the encoder pipeline flowing on
+// low-latency networks (roughly two video frames at 30 FPS). See
+// crbug.com/498035450.
+constexpr Clock::duration kMinSenderInFlight =
+    Clock::to_duration(milliseconds(66));
+
+}  // namespace
+
+using clock_operators::operator<<;
+
+SenderImpl::SenderImpl(Environment& environment,
+                       SenderPacketRouter& packet_router,
+                       SessionConfig config,
+                       RtpPayloadType rtp_payload_type)
+    : config_(config),
+      packet_router_(packet_router),
+      rtcp_session_(config.sender_ssrc,
+                    config.receiver_ssrc,
+                    environment.now()),
+      rtcp_parser_(rtcp_session_, *this),
+      sender_report_builder_(rtcp_session_),
+      rtp_packetizer_(rtp_payload_type,
+                      config.sender_ssrc,
+                      packet_router_->max_packet_size()),
+      rtp_timebase_(config.rtp_timebase),
+      crypto_(config.aes_secret_key, config.aes_iv_mask),
+      statistics_dispatcher_(environment),
+      target_playout_delay_(config.target_playout_delay) {
+  OSP_CHECK_NE(rtcp_session_.sender_ssrc(), rtcp_session_.receiver_ssrc());
+  OSP_CHECK_GT(rtp_timebase_, 0);
+  OSP_CHECK_GT(target_playout_delay_, milliseconds::zero());
+
+  pending_sender_report_.reference_time = SenderPacketRouter::kNever;
+
+  packet_router_->OnSenderCreated(rtcp_session_.receiver_ssrc(), this);
+}
+
+SenderImpl::~SenderImpl() {
+  packet_router_->OnSenderDestroyed(rtcp_session_.receiver_ssrc());
+}
+
+void SenderImpl::SetObserver(openscreen::cast::Sender::Observer* observer) {
+  OSP_CHECK_NE(observer_, observer);
+  observer_ = observer;
+}
+
+size_t SenderImpl::GetInFlightFrameCount() const {
+  return num_frames_in_flight_;
+}
+
+Clock::duration SenderImpl::GetInFlightMediaDuration(
+    RtpTimeTicks next_frame_rtp_timestamp) const {
+  if (num_frames_in_flight_ == 0) {
+    return Clock::duration::zero();  // No frames are currently in-flight.
+  }
+
+  const PendingFrameSlot& oldest_slot = get_slot_for(checkpoint_frame_id_ + 1);
+  // Note: The oldest slot's frame cannot have been canceled because the
+  // protocol does not allow ACK'ing this particular frame without also moving
+  // the checkpoint forward. See "CST2 feedback" discussion in rtp_defines.h.
+  OSP_CHECK(oldest_slot.is_active_for_frame(checkpoint_frame_id_ + 1));
+
+  return (next_frame_rtp_timestamp - oldest_slot.frame->rtp_timestamp)
+      .ToDuration<Clock::duration>(rtp_timebase_);
+}
+
+Clock::duration SenderImpl::GetMaxInFlightMediaDuration() const {
+  // The Sender keeps only enough media in-flight to drive the loss-detection
+  // and retransmit feedback loop, which takes on the order of two network
+  // round-trips (one to detect a loss via NACK, one to retransmit). A small
+  // floor (`kMinSenderInFlight`) keeps the encoder pipeline flowing on
+  // low-latency networks where 2*RTT is negligible.
+  //
+  // The result is capped at a third of the playout delay window so that the
+  // majority of the budget is reserved for the Receiver, which needs buffer to
+  // absorb NACK retransmissions. Bounding the Sender this way also makes it
+  // drop frames earlier during congestion (saving bandwidth and CPU) rather
+  // than over-buffering. See crbug.com/498035450.
+  //
+  // Note: the upper bound is held at or above `kMinSenderInFlight` so the
+  // std::clamp() bounds remain well-ordered even for very small playout delays.
+  const Clock::duration max_in_flight = std::max(
+      kMinSenderInFlight, Clock::to_duration(target_playout_delay_) / 3);
+  return std::clamp(round_trip_time_ * 2, kMinSenderInFlight, max_in_flight);
+}
+
+bool SenderImpl::NeedsKeyFrame() const {
+  return last_enqueued_key_frame_id_ <= picture_lost_at_frame_id_;
+}
+
+FrameId SenderImpl::GetNextFrameId() const {
+  return last_enqueued_frame_id_ + 1;
+}
+
+Clock::duration SenderImpl::GetCurrentRoundTripTime() const {
+  return round_trip_time_;
+}
+
+openscreen::cast::Sender::EnqueueFrameResult SenderImpl::EnqueueFrame(
+    const EncodedFrame& frame) {
+  // Assume the fields of the `frame` have all been set correctly, with
+  // monotonically increasing timestamps and a valid pointer to the data.
+  OSP_CHECK_EQ(frame.frame_id, GetNextFrameId());
+  OSP_CHECK_GE(frame.referenced_frame_id, FrameId::first());
+  if (frame.frame_id != FrameId::first()) {
+    OSP_CHECK_GT(frame.rtp_timestamp, pending_sender_report_.rtp_timestamp);
+    if (frame.reference_time <= pending_sender_report_.reference_time) {
+      OSP_DLOG_WARN << "Frame " << frame.frame_id
+                    << " has non-monotonic reference_time: "
+                    << frame.reference_time
+                    << " <= " << pending_sender_report_.reference_time;
+    }
+  }
+  OSP_CHECK(frame.data.data());
+
+  const auto capture_begin_time =
+      (frame.capture_begin_time > Clock::time_point::min())
+          ? frame.capture_begin_time
+          : Clock::now();
+
+  TRACE_FLOW_BEGIN_WITH_TIME(TraceCategory::kSender, "Frame.Capture",
+                             frame.frame_id, capture_begin_time);
+
+  if (frame.capture_end_time > Clock::time_point::min()) {
+    TRACE_FLOW_STEP_WITH_TIME(TraceCategory::kSender, "Frame.Capture.End",
+                              frame.frame_id, frame.capture_end_time);
+  }
+
+  TRACE_FLOW_STEP(TraceCategory::kSender, "Frame.Encode.End", frame.frame_id);
+
+  // Check whether enqueuing the frame would exceed the design limit for the
+  // span of FrameIds. Even if `num_frames_in_flight_` is less than
+  // kMaxUnackedFrames, it's the span of FrameIds that is restricted.
+  if ((frame.frame_id - checkpoint_frame_id_) > kMaxUnackedFrames) {
+    return REACHED_ID_SPAN_LIMIT;
+  }
+
+  // Check whether enqueuing the frame would exceed the current maximum media
+  // duration limit.
+  if (GetInFlightMediaDuration(frame.rtp_timestamp) >
+      GetMaxInFlightMediaDuration()) {
+    return MAX_DURATION_IN_FLIGHT;
+  }
+
+  // Encrypt the frame and initialize the slot tracking its sending.
+  PendingFrameSlot& slot = get_slot_for(frame.frame_id);
+  OSP_CHECK(!slot.frame);
+  slot.frame = crypto_.Encrypt(frame);
+  const int packet_count = rtp_packetizer_.ComputeNumberOfPackets(*slot.frame);
+  if (packet_count <= 0) {
+    slot.frame.reset();
+    return PAYLOAD_TOO_LARGE;
+  }
+  slot.send_flags.Resize(packet_count, BitVector::SET);
+  slot.packet_sent_times.assign(packet_count, SenderPacketRouter::kNever);
+
+  // Officially record the "enqueue."
+  ++num_frames_in_flight_;
+  last_enqueued_frame_id_ = slot.frame->frame_id;
+  OSP_CHECK_LE(
+      num_frames_in_flight_,
+      static_cast<size_t>(last_enqueued_frame_id_ - checkpoint_frame_id_));
+  if (slot.frame->dependency == EncodedFrame::Dependency::kKeyFrame) {
+    last_enqueued_key_frame_id_ = slot.frame->frame_id;
+  }
+  TRACE_FLOW_STEP(TraceCategory::kSender, "Frame.Enqueued", frame.frame_id);
+
+  // Update the target playout delay, if necessary.
+  if (slot.frame->new_playout_delay > milliseconds::zero()) {
+    target_playout_delay_ = slot.frame->new_playout_delay;
+    playout_delay_change_at_frame_id_ = slot.frame->frame_id;
+  }
+
+  // Update the lip-sync information for the next Sender Report, ensuring that
+  // the reference time is monotonically increasing.
+  pending_sender_report_.reference_time =
+      frame.frame_id == FrameId::first()
+          ? slot.frame->reference_time
+          : std::max(slot.frame->reference_time,
+                     pending_sender_report_.reference_time);
+  pending_sender_report_.rtp_timestamp = slot.frame->rtp_timestamp;
+
+  // If the round trip time hasn't been computed yet, immediately send a RTCP
+  // packet (i.e., before the RTP packets are sent). The RTCP packet will
+  // provide a Sender Report which contains the required lip-sync information
+  // the Receiver needs for timing the media playout.
+  //
+  // Detail: Working backwards, if the round trip time is not known, then this
+  // Sender has never processed a Receiver Report. Thus, the Receiver has never
+  // provided a Receiver Report, which it can only do after having processed a
+  // Sender Report from this Sender. Thus, this Sender really needs to send
+  // that, right now!
+  if (round_trip_time_ == Clock::duration::zero()) {
+    packet_router_->RequestRtcpSend(rtcp_session_.receiver_ssrc());
+  }
+
+  // Re-activate RTP sending if it was suspended.
+  packet_router_->RequestRtpSend(rtcp_session_.receiver_ssrc());
+  statistics_dispatcher_.DispatchEnqueueEvents(config_.stream_type, frame);
+
+  return OK;
+}
+
+void SenderImpl::CancelInFlightData() {
+  TRACE_DEFAULT_SCOPED1(
+      TraceCategory::kSender, "frames_in_flight",
+      std::to_string(last_enqueued_frame_id_ - checkpoint_frame_id_));
+
+  while (checkpoint_frame_id_ < last_enqueued_frame_id_) {
+    ++checkpoint_frame_id_;
+    CancelPendingFrame(checkpoint_frame_id_, /*was_acked*/ false);
+  }
+  DispatchCancellations();
+}
+
+void SenderImpl::ReportFrameDropEvent(FrameId frame_id,
+                                      RtpTimeTicks rtp_timestamp,
+                                      Clock::time_point drop_time) {
+  statistics_dispatcher_.DispatchFrameDropEvent(config_.stream_type, frame_id,
+                                                rtp_timestamp, drop_time);
+}
+
+void SenderImpl::OnReceivedRtcpPacket(Clock::time_point arrival_time,
+                                      ByteView packet) {
+  rtcp_packet_arrival_time_ = arrival_time;
+  // This call to Parse() invoke zero or more of the OnReceiverXYZ() methods in
+  // the current call stack:
+  if (rtcp_parser_.Parse(packet, last_enqueued_frame_id_)) {
+    packet_router_->OnRtcpReceived(arrival_time, round_trip_time_);
+  }
+}
+
+ByteBuffer SenderImpl::GetRtcpPacketForImmediateSend(
+    Clock::time_point send_time,
+    ByteBuffer buffer) {
+  if (pending_sender_report_.reference_time == SenderPacketRouter::kNever) {
+    // Cannot send a report if one is not available (i.e., a frame has never
+    // been enqueued).
+    return buffer.subspan(0, 0);
+  }
+
+  // The Sender Report to be sent is a snapshot of the "pending Sender Report,"
+  // but with its timestamp fields modified. First, the reference time is set to
+  // the RTCP packet's send time. Then, the corresponding RTP timestamp is
+  // translated to match (for lip-sync).
+  RtcpSenderReport sender_report = pending_sender_report_;
+  sender_report.reference_time = send_time;
+  sender_report.rtp_timestamp += RtpTimeDelta::FromDuration(
+      sender_report.reference_time - pending_sender_report_.reference_time,
+      rtp_timebase_);
+
+  return sender_report_builder_.BuildPacket(sender_report, buffer).first;
+}
+
+ByteBuffer SenderImpl::GetRtpPacketForImmediateSend(Clock::time_point send_time,
+                                                    ByteBuffer buffer) {
+  ChosenPacket chosen = ChooseNextRtpPacketNeedingSend();
+
+  // If no packets need sending (i.e., all packets have been sent at least once
+  // and do not need to be re-sent yet), check whether a Kickstart packet should
+  // be sent. It's possible that there has been complete packet loss of some
+  // frames, and the Receiver may not be aware of the existence of the latest
+  // frame(s). Kickstarting is the only way the Receiver can discover the newer
+  // frames it doesn't know about.
+  if (!chosen) {
+    const ChosenPacketAndWhen kickstart = ChooseKickstartPacket();
+    if (kickstart.when > send_time) {
+      // Nothing to send, so return "empty" signal to the packet router. The
+      // packet router will suspend RTP sending until this Sender explicitly
+      // resumes it.
+      return buffer.subspan(0, 0);
+    }
+    chosen = kickstart;
+    OSP_CHECK(chosen);
+  }
+
+  const ByteBuffer result = rtp_packetizer_.GeneratePacket(
+      *chosen.slot->frame, chosen.packet_id, buffer);
+  chosen.slot->send_flags.Clear(chosen.packet_id);
+  chosen.slot->packet_sent_times[chosen.packet_id] = send_time;
+
+  ++pending_sender_report_.send_packet_count;
+  // According to RFC3550, the octet count does not include the RTP header. The
+  // following is just a good approximation, however, because the header size
+  // will very infrequently be 4 bytes greater (see
+  // RtpPacketizer::kAdaptiveLatencyHeaderSize). No known Cast Streaming
+  // Receiver implementations use this for anything, and so this should be fine.
+  const int approximate_octet_count =
+      static_cast<int>(result.size()) - RtpPacketizer::kBaseRtpHeaderSize;
+  OSP_CHECK_GE(approximate_octet_count, 0);
+  pending_sender_report_.send_octet_count += approximate_octet_count;
+
+  return result;
+}
+
+Clock::time_point SenderImpl::GetRtpResumeTime() {
+  if (ChooseNextRtpPacketNeedingSend()) {
+    return Alarm::kImmediately;
+  }
+  return ChooseKickstartPacket().when;
+}
+
+RtpTimeTicks SenderImpl::GetLastRtpTimestamp() const {
+  return {};
+}
+
+StreamType SenderImpl::GetStreamType() const {
+  return config_.stream_type;
+}
+
+void SenderImpl::OnReceiverReferenceTimeAdvanced(
+    Clock::time_point reference_time) {
+  // Not used.
+}
+
+// static
+Clock::duration SenderImpl::SmoothRoundTripTime(Clock::duration estimate,
+                                                Clock::duration measurement) {
+  // Measurements typically have high variance, so smooth them with an
+  // exponentially-weighted moving average. The filter is asymmetric ("fast
+  // attack, slow decay"): it reacts quickly to upward spikes so the Sender
+  // notices congestion onset promptly and backs off, but decays slowly on the
+  // way down so a single low sample doesn't collapse the estimate. See
+  // crbug.com/498036656.
+  if (estimate == Clock::duration::zero()) {
+    return measurement;
+  }
+  if (measurement > estimate) {
+    // Spike / congestion onset: give the new measurement half the weight so the
+    // estimate climbs quickly.
+    return (estimate + measurement) / 2;
+  }
+  // Recovery: give the new measurement 1/8 weight (and the old estimate 7/8) to
+  // de-noise, since downward measurements are typically the network settling
+  // rather than a sustained improvement.
+  constexpr int kInertia = 7;
+  return (kInertia * estimate + measurement) / (kInertia + 1);
+}
+
+void SenderImpl::OnReceiverReport(const RtcpReportBlock& receiver_report) {
+  OSP_CHECK_NE(rtcp_packet_arrival_time_, SenderPacketRouter::kNever);
+
+  const Clock::duration total_delay =
+      rtcp_packet_arrival_time_ -
+      sender_report_builder_.GetRecentReportTime(
+          receiver_report.last_status_report_id, rtcp_packet_arrival_time_);
+  const auto non_network_delay =
+      Clock::to_duration(receiver_report.delay_since_last_report);
+
+  // Round trip time measurement: This is the time elapsed since the Sender
+  // Report was sent, minus the time the Receiver did other stuff before sending
+  // the Receiver Report back.
+  //
+  // If the round trip time seems to be less than or equal to zero, assume clock
+  // imprecision by one or both peers caused a bad value to be calculated. The
+  // true value is likely very close to zero (i.e., this is ideal network
+  // behavior); and so just represent this as 75 µs, an optimistic
+  // wired-Ethernet LAN ping time.
+  constexpr auto kNearZeroRoundTripTime = Clock::to_duration(microseconds(75));
+  static_assert(kNearZeroRoundTripTime > Clock::duration::zero(),
+                "More precision in Clock::duration needed!");
+  const Clock::duration measurement =
+      std::max(total_delay - non_network_delay, kNearZeroRoundTripTime);
+
+  // Validate the measurement by using the current target playout delay as a
+  // "reasonable upper-bound." It's certainly possible that the actual network
+  // round-trip time could exceed the target playout delay, but that would mean
+  // the current network performance is totally inadequate for streaming anyway.
+  // We cap the measurement here instead of ignoring it so the Sender still
+  // backs off its estimates during severe network congestion.
+  Clock::duration clamped_measurement = measurement;
+  if (clamped_measurement > target_playout_delay_) {
+    OSP_LOG_WARN << "Capping round-trip time measurement (" << measurement
+                 << ") to the current target playout delay ("
+                 << target_playout_delay_ << ").";
+    clamped_measurement = target_playout_delay_;
+  }
+
+  round_trip_time_ = SmoothRoundTripTime(round_trip_time_, clamped_measurement);
+  TRACE_SCOPED1(TraceCategory::kSender, "UpdatedRoundTripTime",
+                "round_trip_time", ToString(round_trip_time_));
+}
+
+void SenderImpl::OnCastReceiverFrameLogMessages(
+    std::vector<RtcpReceiverFrameLogMessage> messages) {
+  statistics_dispatcher_.DispatchFrameLogMessages(config_.stream_type,
+                                                  messages);
+}
+
+void SenderImpl::OnReceiverIndicatesPictureLoss() {
+  TRACE_DEFAULT_SCOPED1(TraceCategory::kSender, "last_received_frame_id",
+                        picture_lost_at_frame_id_.ToString());
+  // The Receiver will continue the PLI notifications until it has received a
+  // key frame. Thus, if a key frame is already in-flight, don't make a state
+  // change that would cause this Sender to force another expensive key frame.
+  if (checkpoint_frame_id_ < last_enqueued_key_frame_id_) {
+    return;
+  }
+
+  picture_lost_at_frame_id_ = checkpoint_frame_id_;
+
+  if (observer_) {
+    observer_->OnPictureLost();
+  }
+
+  // Note: It may seem that all pending frames should be canceled until
+  // EnqueueFrame() is called with a key frame. However:
+  //
+  //   1. The Receiver should still be the main authority on what frames/packets
+  //      are being ACK'ed and NACK'ed.
+  //
+  //   2. It may be desirable for the Receiver to be "limping along" in the
+  //      meantime. For example, video may be corrupted but mostly watchable,
+  //      and so it's best for the Sender to continue sending the non-key frames
+  //      until the Receiver indicates otherwise.
+}
+
+void SenderImpl::OnReceiverCheckpoint(FrameId frame_id,
+                                      milliseconds playout_delay) {
+  TRACE_DEFAULT_SCOPED2(TraceCategory::kSender, "frame_id", frame_id.ToString(),
+                        "playout_delay", ToString(playout_delay));
+  if (frame_id > last_enqueued_frame_id_) {
+    TRACE_SET_RESULT(Error::Code::kParameterOutOfRange);
+    OSP_LOG_ERROR
+        << "Ignoring checkpoint for " << latest_expected_frame_id_
+        << " because this Sender could not have sent any frames after "
+        << last_enqueued_frame_id_ << '.';
+    return;
+  }
+  // CompoundRtcpParser should guarantee this:
+  OSP_CHECK_GE(playout_delay, milliseconds::zero());
+  while (checkpoint_frame_id_ < frame_id) {
+    ++checkpoint_frame_id_;
+    PendingFrameSlot& slot = get_slot_for(checkpoint_frame_id_);
+    if (slot.is_active_for_frame(checkpoint_frame_id_)) {
+      const RtpTimeTicks rtp_timestamp = slot.frame->rtp_timestamp;
+      statistics_dispatcher_.DispatchAckEvent(
+          config_.stream_type, rtp_timestamp, checkpoint_frame_id_);
+      CancelPendingFrame(checkpoint_frame_id_, /*was_acked*/ true);
+
+      TRACE_FLOW_STEP(TraceCategory::kSender, "Frame.Acked",
+                      checkpoint_frame_id_);
+    }
+  }
+  latest_expected_frame_id_ = std::max(latest_expected_frame_id_, frame_id);
+  DispatchCancellations();
+
+  if (playout_delay != target_playout_delay_ &&
+      frame_id >= playout_delay_change_at_frame_id_) {
+    OSP_LOG_WARN << "Sender's target playout delay (" << target_playout_delay_
+                 << ") disagrees with the Receiver's (" << playout_delay << ")";
+  }
+}
+
+void SenderImpl::OnReceiverHasFrames(std::vector<FrameId> acks) {
+  OSP_DCHECK(!acks.empty() && AreElementsSortedAndUnique(acks));
+  TRACE_DEFAULT_SCOPED1(TraceCategory::kSender, "frame_ids",
+                        string_util::Join(acks));
+
+  if (acks.back() > last_enqueued_frame_id_) {
+    TRACE_SET_RESULT(Error::Code::kParameterOutOfRange);
+    OSP_LOG_ERROR << "Ignoring individual frame ACKs: ACKing frame "
+                  << latest_expected_frame_id_
+                  << " is invalid because this Sender could not have sent any "
+                     "frames after "
+                  << last_enqueued_frame_id_ << '.';
+    return;
+  }
+
+  for (FrameId id : acks) {
+    TRACE_FLOW_STEP(TraceCategory::kSender, "Frame.Acked", id);
+    PendingFrameSlot& slot = get_slot_for(id);
+    if (slot.is_active_for_frame(id)) {
+      const RtpTimeTicks rtp_timestamp = slot.frame->rtp_timestamp;
+      statistics_dispatcher_.DispatchAckEvent(config_.stream_type,
+                                              rtp_timestamp, id);
+    }
+    CancelPendingFrame(id, /*was_acked*/ true);
+  }
+  latest_expected_frame_id_ = std::max(latest_expected_frame_id_, acks.back());
+  DispatchCancellations();
+}
+
+void SenderImpl::OnReceiverIsMissingPackets(std::vector<PacketNack> nacks) {
+  TRACE_DEFAULT_SCOPED1(TraceCategory::kSender, "number_of_packets",
+                        std::to_string(nacks.size()));
+  OSP_DCHECK(!nacks.empty() && AreElementsSortedAndUnique(nacks));
+  OSP_CHECK_NE(rtcp_packet_arrival_time_, SenderPacketRouter::kNever);
+
+  // This is a point-in-time threshold that indicates whether each NACK will
+  // trigger a packet retransmit. The threshold is based on the network round
+  // trip time because a Receiver's NACK may have been issued while the needed
+  // packet was in-flight from the Sender. In such cases, the Receiver's NACK is
+  // likely stale and this Sender should not redundantly re-transmit the packet
+  // again.
+  const Clock::time_point too_recent_a_send_time =
+      rtcp_packet_arrival_time_ - round_trip_time_;
+
+  // Iterate over all the NACKs...
+  bool need_to_send = false;
+  for (auto nack_it = nacks.begin(); nack_it != nacks.end();) {
+    // Find the slot associated with the NACK's frame ID.
+    const FrameId frame_id = nack_it->frame_id;
+    PendingFrameSlot* slot = nullptr;
+    if (frame_id <= last_enqueued_frame_id_) {
+      PendingFrameSlot& candidate_slot = get_slot_for(frame_id);
+      if (candidate_slot.is_active_for_frame(frame_id)) {
+        slot = &candidate_slot;
+      }
+    }
+
+    // If no slot was found (i.e., the NACK is invalid) for the frame, skip-over
+    // all other NACKs for the same frame. While it seems to be a bug that the
+    // Receiver would attempt to NACK a frame that does not yet exist, this can
+    // happen in rare cases where RTCP packets arrive out-of-order (i.e., the
+    // network shuffled them).
+    if (!slot) {
+      TRACE_SCOPED1(TraceCategory::kSender, "MissingNackSlot", "frame_id",
+                    frame_id.ToString());
+      for (++nack_it; nack_it != nacks.end() && nack_it->frame_id == frame_id;
+           ++nack_it) {
+      }
+      continue;
+    }
+
+    latest_expected_frame_id_ = std::max(latest_expected_frame_id_, frame_id);
+
+    const auto HandleIndividualNack = [&](FramePacketId packet_id) {
+      if (slot->packet_sent_times[packet_id] <= too_recent_a_send_time) {
+        slot->send_flags.Set(packet_id);
+        need_to_send = true;
+      }
+    };
+    const FramePacketId range_end = slot->packet_sent_times.size();
+    if (nack_it->packet_id == kAllPacketsLost) {
+      for (FramePacketId packet_id = 0; packet_id < range_end; ++packet_id) {
+        HandleIndividualNack(packet_id);
+      }
+      ++nack_it;
+    } else {
+      do {
+        if (nack_it->packet_id < range_end) {
+          HandleIndividualNack(nack_it->packet_id);
+        } else {
+          OSP_LOG_WARN
+              << "Ignoring NACK for packet that doesn't exist in frame "
+              << frame_id << ": " << static_cast<int>(nack_it->packet_id);
+        }
+        ++nack_it;
+      } while (nack_it != nacks.end() && nack_it->frame_id == frame_id);
+    }
+  }
+
+  if (need_to_send) {
+    packet_router_->RequestRtpSend(rtcp_session_.receiver_ssrc());
+  }
+}
+
+SenderImpl::ChosenPacket SenderImpl::ChooseNextRtpPacketNeedingSend() {
+  // Find the oldest packet needing to be sent (or re-sent).
+  for (FrameId frame_id = checkpoint_frame_id_ + 1;
+       frame_id <= last_enqueued_frame_id_; ++frame_id) {
+    PendingFrameSlot& slot = get_slot_for(frame_id);
+    if (!slot.is_active_for_frame(frame_id)) {
+      continue;  // Frame was canceled. None of its packets need to be sent.
+    }
+    const FramePacketId packet_id = slot.send_flags.FindFirstSet();
+    if (packet_id < slot.send_flags.size()) {
+      return {&slot, packet_id};
+    }
+  }
+
+  return {};  // Nothing needs to be sent.
+}
+
+SenderImpl::ChosenPacketAndWhen SenderImpl::ChooseKickstartPacket() {
+  if (latest_expected_frame_id_ >= last_enqueued_frame_id_) {
+    // Since the Receiver must know about all of the frames currently queued, no
+    // Kickstart packet is necessary.
+    return {};
+  }
+
+  // The Kickstart packet is always in the last-enqueued frame, so that the
+  // Receiver will know about every frame the Sender has. However, which packet
+  // should be chosen? Any would do, since all packets contain the frame's total
+  // packet count. For historical reasons, all sender implementations have
+  // always just sent the last packet; and so that tradition is continued here.
+  ChosenPacketAndWhen chosen;
+  chosen.slot = &get_slot_for(last_enqueued_frame_id_);
+  // Note: This frame cannot have been canceled since
+  // `latest_expected_frame_id_` hasn't yet reached this point.
+  OSP_CHECK(chosen.slot->is_active_for_frame(last_enqueued_frame_id_));
+  chosen.packet_id = chosen.slot->send_flags.size() - 1;
+
+  const Clock::time_point time_last_sent =
+      chosen.slot->packet_sent_times[chosen.packet_id];
+  // Sanity-check: This method should not be called to choose a packet while
+  // there are still unsent packets.
+  OSP_CHECK_NE(time_last_sent, SenderPacketRouter::kNever);
+
+  // The desired Kickstart interval is a fraction of the total
+  // `target_playout_delay_`. The reason for the specific ratio here is based on
+  // lost knowledge (from legacy implementations); but it makes sense (i.e., to
+  // be a good "network citizen") to be less aggressive for larger playout delay
+  // windows, and more aggressive for shorter ones to avoid too-late packet
+  // arrivals.
+  using kWaitFraction = std::ratio<1, 20>;
+  const Clock::duration desired_kickstart_interval =
+      Clock::to_duration(target_playout_delay_) * kWaitFraction::num /
+      kWaitFraction::den;
+  // The actual interval used is increased, if current network performance
+  // warrants waiting longer. Don't send a Kickstart packet until no NACKs
+  // have been received for two network round-trip periods.
+  constexpr int kLowerBoundRoundTrips = 2;
+  const Clock::duration kickstart_interval = std::max(
+      desired_kickstart_interval, round_trip_time_ * kLowerBoundRoundTrips);
+  chosen.when = time_last_sent + kickstart_interval;
+
+  return chosen;
+}
+
+void SenderImpl::CancelPendingFrame(FrameId frame_id, bool was_acked) {
+  TRACE_FLOW_END(TraceCategory::kSender, "Frame.Cancelled", frame_id);
+
+  PendingFrameSlot& slot = get_slot_for(frame_id);
+  if (!slot.is_active_for_frame(frame_id)) {
+    return;  // Frame was already canceled.
+  }
+
+  if (was_acked) {
+    packet_router_->OnPayloadReceived(
+        slot.frame->data.size(), rtcp_packet_arrival_time_, round_trip_time_);
+  }
+
+  slot.frame.reset();
+  OSP_CHECK_GT(num_frames_in_flight_, 0);
+  --num_frames_in_flight_;
+  if (observer_) {
+    pending_cancellations_.emplace_back(frame_id);
+  }
+}
+
+void SenderImpl::DispatchCancellations() {
+  if (observer_) {
+    for (const FrameId id : pending_cancellations_) {
+      observer_->OnFrameCanceled(id);
+    }
+  }
+  pending_cancellations_.clear();
+
+  // At this point, there should either be no frames in flight, or the frame
+  // immediately after `checkpoint_frame_id_` must be valid.
+  OSP_DCHECK((num_frames_in_flight_ == 0) ||
+             get_slot_for(checkpoint_frame_id_ + 1)
+                 .is_active_for_frame(checkpoint_frame_id_ + 1));
+}
+
+SenderImpl::PendingFrameSlot::PendingFrameSlot() = default;
+SenderImpl::PendingFrameSlot::~PendingFrameSlot() = default;
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/sender_impl.h

@@ -0,0 +1,252 @@
+// Copyright 2026 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_SENDER_IMPL_H_
+#define CAST_STREAMING_IMPL_SENDER_IMPL_H_
+
+#include <stdint.h>
+
+#include <array>
+#include <chrono>
+#include <optional>
+#include <vector>
+
+#include "cast/streaming/impl/compound_rtcp_parser.h"
+#include "cast/streaming/impl/frame_crypto.h"
+#include "cast/streaming/impl/rtcp_common.h"
+#include "cast/streaming/impl/rtp_defines.h"
+#include "cast/streaming/impl/rtp_packetizer.h"
+#include "cast/streaming/impl/sender_report_builder.h"
+#include "cast/streaming/impl/statistics_dispatcher.h"
+#include "cast/streaming/public/constants.h"
+#include "cast/streaming/public/frame_id.h"
+#include "cast/streaming/public/sender.h"
+#include "cast/streaming/public/session_config.h"
+#include "cast/streaming/rtp_time.h"
+#include "cast/streaming/sender_packet_router.h"
+#include "platform/api/time.h"
+#include "platform/base/span.h"
+#include "util/bit_vector.h"
+#include "util/raw_ptr.h"
+#include "util/raw_ref.h"
+
+namespace openscreen::cast {
+
+class Environment;
+
+// The Cast Streaming Sender, a peer corresponding to some Cast Streaming
+// Receiver at the other end of a network link. See class level comments for
+// Receiver for a high-level overview.
+class SenderImpl final : public Sender,
+                         public SenderPacketRouter::Sender,
+                         public CompoundRtcpParser::Client {
+ public:
+  // Constructs a Sender that attaches to the given `environment`-provided
+  // resources and `packet_router`. The `config` contains the settings that were
+  // agreed-upon by both sides from the OFFER/ANSWER exchange (i.e., the part of
+  // the overall end-to-end connection process that occurs before Cast Streaming
+  // is started). The `rtp_payload_type` does not affect the behavior of this
+  // Sender. It is simply passed along to a Receiver in the RTP packet stream.
+  SenderImpl(Environment& environment,
+             SenderPacketRouter& packet_router,
+             SessionConfig config,
+             RtpPayloadType rtp_payload_type);
+
+  ~SenderImpl() final;
+
+  // Sender overrides.
+  const SessionConfig& config() const override { return config_; }
+  void SetObserver(Observer* observer) override;
+  size_t GetInFlightFrameCount() const override;
+  Clock::duration GetInFlightMediaDuration(
+      RtpTimeTicks next_frame_rtp_timestamp) const override;
+  Clock::duration GetMaxInFlightMediaDuration() const override;
+  bool NeedsKeyFrame() const override;
+  FrameId GetNextFrameId() const override;
+  Clock::duration GetCurrentRoundTripTime() const override;
+  [[nodiscard]] EnqueueFrameResult EnqueueFrame(
+      const EncodedFrame& frame) override;
+  void CancelInFlightData() override;
+  void ReportFrameDropEvent(FrameId frame_id,
+                            RtpTimeTicks rtp_timestamp,
+                            Clock::time_point drop_time) override;
+
+  // Smooths a new round-trip-time `measurement` into the running `estimate`
+  // using an asymmetric "fast attack, slow decay" filter: the estimate climbs
+  // quickly on an upward spike (so the Sender notices congestion onset) but
+  // decays slowly (so a single low sample does not collapse it). A zero
+  // `estimate` adopts the measurement directly. Static and exposed for testing.
+  static Clock::duration SmoothRoundTripTime(Clock::duration estimate,
+                                             Clock::duration measurement);
+
+ private:
+  // Tracking/Storage for frames that are ready-to-send, and until they are
+  // fully received at the other end.
+  struct PendingFrameSlot {
+    // The frame to send, or nullopt if this slot is not in use.
+    std::optional<EncryptedFrame> frame;
+
+    // Represents which packets need to be sent. Elements are indexed by
+    // FramePacketId. A set bit means a packet needs to be sent (or re-sent).
+    BitVector send_flags;
+
+    // The time when each of the packets was last sent, or
+    // `SenderPacketRouter::kNever` if the packet has not been sent yet.
+    // Elements are indexed by FramePacketId. This is used to avoid
+    // re-transmitting any given packet too frequently.
+    std::vector<Clock::time_point> packet_sent_times;
+
+    PendingFrameSlot();
+    ~PendingFrameSlot();
+
+    bool is_active_for_frame(FrameId frame_id) const {
+      return frame && frame->frame_id == frame_id;
+    }
+  };
+
+  // Return value from the ChooseXYZ() helper methods.
+  struct ChosenPacket {
+    raw_ptr<PendingFrameSlot> slot = nullptr;
+    FramePacketId packet_id{};
+
+    explicit operator bool() const { return !!slot; }
+  };
+
+  // An extension of ChosenPacket that also includes the point-in-time when the
+  // packet should be sent.
+  struct ChosenPacketAndWhen : public ChosenPacket {
+    Clock::time_point when = SenderPacketRouter::kNever;
+  };
+
+  // SenderPacketRouter::Sender implementation.
+  void OnReceivedRtcpPacket(Clock::time_point arrival_time,
+                            ByteView packet) final;
+  ByteBuffer GetRtcpPacketForImmediateSend(Clock::time_point send_time,
+                                           ByteBuffer buffer) final;
+  ByteBuffer GetRtpPacketForImmediateSend(Clock::time_point send_time,
+                                          ByteBuffer buffer) final;
+  Clock::time_point GetRtpResumeTime() final;
+  RtpTimeTicks GetLastRtpTimestamp() const final;
+  StreamType GetStreamType() const final;
+
+  // CompoundRtcpParser::Client implementation.
+  void OnReceiverReferenceTimeAdvanced(Clock::time_point reference_time) final;
+  void OnReceiverReport(const RtcpReportBlock& receiver_report) final;
+  void OnCastReceiverFrameLogMessages(
+      std::vector<RtcpReceiverFrameLogMessage> messages) final;
+  void OnReceiverIndicatesPictureLoss() final;
+  void OnReceiverCheckpoint(FrameId frame_id,
+                            std::chrono::milliseconds playout_delay) final;
+  void OnReceiverHasFrames(std::vector<FrameId> acks) final;
+  void OnReceiverIsMissingPackets(std::vector<PacketNack> nacks) final;
+
+  // Helper to choose which packet to send, from those that have been flagged as
+  // "need to send." Returns a "false" result if nothing needs to be sent.
+  ChosenPacket ChooseNextRtpPacketNeedingSend();
+
+  // Helper that returns the packet that should be used to kick-start the
+  // Receiver, and the time at which the packet should be sent. Returns a kNever
+  // result if kick-starting is not needed.
+  ChosenPacketAndWhen ChooseKickstartPacket();
+
+  // Cancels sending (or resending) the given frame once it is known to have
+  // been either:
+  //   1. Cancelled by the sender (was_acked must be false);
+  //   2. Fully received based on the ACK feedback in a receiver RTCP report
+  //      (was_acked must be true);
+  //   3. The receiver sent a checkpoint frame ID (was_acked must be true).
+  //
+  // This clears the corresponding entry in `pending_frames_` and
+  // adds `frame_id` to the list of pending cancellations to be dispatched as
+  // part of DispatchCancellations().
+  //
+  // NOTE: Every frame_id ends up being "cancelled" at least once.
+  void CancelPendingFrame(FrameId frame_id, bool was_acked);
+
+  // Must be called after one or a series of CancelPendingFrame() calls in order
+  // to notify the observer, if any, about cancellations.
+  void DispatchCancellations();
+
+  // Inline helper to return the slot that would contain the tracking info for
+  // the given `frame_id`.
+  const PendingFrameSlot& get_slot_for(FrameId frame_id) const {
+    return pending_frames_[(frame_id - FrameId::first()) %
+                           pending_frames_.size()];
+  }
+  PendingFrameSlot& get_slot_for(FrameId frame_id) {
+    return pending_frames_[(frame_id - FrameId::first()) %
+                           pending_frames_.size()];
+  }
+
+  const SessionConfig config_;
+  const raw_ref<SenderPacketRouter> packet_router_;
+  RtcpSession rtcp_session_;
+  CompoundRtcpParser rtcp_parser_;
+  SenderReportBuilder sender_report_builder_;
+  RtpPacketizer rtp_packetizer_;
+  const int rtp_timebase_;
+  FrameCrypto crypto_;
+  StatisticsDispatcher statistics_dispatcher_;
+
+  // Ring buffer of PendingFrameSlots. The frame having FrameId x will always
+  // be slotted at position x % pending_frames_.size(). Use get_slot_for() to
+  // access the correct slot for a given FrameId.
+  std::array<PendingFrameSlot, kMaxUnackedFrames> pending_frames_ = {};
+
+  // A count of the number of frames in-flight (i.e., the number of active
+  // entries in `pending_frames_`).
+  size_t num_frames_in_flight_ = 0;
+
+  // The ID of the last frame enqueued.
+  FrameId last_enqueued_frame_id_ = FrameId::leader();
+
+  // Indicates that all of the packets for all frames up to and including this
+  // FrameId have been successfully received (or otherwise do not need to be
+  // re-transmitted).
+  FrameId checkpoint_frame_id_ = FrameId::leader();
+
+  // The ID of the latest frame the Receiver seems to be aware of.
+  FrameId latest_expected_frame_id_ = FrameId::leader();
+
+  // The target playout delay for the last-enqueued frame. This is auto-updated
+  // when a frame is enqueued that changes the delay.
+  std::chrono::milliseconds target_playout_delay_;
+  FrameId playout_delay_change_at_frame_id_ = FrameId::first();
+
+  // The exact arrival time of the last RTCP packet.
+  Clock::time_point rtcp_packet_arrival_time_ = SenderPacketRouter::kNever;
+
+  // The near-term average round trip time. This is updated with each Sender
+  // Report → Receiver Report round trip. This is initially zero, indicating the
+  // round trip time has not been measured yet.
+  Clock::duration round_trip_time_ = {};
+
+  // Maintain current stats in a Sender Report that is ready for sending at any
+  // time. This includes up-to-date lip-sync information, and packet and byte
+  // count stats.
+  RtcpSenderReport pending_sender_report_;
+
+  // These are used to determine whether a key frame needs to be sent to the
+  // Receiver. When the Receiver provides a picture loss notification, the
+  // current checkpoint frame ID is stored in `picture_lost_at_frame_id_`. Then,
+  // while `last_enqueued_key_frame_id_` is less than or equal to
+  // `picture_lost_at_frame_id_`, the Sender knows it still needs to send a key
+  // frame to resolve the picture loss condition. In all other cases, the
+  // Receiver is either in a good state or is in the process of receiving the
+  // key frame that will make that happen.
+  FrameId picture_lost_at_frame_id_ = FrameId::leader();
+  FrameId last_enqueued_key_frame_id_ = FrameId::leader();
+
+  // The current observer (optional).
+  raw_ptr<Observer> observer_ = nullptr;
+
+  // Because the observer may take action when frames are cancelled, such as
+  // calling APIs like EnqueueFrame(), `this` must be in a good state before
+  // the observer is notified of any pending frame cancellations.
+  std::vector<FrameId> pending_cancellations_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_SENDER_IMPL_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/sender_report_builder.cc

@@ -0,0 +1,79 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/sender_report_builder.h"
+
+#include "cast/streaming/impl/packet_util.h"
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+SenderReportBuilder::SenderReportBuilder(RtcpSession& session)
+    : session_(session) {}
+
+SenderReportBuilder::~SenderReportBuilder() = default;
+
+std::pair<ByteBuffer, StatusReportId> SenderReportBuilder::BuildPacket(
+    const RtcpSenderReport& sender_report,
+    ByteBuffer buffer) const {
+  OSP_CHECK_GE(buffer.size(), kRequiredBufferSize);
+
+  uint8_t* const packet_begin = buffer.data();
+
+  RtcpCommonHeader header;
+  header.packet_type = RtcpPacketType::kSenderReport;
+  header.payload_size = kRtcpSenderReportSize;
+  if (sender_report.report_block) {
+    header.with.report_count = 1;
+    header.payload_size += kRtcpReportBlockSize;
+  } else {
+    header.with.report_count = 0;
+  }
+  header.AppendFields(buffer);
+
+  AppendField<uint32_t>(session_->sender_ssrc(), buffer);
+  const NtpTimestamp ntp_timestamp =
+      session_->ntp_converter().ToNtpTimestamp(sender_report.reference_time);
+  AppendField<uint64_t>(ntp_timestamp, buffer);
+  AppendField<uint32_t>(sender_report.rtp_timestamp.lower_32_bits(), buffer);
+  AppendField<uint32_t>(sender_report.send_packet_count, buffer);
+  AppendField<uint32_t>(sender_report.send_octet_count, buffer);
+  if (sender_report.report_block) {
+    sender_report.report_block->AppendFields(buffer);
+  }
+
+  uint8_t* const packet_end = buffer.data();
+  return std::make_pair(ByteBuffer(packet_begin, packet_end - packet_begin),
+                        ToStatusReportId(ntp_timestamp));
+}
+
+Clock::time_point SenderReportBuilder::GetRecentReportTime(
+    StatusReportId report_id,
+    Clock::time_point on_or_before) const {
+  // Assumption: The `report_id` is the middle 32 bits of a 64-bit NtpTimestamp.
+  static_assert(ToStatusReportId(NtpTimestamp{0x0192a3b4c5d6e7f8}) ==
+                    StatusReportId{0xa3b4c5d6},
+                "FIXME: ToStatusReportId() implementation changed.");
+
+  // Compute the maximum possible NtpTimestamp. Then, use its uppermost 16 bits
+  // and the 32 bits from the report_id to produce a reconstructed NtpTimestamp.
+  const NtpTimestamp max_timestamp =
+      session_->ntp_converter().ToNtpTimestamp(on_or_before);
+  // max_timestamp: HH......
+  //     report_id:     LLLL
+  //                ↓↓ ↙↙↙↙
+  // reconstructed: HHLLLL00
+  NtpTimestamp reconstructed = (max_timestamp & (uint64_t{0xffff} << 48)) |
+                               (static_cast<uint64_t>(report_id) << 16);
+  //  If the reconstructed timestamp is greater than the maximum one, rollover
+  //  of the lower 48 bits occurred. Subtract one from the upper 16 bits to
+  //  rectify that.
+  if (reconstructed > max_timestamp) {
+    reconstructed -= uint64_t{1} << 48;
+  }
+
+  return session_->ntp_converter().ToLocalTime(reconstructed);
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/sender_report_builder.h

@@ -0,0 +1,50 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_SENDER_REPORT_BUILDER_H_
+#define CAST_STREAMING_IMPL_SENDER_REPORT_BUILDER_H_
+
+#include <stdint.h>
+
+#include <utility>
+
+#include "cast/streaming/impl/rtcp_common.h"
+#include "cast/streaming/impl/rtcp_session.h"
+#include "cast/streaming/impl/rtp_defines.h"
+#include "platform/api/time.h"
+#include "platform/base/span.h"
+#include "util/raw_ref.h"
+
+namespace openscreen::cast {
+
+// Builds RTCP packets containing one Sender Report.
+class SenderReportBuilder {
+ public:
+  explicit SenderReportBuilder(RtcpSession& session);
+  ~SenderReportBuilder();
+
+  // Serializes the given `sender_report` as a RTCP packet and writes it to
+  // `buffer` (which must be kRequiredBufferSize in size). Returns the subspan
+  // of `buffer` that contains the result and a StatusReportId the receiver
+  // might use in its own reports to reference this specific report.
+  std::pair<ByteBuffer, StatusReportId> BuildPacket(
+      const RtcpSenderReport& sender_report,
+      ByteBuffer buffer) const;
+
+  // Returns the approximate reference time from a recently-built Sender Report,
+  // based on the given `report_id` and maximum possible reference time.
+  Clock::time_point GetRecentReportTime(StatusReportId report_id,
+                                        Clock::time_point on_or_before) const;
+
+  // The required size (in bytes) of the buffer passed to BuildPacket().
+  static constexpr int kRequiredBufferSize =
+      kRtcpCommonHeaderSize + kRtcpSenderReportSize + kRtcpReportBlockSize;
+
+ private:
+  const raw_ref<RtcpSession> session_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_SENDER_REPORT_BUILDER_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/statistics_analyzer.cc

@@ -0,0 +1,573 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/statistics_analyzer.h"
+
+#include <algorithm>
+
+#include "cast/streaming/impl/statistics_common.h"
+#include "platform/base/trivial_clock_traits.h"
+#include "util/chrono_helpers.h"
+
+namespace openscreen::cast {
+
+using openscreen::clock_operators::operator<<;
+
+namespace {
+
+constexpr Clock::duration kAnalysisInterval = std::chrono::milliseconds(500);
+
+constexpr size_t kMaxRecentPacketInfoMapSize = 1000;
+constexpr size_t kMaxRecentFrameInfoMapSize = 200;
+
+constexpr int kDefaultMaxLatencyBucketMs = 800;
+constexpr int kDefaultBucketWidthMs = 20;
+
+double InMilliseconds(Clock::duration duration) {
+  return static_cast<double>(to_milliseconds(duration).count());
+}
+
+bool IsReceiverEvent(StatisticsEvent::Type event) {
+  return event == StatisticsEvent::Type::kFrameAckSent ||
+         event == StatisticsEvent::Type::kFrameDecoded ||
+         event == StatisticsEvent::Type::kFramePlayedOut ||
+         event == StatisticsEvent::Type::kPacketReceived;
+}
+
+}  // namespace
+
+StatisticsAnalyzer::StatisticsAnalyzer(
+    SenderStatsClient* stats_client,
+    ClockNowFunctionPtr now,
+    TaskRunner& task_runner,
+    std::unique_ptr<ClockOffsetEstimator> offset_estimator)
+    : stats_client_(stats_client),
+      offset_estimator_(std::move(offset_estimator)),
+      now_(now),
+      alarm_(now, task_runner),
+      start_time_(now()) {
+  statistics_collector_ = std::make_unique<StatisticsCollector>(now_);
+  InitHistograms();
+}
+
+StatisticsAnalyzer::~StatisticsAnalyzer() = default;
+
+void StatisticsAnalyzer::ScheduleAnalysis() {
+  Clock::time_point next_analysis_time = now_() + kAnalysisInterval;
+  alarm_.Schedule([this] { AnalyzeStatistics(); }, next_analysis_time);
+}
+
+void StatisticsAnalyzer::InitHistograms() {
+  for (auto& histogram : histograms_.audio) {
+    histogram =
+        SimpleHistogram(0, kDefaultMaxLatencyBucketMs, kDefaultBucketWidthMs);
+  }
+  for (auto& histogram : histograms_.video) {
+    histogram =
+        SimpleHistogram(0, kDefaultMaxLatencyBucketMs, kDefaultBucketWidthMs);
+  }
+}
+
+void StatisticsAnalyzer::AnalyzeStatistics() {
+  ProcessFrameEvents(statistics_collector_->TakeRecentFrameEvents());
+  ProcessPacketEvents(statistics_collector_->TakeRecentPacketEvents());
+  SendStatistics();
+  ScheduleAnalysis();
+}
+
+void StatisticsAnalyzer::SendStatistics() {
+  if (!stats_client_) {
+    return;
+  }
+
+  const Clock::time_point end_time = now_();
+  stats_client_->OnStatisticsUpdated(SenderStats{
+      .audio_statistics =
+          ConstructStatisticsList(end_time, StatisticsEvent::MediaType::kAudio),
+      .audio_histograms = histograms_.audio,
+      .video_statistics =
+          ConstructStatisticsList(end_time, StatisticsEvent::MediaType::kVideo),
+      .video_histograms = histograms_.video});
+}
+
+void StatisticsAnalyzer::ProcessFrameEvents(
+    const std::vector<FrameEvent>& frame_events) {
+  for (FrameEvent frame_event : frame_events) {
+    offset_estimator_->OnFrameEvent(frame_event);
+
+    FrameStatsMap& frame_stats_map = frame_stats_.Get(frame_event.media_type);
+    auto it = frame_stats_map.find(frame_event.type);
+    if (it == frame_stats_map.end()) {
+      frame_stats_map.insert(std::make_pair(
+          frame_event.type,
+          FrameStatsAggregate{.event_counter = 1,
+                              .sum_size = frame_event.size,
+                              .sum_delay = frame_event.delay_delta}));
+    } else {
+      ++(it->second.event_counter);
+      it->second.sum_size += frame_event.size;
+      it->second.sum_delay += frame_event.delay_delta;
+    }
+
+    RecordEventTimes(frame_event);
+    RecordFrameLatencies(frame_event);
+  }
+}
+
+void StatisticsAnalyzer::ProcessPacketEvents(
+    const std::vector<PacketEvent>& packet_events) {
+  for (PacketEvent packet_event : packet_events) {
+    offset_estimator_->OnPacketEvent(packet_event);
+
+    PacketStatsMap& packet_stats_map =
+        packet_stats_.Get(packet_event.media_type);
+    auto it = packet_stats_map.find(packet_event.type);
+    if (it == packet_stats_map.end()) {
+      packet_stats_map.insert(
+          std::make_pair(packet_event.type,
+                         PacketStatsAggregate{.event_counter = 1,
+                                              .sum_size = packet_event.size}));
+    } else {
+      ++(it->second.event_counter);
+      it->second.sum_size += packet_event.size;
+    }
+
+    RecordEventTimes(packet_event);
+    if (packet_event.type == StatisticsEvent::Type::kPacketSentToNetwork ||
+        packet_event.type == StatisticsEvent::Type::kPacketReceived) {
+      RecordPacketLatencies(packet_event);
+    } else if (packet_event.type ==
+               StatisticsEvent::Type::kPacketRetransmitted) {
+      // We only measure network latency for packets that are not retransmitted.
+      ErasePacketInfo(packet_event);
+    }
+  }
+}
+
+void StatisticsAnalyzer::RecordFrameLatencies(const FrameEvent& frame_event) {
+  FrameInfoMap& frame_infos = recent_frame_infos_.Get(frame_event.media_type);
+
+  // Event is too old, don't bother.
+  const bool map_is_full = frame_infos.size() == kMaxRecentFrameInfoMapSize;
+  if (map_is_full && frame_event.rtp_timestamp <= frame_infos.begin()->first) {
+    return;
+  }
+
+  auto it = frame_infos.find(frame_event.rtp_timestamp);
+  if (it == frame_infos.end()) {
+    if (map_is_full) {
+      frame_infos.erase(frame_infos.begin());
+    }
+
+    auto emplace_result =
+        frame_infos.emplace(frame_event.rtp_timestamp, FrameInfo{});
+    OSP_CHECK(emplace_result.second);
+    it = emplace_result.first;
+  }
+
+  switch (frame_event.type) {
+    case StatisticsEvent::Type::kFrameCaptureBegin:
+      it->second.capture_begin_time = frame_event.timestamp;
+      break;
+
+    case StatisticsEvent::Type::kFrameCaptureEnd: {
+      it->second.capture_end_time = frame_event.timestamp;
+      if (it->second.capture_begin_time != Clock::time_point::min()) {
+        const Clock::duration capture_latency =
+            frame_event.timestamp - it->second.capture_begin_time;
+        AddToLatencyAggregrate(StatisticType::kAvgCaptureLatencyMs,
+                               capture_latency, frame_event.media_type);
+        AddToHistogram(HistogramType::kCaptureLatencyMs, frame_event.media_type,
+                       InMilliseconds(capture_latency));
+      }
+    } break;
+
+    case StatisticsEvent::Type::kFrameEncoded: {
+      it->second.encode_end_time = frame_event.timestamp;
+      if (it->second.capture_end_time != Clock::time_point::min()) {
+        const Clock::duration encode_latency =
+            frame_event.timestamp - it->second.capture_end_time;
+        AddToLatencyAggregrate(StatisticType::kAvgEncodeTimeMs, encode_latency,
+                               frame_event.media_type);
+        AddToHistogram(HistogramType::kEncodeTimeMs, frame_event.media_type,
+                       InMilliseconds(encode_latency));
+      }
+    } break;
+
+    // Frame latency is the time from when the frame is encoded until the
+    // receiver ack for the frame is sent.
+    case StatisticsEvent::Type::kFrameAckSent: {
+      const auto adjusted_timestamp =
+          ToSenderTimestamp(frame_event.timestamp, frame_event.media_type);
+      if (!adjusted_timestamp) {
+        return;
+      }
+
+      if (it->second.encode_end_time != Clock::time_point::min()) {
+        const Clock::duration frame_latency =
+            *adjusted_timestamp - it->second.encode_end_time;
+        AddToLatencyAggregrate(StatisticType::kAvgFrameLatencyMs, frame_latency,
+                               frame_event.media_type);
+      }
+    } break;
+
+    case StatisticsEvent::Type::kFramePlayedOut: {
+      const auto adjusted_timestamp =
+          ToSenderTimestamp(frame_event.timestamp, frame_event.media_type);
+      if (!adjusted_timestamp) {
+        return;
+      }
+
+      if (it->second.capture_begin_time != Clock::time_point::min()) {
+        const Clock::duration e2e_latency =
+            *adjusted_timestamp - it->second.capture_begin_time;
+        AddToLatencyAggregrate(StatisticType::kAvgEndToEndLatencyMs,
+                               e2e_latency, frame_event.media_type);
+        AddToHistogram(HistogramType::kEndToEndLatencyMs,
+                       frame_event.media_type, InMilliseconds(e2e_latency));
+      }
+
+      // Positive delay means the frame is late.
+      if (frame_event.delay_delta > Clock::duration::zero()) {
+        session_stats_.Get(frame_event.media_type).late_frame_counter += 1;
+        AddToHistogram(HistogramType::kFrameLatenessMs, frame_event.media_type,
+                       InMilliseconds(frame_event.delay_delta));
+      }
+    } break;
+
+    default:
+      break;
+  }
+}
+
+void StatisticsAnalyzer::RecordPacketLatencies(
+    const PacketEvent& packet_event) {
+  FrameInfoMap& frame_infos = recent_frame_infos_.Get(packet_event.media_type);
+
+  // Queueing latency is the time from when a frame is encoded to when the
+  // packet is first sent.
+  if (packet_event.type == StatisticsEvent::Type::kPacketSentToNetwork) {
+    const auto it = frame_infos.find(packet_event.rtp_timestamp);
+
+    // We have an encode end time for a frame associated with this packet.
+    if (it != frame_infos.end()) {
+      const Clock::duration queueing_latency =
+          packet_event.timestamp - it->second.encode_end_time;
+      AddToLatencyAggregrate(StatisticType::kAvgQueueingLatencyMs,
+                             queueing_latency, packet_event.media_type);
+      AddToHistogram(HistogramType::kQueueingLatencyMs, packet_event.media_type,
+                     InMilliseconds(queueing_latency));
+    }
+  }
+
+  StatisticsAnalyzer::PacketKey key =
+      std::make_pair(packet_event.rtp_timestamp, packet_event.packet_id);
+  PacketInfoMap& packet_infos =
+      recent_packet_infos_.Get(packet_event.media_type);
+
+  const auto it = packet_infos.find(key);
+  if (it == packet_infos.end()) {
+    packet_infos.insert(
+        std::make_pair(key, PacketInfo{.timestamp = packet_event.timestamp,
+                                       .type = packet_event.type}));
+    if (packet_infos.size() > kMaxRecentPacketInfoMapSize) {
+      packet_infos.erase(packet_infos.begin());
+    }
+  } else {  // We know when this packet was sent, and when it arrived.
+    PacketInfo value = it->second;
+    StatisticsEvent::Type recorded_type = value.type;
+    Clock::time_point packet_sent_time;
+    Clock::time_point packet_received_time;
+    if (recorded_type == StatisticsEvent::Type::kPacketSentToNetwork &&
+        packet_event.type == StatisticsEvent::Type::kPacketReceived) {
+      packet_sent_time = value.timestamp;
+      packet_received_time = packet_event.timestamp;
+    } else if (recorded_type == StatisticsEvent::Type::kPacketReceived &&
+               packet_event.type ==
+                   StatisticsEvent::Type::kPacketSentToNetwork) {
+      packet_sent_time = packet_event.timestamp;
+      packet_received_time = value.timestamp;
+    } else {
+      return;
+    }
+
+    packet_infos.erase(it);
+
+    // Use the offset estimator directly since we are trying to calculate the
+    // average network latency.
+    const std::optional<Clock::duration> receiver_offset =
+        offset_estimator_->GetEstimatedOffset();
+    if (!receiver_offset) {
+      return;
+    }
+    packet_received_time -= *receiver_offset;
+
+    const auto latency = packet_received_time - packet_sent_time;
+    AddToLatencyAggregrate(StatisticType::kAvgNetworkLatencyMs, latency,
+                           packet_event.media_type);
+    AddToHistogram(HistogramType::kNetworkLatencyMs, packet_event.media_type,
+                   InMilliseconds(latency));
+
+    // Packet latency is the time from when a frame is encoded until when the
+    // packet is received.
+    const auto frame_it = frame_infos.find(packet_event.rtp_timestamp);
+    if (frame_it != frame_infos.end()) {
+      const Clock::duration packet_latency =
+          packet_received_time - frame_it->second.encode_end_time;
+      AddToLatencyAggregrate(StatisticType::kAvgPacketLatencyMs, packet_latency,
+                             packet_event.media_type);
+      AddToHistogram(HistogramType::kPacketLatencyMs, packet_event.media_type,
+                     InMilliseconds(packet_latency));
+    }
+  }
+}
+
+void StatisticsAnalyzer::RecordEventTimes(const StatisticsEvent& event) {
+  SessionStats& session_stats = session_stats_.Get(event.media_type);
+
+  Clock::time_point sender_timestamp = event.timestamp;
+  if (IsReceiverEvent(event.type)) {
+    const auto latency = offset_estimator_->GetEstimatedLatency();
+    if (latency) {
+      const Clock::time_point estimated_sent_time =
+          event.received_timestamp - *latency;
+      session_stats.last_response_received_time = std::max(
+          session_stats.last_response_received_time, estimated_sent_time);
+    }
+
+    const auto result = ToSenderTimestamp(event.timestamp, event.media_type);
+    if (!result) {
+      return;
+    }
+    sender_timestamp = *result;
+  }
+
+  session_stats.first_event_time =
+      std::min(session_stats.first_event_time, sender_timestamp);
+  session_stats.last_event_time =
+      std::max(session_stats.last_event_time, sender_timestamp);
+}
+
+void StatisticsAnalyzer::ErasePacketInfo(const PacketEvent& packet_event) {
+  const StatisticsAnalyzer::PacketKey key =
+      std::make_pair(packet_event.rtp_timestamp, packet_event.packet_id);
+  PacketInfoMap& packet_infos =
+      recent_packet_infos_.Get(packet_event.media_type);
+  packet_infos.erase(key);
+}
+
+void StatisticsAnalyzer::AddToLatencyAggregrate(
+    StatisticType latency_stat,
+    Clock::duration latency_delta,
+    StatisticsEvent::MediaType media_type) {
+  LatencyStatsMap& latency_stats = latency_stats_.Get(media_type);
+
+  auto it = latency_stats.find(latency_stat);
+  if (it == latency_stats.end()) {
+    latency_stats.insert(std::make_pair(
+        latency_stat, LatencyStatsAggregate{.data_point_counter = 1,
+                                            .sum_latency = latency_delta}));
+  } else {
+    ++(it->second.data_point_counter);
+    it->second.sum_latency += latency_delta;
+  }
+}
+
+void StatisticsAnalyzer::AddToHistogram(HistogramType histogram,
+                                        StatisticsEvent::MediaType media_type,
+                                        int64_t sample) {
+  histograms_.Get(media_type)[static_cast<int>(histogram)].Add(sample);
+}
+
+SenderStats::StatisticsList StatisticsAnalyzer::ConstructStatisticsList(
+    Clock::time_point end_time,
+    StatisticsEvent::MediaType media_type) {
+  SenderStats::StatisticsList stats_list;
+
+  PopulateFrameCountStat(StatisticsEvent::Type::kFrameDroppedByEncoder,
+                         StatisticType::kNumFramesDroppedByEncoder, media_type,
+                         stats_list);
+
+  PopulateFrameCountStat(StatisticsEvent::Type::kFrameCaptureEnd,
+                         StatisticType::kNumFramesCaptured, media_type,
+                         stats_list);
+
+  // kEnqueueFps
+  PopulateFpsStat(StatisticsEvent::Type::kFrameEncoded,
+                  StatisticType::kEnqueueFps, media_type, end_time, stats_list);
+
+  constexpr StatisticType kSupportedLatencyStats[] = {
+      StatisticType::kAvgEncodeTimeMs,      StatisticType::kAvgCaptureLatencyMs,
+      StatisticType::kAvgQueueingLatencyMs, StatisticType::kAvgNetworkLatencyMs,
+      StatisticType::kAvgPacketLatencyMs,   StatisticType::kAvgFrameLatencyMs,
+      StatisticType::kAvgEndToEndLatencyMs,
+  };
+  for (StatisticType type : kSupportedLatencyStats) {
+    PopulateAvgLatencyStat(type, media_type, stats_list);
+  }
+
+  // kEncodeRateKbps
+  PopulateFrameBitrateStat(StatisticsEvent::Type::kFrameEncoded,
+                           StatisticType::kEncodeRateKbps, media_type, end_time,
+                           stats_list);
+
+  // kPacketTransmissionRateKbps
+  PopulatePacketBitrateStat(StatisticsEvent::Type::kPacketSentToNetwork,
+                            StatisticType::kPacketTransmissionRateKbps,
+                            media_type, end_time, stats_list);
+
+  // kNumPacketsSent
+  PopulatePacketCountStat(StatisticsEvent::Type::kPacketSentToNetwork,
+                          StatisticType::kNumPacketsSent, media_type,
+                          stats_list);
+
+  // kNumPacketsReceived
+  PopulatePacketCountStat(StatisticsEvent::Type::kPacketReceived,
+                          StatisticType::kNumPacketsReceived, media_type,
+                          stats_list);
+
+  // kTimeSinceLastReceiverResponseMs
+  // kFirstEventTimeMs
+  // kLastEventTimeMs
+  // kNumLateFrames
+  PopulateSessionStats(media_type, end_time, stats_list);
+
+  return stats_list;
+}
+
+void StatisticsAnalyzer::PopulatePacketCountStat(
+    StatisticsEvent::Type event,
+    StatisticType stat,
+    StatisticsEvent::MediaType media_type,
+    SenderStats::StatisticsList& stats_list) {
+  PacketStatsMap& stats_map = packet_stats_.Get(media_type);
+
+  auto it = stats_map.find(event);
+  if (it != stats_map.end()) {
+    stats_list[static_cast<int>(stat)] = it->second.event_counter;
+  }
+}
+
+void StatisticsAnalyzer::PopulateFrameCountStat(
+    StatisticsEvent::Type event,
+    StatisticType stat,
+    StatisticsEvent::MediaType media_type,
+    SenderStats::StatisticsList& stats_list) {
+  FrameStatsMap& stats_map = frame_stats_.Get(media_type);
+
+  const auto it = stats_map.find(event);
+  if (it != stats_map.end()) {
+    stats_list[static_cast<int>(stat)] = it->second.event_counter;
+  }
+}
+
+void StatisticsAnalyzer::PopulateFpsStat(
+    StatisticsEvent::Type event,
+    StatisticType stat,
+    StatisticsEvent::MediaType media_type,
+    Clock::time_point end_time,
+    SenderStats::StatisticsList& stats_list) {
+  FrameStatsMap& stats_map = frame_stats_.Get(media_type);
+
+  const auto it = stats_map.find(event);
+  if (it != stats_map.end()) {
+    const Clock::duration duration = end_time - start_time_;
+    if (duration != Clock::duration::zero()) {
+      const int count = it->second.event_counter;
+      const double fps = (count / InMilliseconds(duration)) * 1000;
+      stats_list[static_cast<int>(stat)] = fps;
+    }
+  }
+}
+
+void StatisticsAnalyzer::PopulateAvgLatencyStat(
+    StatisticType stat,
+    StatisticsEvent::MediaType media_type,
+    SenderStats::StatisticsList& stats_list
+
+) {
+  LatencyStatsMap& latency_map = latency_stats_.Get(media_type);
+
+  const auto it = latency_map.find(stat);
+  if (it != latency_map.end() && it->second.data_point_counter > 0) {
+    const double avg_latency =
+        InMilliseconds(it->second.sum_latency) / it->second.data_point_counter;
+    stats_list[static_cast<int>(stat)] = avg_latency;
+  }
+}
+
+void StatisticsAnalyzer::PopulateFrameBitrateStat(
+    StatisticsEvent::Type event,
+    StatisticType stat,
+    StatisticsEvent::MediaType media_type,
+    Clock::time_point end_time,
+    SenderStats::StatisticsList& stats_list) {
+  FrameStatsMap& stats_map = frame_stats_.Get(media_type);
+
+  const auto it = stats_map.find(event);
+  if (it != stats_map.end()) {
+    const Clock::duration duration = end_time - start_time_;
+    if (duration != Clock::duration::zero()) {
+      const double kbps = it->second.sum_size / InMilliseconds(duration) * 8;
+      stats_list[static_cast<int>(stat)] = kbps;
+    }
+  }
+}
+
+void StatisticsAnalyzer::PopulatePacketBitrateStat(
+    StatisticsEvent::Type event,
+    StatisticType stat,
+    StatisticsEvent::MediaType media_type,
+    Clock::time_point end_time,
+    SenderStats::StatisticsList& stats_list) {
+  PacketStatsMap& stats_map = packet_stats_.Get(media_type);
+
+  auto it = stats_map.find(event);
+  if (it != stats_map.end()) {
+    const Clock::duration duration = end_time - start_time_;
+    if (duration != Clock::duration::zero()) {
+      const double kbps = it->second.sum_size / InMilliseconds(duration) * 8;
+      stats_list[static_cast<int>(stat)] = kbps;
+    }
+  }
+}
+
+void StatisticsAnalyzer::PopulateSessionStats(
+    StatisticsEvent::MediaType media_type,
+    Clock::time_point end_time,
+    SenderStats::StatisticsList& stats_list) {
+  SessionStats& session_stats = session_stats_.Get(media_type);
+
+  if (session_stats.first_event_time != Clock::time_point::min()) {
+    stats_list[static_cast<int>(StatisticType::kFirstEventTimeMs)] =
+        InMilliseconds(session_stats.first_event_time.time_since_epoch());
+  }
+
+  if (session_stats.last_event_time != Clock::time_point::min()) {
+    stats_list[static_cast<int>(StatisticType::kLastEventTimeMs)] =
+        InMilliseconds(session_stats.last_event_time.time_since_epoch());
+  }
+
+  if (session_stats.last_response_received_time != Clock::time_point::min()) {
+    stats_list[static_cast<int>(
+        StatisticType::kTimeSinceLastReceiverResponseMs)] =
+        InMilliseconds(end_time - session_stats.last_response_received_time);
+  }
+
+  stats_list[static_cast<int>(StatisticType::kNumLateFrames)] =
+      session_stats.late_frame_counter;
+}
+
+std::optional<Clock::time_point> StatisticsAnalyzer::ToSenderTimestamp(
+    Clock::time_point receiver_timestamp,
+    StatisticsEvent::MediaType media_type) const {
+  const std::optional<Clock::duration> receiver_offset =
+      offset_estimator_->GetEstimatedOffset();
+  if (!receiver_offset) {
+    return {};
+  }
+  return receiver_timestamp - *receiver_offset;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/statistics_analyzer.h

@@ -0,0 +1,208 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_STATISTICS_ANALYZER_H_
+#define CAST_STREAMING_IMPL_STATISTICS_ANALYZER_H_
+
+#include <map>
+#include <memory>
+#include <optional>
+#include <utility>
+#include <vector>
+
+#include "cast/streaming/impl/clock_offset_estimator.h"
+#include "cast/streaming/impl/statistics_collector.h"
+#include "cast/streaming/public/statistics.h"
+#include "platform/api/time.h"
+#include "util/alarm.h"
+#include "util/raw_ptr.h"
+
+namespace openscreen::cast {
+
+class StatisticsAnalyzer {
+ public:
+  StatisticsAnalyzer(SenderStatsClient* stats_client,
+                     ClockNowFunctionPtr now,
+                     TaskRunner& task_runner,
+                     std::unique_ptr<ClockOffsetEstimator> offset_estimator);
+  ~StatisticsAnalyzer();
+
+  void ScheduleAnalysis();
+
+  // Get the statistics collector managed by this analyzer.
+  StatisticsCollector* statistics_collector() {
+    return statistics_collector_.get();
+  }
+
+ private:
+  struct FrameStatsAggregate {
+    int event_counter;
+    uint32_t sum_size;
+    Clock::duration sum_delay;
+  };
+
+  struct PacketStatsAggregate {
+    int event_counter;
+    uint32_t sum_size;
+  };
+
+  struct LatencyStatsAggregate {
+    int data_point_counter;
+    Clock::duration sum_latency;
+  };
+
+  struct FrameInfo {
+    Clock::time_point capture_begin_time = Clock::time_point::min();
+    Clock::time_point capture_end_time = Clock::time_point::min();
+    Clock::time_point encode_end_time = Clock::time_point::min();
+  };
+
+  struct PacketInfo {
+    Clock::time_point timestamp;
+    StatisticsEvent::Type type;
+  };
+
+  struct SessionStats {
+    Clock::time_point first_event_time = Clock::time_point::max();
+    Clock::time_point last_event_time = Clock::time_point::min();
+    Clock::time_point last_response_received_time = Clock::time_point::min();
+    int late_frame_counter = 0;
+  };
+
+  // Named std::pair equivalent for audio + video classes.
+  template <typename T>
+  struct AVPair {
+    T audio;
+    T video;
+
+    const T& Get(StatisticsEvent::MediaType media_type) const {
+      if (media_type == StatisticsEvent::MediaType::kAudio) {
+        return audio;
+      }
+      OSP_CHECK(media_type == StatisticsEvent::MediaType::kVideo);
+      return video;
+    }
+    T& Get(StatisticsEvent::MediaType media_type) {
+      return const_cast<T&>(const_cast<const AVPair*>(this)->Get(media_type));
+    }
+  };
+
+  using FrameStatsMap = std::map<StatisticsEvent::Type, FrameStatsAggregate>;
+  using PacketStatsMap = std::map<StatisticsEvent::Type, PacketStatsAggregate>;
+  using LatencyStatsMap = std::map<StatisticType, LatencyStatsAggregate>;
+
+  using FrameInfoMap = std::map<RtpTimeTicks, FrameInfo>;
+  using PacketKey = std::pair<RtpTimeTicks, uint16_t>;
+  using PacketInfoMap = std::map<PacketKey, PacketInfo>;
+
+  // Initialize the stats histograms with the preferred min, max, and width.
+  void InitHistograms();
+
+  // Takes the Frame and Packet events from the `collector_`, and processes them
+  // into a form expected by `stats_client_`. Then sends the stats, and
+  // schedules a future analysis.
+  void AnalyzeStatistics();
+
+  // Constructs a stats list, and sends it to `stats_client_`;
+  void SendStatistics();
+
+  // Handles incoming stat events, and adds their infos to all of the proper
+  // stats maps / aggregates.
+  void ProcessFrameEvents(const std::vector<FrameEvent>& frame_events);
+  void ProcessPacketEvents(const std::vector<PacketEvent>& packet_events);
+  void RecordFrameLatencies(const FrameEvent& frame_event);
+  void RecordPacketLatencies(const PacketEvent& packet_event);
+  void RecordEventTimes(const StatisticsEvent& event);
+  void ErasePacketInfo(const PacketEvent& packet_event);
+  void AddToLatencyAggregrate(StatisticType latency_stat,
+                              Clock::duration latency_delta,
+                              StatisticsEvent::MediaType media_type);
+  void AddToHistogram(HistogramType histogram,
+                      StatisticsEvent::MediaType media_type,
+                      int64_t sample);
+
+  // Creates a stats list, and populates the entries based on stored stats info
+  // / aggregates for each stat field.
+  SenderStats::StatisticsList ConstructStatisticsList(
+      Clock::time_point end_time,
+      StatisticsEvent::MediaType media_type);
+
+  void PopulatePacketCountStat(StatisticsEvent::Type event,
+                               StatisticType stat,
+                               StatisticsEvent::MediaType media_type,
+                               SenderStats::StatisticsList& stats_list);
+
+  void PopulateFrameCountStat(StatisticsEvent::Type event,
+                              StatisticType stat,
+                              StatisticsEvent::MediaType media_type,
+                              SenderStats::StatisticsList& stats_list);
+
+  void PopulateFpsStat(StatisticsEvent::Type event,
+                       StatisticType stat,
+                       StatisticsEvent::MediaType media_type,
+                       Clock::time_point end_time,
+                       SenderStats::StatisticsList& stats_list);
+
+  void PopulateAvgLatencyStat(StatisticType stat,
+                              StatisticsEvent::MediaType media_type,
+                              SenderStats::StatisticsList& stats_list);
+
+  void PopulateFrameBitrateStat(StatisticsEvent::Type event,
+                                StatisticType stat,
+                                StatisticsEvent::MediaType media_type,
+                                Clock::time_point end_time,
+                                SenderStats::StatisticsList& stats_list);
+
+  void PopulatePacketBitrateStat(StatisticsEvent::Type event,
+                                 StatisticType stat,
+                                 StatisticsEvent::MediaType media_type,
+                                 Clock::time_point end_time,
+                                 SenderStats::StatisticsList& stats_list);
+
+  void PopulateSessionStats(StatisticsEvent::MediaType media_type,
+                            Clock::time_point end_time,
+                            SenderStats::StatisticsList& stats_list);
+
+  // Calculates the offset between the sender and receiver clocks and returns
+  // the sender-side version of this receiver timestamp, if possible.
+  std::optional<Clock::time_point> ToSenderTimestamp(
+      Clock::time_point receiver_timestamp,
+      StatisticsEvent::MediaType media_type) const;
+
+  // The statistics client to which we report analyzed statistics.
+  const raw_ptr<SenderStatsClient> stats_client_;
+
+  // The statistics collector from which we take the un-analyzed stats packets.
+  std::unique_ptr<StatisticsCollector> statistics_collector_;
+
+  // Keeps track of the best-guess clock offset between the sender and receiver.
+  std::unique_ptr<ClockOffsetEstimator> offset_estimator_;
+
+  // Keep track of time and events for this analyzer.
+  ClockNowFunctionPtr now_;
+  Alarm alarm_;
+  Clock::time_point start_time_;
+
+  // Maps of frame / packet infos used for stats that rely on seeing multiple
+  // events. For example, network latency is the calculated time difference
+  // between went a packet is sent, and when it is received.
+  AVPair<FrameInfoMap> recent_frame_infos_;
+  AVPair<PacketInfoMap> recent_packet_infos_;
+
+  // Aggregate statistics.
+  AVPair<FrameStatsMap> frame_stats_;
+  AVPair<PacketStatsMap> packet_stats_;
+  AVPair<LatencyStatsMap> latency_stats_;
+
+  // Stats that relate to the entirety of the session. For example, total late
+  // frames, or time of last event.
+  AVPair<SessionStats> session_stats_;
+
+  // Histograms.
+  AVPair<SenderStats::HistogramsList> histograms_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_STATISTICS_ANALYZER_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/statistics_collector.cc

@@ -0,0 +1,74 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/statistics_collector.h"
+
+#include <stdint.h>
+
+#include <limits>
+#include <utility>
+
+#include "cast/streaming/public/environment.h"
+#include "util/big_endian.h"
+
+namespace openscreen::cast {
+
+StatisticsCollector::StatisticsCollector(ClockNowFunctionPtr now) : now_(now) {}
+StatisticsCollector::~StatisticsCollector() = default;
+
+void StatisticsCollector::CollectPacketSentEvent(ByteView packet,
+                                                 PacketMetadata metadata) {
+  PacketEvent event;
+
+  // Populate the new PacketEvent by parsing the wire-format `packet`.
+  event.timestamp = now_();
+  event.type = StatisticsEvent::Type::kPacketSentToNetwork;
+
+  BigEndianReader reader(packet.data(), packet.size());
+  bool success = reader.Skip(4);
+  uint32_t truncated_rtp_timestamp = 0;
+  success &= reader.Read<uint32_t>(&truncated_rtp_timestamp);
+  success &= reader.Skip(4);
+
+  event.rtp_timestamp = metadata.rtp_timestamp.Expand(truncated_rtp_timestamp);
+  event.media_type = StatisticsEvent::ToMediaType(metadata.stream_type);
+
+  success &= reader.Skip(2);
+  success &= reader.Read<uint16_t>(&event.packet_id);
+  success &= reader.Read<uint16_t>(&event.max_packet_id);
+
+  // Check that the cast is safe.
+  // TODO(issuetracker.google.com/3576782): move to checked casts when ready.
+  static_assert(static_cast<uint64_t>(std::numeric_limits<uint32_t>::max()) <=
+                    static_cast<uint64_t>(std::numeric_limits<size_t>::max()),
+                "invalid type cast assumption");
+  OSP_CHECK_LE(packet.size(),
+               static_cast<size_t>(std::numeric_limits<uint32_t>::max()));
+  event.size = static_cast<uint32_t>(packet.size());
+  OSP_CHECK(success);
+
+  recent_packet_events_.emplace_back(event);
+}
+
+void StatisticsCollector::CollectPacketEvent(PacketEvent event) {
+  recent_packet_events_.emplace_back(event);
+}
+
+void StatisticsCollector::CollectFrameEvent(FrameEvent event) {
+  recent_frame_events_.emplace_back(event);
+}
+
+std::vector<PacketEvent> StatisticsCollector::TakeRecentPacketEvents() {
+  std::vector<PacketEvent> out;
+  recent_packet_events_.swap(out);
+  return out;
+}
+
+std::vector<FrameEvent> StatisticsCollector::TakeRecentFrameEvents() {
+  std::vector<FrameEvent> out;
+  recent_frame_events_.swap(out);
+  return out;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/statistics_collector.h

@@ -0,0 +1,64 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_STATISTICS_COLLECTOR_H_
+#define CAST_STREAMING_IMPL_STATISTICS_COLLECTOR_H_
+
+#include <vector>
+
+#include "cast/streaming/impl/statistics_common.h"
+#include "platform/api/time.h"
+#include "platform/base/span.h"
+
+namespace openscreen::cast {
+
+// This POD struct contains helpful information about a given packet that is
+// not stored directly on the packet itself.
+struct PacketMetadata {
+  // The stream type (audio, video, unknown) of this packet.
+  StreamType stream_type;
+
+  // The RTP timestamp associated with this packet.
+  RtpTimeTicks rtp_timestamp;
+};
+
+// This class is responsible for gathering packet and frame statistics using its
+// Collect*() methods, that can then be taken by consumers using the Take*()
+// methods.
+class StatisticsCollector {
+ public:
+  explicit StatisticsCollector(ClockNowFunctionPtr now);
+  ~StatisticsCollector();
+
+  // Informs the collector that a packet has been sent. The collector will then
+  // generate a packet event that is then  added to `recent_packet_events_`.
+  void CollectPacketSentEvent(ByteView packet, PacketMetadata metadata);
+
+  // Informs the collector that a packet event has occurred. This event is then
+  // added to `recent_packet_events_`.
+  void CollectPacketEvent(PacketEvent event);
+
+  // Informs the collector that a frame event has occurred. This event is then
+  // added to `recent_frame_events_`.
+  void CollectFrameEvent(FrameEvent event);
+
+  // Returns the current collection of packet events stored in
+  // `recent_packet_events_`. After calling this method, `recent_packet_events_`
+  // is reset to an empty vector.
+  std::vector<PacketEvent> TakeRecentPacketEvents();
+
+  // Returns the current collection of frame events stored in
+  // `recent_frame_events_`. After calling this method, `recent_frame_events_`
+  // is reset to an empty vector.
+  std::vector<FrameEvent> TakeRecentFrameEvents();
+
+ private:
+  ClockNowFunctionPtr now_;
+  std::vector<PacketEvent> recent_packet_events_;
+  std::vector<FrameEvent> recent_frame_events_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_STATISTICS_COLLECTOR_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/statistics_common.cc

@@ -0,0 +1,115 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/statistics_common.h"
+
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+// static
+StatisticsEvent::Type StatisticsEvent::FromWireType(WireType wire_type) {
+  switch (wire_type) {
+    case WireType::kAudioAckSent:
+    case WireType::kVideoAckSent:
+    case WireType::kUnifiedAckSent:
+      return Type::kFrameAckSent;
+
+    case WireType::kAudioPlayoutDelay:
+    case WireType::kVideoRenderDelay:
+    case WireType::kUnifiedRenderDelay:
+      return Type::kFramePlayedOut;
+
+    case WireType::kAudioFrameDecoded:
+    case WireType::kVideoFrameDecoded:
+    case WireType::kUnifiedFrameDecoded:
+      return Type::kFrameDecoded;
+
+    case WireType::kAudioPacketReceived:
+    case WireType::kVideoPacketReceived:
+    case WireType::kUnifiedPacketReceived:
+      return Type::kPacketReceived;
+
+    default:
+      OSP_VLOG << "Unexpected RTCP log message received: "
+               << static_cast<int>(wire_type);
+      return Type::kUnknown;
+  }
+}
+
+// static
+StatisticsEvent::WireType StatisticsEvent::ToWireType(Type type) {
+  switch (type) {
+    case Type::kUnknown:
+      return WireType::kUnknown;
+
+    case Type::kFrameAckSent:
+      return WireType::kUnifiedAckSent;
+
+    case Type::kFramePlayedOut:
+      return WireType::kUnifiedRenderDelay;
+
+    case Type::kFrameDecoded:
+      return WireType::kUnifiedFrameDecoded;
+
+    case Type::kPacketReceived:
+      return WireType::kUnifiedPacketReceived;
+
+    default:
+      OSP_VLOG << "Unknown RTCP log message event type: "
+               << static_cast<int>(type);
+      return WireType::kUnknown;
+  }
+}
+
+// static
+StatisticsEvent::MediaType StatisticsEvent::ToMediaType(StreamType type) {
+  switch (type) {
+    case StreamType::kUnknown:
+      return MediaType::kUnknown;
+    case StreamType::kAudio:
+      return MediaType::kAudio;
+    case StreamType::kVideo:
+      return MediaType::kVideo;
+  }
+
+  OSP_NOTREACHED();
+}
+
+StatisticsEvent::StatisticsEvent(const StatisticsEvent& other) = default;
+StatisticsEvent::StatisticsEvent(StatisticsEvent&& other) noexcept = default;
+StatisticsEvent& StatisticsEvent::operator=(const StatisticsEvent& other) =
+    default;
+StatisticsEvent& StatisticsEvent::operator=(StatisticsEvent&& other) = default;
+
+bool StatisticsEvent::operator==(const StatisticsEvent& other) const {
+  return frame_id == other.frame_id && type == other.type &&
+         media_type == other.media_type &&
+         rtp_timestamp == other.rtp_timestamp && size == other.size &&
+         timestamp == other.timestamp &&
+         received_timestamp == other.received_timestamp;
+}
+
+FrameEvent::FrameEvent(const FrameEvent& other) = default;
+FrameEvent::FrameEvent(FrameEvent&& other) noexcept = default;
+FrameEvent& FrameEvent::operator=(const FrameEvent& other) = default;
+FrameEvent& FrameEvent::operator=(FrameEvent&& other) = default;
+
+bool FrameEvent::operator==(const FrameEvent& other) const {
+  return StatisticsEvent::operator==(other) && width == other.width &&
+         height == other.height && delay_delta == other.delay_delta &&
+         key_frame == other.key_frame && target_bitrate == other.target_bitrate;
+}
+
+PacketEvent::PacketEvent(const PacketEvent& other) = default;
+PacketEvent::PacketEvent(PacketEvent&& other) noexcept = default;
+PacketEvent& PacketEvent::operator=(const PacketEvent& other) = default;
+PacketEvent& PacketEvent::operator=(PacketEvent&& other) = default;
+
+bool PacketEvent::operator==(const PacketEvent& other) const {
+  return StatisticsEvent::operator==(other) && packet_id == other.packet_id &&
+         max_packet_id == other.max_packet_id;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/statistics_common.h

@@ -0,0 +1,223 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_STATISTICS_COMMON_H_
+#define CAST_STREAMING_IMPL_STATISTICS_COMMON_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "cast/streaming/public/constants.h"
+#include "cast/streaming/public/frame_id.h"
+#include "cast/streaming/rtp_time.h"
+#include "platform/api/time.h"
+
+namespace openscreen::cast {
+
+struct StatisticsEvent {
+  enum class Type : int {
+    kUnknown = 0,
+
+    // Sender side frame events.
+    kFrameCaptureBegin = 1,
+    kFrameCaptureEnd = 2,
+    kFrameEncoded = 3,
+    kFrameAckReceived = 4,
+
+    // Receiver side frame events.
+    kFrameAckSent = 5,
+    kFrameDecoded = 6,
+    kFramePlayedOut = 7,
+
+    // Sender side packet events.
+    kPacketSentToNetwork = 8,
+    kPacketRetransmitted = 9,
+    kPacketRtxRejected = 10,
+
+    // Receiver side packet events.
+    kPacketReceived = 11,
+    kFrameDroppedByEncoder = 15,
+
+    kNumOfEvents = kFrameDroppedByEncoder + 1
+  };
+
+  // Serialized values for the statistics events for use by the RTCP builder
+  // and parser logic. *Do not modify existing values* since they are shared by
+  // both libcast-based devices as well as a variety of legacy implementations.
+  //
+  // NOTE: Events 1 to 8 have been replaced with events 11 to 14 (e.g.
+  // kAudioAckSent and kVideoAckSent merged into a single event kAckSent).
+  // Events 9 and 10 (to log duplicated packets) have been fully removed. Future
+  // events may reuse those values.
+  enum class WireType : uint8_t {
+    kUnknown = 0,
+
+    // Legacy audio event types.
+    kAudioAckSent = 1,
+    kAudioPlayoutDelay = 2,
+    kAudioFrameDecoded = 3,
+    kAudioPacketReceived = 4,
+
+    // Legacy video event types.
+    kVideoAckSent = 5,
+    kVideoRenderDelay = 6,
+    kVideoFrameDecoded = 7,
+    kVideoPacketReceived = 8,
+
+    // New unified event types.
+    kUnifiedAckSent = 11,
+    kUnifiedRenderDelay = 12,
+    kUnifiedFrameDecoded = 13,
+    kUnifiedPacketReceived = 14,
+
+    kNumOfEvents = kUnifiedPacketReceived + 1
+  };
+
+  enum class MediaType : int { kUnknown = 0, kAudio = 1, kVideo = 2 };
+
+  static Type FromWireType(WireType wire_type);
+  static WireType ToWireType(Type type);
+  static MediaType ToMediaType(StreamType type);
+
+  constexpr StatisticsEvent(FrameId frame_id,
+                            Type type,
+                            MediaType media_type,
+                            RtpTimeTicks rtp_timestamp,
+                            uint32_t size,
+                            Clock::time_point timestamp,
+                            Clock::time_point received_timestamp)
+      : frame_id(frame_id),
+        type(type),
+        media_type(media_type),
+        rtp_timestamp(rtp_timestamp),
+        size(size),
+        timestamp(timestamp),
+        received_timestamp(received_timestamp) {}
+
+  constexpr StatisticsEvent() = default;
+  StatisticsEvent(const StatisticsEvent& other);
+  StatisticsEvent(StatisticsEvent&& other) noexcept;
+  StatisticsEvent& operator=(const StatisticsEvent& other);
+  StatisticsEvent& operator=(StatisticsEvent&& other);
+  ~StatisticsEvent() = default;
+
+  bool operator==(const StatisticsEvent& other) const;
+
+  // The frame this event is associated with.
+  FrameId frame_id;
+
+  // The type of this frame event.
+  Type type = Type::kUnknown;
+
+  // Whether this was audio or video (or unknown).
+  MediaType media_type = MediaType::kUnknown;
+
+  // The RTP timestamp of the frame this event is associated with.
+  RtpTimeTicks rtp_timestamp;
+
+  // Size of this packet, or the frame it is associated with.
+  // Note: we use uint32_t instead of size_t for byte count because this struct
+  // is sent over IPC which could span 32 & 64 bit processes.
+  uint32_t size = 0;
+
+  // Time of event logged.
+  Clock::time_point timestamp;
+
+  // Time that the event was received by the sender. Only set for receiver-side
+  // events.
+  Clock::time_point received_timestamp;
+};
+
+struct FrameEvent : public StatisticsEvent {
+  constexpr FrameEvent(FrameId frame_id_in,
+                       Type type_in,
+                       MediaType media_type_in,
+                       RtpTimeTicks rtp_timestamp_in,
+                       uint32_t size_in,
+                       Clock::time_point timestamp_in,
+                       Clock::time_point received_timestamp_in,
+                       int width,
+                       int height,
+                       Clock::duration delay_delta,
+                       bool key_frame,
+                       int target_bitrate)
+      : StatisticsEvent(frame_id_in,
+                        type_in,
+                        media_type_in,
+                        rtp_timestamp_in,
+                        size_in,
+                        timestamp_in,
+                        received_timestamp_in),
+        width(width),
+        height(height),
+        delay_delta(delay_delta),
+        key_frame(key_frame),
+        target_bitrate(target_bitrate) {}
+
+  constexpr FrameEvent() = default;
+  FrameEvent(const FrameEvent& other);
+  FrameEvent(FrameEvent&& other) noexcept;
+  FrameEvent& operator=(const FrameEvent& other);
+  FrameEvent& operator=(FrameEvent&& other);
+  ~FrameEvent() = default;
+
+  bool operator==(const FrameEvent& other) const;
+
+  // Resolution of the frame. Only set for video FRAME_CAPTURE_END events.
+  int width = 0;
+  int height = 0;
+
+  // Only set for FRAME_PLAYOUT events.
+  // If this value is zero the frame is rendered on time.
+  // If this value is positive it means the frame is rendered late.
+  // If this value is negative it means the frame is rendered early.
+  Clock::duration delay_delta{};
+
+  // Whether the frame is a key frame. Only set for video FRAME_ENCODED event.
+  bool key_frame = false;
+
+  // The requested target bitrate of the encoder at the time the frame is
+  // encoded. Only set for video FRAME_ENCODED event.
+  int target_bitrate = 0;
+};
+
+struct PacketEvent : public StatisticsEvent {
+  constexpr PacketEvent(FrameId frame_id_in,
+                        Type type_in,
+                        MediaType media_type_in,
+                        RtpTimeTicks rtp_timestamp_in,
+                        uint32_t size_in,
+                        Clock::time_point timestamp_in,
+                        Clock::time_point received_timestamp_in,
+                        uint16_t packet_id,
+                        uint16_t max_packet_id)
+      : StatisticsEvent(frame_id_in,
+                        type_in,
+                        media_type_in,
+                        rtp_timestamp_in,
+                        size_in,
+                        timestamp_in,
+                        received_timestamp_in),
+        packet_id(packet_id),
+        max_packet_id(max_packet_id) {}
+
+  constexpr PacketEvent() = default;
+  PacketEvent(const PacketEvent& other);
+  PacketEvent(PacketEvent&& other) noexcept;
+  PacketEvent& operator=(const PacketEvent& other);
+  PacketEvent& operator=(PacketEvent&& other);
+  ~PacketEvent() = default;
+
+  bool operator==(const PacketEvent& other) const;
+
+  // The packet this event is associated with.
+  uint16_t packet_id = 0;
+
+  // The highest packet ID seen so far at time of event.
+  uint16_t max_packet_id = 0;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_STATISTICS_COMMON_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/statistics_dispatcher.cc

@@ -0,0 +1,163 @@
+// Copyright 2025 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/impl/statistics_dispatcher.h"
+
+#include <utility>
+
+#include "cast/streaming/impl/rtcp_common.h"
+#include "cast/streaming/impl/rtp_defines.h"
+#include "cast/streaming/impl/statistics_collector.h"
+#include "cast/streaming/impl/statistics_common.h"
+#include "cast/streaming/public/encoded_frame.h"
+#include "cast/streaming/public/environment.h"
+#include "cast/streaming/public/session_config.h"
+#include "platform/base/trivial_clock_traits.h"
+#include "util/chrono_helpers.h"
+#include "util/osp_logging.h"
+#include "util/std_util.h"
+#include "util/trace_logging.h"
+
+namespace openscreen::cast {
+
+using clock_operators::operator<<;
+
+StatisticsDispatcher::StatisticsDispatcher(Environment& environment)
+    : environment_(environment) {}
+StatisticsDispatcher::~StatisticsDispatcher() = default;
+
+void StatisticsDispatcher::DispatchEnqueueEvents(StreamType stream_type,
+                                                 const EncodedFrame& frame) {
+  if (!environment_->statistics_collector()) {
+    return;
+  }
+  const auto media_type = StatisticsEvent::ToMediaType(stream_type);
+
+  // Submit a capture begin event.
+  FrameEvent capture_begin_event;
+  capture_begin_event.type = StatisticsEvent::Type::kFrameCaptureBegin;
+  capture_begin_event.media_type = media_type;
+  capture_begin_event.rtp_timestamp = frame.rtp_timestamp;
+  capture_begin_event.timestamp =
+      (frame.capture_begin_time > Clock::time_point::min())
+          ? frame.capture_begin_time
+          : environment_->now();
+  environment_->statistics_collector()->CollectFrameEvent(
+      std::move(capture_begin_event));
+
+  // Submit a capture end event.
+  FrameEvent capture_end_event;
+  capture_end_event.type = StatisticsEvent::Type::kFrameCaptureEnd;
+  capture_end_event.media_type = media_type;
+  capture_end_event.rtp_timestamp = frame.rtp_timestamp;
+  capture_end_event.timestamp =
+      (frame.capture_end_time > Clock::time_point::min())
+          ? frame.capture_end_time
+          : environment_->now();
+  environment_->statistics_collector()->CollectFrameEvent(
+      std::move(capture_end_event));
+
+  // Submit an encoded event.
+  FrameEvent encode_event;
+  encode_event.timestamp = environment_->now();
+  encode_event.type = StatisticsEvent::Type::kFrameEncoded;
+  encode_event.media_type = media_type;
+  encode_event.rtp_timestamp = frame.rtp_timestamp;
+  encode_event.frame_id = frame.frame_id;
+  encode_event.size = static_cast<uint32_t>(frame.data.size());
+  encode_event.key_frame =
+      frame.dependency == openscreen::cast::EncodedFrame::Dependency::kKeyFrame;
+
+  environment_->statistics_collector()->CollectFrameEvent(
+      std::move(encode_event));
+}
+
+void StatisticsDispatcher::DispatchAckEvent(StreamType stream_type,
+                                            RtpTimeTicks rtp_timestamp,
+                                            FrameId frame_id) {
+  if (!environment_->statistics_collector()) {
+    return;
+  }
+
+  FrameEvent ack_event;
+  ack_event.timestamp = environment_->now();
+  ack_event.type = StatisticsEvent::Type::kFrameAckReceived;
+  ack_event.media_type = StatisticsEvent::ToMediaType(stream_type);
+  ack_event.rtp_timestamp = rtp_timestamp;
+  ack_event.frame_id = frame_id;
+
+  environment_->statistics_collector()->CollectFrameEvent(std::move(ack_event));
+}
+
+void StatisticsDispatcher::DispatchFrameDropEvent(StreamType stream_type,
+                                                  FrameId frame_id,
+                                                  RtpTimeTicks rtp_timestamp,
+                                                  Clock::time_point drop_time) {
+  if (!environment_->statistics_collector()) {
+    return;
+  }
+
+  FrameEvent drop_event;
+  drop_event.timestamp = drop_time;
+  drop_event.type = StatisticsEvent::Type::kFrameDroppedByEncoder;
+  drop_event.media_type = StatisticsEvent::ToMediaType(stream_type);
+  drop_event.rtp_timestamp = rtp_timestamp;
+  drop_event.frame_id = frame_id;
+
+  environment_->statistics_collector()->CollectFrameEvent(
+      std::move(drop_event));
+}
+
+void StatisticsDispatcher::DispatchFrameLogMessages(
+    StreamType stream_type,
+    const std::vector<RtcpReceiverFrameLogMessage>& messages) {
+  if (!environment_->statistics_collector()) {
+    return;
+  }
+
+  const Clock::time_point now = environment_->now();
+  const auto media_type = StatisticsEvent::ToMediaType(stream_type);
+  for (const RtcpReceiverFrameLogMessage& log_message : messages) {
+    for (const RtcpReceiverEventLogMessage& event_message :
+         log_message.messages) {
+      switch (event_message.type) {
+        case StatisticsEvent::Type::kPacketReceived: {
+          PacketEvent event;
+          event.timestamp = event_message.timestamp;
+          event.received_timestamp = now;
+          event.type = event_message.type;
+          event.media_type = media_type;
+          event.rtp_timestamp = log_message.rtp_timestamp;
+          event.packet_id = event_message.packet_id;
+          environment_->statistics_collector()->CollectPacketEvent(
+              std::move(event));
+        } break;
+
+        case StatisticsEvent::Type::kFrameAckSent:
+        case StatisticsEvent::Type::kFrameDecoded:
+        case StatisticsEvent::Type::kFramePlayedOut: {
+          FrameEvent event;
+          event.timestamp = event_message.timestamp;
+          event.received_timestamp = now;
+          event.type = event_message.type;
+          event.media_type = media_type;
+          event.rtp_timestamp = log_message.rtp_timestamp;
+          if (event.type == StatisticsEvent::Type::kFramePlayedOut) {
+            event.delay_delta = event_message.delay;
+          }
+          environment_->statistics_collector()->CollectFrameEvent(
+              std::move(event));
+        } break;
+
+        default:
+          OSP_VLOG << "Received log message via RTCP that we did not expect, "
+                      "StatisticsEvent::Type="
+                   << static_cast<int>(event_message.type);
+          break;
+      }
+    }
+  }
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/impl/statistics_dispatcher.h

@@ -0,0 +1,58 @@
+// Copyright 2025 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_IMPL_STATISTICS_DISPATCHER_H_
+#define CAST_STREAMING_IMPL_STATISTICS_DISPATCHER_H_
+
+#include <vector>
+
+#include "cast/streaming/impl/statistics_common.h"
+#include "platform/api/time.h"
+#include "platform/base/span.h"
+#include "util/raw_ref.h"
+
+namespace openscreen::cast {
+
+class StatisticsCollector;
+class Environment;
+struct EncodedFrame;
+struct RtcpReceiverFrameLogMessage;
+
+// This class is responsible for dispatching statistics events.
+class StatisticsDispatcher {
+ public:
+  explicit StatisticsDispatcher(Environment& environment);
+
+  StatisticsDispatcher(const StatisticsDispatcher&) = delete;
+  StatisticsDispatcher& operator=(const StatisticsDispatcher&) = delete;
+  StatisticsDispatcher(StatisticsDispatcher&&) noexcept = delete;
+  StatisticsDispatcher& operator=(StatisticsDispatcher&&) = delete;
+  ~StatisticsDispatcher();
+
+  // Dispatches enqueue events for a given frame.
+  void DispatchEnqueueEvents(StreamType stream_type, const EncodedFrame& frame);
+
+  // Dispatches frame log messages.
+  void DispatchFrameLogMessages(
+      StreamType stream_type,
+      const std::vector<RtcpReceiverFrameLogMessage>& messages);
+
+  // Dispatches an ack event.
+  void DispatchAckEvent(StreamType stream_type,
+                        RtpTimeTicks rtp_timestamp,
+                        FrameId frame_id);
+
+  // Dispatches a frame dropped by encoder event.
+  void DispatchFrameDropEvent(StreamType stream_type,
+                              FrameId frame_id,
+                              RtpTimeTicks rtp_timestamp,
+                              Clock::time_point drop_time);
+
+ private:
+  const raw_ref<Environment> environment_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_IMPL_STATISTICS_DISPATCHER_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/message_fields.cc

@@ -0,0 +1,47 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/message_fields.h"
+
+#include <array>
+#include <utility>
+
+#include "util/enum_name_table.h"
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+namespace {
+
+constexpr EnumNameTable<AudioCodec, 3> kAudioCodecNames{
+    {{"aac", AudioCodec::kAac},
+     {"opus", AudioCodec::kOpus},
+     {"REMOTE_AUDIO", AudioCodec::kNotSpecified}}};
+
+constexpr EnumNameTable<VideoCodec, 6> kVideoCodecNames{
+    {{"h264", VideoCodec::kH264},
+     {"vp8", VideoCodec::kVp8},
+     {"hevc", VideoCodec::kHevc},
+     {"REMOTE_VIDEO", VideoCodec::kNotSpecified},
+     {"vp9", VideoCodec::kVp9},
+     {"av1", VideoCodec::kAv1}}};
+
+}  // namespace
+
+const char* CodecToString(AudioCodec codec) {
+  return GetEnumName(kAudioCodecNames, codec).value();
+}
+
+ErrorOr<AudioCodec> StringToAudioCodec(std::string_view name) {
+  return GetEnum(kAudioCodecNames, name);
+}
+
+const char* CodecToString(VideoCodec codec) {
+  return GetEnumName(kVideoCodecNames, codec).value();
+}
+
+ErrorOr<VideoCodec> StringToVideoCodec(std::string_view name) {
+  return GetEnum(kVideoCodecNames, name);
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/message_fields.h

@@ -0,0 +1,59 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_MESSAGE_FIELDS_H_
+#define CAST_STREAMING_MESSAGE_FIELDS_H_
+
+#include <string>
+#include <string_view>
+
+#include "cast/streaming/public/constants.h"
+#include "platform/base/error.h"
+
+namespace openscreen::cast {
+
+/// NOTE: Constants here are all taken from the Cast V2: Mirroring Control
+/// Protocol specification.
+
+// Namespace for OFFER/ANSWER messages.
+inline constexpr char kCastWebrtcNamespace[] =
+    "urn:x-cast:com.google.cast.webrtc";
+inline constexpr char kCastRemotingNamespace[] =
+    "urn:x-cast:com.google.cast.remoting";
+
+// JSON message field values specific to the Sender Session.
+inline constexpr char kMessageType[] = "type";
+
+// List of OFFER message fields.
+inline constexpr char kMessageTypeOffer[] = "OFFER";
+inline constexpr char kOfferMessageBody[] = "offer";
+inline constexpr char kSequenceNumber[] = "seqNum";
+inline constexpr char kCodecName[] = "codecName";
+
+/// ANSWER message fields.
+inline constexpr char kMessageTypeAnswer[] = "ANSWER";
+inline constexpr char kAnswerMessageBody[] = "answer";
+inline constexpr char kResult[] = "result";
+inline constexpr char kResultOk[] = "ok";
+inline constexpr char kResultError[] = "error";
+inline constexpr char kErrorMessageBody[] = "error";
+inline constexpr char kErrorCode[] = "code";
+inline constexpr char kErrorDescription[] = "description";
+
+// Other message fields.
+inline constexpr char kRpcMessageBody[] = "rpc";
+inline constexpr char kInputMessageBody[] = "input";
+inline constexpr char kCapabilitiesMessageBody[] = "capabilities";
+inline constexpr char kStatusMessageBody[] = "status";
+
+// Conversion methods for codec message fields.
+const char* CodecToString(AudioCodec codec);
+ErrorOr<AudioCodec> StringToAudioCodec(std::string_view name);
+
+const char* CodecToString(VideoCodec codec);
+ErrorOr<VideoCodec> StringToVideoCodec(std::string_view name);
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_MESSAGE_FIELDS_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/answer_messages.cc

@@ -0,0 +1,498 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/answer_messages.h"
+
+#include <string_view>
+#include <utility>
+
+#include "cast/streaming/public/constants.h"
+#include "platform/base/error.h"
+#include "util/enum_name_table.h"
+#include "util/json/json_helpers.h"
+#include "util/osp_logging.h"
+#include "util/string_parse.h"
+#include "util/string_util.h"
+#include "util/stringprintf.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+/// Constraint properties.
+// Audio constraints. See properties below.
+constexpr char kAudio[] = "audio";
+// Video constraints. See properties below.
+constexpr char kVideo[] = "video";
+
+// An optional field representing the minimum bits per second. If not specified
+// by the receiver, the sender will use kDefaultAudioMinBitRate and
+// kDefaultVideoMinBitRate, which represent the true operational minimum.
+constexpr char kMinBitRate[] = "minBitRate";
+
+// Maximum encoded bits per second. This is the lower of (1) the max capability
+// of the decoder, or (2) the max data transfer rate.
+constexpr char kMaxBitRate[] = "maxBitRate";
+// Maximum supported end-to-end latency, in milliseconds. Proportional to the
+// size of the data buffers in the receiver.
+constexpr char kMaxDelay[] = "maxDelay";
+
+/// Video constraint properties.
+// Maximum pixel rate (width * height * framerate). Is often less than
+// multiplying the fields in maxDimensions. This field is used to set the
+// maximum processing rate.
+constexpr char kMaxPixelsPerSecond[] = "maxPixelsPerSecond";
+// Minimum dimensions. If omitted, the sender will assume a reasonable minimum
+// with the same aspect ratio as maxDimensions, as close to 320*180 as possible.
+// Should reflect the true operational minimum.
+constexpr char kMinResolution[] = "minResolution";
+// Maximum dimensions, not necessarily ideal dimensions.
+constexpr char kMaxDimensions[] = "maxDimensions";
+
+/// Audio constraint properties.
+// Maximum supported sampling frequency (not necessarily ideal).
+constexpr char kMaxSampleRate[] = "maxSampleRate";
+// Maximum number of audio channels (1 is mono, 2 is stereo, etc.).
+constexpr char kMaxChannels[] = "maxChannels";
+
+/// Display description properties
+// If this optional field is included in the ANSWER message, the receiver is
+// attached to a fixed display that has the given dimensions and frame rate
+// configuration. These may exceed, be the same, or be less than the values in
+// constraints. If undefined, we assume the display is not fixed (e.g. a Google
+// Hangouts UI panel).
+constexpr char kDimensions[] = "dimensions";
+// An optional field. When missing and dimensions are specified, the sender
+// will assume square pixels and the dimensions imply the aspect ratio of the
+// fixed display. WHen present and dimensions are also specified, implies the
+// pixels are not square.
+constexpr char kAspectRatio[] = "aspectRatio";
+// The delimeter used for the aspect ratio format ("A:B").
+constexpr char kAspectRatioDelimiter = ':';
+// Sets the aspect ratio constraints. Value must be either "sender" or
+// "receiver", see kScalingSender and kScalingReceiver below.
+constexpr char kScaling[] = "scaling";
+// scaling = "sender" means that the sender must provide video frames of a fixed
+// aspect ratio. In this case, the dimensions object must be passed or an error
+// case will occur.
+constexpr char kScalingSender[] = "sender";
+// scaling = "receiver" means that the sender may send arbitrarily sized frames,
+// and the receiver will handle scaling and letterboxing as necessary.
+constexpr char kScalingReceiver[] = "receiver";
+
+/// Answer properties.
+// A number specifying the UDP port used for all streams in this session.
+// Must have a value between kUdpPortMin and kUdpPortMax.
+constexpr char kUdpPort[] = "udpPort";
+constexpr int kUdpPortMin = 1;
+constexpr int kUdpPortMax = 65535;
+// Numbers specifying the indexes chosen from the offer message.
+constexpr char kSendIndexes[] = "sendIndexes";
+// uint32_t values specifying the RTP SSRC values used to send the RTCP feedback
+// of the stream indicated in kSendIndexes.
+constexpr char kSsrcs[] = "ssrcs";
+// Provides detailed maximum and minimum capabilities of the receiver for
+// processing the selected streams. The sender may alter video resolution and
+// frame rate throughout the session, and the constraints here determine how
+// much data volume is allowed.
+constexpr char kConstraints[] = "constraints";
+// Provides details about the display on the receiver.
+constexpr char kDisplay[] = "display";
+// std::optional array of numbers specifying the indexes of streams that will
+// send event logs through RTCP.
+constexpr char kReceiverRtcpEventLog[] = "receiverRtcpEventLog";
+// Optional array of numbers specifying the indexes of streams that will use
+// DSCP values specified in the OFFER message for RTCP packets.
+constexpr char kReceiverRtcpDscp[] = "receiverRtcpDscp";
+// If this optional field is present the receiver supports the specific
+// RTP extensions (such as adaptive playout delay).
+constexpr char kRtpExtensions[] = "rtpExtensions";
+
+EnumNameTable<AspectRatioConstraint, 2> kAspectRatioConstraintNames{
+    {{kScalingReceiver, AspectRatioConstraint::kVariable},
+     {kScalingSender, AspectRatioConstraint::kFixed}}};
+
+Json::Value AspectRatioConstraintToJson(AspectRatioConstraint aspect_ratio) {
+  return Json::Value(GetEnumName(kAspectRatioConstraintNames, aspect_ratio)
+                         .value(kScalingSender));
+}
+
+std::optional<AspectRatioConstraint> TryParseAspectRatioConstraint(
+    const Json::Value& value) {
+  std::string aspect_ratio;
+  if (!json::TryParseString(value, &aspect_ratio)) {
+    return std::nullopt;
+  }
+
+  ErrorOr<AspectRatioConstraint> constraint =
+      GetEnum(kAspectRatioConstraintNames, aspect_ratio);
+  if (constraint.is_error()) {
+    return std::nullopt;
+  }
+  return constraint.value();
+}
+
+template <typename T>
+ErrorOr<std::optional<T>> ParseOptional(const Json::Value& value) {
+  if (!value) {
+    return std::optional<T>{};
+  }
+  auto out = T::TryParse(value);
+  if (out.is_error()) {
+    return out.error();
+  }
+  return std::optional<T>{std::move(out.value())};
+}
+
+}  // namespace
+
+// static
+ErrorOr<AspectRatio> AspectRatio::TryParse(const Json::Value& value) {
+  std::string parsed_value;
+  if (!json::TryParseString(value, &parsed_value)) {
+    return Error(Error::Code::kJsonParseError, "Invalid aspect ratio string");
+  }
+
+  std::vector<std::string_view> fields =
+      string_util::Split(parsed_value, kAspectRatioDelimiter);
+  if (fields.size() != 2) {
+    return Error(Error::Code::kJsonParseError, "Invalid aspect ratio format");
+  }
+
+  AspectRatio out;
+  if (!string_parse::ParseAsciiNumber(fields[0], out.width) ||
+      !string_parse::ParseAsciiNumber(fields[1], out.height)) {
+    return Error(Error::Code::kJsonParseError, "Invalid aspect ratio values");
+  }
+  if (!out.IsValid()) {
+    return Error(Error::Code::kJsonParseError, "Invalid aspect ratio");
+  }
+  return out;
+}
+
+bool AspectRatio::IsValid() const {
+  return width > 0 && height > 0;
+}
+
+// static
+ErrorOr<AudioConstraints> AudioConstraints::TryParse(const Json::Value& root) {
+  if (!root.isObject()) {
+    return Error(Error::Code::kJsonParseError,
+                 "Audio constraints is not a JSON object");
+  }
+
+  AudioConstraints out;
+  if (!json::TryParseInt(root[kMaxSampleRate], &out.max_sample_rate) ||
+      !json::TryParseInt(root[kMaxChannels], &out.max_channels) ||
+      !json::TryParseInt(root[kMaxBitRate], &out.max_bit_rate)) {
+    return Error(Error::Code::kJsonParseError, "Invalid audio constraints");
+  }
+
+  std::chrono::milliseconds max_delay;
+  if (json::TryParseMilliseconds(root[kMaxDelay], &max_delay)) {
+    out.max_delay = max_delay;
+  }
+
+  if (!json::TryParseInt(root[kMinBitRate], &out.min_bit_rate)) {
+    out.min_bit_rate = kDefaultAudioMinBitRate;
+  }
+  if (!out.IsValid()) {
+    return Error(Error::Code::kJsonParseError, "Invalid audio constraints");
+  }
+  return out;
+}
+
+Json::Value AudioConstraints::ToJson() const {
+  OSP_CHECK(IsValid());
+  Json::Value root;
+  root[kMaxSampleRate] = max_sample_rate;
+  root[kMaxChannels] = max_channels;
+  root[kMinBitRate] = min_bit_rate;
+  root[kMaxBitRate] = max_bit_rate;
+  if (max_delay.has_value()) {
+    root[kMaxDelay] = Json::Value::Int64(max_delay->count());
+  }
+  return root;
+}
+
+bool AudioConstraints::IsValid() const {
+  return max_sample_rate > 0 && max_channels > 0 && min_bit_rate > 0 &&
+         max_bit_rate >= min_bit_rate;
+}
+
+// static
+ErrorOr<VideoConstraints> VideoConstraints::TryParse(const Json::Value& root) {
+  if (!root.isObject()) {
+    return Error(Error::Code::kJsonParseError,
+                 "Video constraints is not a JSON object");
+  }
+
+  VideoConstraints out;
+
+  auto max_dimensions = Dimensions::TryParse(root[kMaxDimensions]);
+  if (max_dimensions.is_error()) {
+    return max_dimensions.error();
+  }
+  out.max_dimensions = std::move(max_dimensions.value());
+
+  if (!json::TryParseInt(root[kMaxBitRate], &out.max_bit_rate)) {
+    return Error(Error::Code::kJsonParseError,
+                 "Invalid video constraints: missing maxBitRate");
+  }
+
+  auto min_resolution = ParseOptional<Dimensions>(root[kMinResolution]);
+  if (min_resolution.is_error()) {
+    return min_resolution.error();
+  }
+  out.min_resolution = std::move(min_resolution.value());
+
+  std::chrono::milliseconds max_delay;
+  if (json::TryParseMilliseconds(root[kMaxDelay], &max_delay)) {
+    out.max_delay = max_delay;
+  }
+
+  double max_pixels_per_second;
+  if (json::TryParseDouble(root[kMaxPixelsPerSecond], &max_pixels_per_second)) {
+    out.max_pixels_per_second = max_pixels_per_second;
+  }
+
+  if (!json::TryParseInt(root[kMinBitRate], &out.min_bit_rate)) {
+    out.min_bit_rate = kDefaultVideoMinBitRate;
+  }
+  if (!out.IsValid()) {
+    return Error(Error::Code::kJsonParseError, "Invalid video constraints");
+  }
+  return out;
+}
+
+bool VideoConstraints::IsValid() const {
+  return max_pixels_per_second > 0 && min_bit_rate > 0 &&
+         max_bit_rate > min_bit_rate &&
+         (!max_delay.has_value() || max_delay->count() > 0) &&
+         max_dimensions.IsValid() &&
+         (!min_resolution.has_value() || min_resolution->IsValid()) &&
+         max_dimensions.frame_rate.numerator() > 0;
+}
+
+Json::Value VideoConstraints::ToJson() const {
+  OSP_CHECK(IsValid());
+  Json::Value root;
+  root[kMaxDimensions] = max_dimensions.ToJson();
+  root[kMinBitRate] = min_bit_rate;
+  root[kMaxBitRate] = max_bit_rate;
+  if (max_pixels_per_second.has_value()) {
+    root[kMaxPixelsPerSecond] = max_pixels_per_second.value();
+  }
+
+  if (min_resolution.has_value()) {
+    root[kMinResolution] = min_resolution->ToJson();
+  }
+
+  if (max_delay.has_value()) {
+    root[kMaxDelay] = Json::Value::Int64(max_delay->count());
+  }
+  return root;
+}
+
+// static
+ErrorOr<Constraints> Constraints::TryParse(const Json::Value& root) {
+  if (!root.isObject()) {
+    return Error(Error::Code::kJsonParseError,
+                 "Constraints is not a JSON object");
+  }
+
+  Constraints out;
+
+  auto audio = AudioConstraints::TryParse(root[kAudio]);
+  if (audio.is_error()) {
+    return audio.error();
+  }
+  out.audio = std::move(audio.value());
+
+  auto video = VideoConstraints::TryParse(root[kVideo]);
+  if (video.is_error()) {
+    return video.error();
+  }
+  out.video = std::move(video.value());
+
+  if (!out.IsValid()) {
+    return Error(Error::Code::kJsonParseError, "Invalid constraints");
+  }
+  return out;
+}
+
+bool Constraints::IsValid() const {
+  return audio.IsValid() && video.IsValid();
+}
+
+Json::Value Constraints::ToJson() const {
+  OSP_CHECK(IsValid());
+  Json::Value root;
+  root[kAudio] = audio.ToJson();
+  root[kVideo] = video.ToJson();
+  return root;
+}
+
+// static
+ErrorOr<DisplayDescription> DisplayDescription::TryParse(
+    const Json::Value& root) {
+  if (!root.isObject()) {
+    return Error(Error::Code::kJsonParseError,
+                 "Display description is not a JSON object");
+  }
+
+  DisplayDescription out;
+
+  auto dimensions = ParseOptional<Dimensions>(root[kDimensions]);
+  if (dimensions.is_error()) {
+    return dimensions.error();
+  }
+  out.dimensions = std::move(dimensions.value());
+
+  auto aspect_ratio = ParseOptional<AspectRatio>(root[kAspectRatio]);
+  if (aspect_ratio.is_error()) {
+    return aspect_ratio.error();
+  }
+  out.aspect_ratio = std::move(aspect_ratio.value());
+
+  auto constraint = TryParseAspectRatioConstraint(root[kScaling]);
+  if (constraint.has_value()) {
+    out.aspect_ratio_constraint = constraint.value();
+  } else {
+    out.aspect_ratio_constraint = std::nullopt;
+  }
+
+  if (!out.IsValid()) {
+    return Error(Error::Code::kJsonParseError, "Invalid display description");
+  }
+  return out;
+}
+
+bool DisplayDescription::IsValid() const {
+  // At least one of the properties must be set, and if a property is set
+  // it must be valid.
+  if (aspect_ratio.has_value() && !aspect_ratio->IsValid()) {
+    return false;
+  }
+
+  if (dimensions.has_value() && !dimensions->IsValid()) {
+    return false;
+  }
+
+  // Sender behavior is undefined if the aspect ratio is fixed but no
+  // dimensions or aspect ratio are provided.
+  if (aspect_ratio_constraint.has_value() &&
+      (aspect_ratio_constraint.value() == AspectRatioConstraint::kFixed) &&
+      !dimensions.has_value() && !aspect_ratio.has_value()) {
+    return false;
+  }
+  return aspect_ratio.has_value() || dimensions.has_value() ||
+         aspect_ratio_constraint.has_value();
+}
+
+Json::Value DisplayDescription::ToJson() const {
+  OSP_CHECK(IsValid());
+  Json::Value root;
+  if (aspect_ratio.has_value()) {
+    root[kAspectRatio] =
+        StringFormat("{}{}{}", aspect_ratio->width, kAspectRatioDelimiter,
+                     aspect_ratio->height);
+  }
+  if (dimensions.has_value()) {
+    root[kDimensions] = dimensions->ToJson();
+  }
+  if (aspect_ratio_constraint.has_value()) {
+    root[kScaling] =
+        AspectRatioConstraintToJson(aspect_ratio_constraint.value());
+  }
+  return root;
+}
+
+ErrorOr<Answer> Answer::TryParse(const Json::Value& root) {
+  if (!root.isObject()) {
+    return Error(Error::Code::kJsonParseError, "Answer is not a JSON object");
+  }
+
+  Answer out;
+  if (!json::TryParseInt(root[kUdpPort], &out.udp_port) ||
+      !json::TryParseIntArray(root[kSendIndexes], &out.send_indexes) ||
+      !json::TryParseUintArray(root[kSsrcs], &out.ssrcs)) {
+    return Error(Error::Code::kJsonParseError,
+                 "Invalid answer: missing or invalid mandatory fields");
+  }
+
+  auto constraints = ParseOptional<Constraints>(root[kConstraints]);
+  if (constraints.is_error()) {
+    return constraints.error();
+  }
+  out.constraints = std::move(constraints.value());
+
+  auto display = ParseOptional<DisplayDescription>(root[kDisplay]);
+  if (display.is_error()) {
+    return display.error();
+  }
+  out.display = std::move(display.value());
+
+  // These functions set to empty array if not present, so we can ignore
+  // the return value for optional values.
+  json::TryParseIntArray(root[kReceiverRtcpEventLog],
+                         &out.receiver_rtcp_event_log);
+  json::TryParseIntArray(root[kReceiverRtcpDscp], &out.receiver_rtcp_dscp);
+  json::TryParseNestedStringArray(root[kRtpExtensions], &out.rtp_extensions);
+
+  if (!out.IsValid()) {
+    return Error(Error::Code::kJsonParseError, "Invalid answer");
+  }
+  return out;
+}
+
+bool Answer::IsValid() const {
+  if (ssrcs.empty() || send_indexes.empty()) {
+    return false;
+  }
+
+  // We don't know what the indexes used in the offer were here, so we just
+  // sanity check.
+  for (const int index : send_indexes) {
+    if (index < 0) {
+      return false;
+    }
+  }
+  if (constraints.has_value() && !constraints->IsValid()) {
+    return false;
+  }
+  if (display.has_value() && !display->IsValid()) {
+    return false;
+  }
+  return kUdpPortMin <= udp_port && udp_port <= kUdpPortMax;
+}
+
+Json::Value Answer::ToJson() const {
+  OSP_CHECK(IsValid());
+  Json::Value root;
+  if (constraints.has_value()) {
+    root[kConstraints] = constraints->ToJson();
+  }
+  if (display.has_value()) {
+    root[kDisplay] = display->ToJson();
+  }
+  root[kUdpPort] = udp_port;
+  root[kSendIndexes] = json::PrimitiveVectorToJson(send_indexes);
+  root[kSsrcs] = json::PrimitiveVectorToJson(ssrcs);
+  // Some sender do not handle empty array properly, so we omit these fields
+  // if they are empty.
+  if (!receiver_rtcp_event_log.empty()) {
+    root[kReceiverRtcpEventLog] =
+        json::PrimitiveVectorToJson(receiver_rtcp_event_log);
+  }
+  if (!receiver_rtcp_dscp.empty()) {
+    root[kReceiverRtcpDscp] = json::PrimitiveVectorToJson(receiver_rtcp_dscp);
+  }
+  if (!rtp_extensions.empty()) {
+    root[kRtpExtensions] = json::NestedStringArrayToJson(rtp_extensions);
+  }
+  return root;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/answer_messages.h

@@ -0,0 +1,122 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_ANSWER_MESSAGES_H_
+#define CAST_STREAMING_PUBLIC_ANSWER_MESSAGES_H_
+
+#include <array>
+#include <chrono>
+#include <cstdint>
+#include <initializer_list>
+#include <memory>
+#include <optional>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "cast/streaming/resolution.h"
+#include "cast/streaming/ssrc.h"
+#include "json/value.h"
+#include "platform/base/error.h"
+#include "util/simple_fraction.h"
+
+namespace openscreen::cast {
+
+// For each of the below classes, though a number of methods are shared, the use
+// of a shared base class has intentionally been avoided. This is to improve
+// readability of the structs provided in this file by cutting down on the
+// amount of obscuring boilerplate code. For each of the following struct
+// definitions, the following method definitions are shared:
+// (1) TryParse. Shall return a boolean indicating whether the out
+//     parameter is in a valid state after checking bounds and restrictions.
+// (2) ToJson. Should return a proper JSON object. Assumes that IsValid()
+//     has been called already, OSP_CHECKs if not IsValid().
+// (3) IsValid. Used by both TryParse and ToJson to ensure that the
+//     object is in a good state.
+struct AudioConstraints {
+  static ErrorOr<AudioConstraints> TryParse(const Json::Value& value);
+  Json::Value ToJson() const;
+  bool IsValid() const;
+
+  int max_sample_rate = 0;
+  int max_channels = 0;
+  int min_bit_rate = 0;  // optional
+  int max_bit_rate = 0;
+  std::optional<std::chrono::milliseconds> max_delay = {};
+};
+
+struct VideoConstraints {
+  static ErrorOr<VideoConstraints> TryParse(const Json::Value& value);
+  Json::Value ToJson() const;
+  bool IsValid() const;
+
+  std::optional<double> max_pixels_per_second = {};
+  std::optional<Dimensions> min_resolution = {};
+  Dimensions max_dimensions = {};
+  int min_bit_rate = 0;  // optional
+  int max_bit_rate = 0;
+  std::optional<std::chrono::milliseconds> max_delay = {};
+};
+
+struct Constraints {
+  static ErrorOr<Constraints> TryParse(const Json::Value& value);
+  Json::Value ToJson() const;
+  bool IsValid() const;
+
+  AudioConstraints audio;
+  VideoConstraints video;
+};
+
+// Decides whether the Sender scales and letterboxes content to 16:9, or if
+// it may send video frames of any arbitrary size and the Receiver must
+// handle the presentation details.
+enum class AspectRatioConstraint : uint8_t { kVariable = 0, kFixed };
+
+struct AspectRatio {
+  static ErrorOr<AspectRatio> TryParse(const Json::Value& value);
+  bool IsValid() const;
+
+  bool operator==(const AspectRatio& other) const {
+    return width == other.width && height == other.height;
+  }
+
+  int width = 0;
+  int height = 0;
+};
+
+struct DisplayDescription {
+  static ErrorOr<DisplayDescription> TryParse(const Json::Value& value);
+  Json::Value ToJson() const;
+  bool IsValid() const;
+
+  // May exceed, be the same, or less than those mentioned in the
+  // video constraints.
+  std::optional<Dimensions> dimensions;
+  std::optional<AspectRatio> aspect_ratio = {};
+  std::optional<AspectRatioConstraint> aspect_ratio_constraint = {};
+};
+
+struct Answer {
+  static ErrorOr<Answer> TryParse(const Json::Value& value);
+  Json::Value ToJson() const;
+  bool IsValid() const;
+
+  int udp_port = 0;
+  std::vector<int> send_indexes;
+  std::vector<Ssrc> ssrcs;
+
+  // Constraints and display descriptions are optional fields, and maybe null in
+  // the valid case.
+  std::optional<Constraints> constraints;
+  std::optional<DisplayDescription> display;
+  std::vector<int> receiver_rtcp_event_log;
+  std::vector<int> receiver_rtcp_dscp;
+
+  // RTP extensions should be empty, but not null.
+  std::vector<std::vector<std::string>> rtp_extensions = {};
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_ANSWER_MESSAGES_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/capture_recommendations.cc

@@ -0,0 +1,157 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/capture_recommendations.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "cast/streaming/public/answer_messages.h"
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+namespace capture_recommendations {
+namespace {
+
+void ApplyDisplay(const DisplayDescription& description,
+                  Recommendations* recommendations) {
+  recommendations->video.supports_scaling =
+      (description.aspect_ratio_constraint &&
+       (description.aspect_ratio_constraint.value() ==
+        AspectRatioConstraint::kVariable));
+
+  // We should never exceed the display's resolution, since it will always
+  // force scaling.
+  if (description.dimensions) {
+    recommendations->video.maximum = description.dimensions.value();
+    recommendations->video.bit_rate_limits.maximum =
+        recommendations->video.maximum.effective_bit_rate();
+
+    if (recommendations->video.maximum.width <
+        recommendations->video.minimum.width) {
+      recommendations->video.minimum =
+          recommendations->video.maximum.ToResolution();
+    }
+  }
+
+  // If the receiver gives us an aspect ratio that doesn't match the display
+  // resolution they give us, the behavior is undefined from the spec.
+  // Here we prioritize the aspect ratio, and the receiver can scale the frame
+  // as they wish.
+  double aspect_ratio = 0.0;
+  if (description.aspect_ratio) {
+    aspect_ratio = static_cast<double>(description.aspect_ratio->width) /
+                   description.aspect_ratio->height;
+    recommendations->video.maximum.width =
+        recommendations->video.maximum.height * aspect_ratio;
+  } else if (description.dimensions) {
+    aspect_ratio = static_cast<double>(description.dimensions->width) /
+                   description.dimensions->height;
+  } else {
+    return;
+  }
+  recommendations->video.minimum.width =
+      recommendations->video.minimum.height * aspect_ratio;
+}
+
+void ApplyConstraints(const Constraints& constraints,
+                      Recommendations* recommendations) {
+  // Audio has no fields in the display description, so we can safely
+  // ignore the current recommendations when setting values here.
+  if (constraints.audio.max_delay.has_value()) {
+    recommendations->audio.max_delay = constraints.audio.max_delay.value();
+  }
+  recommendations->audio.max_channels = constraints.audio.max_channels;
+  recommendations->audio.max_sample_rate = constraints.audio.max_sample_rate;
+
+  recommendations->audio.bit_rate_limits = BitRateLimits{
+      std::max(constraints.audio.min_bit_rate, kDefaultAudioMinBitRate),
+      std::max(constraints.audio.max_bit_rate, kDefaultAudioMinBitRate)};
+
+  // With video, we take the intersection of values of the constraints and
+  // the display description.
+  if (constraints.video.max_delay.has_value()) {
+    recommendations->video.max_delay = constraints.video.max_delay.value();
+  }
+
+  if (constraints.video.max_pixels_per_second.has_value()) {
+    recommendations->video.max_pixels_per_second =
+        constraints.video.max_pixels_per_second.value();
+  }
+
+  recommendations->video.bit_rate_limits =
+      BitRateLimits{std::max(constraints.video.min_bit_rate,
+                             recommendations->video.bit_rate_limits.minimum),
+                    std::min(constraints.video.max_bit_rate,
+                             recommendations->video.bit_rate_limits.maximum)};
+  Dimensions dimensions = constraints.video.max_dimensions;
+  if (dimensions.width <= kDefaultMinResolution.width) {
+    recommendations->video.maximum = {kDefaultMinResolution.width,
+                                      kDefaultMinResolution.height,
+                                      kDefaultFrameRate};
+  } else if (dimensions.width < recommendations->video.maximum.width) {
+    recommendations->video.maximum = std::move(dimensions);
+  }
+
+  if (constraints.video.min_resolution) {
+    const Resolution& min = constraints.video.min_resolution->ToResolution();
+    if (kDefaultMinResolution.width < min.width) {
+      recommendations->video.minimum = std::move(min);
+    }
+  }
+}
+
+// The receiver's video constraints, even when each is individually valid, can
+// intersect with the display description to produce an inverted range: a
+// minimum bit rate above the display-limited maximum, or a minimum resolution
+// larger than the display. (Audio cannot invert: AudioConstraints::IsValid()
+// already requires max_bit_rate >= min_bit_rate.) Resolve any such
+// contradiction in favor of the maximum, which reflects what the
+// receiver/display can actually handle.
+void ClampVideoToWellOrderedRanges(Video& video) {
+  video.bit_rate_limits.minimum =
+      std::min(video.bit_rate_limits.minimum, video.bit_rate_limits.maximum);
+  video.minimum.width = std::min(video.minimum.width, video.maximum.width);
+  video.minimum.height =
+      std::min(video.minimum.height, video.maximum.height);
+}
+
+}  // namespace
+
+bool BitRateLimits::operator==(const BitRateLimits& other) const {
+  return std::tie(minimum, maximum) == std::tie(other.minimum, other.maximum);
+}
+
+bool Audio::operator==(const Audio& other) const {
+  return std::tie(bit_rate_limits, max_delay, max_channels, max_sample_rate) ==
+         std::tie(other.bit_rate_limits, other.max_delay, other.max_channels,
+                  other.max_sample_rate);
+}
+
+bool Video::operator==(const Video& other) const {
+  return std::tie(bit_rate_limits, minimum, maximum, supports_scaling,
+                  max_delay, max_pixels_per_second) ==
+         std::tie(other.bit_rate_limits, other.minimum, other.maximum,
+                  other.supports_scaling, other.max_delay,
+                  other.max_pixels_per_second);
+}
+
+bool Recommendations::operator==(const Recommendations& other) const {
+  return std::tie(audio, video) == std::tie(other.audio, other.video);
+}
+
+Recommendations GetRecommendations(const Answer& answer) {
+  Recommendations recommendations;
+  if (answer.display.has_value() && answer.display->IsValid()) {
+    ApplyDisplay(answer.display.value(), &recommendations);
+  }
+  if (answer.constraints.has_value() && answer.constraints->IsValid()) {
+    ApplyConstraints(answer.constraints.value(), &recommendations);
+  }
+  ClampVideoToWellOrderedRanges(recommendations.video);
+  return recommendations;
+}
+
+}  // namespace capture_recommendations
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/capture_recommendations.h

@@ -0,0 +1,151 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_CAPTURE_RECOMMENDATIONS_H_
+#define CAST_STREAMING_PUBLIC_CAPTURE_RECOMMENDATIONS_H_
+
+#include <chrono>
+#include <cmath>
+#include <memory>
+#include <tuple>
+
+#include "cast/streaming/public/constants.h"
+#include "cast/streaming/resolution.h"
+namespace openscreen::cast {
+
+struct Answer;
+
+// This namespace contains classes and functions to be used by senders for
+// determining what constraints are recommended for the capture device, based on
+// the limits reported by the receiver.
+//
+// A general note about recommendations: they are NOT maximum operational
+// limits, instead they are targeted to provide a delightful cast experience.
+// For example, if a receiver is connected to a 1080P display but cannot provide
+// 1080P at a stable FPS with a good experience, 1080P will not be recommended.
+namespace capture_recommendations {
+
+// Default maximum delay for both audio and video. Used if the sender fails
+// to provide any constraints.
+inline constexpr std::chrono::milliseconds kDefaultMaxDelayMs(400);
+
+// Bit rate limits, used for both audio and video streams.
+struct BitRateLimits {
+  bool operator==(const BitRateLimits& other) const;
+
+  // Minimum bit rate, in bits per second.
+  int minimum;
+
+  // Maximum bit rate, in bits per second.
+  int maximum;
+};
+
+// The mirroring control protocol specifies 32kbps as the absolute minimum
+// for audio. Depending on the type of audio content (narrowband, fullband,
+// etc.) Opus specifically can perform very well at this bitrate.
+// See: https://research.google/pubs/pub41650/
+inline constexpr int kDefaultAudioMinBitRate = 32 * 1000;
+
+// Opus generally sees little improvement above 192kbps, but some older codecs
+// that we may consider supporting improve at up to 256kbps.
+inline constexpr int kDefaultAudioMaxBitRate = 256 * 1000;
+inline constexpr BitRateLimits kDefaultAudioBitRateLimits{
+    kDefaultAudioMinBitRate, kDefaultAudioMaxBitRate};
+
+// While generally audio should be captured at the maximum sample rate, 16kHz is
+// the recommended absolute minimum.
+inline constexpr int kDefaultAudioMinSampleRate = 16000;
+
+// Audio capture recommendations. Maximum delay is determined by buffer
+// constraints, and capture bit rate may vary between limits as appropriate.
+struct Audio {
+  bool operator==(const Audio& other) const;
+
+  // Represents the recommended bit rate range.
+  BitRateLimits bit_rate_limits = kDefaultAudioBitRateLimits;
+
+  // Represents the maximum audio delay, in milliseconds.
+  std::chrono::milliseconds max_delay = kDefaultMaxDelayMs;
+
+  // Represents the maximum number of audio channels.
+  int max_channels = kDefaultAudioChannels;
+
+  // Represents the maximum samples per second.
+  int max_sample_rate = kDefaultAudioSampleRate;
+
+  // Represents the absolute minimum samples per second. Generally speaking,
+  // audio should be captured at the maximum samples per second rate.
+  int min_sample_rate = kDefaultAudioMinSampleRate;
+};
+
+// The minimum dimensions are as close as possible to low-definition
+// television, factoring in the receiver's aspect ratio if provided.
+inline constexpr Resolution kDefaultMinResolution{kMinVideoWidth,
+                                                  kMinVideoHeight};
+
+// Currently mirroring only supports 1080P.
+inline constexpr Dimensions kDefaultMaxResolution{1920, 1080,
+                                                  kDefaultFrameRate};
+
+// The mirroring spec suggests 300kbps as the absolute minimum bitrate.
+inline constexpr int kDefaultVideoMinBitRate = 300 * 1000;
+
+// The theoretical maximum pixels per second is the maximum bit rate
+// divided by 8 (the max byte rate). In practice it should generally be
+// less.
+inline constexpr int kDefaultVideoMaxPixelsPerSecond =
+    kDefaultMaxResolution.effective_bit_rate() / 8;
+
+// Our default limits are merely the product of the minimum and maximum
+// dimensions, and are only used if the receiver fails to give better
+// constraint information.
+inline constexpr BitRateLimits kDefaultVideoBitRateLimits{
+    kDefaultVideoMinBitRate, kDefaultMaxResolution.effective_bit_rate()};
+
+// Video capture recommendations.
+struct Video {
+  bool operator==(const Video& other) const;
+
+  // Represents the recommended bit rate range.
+  BitRateLimits bit_rate_limits = kDefaultVideoBitRateLimits;
+
+  // Represents the recommended minimum resolution.
+  Resolution minimum = kDefaultMinResolution;
+
+  // Represents the recommended maximum resolution.
+  Dimensions maximum = kDefaultMaxResolution;
+
+  // Indicates whether the receiver can scale frames from a different aspect
+  // ratio, or if it needs to be done by the sender. Default is false, meaning
+  // that the sender is responsible for letterboxing.
+  bool supports_scaling = false;
+
+  // Represents the maximum video delay, in milliseconds.
+  std::chrono::milliseconds max_delay = kDefaultMaxDelayMs;
+
+  // Represents the maximum pixels per second, not necessarily correlated
+  // to bit rate.
+  int max_pixels_per_second = kDefaultVideoMaxPixelsPerSecond;
+};
+
+// Outputted recommendations for usage by capture devices. Note that we always
+// return both audio and video (it is up to the sender to determine what
+// streams actually get created). If the receiver doesn't give us any
+// information for making recommendations, the defaults are used.
+struct Recommendations {
+  bool operator==(const Recommendations& other) const;
+
+  // Audio specific recommendations.
+  Audio audio;
+
+  // Video specific recommendations.
+  Video video;
+};
+
+Recommendations GetRecommendations(const Answer& answer);
+
+}  // namespace capture_recommendations
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_CAPTURE_RECOMMENDATIONS_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/constants.cc

@@ -0,0 +1,57 @@
+// Copyright 2024 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/constants.h"
+
+#include <ostream>
+
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+std::ostream& operator<<(std::ostream& os, VideoCodec codec) {
+  const char* str = nullptr;
+  switch (codec) {
+    case VideoCodec::kH264:
+      str = "H264";
+      break;
+    case VideoCodec::kVp8:
+      str = "VP8";
+      break;
+    case VideoCodec::kHevc:
+      str = "HEVC";
+      break;
+    case VideoCodec::kNotSpecified:
+      str = "NotSpecified";
+      break;
+    case VideoCodec::kVp9:
+      str = "VP9";
+      break;
+    case VideoCodec::kAv1:
+      str = "AV1";
+      break;
+    default:
+      OSP_NOTREACHED();
+  }
+  os << str;
+  return os;
+}
+
+std::ostream& operator<<(std::ostream& os, CastMode mode) {
+  const char* str = nullptr;
+  switch (mode) {
+    case CastMode::kMirroring:
+      str = "mirroring";
+      break;
+    case CastMode::kRemoting:
+      str = "remoting";
+      break;
+    default:
+      OSP_NOTREACHED();
+  }
+  os << str;
+  return os;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/constants.h

@@ -0,0 +1,122 @@
+// Copyright 2015 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_CONSTANTS_H_
+#define CAST_STREAMING_PUBLIC_CONSTANTS_H_
+
+////////////////////////////////////////////////////////////////////////////////
+// NOTE: This file should only contain constants that are reasonably globally
+// used (i.e., by many modules, and in all or nearly all subdirs).  Do NOT add
+// non-POD constants, functions, interfaces, or any logic to this module,
+// except for std::ostream operators on an as-needed basis.
+////////////////////////////////////////////////////////////////////////////////
+
+#include <chrono>
+#include <ostream>
+#include <ratio>
+
+namespace openscreen::cast {
+
+// Default target playout delay. The playout delay is the window of time between
+// capture from the source until presentation at the receiver.
+inline constexpr std::chrono::milliseconds kDefaultTargetPlayoutDelay(400);
+
+// Default UDP port, bound at the Receiver, for Cast Streaming. An
+// implementation is required to use the port specified by the Receiver in its
+// ANSWER control message, which may or may not match this port number here.
+inline constexpr int kDefaultCastStreamingPort = 2344;
+
+// Default TCP port, bound at the TLS server socket level, for Cast Streaming.
+// An implementation must use the port specified in the DNS-SD published record
+// for connecting over TLS, which may or may not match this port number here.
+inline constexpr int kDefaultCastPort = 8010;
+
+// Target number of milliseconds between the sending of RTCP reports.  Both
+// senders and receivers regularly send RTCP reports to their peer.
+inline constexpr std::chrono::milliseconds kRtcpReportInterval(500);
+
+// This is an important system-wide constant.  This limits how much history
+// the implementation must retain in order to process the acknowledgements of
+// past frames.
+//
+// This value is carefully choosen such that it fits in the 8-bits range for
+// frame IDs. It is also less than half of the full 8-bits range such that
+// logic can handle wrap around and compare two frame IDs meaningfully.
+inline constexpr int kMaxUnackedFrames = 120;
+
+// The network must support a packet size of at least this many bytes.
+inline constexpr int kRequiredNetworkPacketSize = 256;
+
+// The spec declares RTP timestamps must always have a timebase of 90000 ticks
+// per second for video.
+inline constexpr int kRtpVideoTimebase = 90000;
+
+// Minimum resolution is 320x240.
+inline constexpr int kMinVideoHeight = 240;
+inline constexpr int kMinVideoWidth = 320;
+
+// The default frame rate for capture options is 30FPS.
+inline constexpr int kDefaultFrameRate = 30;
+
+// The mirroring spec suggests 300kbps as the absolute minimum bitrate.
+inline constexpr int kDefaultVideoMinBitRate = 300 * 1000;
+
+// Default video max bitrate is based on 1080P @ 30FPS, which can be played back
+// at good quality around 10mbps.
+inline constexpr int kDefaultVideoMaxBitRate = 10 * 1000 * 1000;
+
+// The mirroring control protocol specifies 32kbps as the absolute minimum
+// for audio. Depending on the type of audio content (narrowband, fullband,
+// etc.) Opus specifically can perform very well at this bitrate.
+// See: https://research.google/pubs/pub41650/
+inline constexpr int kDefaultAudioMinBitRate = 32 * 1000;
+
+// Opus generally sees little improvement above 192kbps, but some older codecs
+// that we may consider supporting improve at up to 256kbps.
+inline constexpr int kDefaultAudioMaxBitRate = 256 * 1000;
+
+// While generally audio should be captured at the maximum sample rate, 16kHz is
+// the recommended absolute minimum.
+inline constexpr int kDefaultAudioMinSampleRate = 16000;
+
+// The default audio sample rate is 48kHz, slightly higher than standard
+// consumer audio.
+inline constexpr int kDefaultAudioSampleRate = 48000;
+
+// The default audio number of channels is set to stereo.
+inline constexpr int kDefaultAudioChannels = 2;
+
+// Default maximum delay for both audio and video. Used if the sender fails
+// to provide any constraints.
+inline constexpr std::chrono::milliseconds kDefaultMaxDelayMs(1500);
+
+// TODO(issuetracker.google.com/184189100): As part of updating remoting
+// OFFER/ANSWER and capabilities exchange, remoting version should be updated
+// to 3.
+inline constexpr int kSupportedRemotingVersion = 2;
+
+// Used for RTCP message support.
+constexpr uint32_t kCastName = ('C' << 24) + ('A' << 16) + ('S' << 8) + 'T';
+
+// Codecs known and understood by cast senders and receivers. Note: receivers
+// are required to implement the following codecs to be Cast V2 compliant: H264,
+// VP8, AAC, Opus. Senders have to implement at least one codec from this
+// list for audio or video to start a session.
+// `kNotSpecified` is used in remoting to indicate that the stream is being
+// remoted and is not specified as part of the OFFER message (indicated as
+// "REMOTE_AUDIO" or "REMOTE_VIDEO").
+enum class AudioCodec { kAac, kOpus, kNotSpecified };
+
+enum class VideoCodec { kH264, kVp8, kHevc, kNotSpecified, kVp9, kAv1 };
+std::ostream& operator<<(std::ostream& os, VideoCodec codec);
+
+// The type (audio, video, or unknown) of the stream.
+enum class StreamType { kUnknown, kAudio, kVideo };
+
+enum class CastMode : uint8_t { kMirroring, kRemoting };
+std::ostream& operator<<(std::ostream& os, CastMode mode);
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_CONSTANTS_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/encoded_frame.cc

@@ -0,0 +1,60 @@
+// Copyright 2014 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/encoded_frame.h"
+
+namespace openscreen::cast {
+
+EncodedFrame::EncodedFrame(Dependency dependency,
+                           FrameId frame_id,
+                           FrameId referenced_frame_id,
+                           RtpTimeTicks rtp_timestamp,
+                           Clock::time_point reference_time,
+                           std::chrono::milliseconds new_playout_delay,
+                           Clock::time_point capture_begin_time,
+                           Clock::time_point capture_end_time,
+                           ByteView data)
+    : dependency(dependency),
+      frame_id(frame_id),
+      referenced_frame_id(referenced_frame_id),
+      rtp_timestamp(rtp_timestamp),
+      reference_time(reference_time),
+      new_playout_delay(new_playout_delay),
+      capture_begin_time(capture_begin_time),
+      capture_end_time(capture_end_time),
+      data(data) {}
+
+EncodedFrame::EncodedFrame(Dependency dependency,
+                           FrameId frame_id,
+                           FrameId referenced_frame_id,
+                           RtpTimeTicks rtp_timestamp,
+                           Clock::time_point reference_time,
+                           std::chrono::milliseconds new_playout_delay,
+                           ByteView data)
+    : dependency(dependency),
+      frame_id(frame_id),
+      referenced_frame_id(referenced_frame_id),
+      rtp_timestamp(rtp_timestamp),
+      reference_time(reference_time),
+      new_playout_delay(new_playout_delay),
+      data(data) {}
+
+EncodedFrame::EncodedFrame() = default;
+EncodedFrame::~EncodedFrame() = default;
+
+EncodedFrame::EncodedFrame(EncodedFrame&&) noexcept = default;
+EncodedFrame& EncodedFrame::operator=(EncodedFrame&&) = default;
+
+void EncodedFrame::CopyMetadataTo(EncodedFrame* dest) const {
+  dest->dependency = this->dependency;
+  dest->frame_id = this->frame_id;
+  dest->referenced_frame_id = this->referenced_frame_id;
+  dest->rtp_timestamp = this->rtp_timestamp;
+  dest->reference_time = this->reference_time;
+  dest->new_playout_delay = this->new_playout_delay;
+  dest->capture_begin_time = this->capture_begin_time;
+  dest->capture_end_time = this->capture_end_time;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/encoded_frame.h

@@ -0,0 +1,119 @@
+// Copyright 2014 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_ENCODED_FRAME_H_
+#define CAST_STREAMING_PUBLIC_ENCODED_FRAME_H_
+
+#include <stdint.h>
+
+#include <chrono>
+#include <vector>
+
+#include "cast/streaming/public/frame_id.h"
+#include "cast/streaming/rtp_time.h"
+#include "platform/api/time.h"
+#include "platform/base/span.h"
+
+namespace openscreen::cast {
+
+// A combination of metadata and data for one encoded frame.  This can contain
+// audio data or video data or other.
+struct EncodedFrame {
+  enum class Dependency : int8_t {
+    // "null" value, used to indicate whether `dependency` has been set.
+    kUnknown,
+
+    // Not decodable without the reference frame indicated by
+    // `referenced_frame_id`.
+    kDependent,
+
+    // Independently decodable.
+    kIndependent,
+
+    // Independently decodable, and no future frames will depend on any frames
+    // before this one.
+    kKeyFrame,
+  };
+
+  EncodedFrame(Dependency dependency,
+               FrameId frame_id,
+               FrameId referenced_frame_id,
+               RtpTimeTicks rtp_timestamp,
+               Clock::time_point reference_time,
+               std::chrono::milliseconds new_playout_delay,
+               Clock::time_point capture_begin_time,
+               Clock::time_point capture_end_time,
+               ByteView data);
+
+  // TODO(issuetracker.google.com/285905175): remove remaining optional fields
+  // (new_playout_delay) once Chrome provides the capture begin and end
+  // timestamps, so this constructor only provides the required fields.
+  EncodedFrame(Dependency dependency,
+               FrameId frame_id,
+               FrameId referenced_frame_id,
+               RtpTimeTicks rtp_timestamp,
+               Clock::time_point reference_time,
+               std::chrono::milliseconds new_playout_delay,
+               ByteView data);
+  EncodedFrame();
+  EncodedFrame(const EncodedFrame&) = delete;
+  EncodedFrame& operator=(const EncodedFrame&) = delete;
+  EncodedFrame(EncodedFrame&&) noexcept;
+  EncodedFrame& operator=(EncodedFrame&&);
+  ~EncodedFrame();
+
+  // Copies all members except `data` to `dest`. Does not modify |dest->data|.
+  void CopyMetadataTo(EncodedFrame* dest) const;
+
+  // This frame's dependency relationship with respect to other frames.
+  Dependency dependency = Dependency::kUnknown;
+
+  // The label associated with this frame.  Implies an ordering relative to
+  // other frames in the same stream.
+  FrameId frame_id;
+
+  // The label associated with the frame upon which this frame depends.  If
+  // this frame does not require any other frame in order to become decodable
+  // (e.g., key frames), `referenced_frame_id` must equal `frame_id`.
+  FrameId referenced_frame_id;
+
+  // The stream timestamp, on the timeline of the signal data. For example, RTP
+  // timestamps for audio are usually defined as the total number of audio
+  // samples encoded in all prior frames. A playback system uses this value to
+  // detect gaps in the stream, and otherwise stretch the signal to gradually
+  // re-align towards playout targets when too much drift has occurred (see
+  // `reference_time`, below).
+  RtpTimeTicks rtp_timestamp;
+
+  // The common reference clock timestamp for this frame. Over a sequence of
+  // frames, this time value is expected to drift with respect to the elapsed
+  // time implied by the RTP timestamps; and this may not necessarily increment
+  // with precise regularity.
+  //
+  // This value originates from a sender, and is the time at which the frame was
+  // captured/recorded. In the receiver context, this value is the computed
+  // target playout time, which is used for guiding the timing of presentation
+  // (see `rtp_timestamp`, above). It is also meant to be used to synchronize
+  // the presentation of multiple streams (e.g., audio and video), commonly
+  // known as "lip-sync." It is NOT meant to be a mandatory/exact playout time.
+  Clock::time_point reference_time;
+
+  // Playout delay for this and all future frames. Used by the Adaptive
+  // Playout delay extension. Non-positive values means no change.
+  std::chrono::milliseconds new_playout_delay{};
+
+  // Video capture begin/end timestamps. If set to a value other than
+  // Clock::time_point::min(), used for improved statistics gathering.
+  Clock::time_point capture_begin_time = Clock::time_point::min();
+  Clock::time_point capture_end_time = Clock::time_point::min();
+
+  // A buffer containing the encoded signal data for the frame. In the sender
+  // context, this points to the data to be sent. In the receiver context, this
+  // is set to the region of a client-provided buffer that was populated.
+  ByteView data;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_ENCODED_FRAME_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/environment.cc

@@ -0,0 +1,171 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/environment.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "cast/streaming/impl/rtp_defines.h"
+#include "platform/api/task_runner.h"
+#include "platform/base/span.h"
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+Environment::PacketConsumer::~PacketConsumer() = default;
+
+Environment::SocketSubscriber::~SocketSubscriber() = default;
+
+Environment::Environment(ClockNowFunctionPtr now_function,
+                         TaskRunner& task_runner,
+                         const IPEndpoint& local_endpoint)
+    : now_function_(now_function), task_runner_(task_runner) {
+  OSP_CHECK(now_function_);
+  ErrorOr<std::unique_ptr<UdpSocket>> result =
+      UdpSocket::Create(*task_runner_, this, local_endpoint);
+  if (result.is_error()) {
+    OSP_LOG_ERROR << "Unable to create a UDP socket bound to " << local_endpoint
+                  << ": " << result.error();
+    return;
+  }
+  const_cast<std::unique_ptr<UdpSocket>&>(socket_) = std::move(result.value());
+  OSP_CHECK(socket_);
+  socket_->Bind();
+}
+
+Environment::~Environment() = default;
+
+IPEndpoint Environment::GetBoundLocalEndpoint() const {
+  if (socket_) {
+    return socket_->GetLocalEndpoint();
+  }
+  return IPEndpoint{};
+}
+
+void Environment::SetSocketStateForTesting(SocketState state) {
+  state_ = state;
+  if (socket_subscriber_) {
+    switch (state_) {
+      case SocketState::kReady:
+        socket_subscriber_->OnSocketReady();
+        break;
+      case SocketState::kInvalid:
+        socket_subscriber_->OnSocketInvalid(Error::Code::kSocketFailure);
+        break;
+      default:
+        break;
+    }
+  }
+}
+
+void Environment::SetSocketSubscriber(SocketSubscriber* subscriber) {
+  socket_subscriber_ = subscriber;
+}
+
+void Environment::SetStatisticsCollector(StatisticsCollector* collector) {
+  statistics_collector_ = collector;
+}
+
+void Environment::ConsumeIncomingPackets(PacketConsumer* packet_consumer) {
+  OSP_CHECK(packet_consumer);
+  OSP_CHECK(!packet_consumer_);
+  packet_consumer_ = packet_consumer;
+}
+
+void Environment::DropIncomingPackets() {
+  packet_consumer_ = nullptr;
+}
+
+int Environment::GetMaxPacketSize() const {
+  // Return hard-coded values for UDP over wired Ethernet (which is a smaller
+  // MTU than typical defaults for UDP over 802.11 wireless). Performance would
+  // be more-optimized if the network were probed for the actual value. See
+  // discussion in rtp_defines.h.
+  switch (remote_endpoint_.address.version()) {
+    case IPAddress::Version::kV4:
+      return kMaxRtpPacketSizeForIpv4UdpOnEthernet;
+    case IPAddress::Version::kV6:
+      return kMaxRtpPacketSizeForIpv6UdpOnEthernet;
+    default:
+      OSP_NOTREACHED();
+  }
+}
+
+void Environment::SetDscp(UdpSocket::DscpMode mode) {
+  if (socket_) {
+    socket_->SetDscp(mode);
+  }
+}
+
+void Environment::SendPacket(ByteView packet, PacketMetadata metadata) {
+  OSP_CHECK(remote_endpoint_.address);
+  OSP_CHECK_NE(remote_endpoint_.port, 0);
+  if (socket_) {
+    socket_->SendMessage(packet, remote_endpoint_);
+  }
+  if (statistics_collector_) {
+    statistics_collector_->CollectPacketSentEvent(packet, metadata);
+  }
+}
+
+void Environment::OnBound(UdpSocket* socket) {
+  OSP_CHECK_EQ(socket, socket_.get());
+  state_ = SocketState::kReady;
+
+  if (socket_subscriber_) {
+    socket_subscriber_->OnSocketReady();
+  }
+}
+
+void Environment::OnError(UdpSocket* socket, const Error& error) {
+  OSP_CHECK_EQ(socket, socket_.get());
+  // Usually OnError() is only called for non-recoverable Errors. However,
+  // OnSendError() and OnRead() delegate to this method, to handle their hard
+  // error cases as well. So, return early here if `error` is recoverable.
+  if (error.ok() || error.code() == Error::Code::kAgain) {
+    return;
+  }
+
+  state_ = SocketState::kInvalid;
+  if (socket_subscriber_) {
+    socket_subscriber_->OnSocketInvalid(error);
+  } else {
+    // Default behavior when there are no subscribers.
+    OSP_LOG_ERROR << "For UDP socket bound to " << socket_->GetLocalEndpoint()
+                  << ": " << error;
+  }
+}
+
+void Environment::OnSendError(UdpSocket* socket, const Error& error) {
+  OnError(socket, error);
+}
+
+void Environment::OnRead(UdpSocket* socket,
+                         ErrorOr<UdpPacket> packet_or_error) {
+  if (!packet_consumer_) {
+    return;
+  }
+
+  if (packet_or_error.is_error()) {
+    OnError(socket, packet_or_error.error());
+    return;
+  }
+
+  // Ideally, the arrival time would come from the operating system's network
+  // stack (e.g., by using the SO_TIMESTAMP sockopt on POSIX systems). However,
+  // there would still be the problem of mapping the timestamp to a value in
+  // terms of Clock::time_point. So, just sample the Clock here and call that
+  // the "arrival time." While this can add variance within the system, it
+  // should be minimal, assuming not too much time has elapsed between the
+  // actual packet receive event and the when this code here is executing.
+  const Clock::time_point arrival_time = now_function_();
+
+  UdpPacket packet = std::move(packet_or_error.value());
+  packet_consumer_->OnReceivedPacket(
+      packet.source(), arrival_time,
+      std::move(static_cast<std::vector<uint8_t>&>(packet)));
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/environment.h

@@ -0,0 +1,164 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_ENVIRONMENT_H_
+#define CAST_STREAMING_PUBLIC_ENVIRONMENT_H_
+
+#include <stdint.h>
+
+#include <functional>
+#include <memory>
+#include <vector>
+
+#include "cast/streaming/impl/statistics_collector.h"
+#include "platform/api/time.h"
+#include "platform/api/udp_socket.h"
+#include "platform/base/ip_address.h"
+#include "platform/base/span.h"
+#include "util/raw_ptr.h"
+#include "util/raw_ref.h"
+
+namespace openscreen::cast {
+
+// Provides the common environment for operating system resources shared by
+// multiple components.
+class Environment : public UdpSocket::Client {
+ public:
+  class PacketConsumer {
+   public:
+    virtual void OnReceivedPacket(const IPEndpoint& source,
+                                  Clock::time_point arrival_time,
+                                  std::vector<uint8_t> packet) = 0;
+
+   protected:
+    virtual ~PacketConsumer();
+  };
+
+  // Consumers of the environment's UDP socket should be careful to check the
+  // socket's state before accessing its methods, especially
+  // GetBoundLocalEndpoint(). If the environment is `kStarting`, the
+  // local endpoint may not be set yet and will be zero initialized.
+  enum class SocketState {
+    // Socket is still initializing. Usually the UDP socket bind is
+    // the last piece.
+    kStarting,
+
+    // The socket is ready for use and has been bound.
+    kReady,
+
+    // The socket is either closed (normally or due to an error) or in an
+    // invalid state. Currently the environment does not create a new socket
+    // in this case, so to be used again the environment itself needs to be
+    // recreated.
+    kInvalid
+  };
+
+  // Classes concerned with the Environment's UDP socket state may inherit from
+  // `Subscriber` and then `Subscribe`.
+  class SocketSubscriber {
+   public:
+    // Event that occurs when the environment is ready for use.
+    virtual void OnSocketReady() = 0;
+
+    // Event that occurs when the environment has experienced a fatal error.
+    virtual void OnSocketInvalid(const Error& error) = 0;
+
+   protected:
+    virtual ~SocketSubscriber();
+  };
+
+  // Construct with the given clock source and TaskRunner. Creates and
+  // internally-owns a UdpSocket, and immediately binds it to the given
+  // `local_endpoint`. Default behavior if `local_endpoint` is omitted is to
+  // bind to all available interfaces using IPv4.
+  Environment(ClockNowFunctionPtr now_function,
+              TaskRunner& task_runner,
+              const IPEndpoint& local_endpoint = IPEndpoint::kAnyV4());
+
+  ~Environment() override;
+
+  ClockNowFunctionPtr now_function() const { return now_function_; }
+  Clock::time_point now() const { return now_function_(); }
+  TaskRunner& task_runner() const { return *task_runner_; }
+
+  // Returns the local endpoint the socket is bound to, or the zero IPEndpoint
+  // if socket creation/binding failed.
+  //
+  // Note: This method is virtual to allow unit tests to fake that there really
+  // is a bound socket.
+  virtual IPEndpoint GetBoundLocalEndpoint() const;
+
+  // Get/Set the remote endpoint. This is separate from the constructor because
+  // the remote endpoint is, in some cases, discovered only after receiving a
+  // packet.
+  const IPEndpoint& remote_endpoint() const { return remote_endpoint_; }
+  void set_remote_endpoint(const IPEndpoint& endpoint) {
+    remote_endpoint_ = endpoint;
+  }
+
+  SocketState socket_state() const { return state_; }
+  void SetSocketStateForTesting(SocketState state);
+
+  // Subscribe to socket changes. Callers can unsubscribe by passing
+  // nullptr.
+  void SetSocketSubscriber(SocketSubscriber* subscriber);
+
+  // Subscribe to frame and packet events. Callers can unsubscribe by passing
+  // nullptr. Note that if the collector is destroyed before the environment,
+  // callers MUST unsubscribe to avoid an access exception.
+  void SetStatisticsCollector(StatisticsCollector* subscriber);
+  StatisticsCollector* statistics_collector() {
+    return statistics_collector_.get();
+  }
+
+  // Start/Resume delivery of incoming packets to the given `packet_consumer`.
+  // Delivery will continue until DropIncomingPackets() is called.
+  void ConsumeIncomingPackets(PacketConsumer* packet_consumer);
+
+  // Stop delivery of incoming packets, dropping any that do come in. All
+  // internal references to the PacketConsumer that was provided in the last
+  // call to ConsumeIncomingPackets() are cleared.
+  void DropIncomingPackets();
+
+  // Returns the maximum packet size for the network. This will always return a
+  // value of at least kRequiredNetworkPacketSize.
+  int GetMaxPacketSize() const;
+
+  // Sets the DSCP value for the underlying UDP socket.
+  void SetDscp(UdpSocket::DscpMode mode);
+
+  // Sends the given `packet` to the remote endpoint, best-effort.
+  // set_remote_endpoint() must be called beforehand with a valid IPEndpoint.
+  //
+  // Note: This method is virtual to allow unit tests to intercept packets
+  // before they actually head-out through the socket.
+  virtual void SendPacket(ByteView packet, PacketMetadata metadata);
+
+ private:
+  // UdpSocket::Client implementation.
+  void OnBound(UdpSocket* socket) final;
+  void OnError(UdpSocket* socket, const Error& error) final;
+  void OnSendError(UdpSocket* socket, const Error& error) final;
+  void OnRead(UdpSocket* socket, ErrorOr<UdpPacket> packet_or_error) final;
+
+  ClockNowFunctionPtr now_function_;
+  const raw_ref<TaskRunner> task_runner_;
+
+  // The UDP socket bound to the local endpoint that was passed into the
+  // constructor, or null if socket creation failed.
+  const std::unique_ptr<UdpSocket> socket_;
+
+  // These are externally set/cleared. Behaviors are described in getter/setter
+  // method comments above.
+  IPEndpoint local_endpoint_{};
+  IPEndpoint remote_endpoint_{};
+  raw_ptr<PacketConsumer> packet_consumer_ = nullptr;
+  SocketState state_ = SocketState::kStarting;
+  raw_ptr<SocketSubscriber> socket_subscriber_ = nullptr;
+  raw_ptr<StatisticsCollector> statistics_collector_ = nullptr;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_ENVIRONMENT_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/frame_id.cc

@@ -0,0 +1,20 @@
+// Copyright 2016 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/frame_id.h"
+
+namespace openscreen::cast {
+
+std::ostream& operator<<(std::ostream& out, const FrameId rhs) {
+  return out << rhs.ToString();
+}
+
+std::string FrameId::ToString() const {
+  if (is_null())
+    return "F<null>";
+
+  return "F" + std::to_string(value());
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/frame_id.h

@@ -0,0 +1,121 @@
+// Copyright 2016 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_FRAME_ID_H_
+#define CAST_STREAMING_PUBLIC_FRAME_ID_H_
+
+#include <stdint.h>
+
+#include <limits>
+#include <sstream>
+#include <string>
+
+#include "cast/streaming/impl/expanded_value_base.h"
+
+namespace openscreen::cast {
+
+// Forward declaration (see below).
+class FrameId;
+
+// Convenience operator overloads for logging.
+std::ostream& operator<<(std::ostream& out, const FrameId rhs);
+
+// Unique identifier for a frame in a RTP media stream.  FrameIds are truncated
+// to 8-bit values in RTP and RTCP headers, and then expanded back by the other
+// endpoint when parsing the headers.
+//
+// Usage example:
+//
+//   // Distance/offset math.
+//   FrameId first = FrameId::first();
+//   FrameId second = first + 1;
+//   FrameId third = second + 1;
+//   int64_t offset = third - first;
+//   FrameId fourth = second + offset;
+//
+//   // Logging convenience.
+//   OSP_DLOG_INFO << "The current frame is " << fourth;
+class FrameId : public ExpandedValueBase<int64_t, FrameId> {
+ public:
+  // The "null" FrameId constructor.  Represents a FrameId field that has not
+  // been set and/or a "not applicable" indicator.
+  constexpr FrameId() : FrameId(std::numeric_limits<int64_t>::min()) {}
+
+  constexpr explicit FrameId(int64_t value) : ExpandedValueBase(value) {}
+
+  // Allow copy construction and assignment.
+  constexpr FrameId(const FrameId&) = default;
+  constexpr FrameId& operator=(const FrameId&) = default;
+
+  // Returns true if this is the special value representing null.
+  constexpr bool is_null() const { return *this == FrameId(); }
+
+  // Distance operator.
+  int64_t operator-(FrameId rhs) const {
+    OSP_CHECK(!is_null());
+    OSP_CHECK(!rhs.is_null());
+    return value_ - rhs.value_;
+  }
+
+  // Operators to compute advancement by incremental amounts.
+  constexpr FrameId operator+(int64_t rhs) const {
+    OSP_CHECK(!is_null());
+    return FrameId(value_ + rhs);
+  }
+  constexpr FrameId operator-(int64_t rhs) const {
+    OSP_CHECK(!is_null());
+    return FrameId(value_ - rhs);
+  }
+  constexpr FrameId& operator+=(int64_t rhs) {
+    OSP_CHECK(!is_null());
+    return (*this = (*this + rhs));
+  }
+  constexpr FrameId& operator-=(int64_t rhs) {
+    OSP_CHECK(!is_null());
+    return (*this = (*this - rhs));
+  }
+  constexpr FrameId& operator++() {
+    OSP_CHECK(!is_null());
+    ++value_;
+    return *this;
+  }
+  constexpr FrameId& operator--() {
+    OSP_CHECK(!is_null());
+    --value_;
+    return *this;
+  }
+  constexpr FrameId operator++(int) {
+    OSP_CHECK(!is_null());
+    return FrameId(value_++);
+  }
+  constexpr FrameId operator--(int) {
+    OSP_CHECK(!is_null());
+    return FrameId(value_--);
+  }
+
+  // The identifier for the first frame in a stream.
+  static constexpr FrameId first() { return FrameId(0); }
+
+  // A virtual identifier, representing the frame before the first. There should
+  // never actually be a frame streamed with this identifier. Instead, this is
+  // used in various components to represent a "not yet seen/processed the first
+  // frame" state.
+  //
+  // The name "leader" comes from the terminology used in tape reels, which
+  // refers to the non-data-carrying segment of tape before the recording
+  // begins.
+  static constexpr FrameId leader() { return FrameId(-1); }
+
+  constexpr int64_t value() const { return value_; }
+
+  std::string ToString() const;
+
+ private:
+  friend class ExpandedValueBase<int64_t, FrameId>;
+  friend std::ostream& operator<<(std::ostream& out, const FrameId rhs);
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_FRAME_ID_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/offer_messages.cc

@@ -0,0 +1,487 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/offer_messages.h"
+
+#include <inttypes.h>
+
+#include <algorithm>
+#include <limits>
+#include <ranges>
+#include <string>
+#include <string_view>
+#include <utility>
+
+#include "cast/streaming/public/constants.h"
+#include "platform/base/error.h"
+#include "util/big_endian.h"
+#include "util/enum_name_table.h"
+#include "util/json/json_helpers.h"
+#include "util/json/json_serialization.h"
+#include "util/osp_logging.h"
+#include "util/string_util.h"
+#include "util/stringprintf.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+constexpr char kSupportedStreams[] = "supportedStreams";
+constexpr char kAudioSourceType[] = "audio_source";
+constexpr char kVideoSourceType[] = "video_source";
+constexpr char kStreamType[] = "type";
+
+[[nodiscard]] constexpr bool CodecParameterIsValid(VideoCodec codec,
+                                                   std::string_view parameter) {
+  if (parameter.empty()) {
+    return true;
+  }
+  switch (codec) {
+    using enum VideoCodec;
+    case kVp8:
+      return parameter.starts_with("vp08");
+    case kVp9:
+      return parameter.starts_with("vp09");
+    case kAv1:
+      return parameter.starts_with("av01");
+    case kHevc:
+      return parameter.starts_with("hev1");
+    case kH264:
+      return parameter.starts_with("avc1");
+    case kNotSpecified:
+      return false;
+  }
+  OSP_NOTREACHED();
+}
+
+bool CodecParameterIsValid(AudioCodec codec,
+                           const std::string& codec_parameter) {
+  if (codec_parameter.empty()) {
+    return true;
+  }
+  switch (codec) {
+    case AudioCodec::kAac:
+      return codec_parameter.starts_with("mp4a.");
+
+    // Opus doesn't use codec parameters.
+    case AudioCodec::kOpus:  // fallthrough
+    case AudioCodec::kNotSpecified:
+      return false;
+  }
+  OSP_NOTREACHED();
+}
+
+EnumNameTable<CastMode, 2> kCastModeNames{
+    {{"mirroring", CastMode::kMirroring}, {"remoting", CastMode::kRemoting}}};
+
+bool TryParseRtpPayloadType(const Json::Value& value, RtpPayloadType* out) {
+  int t;
+  if (!json::TryParseInt(value, &t)) {
+    return false;
+  }
+
+  uint8_t t_small = t;
+  if (t_small != t || !IsRtpPayloadType(t_small)) {
+    return false;
+  }
+
+  *out = static_cast<RtpPayloadType>(t_small);
+  return true;
+}
+
+bool TryParseRtpTimebase(const Json::Value& value, int* out) {
+  std::string raw_timebase;
+  if (!json::TryParseString(value, &raw_timebase)) {
+    return false;
+  }
+
+  // The spec demands a leading 1, so this isn't really a fraction.
+  const auto fraction = SimpleFraction::FromString(raw_timebase);
+  if (fraction.is_error() || !fraction.value().is_positive() ||
+      fraction.value().numerator() != 1) {
+    return false;
+  }
+
+  *out = fraction.value().denominator();
+  return true;
+}
+
+// For a hex byte, the conversion is 4 bits to 1 character, e.g.
+// 0b11110001 becomes F1, so 1 byte is two characters.
+constexpr int kHexDigitsPerByte = 2;
+constexpr int kAesBytesSize = 16;
+constexpr int kAesStringLength = kAesBytesSize * kHexDigitsPerByte;
+bool TryParseAesHexBytes(const Json::Value& value,
+                         std::array<uint8_t, kAesBytesSize>* out) {
+  std::string hex_string;
+  if (!json::TryParseString(value, &hex_string)) {
+    return false;
+  }
+
+  constexpr int kHexDigitsPerScanField = 16;
+  constexpr int kNumScanFields = kAesStringLength / kHexDigitsPerScanField;
+  uint64_t quads[kNumScanFields];
+  int chars_scanned;
+  if (hex_string.size() == kAesStringLength &&
+      sscanf(hex_string.c_str(), "%16" SCNx64 "%16" SCNx64 "%n", &quads[0],
+             &quads[1], &chars_scanned) == kNumScanFields &&
+      chars_scanned == kAesStringLength &&
+      std::none_of(hex_string.begin(), hex_string.end(),
+                   [](char c) { return std::isspace(c); })) {
+    WriteBigEndian(quads[0], out->data());
+    WriteBigEndian(quads[1], out->data() + 8);
+    return true;
+  }
+
+  return false;
+}
+
+std::string_view ToString(Stream::Type type) {
+  switch (type) {
+    case Stream::Type::kAudioSource:
+      return kAudioSourceType;
+    case Stream::Type::kVideoSource:
+      return kVideoSourceType;
+    default: {
+      OSP_NOTREACHED();
+    }
+  }
+}
+
+bool TryParseResolutions(const Json::Value& value,
+                         std::vector<Resolution>* out) {
+  out->clear();
+
+  // Some legacy senders don't provide resolutions, so just return empty.
+  if (!value.isArray() || value.empty()) {
+    return false;
+  }
+
+  for (Json::ArrayIndex i = 0; i < value.size(); ++i) {
+    auto resolution = Resolution::TryParse(value[i]);
+    if (resolution.is_error()) {
+      out->clear();
+      return false;
+    }
+    out->push_back(std::move(resolution.value()));
+  }
+
+  return true;
+}
+
+}  // namespace
+
+ErrorOr<Stream> Stream::TryParse(const Json::Value& value, Stream::Type type) {
+  if (!value.isObject()) {
+    return Error(Error::Code::kJsonParseError, "Stream is not a JSON object");
+  }
+
+  Stream out;
+  out.type = type;
+
+  if (!json::TryParseInt(value["index"], &out.index) ||
+      !json::TryParseUint(value["ssrc"], &out.ssrc) ||
+      !TryParseRtpPayloadType(value["rtpPayloadType"], &out.rtp_payload_type) ||
+      !TryParseRtpTimebase(value["timeBase"], &out.rtp_timebase)) {
+    return Error(Error::Code::kJsonParseError,
+                 "Offer stream has missing or invalid mandatory field");
+  }
+
+  if (!json::TryParseInt(value["channels"], &out.channels)) {
+    out.channels = out.type == Stream::Type::kAudioSource
+                       ? kDefaultNumAudioChannels
+                       : kDefaultNumVideoChannels;
+  } else if (out.channels <= 0) {
+    return Error(Error::Code::kJsonParseError, "Invalid channel count");
+  }
+
+  if (!TryParseAesHexBytes(value["aesKey"], &out.aes_key) ||
+      !TryParseAesHexBytes(value["aesIvMask"], &out.aes_iv_mask)) {
+    return Error(Error::Code::kUnencryptedOffer,
+                 "Offer stream must have both a valid aesKey and aesIvMask");
+  }
+  if (out.rtp_timebase <
+          std::min(kDefaultAudioMinSampleRate, kRtpVideoTimebase) ||
+      out.rtp_timebase > kRtpVideoTimebase) {
+    return Error(Error::Code::kJsonParseError, "rtp_timebase (sample rate)");
+  }
+
+  out.target_delay = kDefaultTargetPlayoutDelay;
+  int target_delay;
+  if (json::TryParseInt(value["targetDelay"], &target_delay)) {
+    auto d = std::chrono::milliseconds(target_delay);
+    if (kMinTargetPlayoutDelay <= d && d <= kMaxTargetPlayoutDelay) {
+      out.target_delay = d;
+    }
+  }
+
+  json::TryParseBool(value["receiverRtcpEventLog"],
+                     &out.receiver_rtcp_event_log);
+  int dscp_value;
+  if (json::TryParseInt(value["receiverRtcpDscp"], &dscp_value)) {
+    // DSCP values are clamped to [0, 63].
+    if (dscp_value < 0 || dscp_value > 63) {
+      return Error(Error::Code::kJsonParseError,
+                   "receiverRtcpDscp (invalid DSCP value)");
+    }
+    out.receiver_rtcp_dscp = dscp_value;
+  }
+
+  json::TryParseStringArray(value["rtpExtensions"], &out.rtp_extensions);
+  json::TryParseString(value["codecParameter"], &out.codec_parameter);
+
+  return out;
+}
+
+Json::Value Stream::ToJson() const {
+  OSP_CHECK(IsValid());
+
+  Json::Value root;
+  root["index"] = index;
+  root["type"] = std::string(ToString(type));
+  root["channels"] = channels;
+  root["rtpPayloadType"] = static_cast<int>(rtp_payload_type);
+  // rtpProfile is technically required by the spec, although it is always set
+  // to cast. We set it here to be compliant with all spec implementers.
+  root["rtpProfile"] = "cast";
+  static_assert(sizeof(ssrc) <= sizeof(Json::UInt),
+                "this code assumes Ssrc fits in a Json::UInt");
+  root["ssrc"] = static_cast<Json::UInt>(ssrc);
+  root["targetDelay"] = static_cast<int>(target_delay.count());
+  root["aesKey"] = HexEncode(aes_key.data(), aes_key.size());
+  root["aesIvMask"] = HexEncode(aes_iv_mask.data(), aes_iv_mask.size());
+  root["receiverRtcpEventLog"] = receiver_rtcp_event_log;
+  if (receiver_rtcp_dscp.has_value()) {
+    root["receiverRtcpDscp"] = receiver_rtcp_dscp.value();
+  }
+  root["timeBase"] = "1/" + std::to_string(rtp_timebase);
+  root["codecParameter"] = codec_parameter;
+  if (!rtp_extensions.empty()) {
+    root["rtpExtensions"] = json::PrimitiveVectorToJson(rtp_extensions);
+  }
+  return root;
+}
+
+bool Stream::IsValid() const {
+  return channels >= 1 && index >= 0 && target_delay.count() > 0 &&
+         target_delay.count() <= std::numeric_limits<int>::max() &&
+         rtp_timebase >= 1;
+}
+
+ErrorOr<AudioStream> AudioStream::TryParse(const Json::Value& value) {
+  if (!value.isObject()) {
+    return Error(Error::Code::kJsonParseError,
+                 "Audio stream is not a JSON object");
+  }
+
+  auto stream_or_error = Stream::TryParse(value, Stream::Type::kAudioSource);
+  if (stream_or_error.is_error()) {
+    return stream_or_error.error();
+  }
+
+  AudioStream out;
+  out.stream = std::move(stream_or_error.value());
+
+  std::string codec_name;
+  if (!json::TryParseInt(value["bitRate"], &out.bit_rate) || out.bit_rate < 0 ||
+      !json::TryParseString(value[kCodecName], &codec_name)) {
+    return Error(Error::Code::kJsonParseError, "Invalid audio stream field");
+  }
+  ErrorOr<AudioCodec> codec = StringToAudioCodec(codec_name);
+  if (!codec) {
+    return Error(Error::Code::kUnknownCodec,
+                 "Codec is not known, can't use stream");
+  }
+  out.codec = codec.value();
+  if (!CodecParameterIsValid(codec.value(), out.stream.codec_parameter)) {
+    return Error(Error::Code::kInvalidCodecParameter,
+                 StringFormat("Invalid audio codec parameter ({} for codec {})",
+                              out.stream.codec_parameter.c_str(),
+                              CodecToString(codec.value())));
+  }
+  return out;
+}
+
+Json::Value AudioStream::ToJson() const {
+  OSP_CHECK(IsValid());
+
+  Json::Value out = stream.ToJson();
+  out[kCodecName] = CodecToString(codec);
+  out["bitRate"] = bit_rate;
+  return out;
+}
+
+bool AudioStream::IsValid() const {
+  return bit_rate >= 0 && stream.IsValid();
+}
+
+ErrorOr<VideoStream> VideoStream::TryParse(const Json::Value& value) {
+  if (!value.isObject()) {
+    return Error(Error::Code::kJsonParseError,
+                 "Video stream is not a JSON object");
+  }
+
+  auto stream_or_error = Stream::TryParse(value, Stream::Type::kVideoSource);
+  if (stream_or_error.is_error()) {
+    return stream_or_error.error();
+  }
+
+  VideoStream out;
+  out.stream = std::move(stream_or_error.value());
+
+  std::string codec_name;
+  if (!json::TryParseString(value[kCodecName], &codec_name)) {
+    return Error(Error::Code::kJsonParseError, "Video stream missing codec");
+  }
+  ErrorOr<VideoCodec> codec = StringToVideoCodec(codec_name);
+  if (!codec) {
+    return Error(Error::Code::kUnknownCodec,
+                 "Codec is not known, can't use stream");
+  }
+  out.codec = codec.value();
+  if (!CodecParameterIsValid(codec.value(), out.stream.codec_parameter)) {
+    return Error(Error::Code::kInvalidCodecParameter,
+                 StringFormat("Invalid video codec parameter ({} for codec {})",
+                              out.stream.codec_parameter.c_str(),
+                              CodecToString(codec.value())));
+  }
+
+  out.max_frame_rate = SimpleFraction{kDefaultMaxFrameRate, 1};
+  std::string raw_max_frame_rate;
+  if (json::TryParseString(value["maxFrameRate"], &raw_max_frame_rate)) {
+    auto parsed = SimpleFraction::FromString(raw_max_frame_rate);
+    if (parsed.is_value() && parsed.value().is_positive()) {
+      out.max_frame_rate = parsed.value();
+    }
+  }
+
+  TryParseResolutions(value["resolutions"], &out.resolutions);
+  json::TryParseString(value["profile"], &out.profile);
+  json::TryParseString(value["protection"], &out.protection);
+  json::TryParseString(value["level"], &out.level);
+  json::TryParseString(value["errorRecoveryMode"], &out.error_recovery_mode);
+  if (!json::TryParseInt(value["maxBitRate"], &out.max_bit_rate)) {
+    out.max_bit_rate = 4 << 20;
+  }
+
+  return out;
+}
+
+Json::Value VideoStream::ToJson() const {
+  OSP_CHECK(IsValid());
+
+  Json::Value out = stream.ToJson();
+  out["codecName"] = CodecToString(codec);
+  out["maxFrameRate"] = max_frame_rate.ToString();
+  out["maxBitRate"] = max_bit_rate;
+  out["protection"] = protection;
+  out["profile"] = profile;
+  out["level"] = level;
+  out["errorRecoveryMode"] = error_recovery_mode;
+
+  Json::Value rs;
+  for (auto resolution : resolutions) {
+    rs.append(resolution.ToJson());
+  }
+  out["resolutions"] = std::move(rs);
+  return out;
+}
+
+bool VideoStream::IsValid() const {
+  return max_bit_rate > 0 && max_frame_rate.is_positive();
+}
+
+// static
+ErrorOr<Offer> Offer::TryParse(const Json::Value& root) {
+  if (!root.isObject()) {
+    return Error(Error::Code::kJsonParseError, "null offer");
+  }
+  const ErrorOr<CastMode> cast_mode =
+      GetEnum(kCastModeNames, root["castMode"].asString());
+  Json::Value supported_streams = root[kSupportedStreams];
+  if (!supported_streams.isArray()) {
+    return Error(Error::Code::kJsonParseError, "supported streams in offer");
+  }
+
+  std::vector<AudioStream> audio_streams;
+  std::vector<VideoStream> video_streams;
+
+  using Dscp = std::optional<int>;
+  std::optional<Dscp> receiver_rtcp_dscp;
+  for (Json::ArrayIndex i = 0; i < supported_streams.size(); ++i) {
+    const Json::Value& fields = supported_streams[i];
+    std::string type;
+    if (!json::TryParseString(fields[kStreamType], &type)) {
+      return Error(Error::Code::kJsonParseError, "Missing stream type");
+    }
+
+    Error error = Error::None();
+    if (type == kAudioSourceType) {
+      auto stream_or_error = AudioStream::TryParse(fields);
+      if (stream_or_error.is_value()) {
+        auto stream = std::move(stream_or_error.value());
+        if (!receiver_rtcp_dscp) {
+          receiver_rtcp_dscp.emplace(stream.stream.receiver_rtcp_dscp);
+        } else if (stream.stream.receiver_rtcp_dscp != *receiver_rtcp_dscp) {
+          return Error(Error::Code::kJsonParseError,
+                       "Mixed DSCP values in offer");
+        }
+        audio_streams.push_back(std::move(stream));
+      } else {
+        error = stream_or_error.error();
+      }
+    } else if (type == kVideoSourceType) {
+      auto stream_or_error = VideoStream::TryParse(fields);
+      if (stream_or_error.is_value()) {
+        auto stream = std::move(stream_or_error.value());
+        if (!receiver_rtcp_dscp) {
+          receiver_rtcp_dscp.emplace(stream.stream.receiver_rtcp_dscp);
+        } else if (stream.stream.receiver_rtcp_dscp != *receiver_rtcp_dscp) {
+          return Error(Error::Code::kJsonParseError,
+                       "Mixed DSCP values in offer");
+        }
+        video_streams.push_back(std::move(stream));
+      } else {
+        error = stream_or_error.error();
+      }
+    }
+
+    if (!error.ok()) {
+      if (error.code() == Error::Code::kUnknownCodec) {
+        OSP_VLOG << "Dropping audio stream due to unknown codec: " << error;
+        continue;
+      } else {
+        return error;
+      }
+    }
+  }
+
+  return Offer{cast_mode.value(CastMode::kMirroring), std::move(audio_streams),
+               std::move(video_streams)};
+}
+
+Json::Value Offer::ToJson() const {
+  OSP_CHECK(IsValid());
+  Json::Value root;
+  root["castMode"] = GetEnumName(kCastModeNames, cast_mode).value();
+  Json::Value streams;
+  for (auto& stream : audio_streams) {
+    streams.append(stream.ToJson());
+  }
+
+  for (auto& stream : video_streams) {
+    streams.append(stream.ToJson());
+  }
+
+  root[kSupportedStreams] = std::move(streams);
+  return root;
+}
+
+bool Offer::IsValid() const {
+  return std::ranges::all_of(
+             audio_streams, [](const AudioStream& a) { return a.IsValid(); }) &&
+         std::ranges::all_of(video_streams,
+                             [](const VideoStream& v) { return v.IsValid(); });
+}
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/offer_messages.h

@@ -0,0 +1,115 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_OFFER_MESSAGES_H_
+#define CAST_STREAMING_PUBLIC_OFFER_MESSAGES_H_
+
+#include <chrono>
+#include <string>
+#include <vector>
+
+#include "cast/streaming/impl/rtp_defines.h"
+#include "cast/streaming/message_fields.h"
+#include "cast/streaming/public/session_config.h"
+#include "cast/streaming/resolution.h"
+#include "json/value.h"
+#include "platform/base/error.h"
+#include "util/simple_fraction.h"
+
+// This file contains the implementation of the Cast V2 Mirroring Control
+// Protocol offer object definition.
+namespace openscreen::cast {
+
+// If the target delay provided by the sender is not bounded by
+// [kMinTargetDelay, kMaxTargetDelay], it will be set to
+// kDefaultTargetPlayoutDelay.
+inline constexpr auto kMinTargetPlayoutDelay = std::chrono::milliseconds(0);
+inline constexpr auto kMaxTargetPlayoutDelay = std::chrono::milliseconds(5000);
+
+// If the sender provides an invalid maximum frame rate, it ill
+// be set to kDefaultMaxFrameRate.
+inline constexpr int kDefaultMaxFrameRate = 30;
+
+inline constexpr int kDefaultNumVideoChannels = 1;
+inline constexpr int kDefaultNumAudioChannels = 2;
+
+// A stream, as detailed by the CastV2 protocol spec, is a segment of an
+// offer message specifically representing a configuration object for
+// a codec and its related fields, such as maximum bit rate, time base,
+// and other fields.
+// Composed classes include AudioStream and VideoStream, which contain
+// fields specific to audio and video respectively.
+struct Stream {
+  enum class Type : uint8_t { kAudioSource, kVideoSource };
+
+  static ErrorOr<Stream> TryParse(const Json::Value& root, Stream::Type type);
+  Json::Value ToJson() const;
+  bool IsValid() const;
+
+  int index = 0;
+  Type type = {};
+
+  // Default channel count is 1, e.g. for video.
+  int channels = 0;
+  RtpPayloadType rtp_payload_type = {};
+  Ssrc ssrc = {};
+  std::chrono::milliseconds target_delay = {};
+
+  // AES Key and IV mask format is very strict: a 32 digit hex string that
+  // must be converted to a 16 digit byte array.
+  std::array<uint8_t, 16> aes_key = {};
+  std::array<uint8_t, 16> aes_iv_mask = {};
+
+  // The event logs are generally recommended for use in gathering statistics
+  // for the sender session.
+  bool receiver_rtcp_event_log = true;
+  std::optional<int> receiver_rtcp_dscp;
+  int rtp_timebase = 0;
+
+  // The codec parameter field honors the format laid out in RFC 6381:
+  // https://datatracker.ietf.org/doc/html/rfc6381.
+  std::string codec_parameter;
+
+  std::vector<std::string> rtp_extensions;
+};
+
+struct AudioStream {
+  static ErrorOr<AudioStream> TryParse(const Json::Value& root);
+  Json::Value ToJson() const;
+  bool IsValid() const;
+
+  Stream stream;
+  AudioCodec codec = AudioCodec::kNotSpecified;
+  int bit_rate = 0;
+};
+
+struct VideoStream {
+  static ErrorOr<VideoStream> TryParse(const Json::Value& root);
+  Json::Value ToJson() const;
+  bool IsValid() const;
+
+  Stream stream;
+  VideoCodec codec = VideoCodec::kNotSpecified;
+  SimpleFraction max_frame_rate;
+  int max_bit_rate = 0;
+  std::string protection;
+  std::string profile;
+  std::string level;
+  std::vector<Resolution> resolutions;
+  std::string error_recovery_mode;
+};
+
+struct Offer {
+  static ErrorOr<Offer> TryParse(const Json::Value& root);
+  Json::Value ToJson() const;
+  bool IsValid() const;
+
+  CastMode cast_mode = CastMode::kMirroring;
+  std::vector<AudioStream> audio_streams;
+  std::vector<VideoStream> video_streams;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_OFFER_MESSAGES_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/receiver_message.cc

@@ -0,0 +1,300 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/receiver_message.h"
+
+#include <utility>
+#include <variant>
+
+#include "cast/streaming/message_fields.h"
+#include "json/reader.h"
+#include "json/writer.h"
+#include "platform/base/error.h"
+#include "util/base64.h"
+#include "util/enum_name_table.h"
+#include "util/json/json_helpers.h"
+#include "util/json/json_serialization.h"
+#include "util/osp_logging.h"
+#include "util/string_util.h"
+#include "util/stringprintf.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+EnumNameTable<ReceiverMessage::Type, 4> kMessageTypeNames{
+    {{kMessageTypeAnswer, ReceiverMessage::Type::kAnswer},
+     {"CAPABILITIES_RESPONSE", ReceiverMessage::Type::kCapabilitiesResponse},
+     {"RPC", ReceiverMessage::Type::kRpc},
+     {"INPUT", ReceiverMessage::Type::kInput}}};
+
+EnumNameTable<MediaCapability, 10> kMediaCapabilityNames{
+    {{"audio", MediaCapability::kAudio},
+     {"aac", MediaCapability::kAac},
+     {"opus", MediaCapability::kOpus},
+     {"video", MediaCapability::kVideo},
+     {"4k", MediaCapability::k4k},
+     {"h264", MediaCapability::kH264},
+     {"vp8", MediaCapability::kVp8},
+     {"vp9", MediaCapability::kVp9},
+     {"hevc", MediaCapability::kHevc},
+     {"av1", MediaCapability::kAv1}}};
+
+ReceiverMessage::Type GetMessageType(const Json::Value& root) {
+  std::string type;
+  if (!json::TryParseString(root[kMessageType], &type)) {
+    return ReceiverMessage::Type::kUnknown;
+  }
+  string_util::AsciiStrToUpper(type);
+
+  ErrorOr<ReceiverMessage::Type> parsed = GetEnum(kMessageTypeNames, type);
+  return parsed.value(ReceiverMessage::Type::kUnknown);
+}
+
+bool TryParseCapability(const Json::Value& value, MediaCapability* out) {
+  std::string c;
+  if (!json::TryParseString(value, &c)) {
+    return false;
+  }
+
+  const ErrorOr<MediaCapability> capability = GetEnum(kMediaCapabilityNames, c);
+  if (capability.is_error()) {
+    return false;
+  }
+
+  *out = capability.value();
+  return true;
+}
+
+}  // namespace
+
+ReceiverError::ReceiverError(int code, std::string_view description)
+    : code(code), description(description) {
+  if (code >= kOpenscreenErrorOffset) {
+    openscreen_code = static_cast<Error::Code>(code - kOpenscreenErrorOffset);
+  }
+}
+
+ReceiverError::ReceiverError(Error::Code code, std::string_view description)
+    : code(static_cast<int>(code) + kOpenscreenErrorOffset),
+      openscreen_code(code),
+      description(description) {}
+
+ReceiverError::ReceiverError(const Error& error)
+    : code(static_cast<int>(error.code()) + kOpenscreenErrorOffset),
+      openscreen_code(error.code()),
+      description(error.message()) {}
+
+ReceiverError::ReceiverError(const ReceiverError&) = default;
+ReceiverError::ReceiverError(ReceiverError&&) noexcept = default;
+ReceiverError& ReceiverError::operator=(const ReceiverError&) = default;
+ReceiverError& ReceiverError::operator=(ReceiverError&&) = default;
+ReceiverError::~ReceiverError() = default;
+
+// static
+ErrorOr<ReceiverError> ReceiverError::Parse(const Json::Value& value) {
+  if (!value.isObject()) {
+    return Error(Error::Code::kParameterInvalid,
+                 "Empty JSON in receiver error parsing");
+  }
+
+  int code;
+  std::string description;
+  if (!json::TryParseInt(value[kErrorCode], &code) ||
+      !json::TryParseString(value[kErrorDescription], &description)) {
+    return Error::Code::kJsonParseError;
+  }
+
+  return ReceiverError(code, description);
+}
+
+Json::Value ReceiverError::ToJson() const {
+  Json::Value root;
+  root[kErrorCode] = openscreen_code ? static_cast<int>(*openscreen_code) +
+                                           kOpenscreenErrorOffset
+                                     : code;
+  root[kErrorDescription] = description;
+  return root;
+}
+
+Error ReceiverError::ToError() const {
+  if (openscreen_code) {
+    return Error(*openscreen_code, description);
+  }
+
+  std::string full_description = StringFormat("Error code: {}, description: {}",
+                                              code, description.c_str());
+  return Error(Error::Code::kUnknownError, std::move(full_description));
+}
+
+// static
+ErrorOr<ReceiverCapability> ReceiverCapability::Parse(
+    const Json::Value& value) {
+  if (!value.isObject()) {
+    return Error(Error::Code::kParameterInvalid,
+                 "Empty JSON in capabilities parsing");
+  }
+
+  int remoting_version;
+  if (!json::TryParseInt(value["remoting"], &remoting_version)) {
+    remoting_version = ReceiverCapability::kRemotingVersionUnknown;
+  }
+
+  std::vector<MediaCapability> capabilities;
+  if (!json::TryParseArray<MediaCapability>(
+          value["mediaCaps"], TryParseCapability, &capabilities)) {
+    return Error(Error::Code::kJsonParseError,
+                 "Failed to parse media capabilities");
+  }
+
+  return ReceiverCapability{remoting_version, std::move(capabilities)};
+}
+
+Json::Value ReceiverCapability::ToJson() const {
+  Json::Value root;
+  root["remoting"] = remoting_version;
+  Json::Value capabilities(Json::ValueType::arrayValue);
+  for (const auto& capability : media_capabilities) {
+    capabilities.append(GetEnumName(kMediaCapabilityNames, capability).value());
+  }
+  root["mediaCaps"] = std::move(capabilities);
+  return root;
+}
+
+// static
+ErrorOr<ReceiverMessage> ReceiverMessage::Parse(const Json::Value& value) {
+  ReceiverMessage message;
+  if (!value.isObject()) {
+    return Error(Error::Code::kJsonParseError, "Invalid message body");
+  }
+
+  std::string result;
+  if (!json::TryParseString(value[kResult], &result)) {
+    result = kResultError;
+  }
+
+  message.type = GetMessageType(value);
+  message.valid =
+      (result == kResultOk || message.type == ReceiverMessage::Type::kRpc ||
+       message.type == ReceiverMessage::Type::kInput);
+
+  if (message.type != ReceiverMessage::Type::kRpc &&
+      message.type != ReceiverMessage::Type::kInput) {
+    if (!json::TryParseInt(value[kSequenceNumber],
+                           &(message.sequence_number))) {
+      message.sequence_number = -1;
+    }
+
+    // Sequence numbers must be non-negative.
+    if (message.sequence_number < 0) {
+      message.valid = false;
+    }
+  }
+
+  if (!message.valid) {
+    ErrorOr<ReceiverError> error =
+        ReceiverError::Parse(value[kErrorMessageBody]);
+    if (error.is_value()) {
+      message.body = std::move(error.value());
+    }
+    return message;
+  }
+
+  switch (message.type) {
+    case Type::kAnswer: {
+      auto answer_or_error =
+          openscreen::cast::Answer::TryParse(value[kAnswerMessageBody]);
+      if (answer_or_error.is_value()) {
+        message.body = std::move(answer_or_error.value());
+        message.valid = true;
+      }
+    } break;
+
+    case Type::kCapabilitiesResponse: {
+      ErrorOr<ReceiverCapability> capability =
+          ReceiverCapability::Parse(value[kCapabilitiesMessageBody]);
+      if (capability.is_value()) {
+        message.body = std::move(capability.value());
+        message.valid = true;
+      }
+    } break;
+
+    case Type::kRpc: {
+      std::string encoded_rpc;
+      std::vector<uint8_t> rpc;
+      if (json::TryParseString(value[kRpcMessageBody], &encoded_rpc) &&
+          base64::Decode(encoded_rpc, &rpc)) {
+        message.body = std::move(rpc);
+        message.valid = true;
+      }
+    } break;
+
+    case Type::kInput: {
+      std::string encoded_input;
+      std::vector<uint8_t> input;
+      if (json::TryParseString(value[kInputMessageBody], &encoded_input) &&
+          base64::Decode(encoded_input, &input)) {
+        message.body = std::move(input);
+        message.valid = true;
+      }
+    } break;
+
+    default:
+      break;
+  }
+
+  return message;
+}
+
+ErrorOr<Json::Value> ReceiverMessage::ToJson() const {
+  OSP_CHECK(type != ReceiverMessage::Type::kUnknown)
+      << "Trying to send an unknown message is a developer error";
+
+  Json::Value root;
+  root[kMessageType] = GetEnumName(kMessageTypeNames, type).value();
+  if (sequence_number >= 0) {
+    root[kSequenceNumber] = sequence_number;
+  }
+
+  switch (type) {
+    case ReceiverMessage::Type::kAnswer:
+      if (valid) {
+        root[kResult] = kResultOk;
+        root[kAnswerMessageBody] = std::get<Answer>(body).ToJson();
+      } else {
+        root[kResult] = kResultError;
+        root[kErrorMessageBody] = std::get<ReceiverError>(body).ToJson();
+      }
+      break;
+
+    case ReceiverMessage::Type::kCapabilitiesResponse:
+      if (valid) {
+        root[kResult] = kResultOk;
+        root[kCapabilitiesMessageBody] =
+            std::get<ReceiverCapability>(body).ToJson();
+      } else {
+        root[kResult] = kResultError;
+        root[kErrorMessageBody] = std::get<ReceiverError>(body).ToJson();
+      }
+      break;
+
+    // NOTE: RPC messages do NOT have a result field.
+    case ReceiverMessage::Type::kRpc:
+      root[kRpcMessageBody] =
+          base64::Encode(std::get<std::vector<uint8_t>>(body));
+      break;
+
+    case ReceiverMessage::Type::kInput:
+      root[kInputMessageBody] =
+          base64::Encode(std::get<std::vector<uint8_t>>(body));
+      break;
+
+    default:
+      OSP_NOTREACHED();
+  }
+
+  return root;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/receiver_message.h

@@ -0,0 +1,117 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_RECEIVER_MESSAGE_H_
+#define CAST_STREAMING_PUBLIC_RECEIVER_MESSAGE_H_
+
+#include <memory>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <variant>
+#include <vector>
+
+#include "cast/streaming/public/answer_messages.h"
+#include "json/value.h"
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+enum class MediaCapability {
+  kAudio,
+  kAac,
+  kOpus,
+  kVideo,
+  k4k,
+  kH264,
+  kVp8,
+  kVp9,
+  kHevc,
+  kAv1
+};
+
+struct ReceiverCapability {
+  static constexpr int kRemotingVersionUnknown = -1;
+
+  Json::Value ToJson() const;
+  static ErrorOr<ReceiverCapability> Parse(const Json::Value& value);
+
+  // The remoting version that the receiver uses.
+  int remoting_version = kRemotingVersionUnknown;
+
+  // Set of capabilities (e.g., ac3, 4k, hevc, vp9, dolby_vision, etc.).
+  std::vector<MediaCapability> media_capabilities;
+};
+
+// To avoid collisions with legacy error values, all Open Screen receiver errors
+// are offset.
+struct ReceiverError {
+  explicit ReceiverError(int code, std::string_view description = "");
+  explicit ReceiverError(Error::Code code, std::string_view description = "");
+  explicit ReceiverError(const Error& error);
+
+  ReceiverError(const ReceiverError&);
+  ReceiverError(ReceiverError&&) noexcept;
+  ReceiverError& operator=(const ReceiverError&);
+  ReceiverError& operator=(ReceiverError&&);
+  ~ReceiverError();
+
+  Json::Value ToJson() const;
+  static ErrorOr<ReceiverError> Parse(const Json::Value& value);
+  Error ToError() const;
+
+  // All Open Screen errors are offset by a fixed value to avoid overlapping
+  // with legacy values.
+  static constexpr int kOpenscreenErrorOffset = 10000;
+
+  // Raw error code.
+  int32_t code = -1;
+
+  // Parsed openscreen::Error code. May be nullopt if not a match.
+  std::optional<Error::Code> openscreen_code;
+
+  // Error description.
+  std::string description;
+};
+
+struct ReceiverMessage {
+ public:
+  // Receiver response message type.
+  enum class Type {
+    // Unknown message type.
+    kUnknown,
+
+    // Response to OFFER message.
+    kAnswer,
+
+    // Response to GET_CAPABILITIES message.
+    kCapabilitiesResponse,
+
+    // Rpc binary messages. The payload is base64-encoded.
+    kRpc,
+
+    // Input-related binary messages. The payload is base64-encoded.
+    kInput,
+  };
+
+  static ErrorOr<ReceiverMessage> Parse(const Json::Value& value);
+  ErrorOr<Json::Value> ToJson() const;
+
+  Type type = Type::kUnknown;
+
+  int32_t sequence_number = -1;
+
+  bool valid = false;
+
+  std::variant<std::monostate,
+               Answer,
+               std::vector<uint8_t>,  // Binary-encoded protobuf message.
+               ReceiverCapability,
+               ReceiverError>
+      body;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_RECEIVER_MESSAGE_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/sender.cc

@@ -0,0 +1,12 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/sender.h"
+
+namespace openscreen::cast {
+
+Sender::Observer::~Observer() = default;
+Sender::~Sender() = default;
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/sender.h

@@ -0,0 +1,173 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_SENDER_H_
+#define CAST_STREAMING_PUBLIC_SENDER_H_
+
+#include <stdint.h>
+
+#include <chrono>
+
+#include "cast/streaming/public/encoded_frame.h"
+#include "cast/streaming/public/frame_id.h"
+#include "cast/streaming/public/session_config.h"
+#include "cast/streaming/rtp_time.h"
+#include "cast/streaming/ssrc.h"
+#include "platform/api/time.h"
+
+namespace openscreen::cast {
+
+// The Cast Streaming Sender, a peer corresponding to some Cast Streaming
+// Receiver at the other end of a network link.
+//
+// The Sender is the peer responsible for enqueuing EncodedFrames for streaming,
+// guaranteeing their delivery to a Receiver, and handling feedback events from
+// a Receiver. Some feedback events are used for managing the Sender's internal
+// queue of in-flight frames, requesting network packet re-transmits, etc.;
+// while others are exposed via the Sender's public interface. For example,
+// sometimes the Receiver signals that it needs a a key frame to resolve a
+// picture loss condition, and the modules upstream of the Sender (e.g., where
+// encoding happens) should call NeedsKeyFrame() to check for, and handle that.
+//
+// There are usually one or two Senders in a streaming session, one for audio
+// and one for video. Both senders work with the same SenderPacketRouter
+// instance to schedule their transmission of packets, and provide the necessary
+// metrics for estimating bandwidth utilization and availability.
+//
+// It is the responsibility of upstream code modules to handle congestion
+// control. With respect to this Sender, that means the media encoding bit rate
+// should be throttled based on network bandwidth availability. This Sender does
+// not do any throttling, only flow-control. In other words, this Sender can
+// only manage its in-flight queue of frames, and if that queue grows too large,
+// it will eventually reject further enqueuing.
+//
+// General usage: A client should check the in-flight media duration frequently
+// to decide when to pause encoding, to avoid wasting system resources on
+// encoding frames that will likely be rejected by the Sender. The client should
+// also frequently call NeedsKeyFrame() and, when this returns true, direct its
+// encoder to produce a key frame soon. Finally, when using EnqueueFrame(), an
+// EncodedFrame struct should be prepared with its frame_id field set to
+// whatever GetNextFrameId() returns. Please see method comments for
+// more-detailed usage info.
+class Sender {
+ public:
+  // Interface for receiving notifications about events of possible interest.
+  class Observer {
+   public:
+    // Called when a frame was canceled, which may occur in the following cases:
+    //  - The Receiver acknowledged successful receipt of the frame.
+    //  - The Receiver decided to skip over the frame (e.g. it was too late).
+    //  - The Sender decided to skip the frame (e.g. OnFrameCanceled() called).
+    //
+    // Note: Frame cancellations may occur out-of-order.
+    virtual void OnFrameCanceled(FrameId frame_id) = 0;
+
+    // Called when a Receiver begins reporting picture loss, and there is no key
+    // frame currently enqueued in the Sender. The application should enqueue a
+    // key frame as soon as possible.
+    //
+    // This acts as a "push" notification, which is useful for immediately
+    // waking up an application that may be waiting for the next capture tick.
+    // For "pull" state checking inside a continuous encoding loop, see
+    // NeedsKeyFrame().
+    virtual void OnPictureLost() = 0;
+
+   protected:
+    virtual ~Observer();
+  };
+
+  // Result codes for EnqueueFrame().
+  enum EnqueueFrameResult {
+    // The frame has been queued for sending.
+    OK,
+
+    // The frame's payload was too large.
+    PAYLOAD_TOO_LARGE,
+
+    // The span of FrameIds is too large.
+    REACHED_ID_SPAN_LIMIT,
+
+    // Too-large a media duration is in-flight.
+    MAX_DURATION_IN_FLIGHT,
+  };
+
+  virtual ~Sender();
+
+  // The session configuration for this sender. The configuration is generated
+  // from the offer/answer exchange, and includes critical information like the
+  // RTP timebase, SSRCs for sending and receiving, and the AES configuration.
+  virtual const SessionConfig& config() const = 0;
+
+  // Sets an observer for receiving notifications. Call with nullptr to stop
+  // observing.
+  virtual void SetObserver(Observer* observer) = 0;
+
+  // Returns the number of frames currently in-flight. This is only meant to be
+  // informative. Clients should use GetInFlightMediaDuration() to make
+  // throttling decisions.
+  virtual size_t GetInFlightFrameCount() const = 0;
+
+  // Returns the total media duration of the frames currently in-flight,
+  // assuming the next not-yet-enqueued frame will have the given RTP timestamp.
+  // For a better user experience, the result should be compared to
+  // GetMaxInFlightMediaDuration(), and media encoding should be throttled down
+  // before additional EnqueueFrame() calls would cause this to reach the
+  // current maximum limit.
+  virtual Clock::duration GetInFlightMediaDuration(
+      RtpTimeTicks next_frame_rtp_timestamp) const = 0;
+
+  // Return the maximum acceptable in-flight media duration, given the current
+  // target playout delay setting and end-to-end network/system conditions.
+  virtual Clock::duration GetMaxInFlightMediaDuration() const = 0;
+
+  // Returns true if the Receiver requires a key frame. Note that this will
+  // return true until a key frame is accepted by EnqueueFrame(). Thus, when
+  // encoding is pipelined, care should be taken to instruct the encoder to
+  // produce just ONE forced key frame.
+  //
+  // This acts as a stateful "pull" check, which is useful for an encoder loop
+  // to poll right before processing the next image. For "push" notifications
+  // to wake up an idle application, see Observer::OnPictureLost().
+  virtual bool NeedsKeyFrame() const = 0;
+
+  // Returns the next FrameId, the one after the frame enqueued by the last call
+  // to EnqueueFrame(). Note that the next call to EnqueueFrame() assumes this
+  // frame ID be used.
+  virtual FrameId GetNextFrameId() const = 0;
+
+  // Get the current round trip time, defined as the total time between when the
+  // sender report is sent and the receiver report is received. This value is
+  // updated with each receiver report using a weighted moving average of 1/8
+  // for the new value and 7/8 for the previous value. Will be set to
+  // Clock::duration::zero() if no reports have been received yet.
+  // TODO(crbug.com/498036656): move to a more modern approach for estimating
+  // bandwidth.
+  virtual Clock::duration GetCurrentRoundTripTime() const = 0;
+
+  // Enqueues the given `frame` for sending as soon as possible. Returns OK if
+  // the frame is accepted, and some time later Observer::OnFrameCanceled() will
+  // be called once it is no longer in-flight.
+  //
+  // All fields of the `frame` must be set to valid values: the `frame_id` must
+  // be the same as GetNextFrameId(); both the `rtp_timestamp` and
+  // `reference_time` fields must be monotonically increasing relative to the
+  // prior frame; and the frame's `data` pointer must be set.
+  [[nodiscard]] virtual EnqueueFrameResult EnqueueFrame(
+      const EncodedFrame& frame) = 0;
+
+  // Causes all pending operations to discard data when they are processed
+  // later. This will notify observers by invoking OnFrameCanceled() for each
+  // canceled frame.
+  virtual void CancelInFlightData() = 0;
+
+  // May be called by the consumer to report that a frame has been dropped. This
+  // is used to report drop statistics to the sender's statistics collector.
+  virtual void ReportFrameDropEvent(FrameId frame_id,
+                                    RtpTimeTicks rtp_timestamp,
+                                    Clock::time_point drop_time) = 0;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_SENDER_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/session_config.cc

@@ -0,0 +1,54 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/session_config.h"
+
+#include <algorithm>
+#include <utility>
+
+namespace openscreen::cast {
+
+namespace {
+
+bool IsNonZero(uint8_t byte) {
+  return byte > 0;
+}
+
+}  // namespace
+
+SessionConfig::SessionConfig(Ssrc sender_ssrc,
+                             Ssrc receiver_ssrc,
+                             int rtp_timebase,
+                             int channels,
+                             std::chrono::milliseconds target_playout_delay,
+                             std::array<uint8_t, 16> aes_secret_key,
+                             std::array<uint8_t, 16> aes_iv_mask,
+                             bool is_pli_enabled,
+                             StreamType stream_type,
+                             bool are_receiver_event_logs_enabled)
+    : sender_ssrc(sender_ssrc),
+      receiver_ssrc(receiver_ssrc),
+      rtp_timebase(rtp_timebase),
+      channels(channels),
+      target_playout_delay(target_playout_delay),
+      aes_secret_key(std::move(aes_secret_key)),
+      aes_iv_mask(std::move(aes_iv_mask)),
+      is_pli_enabled(is_pli_enabled),
+      stream_type(stream_type),
+      are_receiver_event_logs_enabled(are_receiver_event_logs_enabled) {}
+
+SessionConfig::SessionConfig(const SessionConfig& other) = default;
+SessionConfig::SessionConfig(SessionConfig&& other) noexcept = default;
+SessionConfig& SessionConfig::operator=(const SessionConfig& other) = default;
+SessionConfig& SessionConfig::operator=(SessionConfig&& other) noexcept =
+    default;
+SessionConfig::~SessionConfig() = default;
+
+bool SessionConfig::IsValid() const {
+  return sender_ssrc > 0 && receiver_ssrc > 0 && rtp_timebase > 0 &&
+         channels > 0 &&
+         std::any_of(aes_secret_key.begin(), aes_secret_key.end(), IsNonZero) &&
+         std::any_of(aes_iv_mask.begin(), aes_iv_mask.end(), IsNonZero);
+}
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/session_config.h

@@ -0,0 +1,71 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_SESSION_CONFIG_H_
+#define CAST_STREAMING_PUBLIC_SESSION_CONFIG_H_
+
+#include <array>
+#include <chrono>
+#include <cstdint>
+
+#include "cast/streaming/public/constants.h"
+#include "cast/streaming/ssrc.h"
+
+namespace openscreen::cast {
+
+// Common streaming configuration, established from the OFFER/ANSWER exchange,
+// that the Sender and Receiver are both assuming.
+struct SessionConfig final {
+  SessionConfig(Ssrc sender_ssrc,
+                Ssrc receiver_ssrc,
+                int rtp_timebase,
+                int channels,
+                std::chrono::milliseconds target_playout_delay,
+                std::array<uint8_t, 16> aes_secret_key,
+                std::array<uint8_t, 16> aes_iv_mask,
+                bool is_pli_enabled = false,
+                StreamType stream_type = StreamType::kUnknown,
+                bool are_receiver_event_logs_enabled = true);
+  SessionConfig(const SessionConfig& other);
+  SessionConfig(SessionConfig&& other) noexcept;
+  SessionConfig& operator=(const SessionConfig& other);
+  SessionConfig& operator=(SessionConfig&& other) noexcept;
+  ~SessionConfig();
+
+  bool IsValid() const;
+
+  // The sender and receiver's SSRC identifiers. Note: SSRC identifiers
+  // are defined as unsigned 32 bit integers here:
+  // https://tools.ietf.org/html/rfc5576#page-5
+  Ssrc sender_ssrc = 0;
+  Ssrc receiver_ssrc = 0;
+
+  // RTP timebase: The number of RTP units advanced per second. For audio,
+  // this is the sampling rate. For video, this is 90 kHz by convention.
+  int rtp_timebase = 90000;
+
+  // Number of channels. Must be 1 for video, for audio typically 2.
+  int channels = 1;
+
+  // Initial target playout delay.
+  std::chrono::milliseconds target_playout_delay;
+
+  // The AES-128 crypto key and initialization vector.
+  std::array<uint8_t, 16> aes_secret_key{};
+  std::array<uint8_t, 16> aes_iv_mask{};
+
+  // Whether picture loss indication (PLI) should be used for this session.
+  bool is_pli_enabled = false;
+
+  // The type (e.g. audio or video) of the stream.
+  StreamType stream_type = StreamType::kUnknown;
+
+  // Whether RTCP event logs from the Receiver are enabled. These are used for
+  // generating statistics. It is recommended that this generally be true.
+  bool are_receiver_event_logs_enabled = true;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_SESSION_CONFIG_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/session_messenger.cc

@@ -0,0 +1,388 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/session_messenger.h"
+
+#include <algorithm>
+#include <chrono>
+#include <string>
+
+#include "cast/common/public/message_port.h"
+#include "cast/streaming/message_fields.h"
+#include "platform/base/trivial_clock_traits.h"
+#include "util/json/json_helpers.h"
+#include "util/json/json_serialization.h"
+#include "util/osp_logging.h"
+#include "util/string_util.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+// Default timeout to receive a reply message in response to a request message
+// sent by us.
+constexpr std::chrono::milliseconds kReplyTimeout(4000);
+
+// Special character indicating message was sent to all receivers or senders.
+constexpr char kAnyDestination[] = "*";
+
+void ReplyIfTimedOut(
+    int sequence_number,
+    std::vector<std::pair<int, SenderSessionMessenger::ReplyCallback>>*
+        replies) {
+  for (auto it = replies->begin(); it != replies->end(); ++it) {
+    if (it->first == sequence_number) {
+      OSP_VLOG << "Reply was an error with due to timeout for sequence number: "
+               << sequence_number;
+
+      // We erase before handling the callback, since it may invalidate the
+      // replies vector.
+      SenderSessionMessenger::ReplyCallback callback = std::move(it->second);
+      replies->erase(it);
+      callback(Error(Error::Code::kMessageTimeout,
+                     string_util::StrCat({"message timed out; max delay of ",
+                                          ToString(kReplyTimeout)})));
+      return;
+    }
+  }
+}
+
+}  // namespace
+
+SessionMessenger::SessionMessenger(MessagePort& message_port,
+                                   std::string source_id,
+                                   ErrorCallback cb)
+    : message_port_(message_port),
+      source_id_(source_id),
+      error_callback_(std::move(cb)) {
+  OSP_CHECK(!source_id_.empty());
+  message_port_->SetClient(*this);
+}
+
+SessionMessenger::~SessionMessenger() {
+  message_port_->ResetClient();
+}
+
+Error SessionMessenger::SendMessage(const std::string& destination_id,
+                                    const std::string& namespace_,
+                                    const Json::Value& message_root) {
+  OSP_CHECK(namespace_ == kCastRemotingNamespace ||
+            namespace_ == kCastWebrtcNamespace);
+  auto body_or_error = json::Stringify(message_root);
+  if (body_or_error.is_error()) {
+    return std::move(body_or_error.error());
+  }
+  OSP_VLOG << "Sending message: DESTINATION[" << destination_id
+           << "], NAMESPACE[" << namespace_ << "], BODY:\n"
+           << body_or_error.value();
+  message_port_->PostMessage(destination_id, namespace_, body_or_error.value());
+  return Error::None();
+}
+
+void SessionMessenger::ReportError(const Error& error) {
+  error_callback_(error);
+}
+
+SenderSessionMessenger::SenderSessionMessenger(MessagePort& message_port,
+                                               std::string source_id,
+                                               std::string receiver_id,
+                                               ErrorCallback cb,
+                                               TaskRunner& task_runner)
+    : SessionMessenger(message_port, std::move(source_id), std::move(cb)),
+      task_runner_(task_runner),
+      receiver_id_(std::move(receiver_id)) {}
+
+void SenderSessionMessenger::SetHandler(ReceiverMessage::Type type,
+                                        ReplyCallback cb) {
+  // Currently the only handlers allowed are for RPC and INPUT messages.
+  if (type == ReceiverMessage::Type::kRpc) {
+    rpc_callback_ = std::move(cb);
+  } else if (type == ReceiverMessage::Type::kInput) {
+    input_callback_ = std::move(cb);
+  } else {
+    OSP_NOTREACHED();
+  }
+}
+
+void SenderSessionMessenger::ResetHandler(ReceiverMessage::Type type) {
+  if (type == ReceiverMessage::Type::kRpc) {
+    rpc_callback_ = {};
+  } else if (type == ReceiverMessage::Type::kInput) {
+    input_callback_ = {};
+  } else {
+    OSP_NOTREACHED();
+  }
+}
+
+Error SenderSessionMessenger::SendOutboundMessage(SenderMessage message) {
+  const auto namespace_ = (message.type == SenderMessage::Type::kRpc ||
+                           message.type == SenderMessage::Type::kInput)
+                              ? kCastRemotingNamespace
+                              : kCastWebrtcNamespace;
+
+  ErrorOr<Json::Value> jsonified = message.ToJson();
+  OSP_CHECK(jsonified.is_value()) << "Tried to send an invalid message";
+  return SessionMessenger::SendMessage(receiver_id_, namespace_,
+                                       jsonified.value());
+}
+
+Error SenderSessionMessenger::SendRpcMessage(ByteView message) {
+  return SendOutboundMessage(SenderMessage{
+      openscreen::cast::SenderMessage::Type::kRpc,
+      -1 /* sequence_number, unused by RPC messages */, true /* valid */,
+      std::vector<uint8_t>(message.begin(), message.end())});
+}
+
+Error SenderSessionMessenger::SendInputMessage(ByteView message) {
+  return SendOutboundMessage(SenderMessage{
+      openscreen::cast::SenderMessage::Type::kInput,
+      -1 /* sequence_number, unused by INPUT messages */, true /* valid */,
+      std::vector<uint8_t>(message.begin(), message.end())});
+}
+
+Error SenderSessionMessenger::SendRequest(SenderMessage message,
+                                          ReceiverMessage::Type reply_type,
+                                          ReplyCallback cb) {
+  // RPC and INPUT messages are not meant to be request/reply.
+  OSP_CHECK(reply_type != ReceiverMessage::Type::kRpc);
+  OSP_CHECK(reply_type != ReceiverMessage::Type::kInput);
+
+  if (!cb) {
+    return Error(Error::Code::kParameterInvalid,
+                 "Must provide a reply callback");
+  }
+  const Error error = SendOutboundMessage(message);
+  if (!error.ok()) {
+    return error;
+  }
+
+  OSP_DCHECK(awaiting_replies_.find(message.sequence_number) ==
+             awaiting_replies_.end());
+  awaiting_replies_.emplace_back(message.sequence_number, std::move(cb));
+  task_runner_->PostTaskWithDelay(
+      [self = weak_factory_.GetWeakPtr(), seq_num = message.sequence_number] {
+        if (self) {
+          ReplyIfTimedOut(seq_num, &self->awaiting_replies_);
+        }
+      },
+      kReplyTimeout);
+
+  return Error::None();
+}
+
+void SenderSessionMessenger::OnMessage(const std::string& source_id,
+                                       const std::string& message_namespace,
+                                       const std::string& message) {
+  if (source_id != receiver_id_ && source_id != kAnyDestination) {
+    OSP_DLOG_WARN << "Received message from unknown/incorrect Cast Receiver "
+                  << source_id << ". Currently connected to " << receiver_id_;
+    return;
+  }
+
+  if (message_namespace != kCastWebrtcNamespace &&
+      message_namespace != kCastRemotingNamespace) {
+    OSP_DLOG_WARN << "Received message from unknown namespace: "
+                  << message_namespace << ". Message was " << message;
+    return;
+  }
+
+  ErrorOr<Json::Value> message_body = json::Parse(message);
+  if (!message_body || !message_body.value().isObject()) {
+    ReportError(message_body.error());
+    OSP_DLOG_WARN << "Received an invalid message: " << message;
+    return;
+  }
+
+  // If the message is valid JSON and we don't understand it, there are two
+  // options: (1) it's an unknown type, or (2) the receiver filled out the
+  // message incorrectly. In the first case we can drop it, it's likely just
+  // unsupported. In the second case we might need it, so worth warning the
+  // client.
+  ErrorOr<ReceiverMessage> receiver_message =
+      ReceiverMessage::Parse(message_body.value());
+  if (receiver_message.is_error()) {
+    ReportError(receiver_message.error());
+    OSP_DLOG_WARN << "Received an invalid receiver message: "
+                  << receiver_message.error();
+    return;
+  }
+
+  if (receiver_message.value().type == ReceiverMessage::Type::kRpc) {
+    if (rpc_callback_) {
+      rpc_callback_(receiver_message.value());
+    } else {
+      OSP_DLOG_INFO << "Received RPC message but no callback, dropping";
+    }
+  } else if (receiver_message.value().type == ReceiverMessage::Type::kInput) {
+    if (input_callback_) {
+      input_callback_(receiver_message.value());
+    } else {
+      OSP_DLOG_INFO << "Received INPUT message but no callback, dropping";
+    }
+  } else {
+    const int sequence_number = receiver_message.value().sequence_number;
+    auto it = awaiting_replies_.find(sequence_number);
+    if (it == awaiting_replies_.end()) {
+      OSP_DLOG_WARN << "Received a reply I wasn't waiting for: "
+                    << sequence_number;
+      return;
+    }
+
+    ReplyCallback callback = std::move(it->second);
+    awaiting_replies_.erase(it);
+    callback(std::move(receiver_message.value()));
+  }
+}
+
+void SenderSessionMessenger::OnError(const Error& error) {
+  OSP_DLOG_WARN << "Received an error in the session messenger: " << error;
+  ReportError(error);
+}
+
+ReceiverSessionMessenger::ReceiverSessionMessenger(MessagePort& message_port,
+                                                   std::string source_id,
+                                                   ErrorCallback cb)
+    : SessionMessenger(message_port, std::move(source_id), std::move(cb)) {}
+
+void ReceiverSessionMessenger::SetHandler(SenderMessage::Type type,
+                                          RequestCallback cb) {
+  OSP_DCHECK(callbacks_.find(type) == callbacks_.end());
+  callbacks_.emplace_back(type, std::move(cb));
+}
+
+void ReceiverSessionMessenger::ResetHandler(SenderMessage::Type type) {
+  callbacks_.erase_key(type);
+}
+
+Error ReceiverSessionMessenger::SendRpcMessage(const std::string& source_id,
+                                               ByteView message) {
+  return SendMessage(
+      source_id,
+      ReceiverMessage{ReceiverMessage::Type::kRpc, -1 /* sequence_number */,
+                      true /* valid */,
+                      std::vector<uint8_t>(message.begin(), message.end())});
+}
+
+Error ReceiverSessionMessenger::SendInputMessage(const std::string& source_id,
+                                                 ByteView message) {
+  return SendMessage(
+      source_id,
+      ReceiverMessage{ReceiverMessage::Type::kInput, -1 /* sequence_number */,
+                      true /* valid */,
+                      std::vector<uint8_t>(message.begin(), message.end())});
+}
+
+Error ReceiverSessionMessenger::SendMessage(const std::string& source_id,
+                                            ReceiverMessage message) {
+  if (source_id.empty()) {
+    return Error(Error::Code::kInitializationFailure,
+                 "Cannot send a message without a current source ID.");
+  }
+
+  const auto namespace_ = (message.type == ReceiverMessage::Type::kRpc ||
+                           message.type == ReceiverMessage::Type::kInput)
+                              ? kCastRemotingNamespace
+                              : kCastWebrtcNamespace;
+
+  ErrorOr<Json::Value> message_json = message.ToJson();
+  OSP_CHECK(message_json.is_value()) << "Tried to send an invalid message";
+  return SessionMessenger::SendMessage(source_id, namespace_,
+                                       message_json.value());
+}
+
+void ReceiverSessionMessenger::SetCustomMessageHandler(
+    std::string_view message_namespace,
+    CustomMessageCallback cb) {
+  auto it = std::find_if(custom_message_handlers_.begin(),
+                         custom_message_handlers_.end(),
+                         [&message_namespace](const auto& pair) {
+                           return pair.first == message_namespace;
+                         });
+
+  if (!cb) {
+    if (it != custom_message_handlers_.end()) {
+      custom_message_handlers_.erase(it);
+    }
+    return;
+  }
+
+  if (it != custom_message_handlers_.end()) {
+    OSP_LOG_ERROR << "Handler already exists for namespace: "
+                  << message_namespace;
+    return;
+  } else {
+    custom_message_handlers_.emplace_back(std::string(message_namespace),
+                                          std::move(cb));
+  }
+}
+
+Error ReceiverSessionMessenger::SendMessage(std::string_view destination_id,
+                                            std::string_view message_namespace,
+                                            std::string_view message) {
+  message_port().PostMessage(std::string(destination_id),
+                             std::string(message_namespace),
+                             std::string(message));
+  return Error::None();
+}
+
+void ReceiverSessionMessenger::OnMessage(const std::string& source_id,
+                                         const std::string& message_namespace,
+                                         const std::string& message) {
+  if (message_namespace != kCastWebrtcNamespace &&
+      message_namespace != kCastRemotingNamespace) {
+    auto it = std::find_if(custom_message_handlers_.begin(),
+                           custom_message_handlers_.end(),
+                           [&message_namespace](const auto& pair) {
+                             return pair.first == message_namespace;
+                           });
+    if (it != custom_message_handlers_.end()) {
+      it->second(source_id, message_namespace, message);
+      return;
+    }
+    OSP_DLOG_WARN << "Received message from unknown namespace: "
+                  << message_namespace;
+    return;
+  }
+
+  // If the message is bad JSON, the sender is in a funky state so we
+  // report an error.
+  ErrorOr<Json::Value> message_body = json::Parse(message);
+  if (message_body.is_error() || !message_body.value().isObject()) {
+    ReportError(message_body.error());
+    return;
+  }
+
+  // If the message is valid JSON and we don't understand it, there are two
+  // options: (1) it's an unknown type, or (2) the sender filled out the message
+  // incorrectly. In the first case we can drop it, it's likely just
+  // unsupported. In the second case we might need it, so worth warning the
+  // client.
+  ErrorOr<SenderMessage> sender_message =
+      SenderMessage::Parse(message_body.value());
+  if (sender_message.is_error()) {
+    ReportError(sender_message.error());
+    OSP_DLOG_WARN << "Received an invalid sender message: "
+                  << sender_message.error();
+    return;
+  }
+
+  if (sender_message.value().type == SenderMessage::Type::kOffer ||
+      sender_message.value().type == SenderMessage::Type::kGetCapabilities) {
+    OSP_VLOG << "Received Message:\n" << message;
+  }
+
+  auto it = callbacks_.find(sender_message.value().type);
+  if (it == callbacks_.end()) {
+    OSP_DLOG_INFO << "Received message without a callback, dropping";
+    return;
+  }
+  it->second(source_id, sender_message.value());
+}
+
+void ReceiverSessionMessenger::OnError(const Error& error) {
+  OSP_DLOG_WARN << "Received an error in the session messenger: " << error;
+  ReportError(error);
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/session_messenger.h

@@ -0,0 +1,168 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_SESSION_MESSENGER_H_
+#define CAST_STREAMING_PUBLIC_SESSION_MESSENGER_H_
+
+#include <functional>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "cast/common/public/message_port.h"
+#include "cast/streaming/public/answer_messages.h"
+#include "cast/streaming/public/offer_messages.h"
+#include "cast/streaming/public/receiver_message.h"
+#include "cast/streaming/sender_message.h"
+#include "json/value.h"
+#include "platform/api/task_runner.h"
+#include "platform/base/span.h"
+#include "util/flat_map.h"
+#include "util/raw_ref.h"
+#include "util/weak_ptr.h"
+
+namespace openscreen::cast {
+
+// A message port interface designed specifically for use by the Receiver
+// and Sender session classes.
+class SessionMessenger : public MessagePort::Client {
+ public:
+  using ErrorCallback = std::function<void(Error)>;
+
+  SessionMessenger(MessagePort& message_port,
+                   std::string source_id,
+                   ErrorCallback cb);
+  ~SessionMessenger() override;
+
+  MessagePort& message_port() { return *message_port_; }
+
+ protected:
+  // Barebones message sending method shared by both children.
+  [[nodiscard]] Error SendMessage(const std::string& destination_id,
+                                  const std::string& namespace_,
+                                  const Json::Value& message_root);
+
+  // Used to report errors in subclasses.
+  void ReportError(const Error& error);
+
+  const std::string& source_id() override { return source_id_; }
+
+ private:
+  const raw_ref<MessagePort> message_port_;
+  const std::string source_id_;
+  ErrorCallback error_callback_;
+};
+
+// Message port interface designed to handle sending messages to and
+// from a receiver. When possible, errors receiving messages are reported
+// to the ReplyCallback passed to SendRequest(), otherwise errors are
+// reported to the ErrorCallback passed in the constructor.
+class SenderSessionMessenger final : public SessionMessenger {
+ public:
+  using ReplyCallback = std::function<void(ErrorOr<ReceiverMessage>)>;
+
+  SenderSessionMessenger(MessagePort& message_port,
+                         std::string source_id,
+                         std::string receiver_id,
+                         ErrorCallback cb,
+                         TaskRunner& task_runner);
+
+  // Set receiver message handler. Note that this should only be
+  // applied for messages that don't have sequence numbers, like RPC
+  // and status messages.
+  void SetHandler(ReceiverMessage::Type type, ReplyCallback cb);
+  void ResetHandler(ReceiverMessage::Type type);
+
+  // Send a message that doesn't require a reply.
+  [[nodiscard]] Error SendOutboundMessage(SenderMessage message);
+
+  // Convenience method for sending a valid RPC message.
+  [[nodiscard]] Error SendRpcMessage(ByteView message);
+
+  // Convenience method for sending a valid INPUT message.
+  [[nodiscard]] Error SendInputMessage(ByteView message);
+
+  // Send a request (with optional reply callback).
+  [[nodiscard]] Error SendRequest(SenderMessage message,
+                                  ReceiverMessage::Type reply_type,
+                                  ReplyCallback cb);
+
+  // MessagePort::Client overrides
+  void OnMessage(const std::string& source_id,
+                 const std::string& message_namespace,
+                 const std::string& message) override;
+  void OnError(const Error& error) override;
+
+ private:
+  const raw_ref<TaskRunner> task_runner_;
+
+  // This messenger should only be connected to one receiver, so `receiver_id_`
+  // should not change.
+  const std::string receiver_id_;
+
+  // We keep a list here of replies we are expecting--if the reply is
+  // received for this sequence number, we call its respective callback,
+  // otherwise it is called after an internally specified timeout.
+  FlatMap<int, ReplyCallback> awaiting_replies_;
+
+  // Currently we can only set a handler for RPC messages, so no need for
+  // a flatmap here.
+  ReplyCallback rpc_callback_;
+  ReplyCallback input_callback_;
+
+  WeakPtrFactory<SenderSessionMessenger> weak_factory_{this};
+};
+
+// Message port interface designed for messaging to and from a sender.
+class ReceiverSessionMessenger final : public SessionMessenger {
+ public:
+  using RequestCallback =
+      std::function<void(const std::string&, SenderMessage)>;
+  ReceiverSessionMessenger(MessagePort& message_port,
+                           std::string source_id,
+                           ErrorCallback cb);
+
+  // Set sender message handler.
+  void SetHandler(SenderMessage::Type type, RequestCallback cb);
+  void ResetHandler(SenderMessage::Type type);
+
+  // Convenience method for sending a valid RPC message.
+  [[nodiscard]] Error SendRpcMessage(const std::string& source_id,
+                                     ByteView message);
+
+  // Convenience method for sending a valid INPUT message.
+  [[nodiscard]] Error SendInputMessage(const std::string& source_id,
+                                       ByteView message);
+
+  // Send a JSON message.
+  [[nodiscard]] Error SendMessage(const std::string& source_id,
+                                  ReceiverMessage message);
+
+  // Send a raw string message to a custom namespace.
+  [[nodiscard]] Error SendMessage(std::string_view destination_id,
+                                  std::string_view message_namespace,
+                                  std::string_view message);
+
+  using CustomMessageCallback =
+      std::function<void(const std::string& /* source_id */,
+                         const std::string& /* message_namespace */,
+                         const std::string& /* message */)>;
+  void SetCustomMessageHandler(std::string_view message_namespace,
+                               CustomMessageCallback cb);
+
+  // MessagePort::Client overrides
+  void OnMessage(const std::string& source_id,
+                 const std::string& message_namespace,
+                 const std::string& message) override;
+  void OnError(const Error& error) override;
+
+ private:
+  FlatMap<SenderMessage::Type, RequestCallback> callbacks_;
+  std::vector<std::pair<std::string, CustomMessageCallback>>
+      custom_message_handlers_;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_SESSION_MESSENGER_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/statistics.cc

@@ -0,0 +1,183 @@
+// Copyright 2023 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/public/statistics.h"
+
+#include <algorithm>
+#include <iomanip>
+#include <iostream>
+
+#include "util/enum_name_table.h"
+#include "util/json/json_helpers.h"
+#include "util/json/json_serialization.h"
+#include "util/stringprintf.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+template <typename Type>
+Json::Value ToJson(const Type& t) {
+  return t.ToJson();
+}
+
+template <>
+Json::Value ToJson(const double& t) {
+  return t;
+}
+
+template <typename T, typename Type>
+Json::Value ArrayToJson(
+    const std::array<T, static_cast<size_t>(Type::kNumTypes)>& list,
+    const EnumNameTable<Type, static_cast<size_t>(Type::kNumTypes)>& names) {
+  Json::Value out;
+  for (size_t i = 0; i < list.size(); ++i) {
+    ErrorOr<const char*> name = GetEnumName(names, static_cast<Type>(i));
+    OSP_CHECK(name);
+    out[name.value()] = ToJson(list[i]);
+  }
+  return out;
+}
+
+}  // namespace
+
+// External linkage for unit test
+extern const EnumNameTable<StatisticType,
+                           static_cast<size_t>(StatisticType::kNumTypes)>
+    kStatisticTypeNames = {
+        {{"EnqueueFps", StatisticType::kEnqueueFps},
+         {"AvgCaptureLatencyMs", StatisticType::kAvgCaptureLatencyMs},
+         {"AvgEncodeTimeMs", StatisticType::kAvgEncodeTimeMs},
+         {"AvgQueueingLatencyMs", StatisticType::kAvgQueueingLatencyMs},
+         {"AvgNetworkLatencyMs", StatisticType::kAvgNetworkLatencyMs},
+         {"AvgPacketLatencyMs", StatisticType::kAvgPacketLatencyMs},
+         {"AvgFrameLatencyMs", StatisticType::kAvgFrameLatencyMs},
+         {"AvgEndToEndLatencyMs", StatisticType::kAvgEndToEndLatencyMs},
+         {"EncodeRateKbps", StatisticType::kEncodeRateKbps},
+         {"PacketTransmissionRateKbps",
+          StatisticType::kPacketTransmissionRateKbps},
+         {"TimeSinceLastReceiverResponseMs",
+          StatisticType::kTimeSinceLastReceiverResponseMs},
+         {"NumFramesCaptured", StatisticType::kNumFramesCaptured},
+         {"NumFramesDroppedByEncoder",
+          StatisticType::kNumFramesDroppedByEncoder},
+         {"NumLateFrames", StatisticType::kNumLateFrames},
+         {"NumPacketsSent", StatisticType::kNumPacketsSent},
+         {"NumPacketsReceived", StatisticType::kNumPacketsReceived},
+         {"FirstEventTimeMs", StatisticType::kFirstEventTimeMs},
+         {"LastEventTimeMs", StatisticType::kLastEventTimeMs}}};
+
+// External linkage for unit test
+extern const EnumNameTable<HistogramType,
+                           static_cast<size_t>(HistogramType::kNumTypes)>
+    kHistogramTypeNames = {
+        {{"CaptureLatencyMs", HistogramType::kCaptureLatencyMs},
+         {"EncodeTimeMs", HistogramType::kEncodeTimeMs},
+         {"QueueingLatencyMs", HistogramType::kQueueingLatencyMs},
+         {"NetworkLatencyMs", HistogramType::kNetworkLatencyMs},
+         {"PacketLatencyMs", HistogramType::kPacketLatencyMs},
+         {"EndToEndLatencyMs", HistogramType::kEndToEndLatencyMs},
+         {"FrameLatenessMs", HistogramType::kFrameLatenessMs}}};
+
+SimpleHistogram::SimpleHistogram() = default;
+SimpleHistogram::SimpleHistogram(int64_t min, int64_t max, int64_t width)
+
+    : min(min), max(max), width(width), buckets((max - min) / width + 2) {
+  OSP_CHECK_GT(buckets.size(), 2u);
+  OSP_CHECK_EQ(0, (max - min) % width);
+}
+
+SimpleHistogram::SimpleHistogram(const SimpleHistogram&) = default;
+SimpleHistogram::SimpleHistogram(SimpleHistogram&&) noexcept = default;
+SimpleHistogram& SimpleHistogram::operator=(const SimpleHistogram&) = default;
+SimpleHistogram& SimpleHistogram::operator=(SimpleHistogram&&) = default;
+SimpleHistogram::~SimpleHistogram() = default;
+
+bool SimpleHistogram::operator==(const SimpleHistogram& other) const {
+  return min == other.min && max == other.max && width == other.width &&
+         buckets == other.buckets;
+}
+
+void SimpleHistogram::Add(int64_t sample) {
+  if (sample < min) {
+    ++buckets.front();
+  } else if (sample >= max) {
+    ++buckets.back();
+  } else {
+    size_t index = 1 + (sample - min) / width;
+    OSP_CHECK_LT(index, buckets.size());
+    ++buckets[index];
+  }
+}
+
+void SimpleHistogram::Reset() {
+  buckets.assign(buckets.size(), 0);
+}
+
+Json::Value SimpleHistogram::ToJson() const {
+  // Nest the bucket values in an array instead of a dictionary, so we sort
+  // numerically instead of alphabetically.
+  Json::Value out(Json::ValueType::arrayValue);
+  for (size_t i = 0; i < buckets.size(); ++i) {
+    if (buckets[i] != 0) {
+      Json::Value entry;
+      entry[GetBucketName(i)] = buckets[i];
+      out.append(entry);
+    }
+  }
+  return out;
+}
+
+std::string SimpleHistogram::ToString() const {
+  return json::Stringify(ToJson()).value();
+}
+
+SimpleHistogram::SimpleHistogram(int64_t min,
+                                 int64_t max,
+                                 int64_t width,
+                                 std::vector<int> buckets)
+    : SimpleHistogram(min, max, width) {
+  this->buckets = std::move(buckets);
+}
+
+std::string SimpleHistogram::GetBucketName(size_t index) const {
+  if (index == 0) {
+    return "<" + std::to_string(min);
+  }
+
+  if (index == buckets.size() - 1) {
+    return ">=" + std::to_string(max);
+  }
+
+  // See the constructor comment for an example of how these bucket bounds
+  // are calculated.
+  const int bucket_min = min + width * (index - 1);
+  const int bucket_max = min + index * width - 1;
+  return StringFormat("{}-{}", bucket_min, bucket_max);
+}
+
+Json::Value SenderStats::ToJson() const {
+  Json::Value out;
+  out["audio_statistics"] = ArrayToJson(audio_statistics, kStatisticTypeNames);
+  out["audio_histograms"] = ArrayToJson(audio_histograms, kHistogramTypeNames);
+  out["video_statistics"] = ArrayToJson(video_statistics, kStatisticTypeNames);
+  out["video_histograms"] = ArrayToJson(video_histograms, kHistogramTypeNames);
+  return out;
+}
+
+std::string SenderStats::ToString() const {
+  return json::Stringify(ToJson()).value();
+}
+
+std::ostream& operator<<(std::ostream& out, const SenderStats& stats) {
+  return out << stats.ToString();
+}
+
+std::ostream& operator<<(std::ostream& out, const SimpleHistogram& histogram) {
+  return out << histogram.ToString();
+}
+
+SenderStatsClient::~SenderStatsClient() {}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/statistics.h

@@ -0,0 +1,195 @@
+// Copyright 2024 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_STATISTICS_H_
+#define CAST_STREAMING_PUBLIC_STATISTICS_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "cast/streaming/public/frame_id.h"
+#include "cast/streaming/rtp_time.h"
+#include "json/value.h"
+#include "platform/api/time.h"
+
+namespace openscreen::cast {
+
+// This file must be updated whenever sender_stats.proto is updated.
+enum class StatisticType {
+  // Frame enqueuing rate.
+  kEnqueueFps = 0,
+
+  // Average capture latency in milliseconds.
+  kAvgCaptureLatencyMs,
+
+  // Average encode duration in milliseconds.
+  kAvgEncodeTimeMs,
+
+  // Duration from when a frame is encoded to when the packet is first
+  // sent.
+  kAvgQueueingLatencyMs,
+
+  // Duration from when a packet is transmitted to when it is received.
+  // This measures latency from sender to receiver.
+  kAvgNetworkLatencyMs,
+
+  // Duration from when a frame is encoded to when the packet is first
+  // received.
+  kAvgPacketLatencyMs,
+
+  // Average latency between frame encoded and the moment when the frame
+  // is fully received.
+  kAvgFrameLatencyMs,
+
+  // Duration from when a frame is captured to when it should be played out.
+  kAvgEndToEndLatencyMs,
+
+  // Encode bitrate in kbps.
+  kEncodeRateKbps,
+
+  // Packet transmission bitrate in kbps.
+  kPacketTransmissionRateKbps,
+
+  // Duration in milliseconds since the estimated last time the receiver sent
+  // a response.
+  kTimeSinceLastReceiverResponseMs,
+
+  // Number of frames captured.
+  kNumFramesCaptured,
+
+  // Number of frames dropped by encoder.
+  kNumFramesDroppedByEncoder,
+
+  // Number of late frames.
+  kNumLateFrames,
+
+  // Number of packets that were sent.
+  kNumPacketsSent,
+
+  // Number of packets that were received by receiver.
+  kNumPacketsReceived,
+
+  // Unix time in milliseconds of first event since reset.
+  kFirstEventTimeMs,
+
+  // Unix time in milliseconds of last event since reset.
+  kLastEventTimeMs,
+
+  // The number of statistic types.
+  kNumTypes = kLastEventTimeMs + 1
+};
+
+enum class HistogramType {
+  // Histogram representing the capture latency (in milliseconds).
+  kCaptureLatencyMs,
+
+  // Histogram representing the encode time (in milliseconds).
+  kEncodeTimeMs,
+
+  // Histogram representing the queueing latency (in milliseconds).
+  kQueueingLatencyMs,
+
+  // Histogram representing the network latency (in milliseconds).
+  kNetworkLatencyMs,
+
+  // Histogram representing the packet latency (in milliseconds).
+  kPacketLatencyMs,
+
+  // Histogram representing the end to end latency (in milliseconds).
+  kEndToEndLatencyMs,
+
+  // Histogram representing how late frames are (in milliseconds).
+  kFrameLatenessMs,
+
+  // The number of histogram types.
+  kNumTypes = kFrameLatenessMs + 1
+};
+
+struct SimpleHistogram {
+  // This will create N+2 buckets where N = (max - min) / width:
+  // Underflow bucket: < min
+  // Bucket 0: [min, min + width - 1]
+  // Bucket 1: [min + width, min + 2 * width - 1]
+  // ...
+  // Bucket N-1: [max - width, max - 1]
+  // Overflow bucket: >= max
+  // `min` must be less than `max`.
+  // `width` must divide `max - min` evenly.
+  SimpleHistogram(int64_t min, int64_t max, int64_t width);
+
+  SimpleHistogram();
+  SimpleHistogram(const SimpleHistogram&);
+  SimpleHistogram(SimpleHistogram&&) noexcept;
+  SimpleHistogram& operator=(const SimpleHistogram&);
+  SimpleHistogram& operator=(SimpleHistogram&&);
+  ~SimpleHistogram();
+
+  bool operator==(const SimpleHistogram&) const;
+
+  void Add(int64_t sample);
+  void Reset();
+
+  Json::Value ToJson() const;
+  std::string ToString() const;
+
+  int64_t min = 1;
+  int64_t max = 1;
+  int64_t width = 1;
+  std::vector<int> buckets;
+
+ private:
+  SimpleHistogram(int64_t min,
+                  int64_t max,
+                  int64_t width,
+                  std::vector<int> buckets);
+
+  std::string GetBucketName(size_t index) const;
+};
+
+std::ostream& operator<<(std::ostream& out, const SimpleHistogram& histogram);
+
+struct SenderStats {
+  using StatisticsList =
+      std::array<double, static_cast<size_t>(StatisticType::kNumTypes)>;
+  using HistogramsList =
+      std::array<SimpleHistogram,
+                 static_cast<size_t>(HistogramType::kNumTypes)>;
+
+  // The current audio statistics.
+  StatisticsList audio_statistics = {};
+
+  // The current audio histograms.
+  HistogramsList audio_histograms = {};
+
+  // The current video statistics.
+  StatisticsList video_statistics = {};
+
+  // The current video histograms.
+  HistogramsList video_histograms = {};
+
+  Json::Value ToJson() const;
+  std::string ToString() const;
+};
+
+std::ostream& operator<<(std::ostream& out, const SenderStats& stats);
+
+// The consumer may provide a statistics client if they are interested in
+// getting statistics about the ongoing session.
+class SenderStatsClient {
+ public:
+  // Gets called regularly with updated statistics while they are being
+  // generated.
+  virtual void OnStatisticsUpdated(const SenderStats& updated_stats) = 0;
+
+ protected:
+  virtual ~SenderStatsClient();
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_STATISTICS_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/resolution.cc

@@ -0,0 +1,141 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/resolution.h"
+
+#include <utility>
+
+#include "cast/streaming/message_fields.h"
+#include "platform/base/error.h"
+#include "util/json/json_helpers.h"
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+/// Dimension properties.
+// Width in pixels.
+constexpr char kWidth[] = "width";
+
+// Height in pixels.
+constexpr char kHeight[] = "height";
+
+// Frame rate as a rational decimal number or fraction.
+// E.g. 30 and "3000/1001" are both valid representations.
+constexpr char kFrameRate[] = "frameRate";
+
+// Choice of epsilon for double comparison allows for proper comparison
+// for both aspect ratios and frame rates. For frame rates, it is based on the
+// broadcast rate of 29.97fps, which is actually 29.976. For aspect ratios, it
+// allows for a one-pixel difference at a 4K resolution, we want it to be
+// relatively high to avoid false negative comparison results.
+bool FrameRateEquals(double a, double b) {
+  const double kEpsilonForFrameRateComparisons = .0001;
+  return std::abs(a - b) < kEpsilonForFrameRateComparisons;
+}
+
+}  // namespace
+
+ErrorOr<Resolution> Resolution::TryParse(const Json::Value& root) {
+  if (!root.isObject()) {
+    return Error(Error::Code::kJsonParseError,
+                 "Resolution is not a JSON object");
+  }
+
+  Resolution out;
+  if (!json::TryParseInt(root[kWidth], &out.width) ||
+      !json::TryParseInt(root[kHeight], &out.height)) {
+    return Error(Error::Code::kJsonParseError, "Invalid resolution");
+  }
+  if (!out.IsValid()) {
+    return Error(Error::Code::kJsonParseError, "Invalid resolution values");
+  }
+  return out;
+}
+
+bool Resolution::IsValid() const {
+  return width > 0 && height > 0;
+}
+
+Json::Value Resolution::ToJson() const {
+  OSP_CHECK(IsValid());
+  Json::Value root;
+  root[kWidth] = width;
+  root[kHeight] = height;
+
+  return root;
+}
+
+bool Resolution::operator==(const Resolution& other) const {
+  return std::tie(width, height) == std::tie(other.width, other.height);
+}
+
+bool Resolution::operator!=(const Resolution& other) const {
+  return !(*this == other);
+}
+
+bool Resolution::IsSupersetOf(const Resolution& other) const {
+  return width >= other.width && height >= other.height;
+}
+
+ErrorOr<Dimensions> Dimensions::TryParse(const Json::Value& root) {
+  if (!root.isObject()) {
+    return Error(Error::Code::kJsonParseError,
+                 "Dimensions is not a JSON object");
+  }
+
+  Dimensions out;
+  if (!json::TryParseInt(root[kWidth], &out.width) ||
+      !json::TryParseInt(root[kHeight], &out.height)) {
+    return Error(Error::Code::kJsonParseError, "Invalid dimensions");
+  }
+
+  if (!root[kFrameRate].isNull()) {
+    if (!json::TryParseSimpleFraction(root[kFrameRate], &out.frame_rate)) {
+      return Error(Error::Code::kJsonParseError, "Invalid frame rate");
+    }
+  }
+
+  if (!out.IsValid()) {
+    return Error(Error::Code::kJsonParseError, "Invalid dimensions values");
+  }
+  return out;
+}
+
+bool Dimensions::IsValid() const {
+  return width > 0 && height > 0 && frame_rate.is_positive();
+}
+
+Json::Value Dimensions::ToJson() const {
+  OSP_CHECK(IsValid());
+  Json::Value root;
+  root[kWidth] = width;
+  root[kHeight] = height;
+  root[kFrameRate] = frame_rate.ToString();
+
+  return root;
+}
+
+bool Dimensions::operator==(const Dimensions& other) const {
+  return (std::tie(width, height) == std::tie(other.width, other.height) &&
+          FrameRateEquals(static_cast<double>(frame_rate),
+                          static_cast<double>(other.frame_rate)));
+}
+
+bool Dimensions::operator!=(const Dimensions& other) const {
+  return !(*this == other);
+}
+
+bool Dimensions::IsSupersetOf(const Dimensions& other) const {
+  if (static_cast<double>(frame_rate) !=
+      static_cast<double>(other.frame_rate)) {
+    return static_cast<double>(frame_rate) >=
+           static_cast<double>(other.frame_rate);
+  }
+
+  return ToResolution().IsSupersetOf(other.ToResolution());
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/resolution.h

@@ -0,0 +1,67 @@
+// Copyright 2021 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// Resolutions and dimensions (resolutions with a frame rate) are used
+// extensively throughout cast streaming. Since their serialization to and
+// from JSON is stable and standard, we have a single place definition for
+// these for use both in our public APIs and private messages.
+
+#ifndef CAST_STREAMING_RESOLUTION_H_
+#define CAST_STREAMING_RESOLUTION_H_
+
+#include "json/value.h"
+#include "util/simple_fraction.h"
+
+namespace openscreen::cast {
+
+// A resolution in pixels.
+struct Resolution {
+  static ErrorOr<Resolution> TryParse(const Json::Value& value);
+  bool IsValid() const;
+  Json::Value ToJson() const;
+
+  // Returns true if both `width` and `height` of this instance are greater than
+  // or equal to that of `other`.
+  bool IsSupersetOf(const Resolution& other) const;
+
+  bool operator==(const Resolution& other) const;
+  bool operator!=(const Resolution& other) const;
+
+  // Width and height in pixels.
+  int width = 0;
+  int height = 0;
+};
+
+// A resolution in pixels and a frame rate.
+struct Dimensions {
+  static ErrorOr<Dimensions> TryParse(const Json::Value& value);
+  bool IsValid() const;
+  Json::Value ToJson() const;
+
+  // Returns true if all properties of this instance are greater than or equal
+  // to those of `other`.
+  bool IsSupersetOf(const Dimensions& other) const;
+
+  bool operator==(const Dimensions& other) const;
+  bool operator!=(const Dimensions& other) const;
+
+  // Get just the width and height fields (for comparisons).
+  constexpr Resolution ToResolution() const { return {width, height}; }
+
+  // The effective bit rate is the width * height * frame rate.
+  constexpr int effective_bit_rate() const {
+    return width * height * static_cast<double>(frame_rate);
+  }
+
+  // Width and height in pixels.
+  int width = 0;
+  int height = 0;
+
+  // `frame_rate` is the maximum maintainable frame rate.
+  SimpleFraction frame_rate{0, 1};
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_RESOLUTION_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/rtp_time.cc

@@ -0,0 +1,23 @@
+// Copyright 2015 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/rtp_time.h"
+
+#include <sstream>
+
+namespace openscreen::cast {
+
+std::ostream& operator<<(std::ostream& out, const RtpTimeDelta rhs) {
+  if (rhs.value_ >= 0)
+    out << "RTP+";
+  else
+    out << "RTP";
+  return out << rhs.value_;
+}
+
+std::ostream& operator<<(std::ostream& out, const RtpTimeTicks rhs) {
+  return out << "RTP@" << rhs.value_;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/rtp_time.h

@@ -0,0 +1,257 @@
+// Copyright 2015 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_RTP_TIME_H_
+#define CAST_STREAMING_RTP_TIME_H_
+
+#include <stdint.h>
+
+#include <chrono>
+#include <cmath>
+#include <limits>
+#include <sstream>
+#include <type_traits>
+
+#include "cast/streaming/impl/expanded_value_base.h"
+#include "platform/api/time.h"
+#include "util/saturate_cast.h"
+
+namespace openscreen::cast {
+
+// Forward declarations (see below).
+class RtpTimeDelta;
+class RtpTimeTicks;
+
+// Convenience operator overloads for logging.
+std::ostream& operator<<(std::ostream& out, const RtpTimeDelta rhs);
+std::ostream& operator<<(std::ostream& out, const RtpTimeTicks rhs);
+
+// The difference between two RtpTimeTicks values.  This data type is modeled
+// off of Chromium's base::TimeDelta, and used for performing compiler-checked
+// arithmetic with RtpTimeTicks.
+//
+// This data type wraps a value, providing only the meaningful set of math
+// operations that may be performed on the value.  RtpTimeDeltas may be
+// added/subtracted with other RtpTimeDeltas to produce a RtpTimeDelta holding
+// the sum/difference.  RtpTimeDeltas may also be multiplied or divided by
+// integer amounts.  Finally, RtpTimeDeltas may be divided by other
+// RtpTimeDeltas to compute a number of periods (trunc'ed to an integer), or
+// modulo each other to determine a time period remainder.
+//
+// The base class provides bit truncation/extension features for
+// wire-formatting, and also the comparison operators.
+//
+// Usage example:
+//
+//   // Time math.
+//   RtpTimeDelta zero;
+//   RtpTimeDelta one_second_later =
+//       zero + RtpTimeDelta::FromTicks(kAudioSamplingRate);
+//   RtpTimeDelta ten_seconds_later = one_second_later * 10;
+//   int64_t ten_periods = ten_seconds_later / one_second_later;
+//
+//   // Logging convenience.
+//   OSP_DLOG_INFO << "The RTP time offset is " << ten_seconds_later;
+//
+//   // Convert (approximately!) between RTP timebase and microsecond timebase:
+//   RtpTimeDelta nine_seconds_in_rtp = ten_seconds_later - one_second_later;
+//   using std::chrono::microseconds;
+//   microseconds nine_seconds_duration =
+//       nine_seconds_in_rtp.ToDuration<microseconds>(kAudioSamplingRate);
+//   RtpTimeDelta two_seconds_in_rtp =
+//       RtpTimeDelta::FromDuration(std::chrono::seconds(2),
+//                                  kAudioSamplingRate);
+class RtpTimeDelta : public ExpandedValueBase<int64_t, RtpTimeDelta> {
+ public:
+  constexpr RtpTimeDelta() : ExpandedValueBase(0) {}
+
+  // Arithmetic operators (with other deltas).
+  constexpr RtpTimeDelta operator+(RtpTimeDelta rhs) const {
+    return RtpTimeDelta(value_ + rhs.value_);
+  }
+  constexpr RtpTimeDelta operator-(RtpTimeDelta rhs) const {
+    return RtpTimeDelta(value_ - rhs.value_);
+  }
+  constexpr RtpTimeDelta& operator+=(RtpTimeDelta rhs) {
+    return (*this = (*this + rhs));
+  }
+  constexpr RtpTimeDelta& operator-=(RtpTimeDelta rhs) {
+    return (*this = (*this - rhs));
+  }
+  constexpr RtpTimeDelta operator-() const { return RtpTimeDelta(-value_); }
+
+  // Multiplicative operators (with other deltas).
+  constexpr int64_t operator/(RtpTimeDelta rhs) const {
+    return value_ / rhs.value_;
+  }
+  constexpr RtpTimeDelta operator%(RtpTimeDelta rhs) const {
+    return RtpTimeDelta(value_ % rhs.value_);
+  }
+  constexpr RtpTimeDelta& operator%=(RtpTimeDelta rhs) {
+    return (*this = (*this % rhs));
+  }
+
+  // Multiplicative operators (with integer types).
+  template <typename IntType>
+  constexpr RtpTimeDelta operator*(IntType rhs) const {
+    static_assert(std::numeric_limits<IntType>::is_integer,
+                  "|rhs| must be a POD integer type");
+    return RtpTimeDelta(value_ * rhs);
+  }
+  template <typename IntType>
+  constexpr RtpTimeDelta operator/(IntType rhs) const {
+    static_assert(std::numeric_limits<IntType>::is_integer,
+                  "|rhs| must be a POD integer type");
+    return RtpTimeDelta(value_ / rhs);
+  }
+  template <typename IntType>
+  constexpr RtpTimeDelta& operator*=(IntType rhs) {
+    return (*this = (*this * rhs));
+  }
+  template <typename IntType>
+  constexpr RtpTimeDelta& operator/=(IntType rhs) {
+    return (*this = (*this / rhs));
+  }
+
+  // Maps this RtpTimeDelta to an approximate std::chrono::duration using the
+  // given RTP timebase.  Assumes a zero-valued Duration corresponds to a
+  // zero-valued RtpTimeDelta.
+  template <typename Duration>
+  Duration ToDuration(int rtp_timebase) const {
+    OSP_CHECK_GT(rtp_timebase, 0);
+    constexpr Duration kOneSecond =
+        std::chrono::duration_cast<Duration>(std::chrono::seconds(1));
+    return Duration(ToNearestRepresentativeValue<typename Duration::rep>(
+        static_cast<double>(value_) / rtp_timebase * kOneSecond.count()));
+  }
+
+  // Maps the `duration` to an approximate RtpTimeDelta using the given RTP
+  // timebase.  Assumes a zero-valued Duration corresponds to a zero-valued
+  // RtpTimeDelta.
+  template <typename Duration>
+  static constexpr RtpTimeDelta FromDuration(Duration duration,
+                                             int rtp_timebase) {
+    constexpr Duration kOneSecond =
+        std::chrono::duration_cast<Duration>(std::chrono::seconds(1));
+    static_assert(kOneSecond > Duration::zero(),
+                  "Duration is too coarse-grained to represent one second.");
+    return RtpTimeDelta(ToNearestRepresentativeValue<int64_t>(
+        static_cast<double>(duration.count()) / kOneSecond.count() *
+        rtp_timebase));
+  }
+
+  // Construct a RtpTimeDelta from an exact number of ticks.
+  static constexpr RtpTimeDelta FromTicks(int64_t ticks) {
+    return RtpTimeDelta(ticks);
+  }
+
+ private:
+  friend class ExpandedValueBase<int64_t, RtpTimeDelta>;
+  friend class RtpTimeTicks;
+  friend std::ostream& operator<<(std::ostream& out, const RtpTimeDelta rhs);
+
+  constexpr explicit RtpTimeDelta(int64_t ticks) : ExpandedValueBase(ticks) {}
+
+  constexpr int64_t value() const { return value_; }
+
+  template <typename Rep>
+  static std::enable_if_t<std::is_floating_point<Rep>::value, Rep>
+  ToNearestRepresentativeValue(double ticks) {
+    return Rep(ticks);
+  }
+
+  template <typename Rep>
+  static std::enable_if_t<std::is_integral<Rep>::value, Rep>
+  ToNearestRepresentativeValue(double ticks) {
+    return rounded_saturate_cast<Rep>(ticks);
+  }
+};
+
+// A media timestamp whose timebase matches the periodicity of the content
+// (e.g., for audio, the timebase would be the sampling frequency).  This data
+// type is modeled off of Chromium's base::TimeTicks.
+//
+// This data type wraps a value, providing only the meaningful set of math
+// operations that may be performed on the value.  The difference between two
+// RtpTimeTicks is a RtpTimeDelta.  Likewise, adding or subtracting a
+// RtpTimeTicks with a RtpTimeDelta produces an off-set RtpTimeTicks.
+//
+// The base class provides bit truncation/extension features for
+// wire-formatting, and also the comparison operators.
+//
+// Usage example:
+//
+//   // Time math.
+//   RtpTimeTicks origin;
+//   RtpTimeTicks at_one_second =
+//       origin + RtpTimeDelta::FromTicks(kAudioSamplingRate);
+//   RtpTimeTicks at_two_seconds =
+//       at_one_second + RtpTimeDelta::FromTicks(kAudioSamplingRate);
+//   RtpTimeDelta elasped_in_between = at_two_seconds - at_one_second;
+//   RtpTimeDelta thrice_as_much_elasped = elasped_in_between * 3;
+//   RtpTimeTicks at_four_seconds = at_one_second + thrice_as_much_elasped;
+//
+//   // Logging convenience.
+//   OSP_DLOG_INFO << "The RTP timestamp is " << at_four_seconds;
+//
+//   // Convert (approximately!) between RTP timebase and stream time offsets in
+//   // microsecond timebase:
+//   using std::chrono::microseconds;
+//   microseconds four_seconds_since_stream_start =
+//       at_four_seconds.ToTimeSinceOrigin<microseconds>(kAudioSamplingRate);
+//   RtpTimeTicks at_three_seconds = RtpTimeDelta::FromTimeSinceOrigin(
+//       std::chrono::seconds(3), kAudioSamplingRate);
+class RtpTimeTicks : public ExpandedValueBase<int64_t, RtpTimeTicks> {
+ public:
+  constexpr explicit RtpTimeTicks(int64_t value) : ExpandedValueBase(value) {}
+  constexpr RtpTimeTicks() : ExpandedValueBase(0) {}
+
+  constexpr int64_t value() const { return value_; }
+
+  // Compute the difference between two RtpTimeTickses.
+  constexpr RtpTimeDelta operator-(RtpTimeTicks rhs) const {
+    return RtpTimeDelta(value_ - rhs.value_);
+  }
+
+  // Return a new RtpTimeTicks before or after this one.
+  constexpr RtpTimeTicks operator+(RtpTimeDelta rhs) const {
+    return RtpTimeTicks(value_ + rhs.value());
+  }
+  constexpr RtpTimeTicks operator-(RtpTimeDelta rhs) const {
+    return RtpTimeTicks(value_ - rhs.value());
+  }
+  constexpr RtpTimeTicks& operator+=(RtpTimeDelta rhs) {
+    return (*this = (*this + rhs));
+  }
+  constexpr RtpTimeTicks& operator-=(RtpTimeDelta rhs) {
+    return (*this = (*this - rhs));
+  }
+
+  // Maps this RtpTimeTicks to an approximate std::chrono::duration representing
+  // the amount of time since the origin point (e.g., the start of a stream)
+  // using the given `rtp_timebase`.  Assumes a zero-valued Duration corresponds
+  // to a zero-valued RtpTimeTicks.
+  template <typename Duration>
+  Duration ToTimeSinceOrigin(int rtp_timebase) const {
+    return (*this - RtpTimeTicks()).ToDuration<Duration>(rtp_timebase);
+  }
+
+  // Maps the `time_since_origin` to an approximate RtpTimeTicks using the given
+  // RTP timebase.  Assumes a zero-valued Duration corresponds to a zero-valued
+  // RtpTimeTicks.
+  template <typename Duration>
+  static constexpr RtpTimeTicks FromTimeSinceOrigin(Duration time_since_origin,
+                                                    int rtp_timebase) {
+    return RtpTimeTicks() +
+           RtpTimeDelta::FromDuration(time_since_origin, rtp_timebase);
+  }
+
+ private:
+  friend class ExpandedValueBase<int64_t, RtpTimeTicks>;
+  friend std::ostream& operator<<(std::ostream& out, const RtpTimeTicks rhs);
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_RTP_TIME_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/sender_message.cc

@@ -0,0 +1,128 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/sender_message.h"
+
+#include <utility>
+#include <variant>
+
+#include "cast/streaming/message_fields.h"
+#include "util/base64.h"
+#include "util/enum_name_table.h"
+#include "util/json/json_helpers.h"
+#include "util/json/json_serialization.h"
+#include "util/string_util.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+EnumNameTable<SenderMessage::Type, 4> kMessageTypeNames{
+    {{kMessageTypeOffer, SenderMessage::Type::kOffer},
+     {"GET_CAPABILITIES", SenderMessage::Type::kGetCapabilities},
+     {"RPC", SenderMessage::Type::kRpc},
+     {"INPUT", SenderMessage::Type::kInput}}};
+
+SenderMessage::Type GetMessageType(const Json::Value& root) {
+  std::string type;
+  if (!json::TryParseString(root[kMessageType], &type)) {
+    return SenderMessage::Type::kUnknown;
+  }
+  string_util::AsciiStrToUpper(type);
+  ErrorOr<SenderMessage::Type> parsed = GetEnum(kMessageTypeNames, type);
+
+  return parsed.value(SenderMessage::Type::kUnknown);
+}
+
+}  // namespace
+
+// static
+ErrorOr<SenderMessage> SenderMessage::Parse(const Json::Value& value) {
+  if (!value.isObject()) {
+    return Error(Error::Code::kParameterInvalid,
+                 "SenderMessage body is not a JSON object");
+  }
+
+  SenderMessage message;
+  if (!json::TryParseInt(value[kSequenceNumber], &(message.sequence_number))) {
+    message.sequence_number = -1;
+  }
+
+  message.type = GetMessageType(value);
+  switch (message.type) {
+    case Type::kOffer: {
+      auto offer_or_error = Offer::TryParse(value[kOfferMessageBody]);
+      if (offer_or_error.is_value()) {
+        message.body = std::move(offer_or_error.value());
+        message.valid = true;
+      }
+    } break;
+
+    case Type::kRpc: {
+      std::string rpc_body;
+      std::vector<uint8_t> rpc;
+      if (json::TryParseString(value[kRpcMessageBody], &rpc_body) &&
+          base64::Decode(rpc_body, &rpc)) {
+        message.body = rpc;
+        message.valid = true;
+      }
+    } break;
+
+    case Type::kInput: {
+      std::string input_body;
+      std::vector<uint8_t> input;
+      if (json::TryParseString(value[kInputMessageBody], &input_body) &&
+          base64::Decode(input_body, &input)) {
+        message.body = input;
+        message.valid = true;
+      }
+    } break;
+
+    case Type::kGetCapabilities:
+      message.valid = true;
+      break;
+
+    default:
+      break;
+  }
+
+  return message;
+}
+
+ErrorOr<Json::Value> SenderMessage::ToJson() const {
+  OSP_CHECK(type != SenderMessage::Type::kUnknown)
+      << "Trying to send an unknown message is a developer error";
+
+  Json::Value root;
+  ErrorOr<const char*> message_type = GetEnumName(kMessageTypeNames, type);
+  root[kMessageType] = message_type.value();
+  if (sequence_number >= 0) {
+    root[kSequenceNumber] = sequence_number;
+  }
+
+  switch (type) {
+    case SenderMessage::Type::kOffer:
+      root[kOfferMessageBody] = std::get<Offer>(body).ToJson();
+      break;
+
+    case SenderMessage::Type::kRpc:
+      root[kRpcMessageBody] =
+          base64::Encode(std::get<std::vector<uint8_t>>(body));
+      break;
+
+    case SenderMessage::Type::kInput:
+      root[kInputMessageBody] =
+          base64::Encode(std::get<std::vector<uint8_t>>(body));
+      break;
+
+    case SenderMessage::Type::kGetCapabilities:
+      break;
+
+    default:
+      OSP_NOTREACHED();
+  }
+  return root;
+}
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/sender_message.h

@@ -0,0 +1,55 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_SENDER_MESSAGE_H_
+#define CAST_STREAMING_SENDER_MESSAGE_H_
+
+#include <memory>
+#include <string>
+#include <variant>
+#include <vector>
+
+#include "cast/streaming/public/offer_messages.h"
+#include "json/value.h"
+#include "platform/base/error.h"
+#include "util/osp_logging.h"
+
+namespace openscreen::cast {
+
+struct SenderMessage {
+ public:
+  // Receiver response message type.
+  enum class Type {
+    // Unknown message type.
+    kUnknown,
+
+    // OFFER request message.
+    kOffer,
+
+    // GET_CAPABILITIES request message.
+    kGetCapabilities,
+
+    // Rpc binary messages. The payload is base64-encoded.
+    kRpc,
+
+    // Input-related binary messages. The payload is base64-encoded.
+    kInput,
+  };
+
+  static ErrorOr<SenderMessage> Parse(const Json::Value& value);
+  ErrorOr<Json::Value> ToJson() const;
+
+  Type type = Type::kUnknown;
+  int32_t sequence_number = -1;
+  bool valid = false;
+  std::variant<std::monostate,
+               std::vector<uint8_t>,  // Binary-encoded protobuf message.
+               Offer,
+               std::string>
+      body;
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_SENDER_MESSAGE_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/sender_packet_router.cc

@@ -0,0 +1,273 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/sender_packet_router.h"
+
+#include <algorithm>
+#include <utility>
+
+#include "cast/streaming/impl/packet_util.h"
+#include "cast/streaming/public/constants.h"
+#include "platform/base/span.h"
+#include "util/chrono_helpers.h"
+#include "util/osp_logging.h"
+#include "util/saturate_cast.h"
+#include "util/stringprintf.h"
+
+namespace openscreen::cast {
+
+using clock_operators::operator<<;
+
+SenderPacketRouter::SenderPacketRouter(Environment& environment,
+                                       int max_burst_bitrate)
+    : SenderPacketRouter(
+          environment,
+          ComputeMaxPacketsPerBurst(max_burst_bitrate,
+                                    environment.GetMaxPacketSize(),
+                                    kDefaultBurstInterval),
+          kDefaultBurstInterval) {}
+
+SenderPacketRouter::SenderPacketRouter(Environment& environment,
+                                       int max_packets_per_burst,
+                                       milliseconds burst_interval)
+    : BandwidthEstimator(max_packets_per_burst,
+                         burst_interval,
+                         environment.now()),
+      environment_(environment),
+      packet_buffer_size_(environment.GetMaxPacketSize()),
+      packet_buffer_(new uint8_t[packet_buffer_size_]),
+      max_packets_per_burst_(max_packets_per_burst),
+      burst_interval_(burst_interval),
+      max_burst_bitrate_(ComputeMaxBurstBitrate(packet_buffer_size_,
+                                                max_packets_per_burst_,
+                                                burst_interval_)),
+      alarm_(environment_->now_function(), environment_->task_runner()) {
+  OSP_CHECK_GT(packet_buffer_size_, kRequiredNetworkPacketSize);
+}
+
+SenderPacketRouter::~SenderPacketRouter() {
+  OSP_CHECK(senders_.empty());
+}
+
+void SenderPacketRouter::OnSenderCreated(Ssrc receiver_ssrc, Sender* sender) {
+  OSP_CHECK(FindEntry(receiver_ssrc) == senders_.end());
+  senders_.push_back(SenderEntry{receiver_ssrc, sender, kNever, kNever});
+
+  if (senders_.size() == 1) {
+    environment_->ConsumeIncomingPackets(this);
+  } else {
+    // Sort the list of Senders so that they are iterated in priority order.
+    std::sort(senders_.begin(), senders_.end());
+  }
+}
+
+void SenderPacketRouter::OnSenderDestroyed(Ssrc receiver_ssrc) {
+  const auto it = FindEntry(receiver_ssrc);
+  OSP_CHECK(it != senders_.end());
+  senders_.erase(it);
+
+  // If there are no longer any Senders, suspend receiving RTCP packets.
+  if (senders_.empty()) {
+    environment_->DropIncomingPackets();
+  }
+}
+
+void SenderPacketRouter::RequestRtcpSend(Ssrc receiver_ssrc) {
+  const auto it = FindEntry(receiver_ssrc);
+  OSP_CHECK(it != senders_.end());
+  it->next_rtcp_send_time = Alarm::kImmediately;
+  ScheduleNextBurst();
+}
+
+void SenderPacketRouter::RequestRtpSend(Ssrc receiver_ssrc) {
+  const auto it = FindEntry(receiver_ssrc);
+  OSP_CHECK(it != senders_.end());
+  it->next_rtp_send_time = Alarm::kImmediately;
+  ScheduleNextBurst();
+}
+
+void SenderPacketRouter::OnReceivedPacket(const IPEndpoint& source,
+                                          Clock::time_point arrival_time,
+                                          std::vector<uint8_t> packet) {
+  // If the packet did not come from the expected endpoint, ignore it.
+  OSP_CHECK_NE(source.port, uint16_t{0});
+  if (source != environment_->remote_endpoint()) {
+    return;
+  }
+
+  // Determine which Sender to dispatch the packet to. Senders may only receive
+  // RTCP packets from Receivers. Log a warning containing a pretty-printed dump
+  // if the packet is not an RTCP packet.
+  const std::pair<ApparentPacketType, Ssrc> seems_like =
+      InspectPacketForRouting(packet);
+  if (seems_like.first != ApparentPacketType::RTCP) {
+    constexpr int kMaxPartiaHexDumpSize = 96;
+    const std::size_t encode_size =
+        std::min(packet.size(), static_cast<size_t>(kMaxPartiaHexDumpSize));
+    OSP_LOG_WARN << "UNKNOWN packet of " << packet.size()
+                 << " bytes. Partial hex dump: "
+                 << HexEncode(packet.data(), encode_size);
+    return;
+  }
+  const auto it = FindEntry(seems_like.second);
+  if (it != senders_.end()) {
+    it->sender->OnReceivedRtcpPacket(arrival_time, std::move(packet));
+  }
+}
+
+SenderPacketRouter::SenderEntries::iterator SenderPacketRouter::FindEntry(
+    Ssrc receiver_ssrc) {
+  return std::find_if(senders_.begin(), senders_.end(),
+                      [receiver_ssrc](const SenderEntry& entry) {
+                        return entry.receiver_ssrc == receiver_ssrc;
+                      });
+}
+
+void SenderPacketRouter::ScheduleNextBurst() {
+  // Determine the next burst time by scanning for the earliest of the
+  // next-scheduled send times for each Sender.
+  const Clock::time_point earliest_allowed_burst_time =
+      last_burst_time_ + burst_interval_;
+  Clock::time_point next_burst_time = kNever;
+  for (const SenderEntry& entry : senders_) {
+    const auto next_send_time =
+        std::min(entry.next_rtcp_send_time, entry.next_rtp_send_time);
+    if (next_send_time >= next_burst_time) {
+      continue;
+    }
+    if (next_send_time <= earliest_allowed_burst_time) {
+      next_burst_time = earliest_allowed_burst_time;
+      // No need to continue, since `next_burst_time` cannot become any earlier.
+      break;
+    }
+    next_burst_time = next_send_time;
+  }
+
+  // Schedule the alarm for the next burst time unless none of the Senders has
+  // anything to send.
+  if (next_burst_time == kNever) {
+    alarm_.Cancel();
+  } else {
+    alarm_.Schedule([this] { SendBurstOfPackets(); }, next_burst_time);
+  }
+}
+
+void SenderPacketRouter::SendBurstOfPackets() {
+  // Treat RTCP packets as "critical priority," and so there is no upper limit
+  // on the number to send. Practically, this will always be limited by the
+  // number of Senders; so, this won't be a huge number of packets.
+  const Clock::time_point burst_time = environment_->now();
+  const int num_rtcp_packets_sent = SendJustTheRtcpPackets(burst_time);
+  // Now send all the RTP packets, up to the maximum number allowed in a burst.
+  // Higher priority Senders' RTP packets are sent first.
+  const int num_rtp_packets_sent = SendJustTheRtpPackets(
+      burst_time, max_packets_per_burst_ - num_rtcp_packets_sent);
+  last_burst_time_ = burst_time;
+
+  BandwidthEstimator::OnBurstComplete(
+      num_rtcp_packets_sent + num_rtp_packets_sent, burst_time);
+
+  ScheduleNextBurst();
+}
+
+int SenderPacketRouter::SendJustTheRtcpPackets(Clock::time_point send_time) {
+  int num_sent = 0;
+  for (SenderEntry& entry : senders_) {
+    if (entry.next_rtcp_send_time > send_time) {
+      continue;
+    }
+
+    // Note: Only one RTCP packet is sent from the same Sender in the same
+    // burst. This is because RTCP packets are supposed to always contain the
+    // most up-to-date Sender state. Having multiple RTCP packets in the same
+    // burst would mean that all but the last one are old/irrelevant snapshots
+    // of Sender state, and this would just thrash/confuse the Receiver.
+    const ByteBuffer packet = entry.sender->GetRtcpPacketForImmediateSend(
+        send_time, ByteBuffer(packet_buffer_.get(), packet_buffer_size_));
+    if (!packet.empty()) {
+      environment_->SendPacket(
+          ByteView(packet.data(), packet.size()),
+          PacketMetadata{.stream_type = entry.sender->GetStreamType(),
+                         .rtp_timestamp = entry.sender->GetLastRtpTimestamp()});
+      entry.next_rtcp_send_time = send_time + kRtcpReportInterval;
+      ++num_sent;
+    }
+  }
+
+  return num_sent;
+}
+
+int SenderPacketRouter::SendJustTheRtpPackets(Clock::time_point send_time,
+                                              int num_packets_to_send) {
+  int num_sent = 0;
+  for (SenderEntry& entry : senders_) {
+    if (num_sent >= num_packets_to_send) {
+      break;
+    }
+    if (entry.next_rtp_send_time > send_time) {
+      continue;
+    }
+
+    for (; num_sent < num_packets_to_send; ++num_sent) {
+      const ByteBuffer packet = entry.sender->GetRtpPacketForImmediateSend(
+          send_time, ByteBuffer(packet_buffer_.get(), packet_buffer_size_));
+      if (packet.empty()) {
+        break;
+      }
+      environment_->SendPacket(
+          ByteView(packet.data(), packet.size()),
+          PacketMetadata{.stream_type = entry.sender->GetStreamType(),
+                         .rtp_timestamp = entry.sender->GetLastRtpTimestamp()});
+    }
+    entry.next_rtp_send_time = entry.sender->GetRtpResumeTime();
+  }
+
+  return num_sent;
+}
+
+namespace {
+constexpr int kBitsPerByte = 8;
+constexpr auto kOneSecondInMilliseconds = to_milliseconds(seconds(1));
+}  // namespace
+
+// static
+int SenderPacketRouter::ComputeMaxPacketsPerBurst(int max_burst_bitrate,
+                                                  int packet_size,
+                                                  milliseconds burst_interval) {
+  OSP_CHECK_GT(max_burst_bitrate, 0);
+  OSP_CHECK_GT(packet_size, 0);
+  OSP_CHECK_GT(burst_interval, milliseconds(0));
+  OSP_CHECK_LE(burst_interval, kOneSecondInMilliseconds);
+
+  const int max_packets_per_second =
+      max_burst_bitrate / kBitsPerByte / packet_size;
+  const int bursts_per_second = kOneSecondInMilliseconds / burst_interval;
+  return std::max(max_packets_per_second / bursts_per_second, 1);
+}
+
+// static
+int SenderPacketRouter::ComputeMaxBurstBitrate(int packet_size,
+                                               int max_packets_per_burst,
+                                               milliseconds burst_interval) {
+  OSP_CHECK_GT(packet_size, 0);
+  OSP_CHECK_GT(max_packets_per_burst, 0);
+  OSP_CHECK_GT(burst_interval, milliseconds(0));
+  OSP_CHECK_LE(burst_interval, kOneSecondInMilliseconds);
+
+  const int64_t max_bits_per_burst =
+      int64_t{packet_size} * kBitsPerByte * max_packets_per_burst;
+  const int bursts_per_second = kOneSecondInMilliseconds / burst_interval;
+  return saturate_cast<int>(max_bits_per_burst * bursts_per_second);
+}
+
+SenderPacketRouter::Sender::~Sender() = default;
+
+// static
+constexpr int SenderPacketRouter::kDefaultMaxBurstBitrate;
+// static
+constexpr milliseconds SenderPacketRouter::kDefaultBurstInterval;
+// static
+constexpr Clock::time_point SenderPacketRouter::kNever;
+
+}  // namespace openscreen::cast

breadcast-caststream-sys/vendor/openscreen/cast/streaming/sender_packet_router.h

@@ -0,0 +1,203 @@
+// Copyright 2020 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_SENDER_PACKET_ROUTER_H_
+#define CAST_STREAMING_SENDER_PACKET_ROUTER_H_
+
+#include <stdint.h>
+
+#include <chrono>
+#include <memory>
+#include <vector>
+
+#include "cast/streaming/impl/bandwidth_estimator.h"
+#include "cast/streaming/public/constants.h"
+#include "cast/streaming/public/environment.h"
+#include "cast/streaming/ssrc.h"
+#include "platform/api/time.h"
+#include "platform/base/span.h"
+#include "util/alarm.h"
+#include "util/raw_ptr.h"
+#include "util/raw_ref.h"
+
+namespace openscreen::cast {
+
+// Manages network packet transmission for one or more Senders, directing each
+// inbound packet to a specific Sender instance, pacing the transmission of
+// outbound packets, and employing network bandwidth/availability monitoring and
+// congestion control.
+//
+// Instead of just sending packets whenever they want, Senders must request
+// transmission from the SenderPacketRouter. The router then calls-back to each
+// Sender, in the near future, when it has allocated an available time slice for
+// transmission. The Sender is allowed to decide, at that exact moment, which
+// packet most needs to be sent.
+//
+// Pacing strategy: Packets are sent in bursts. This allows the platform
+// (operating system) to collect many small packets into a short-term buffer,
+// which allows for optimizations at the link layer. For example, multiple
+// packets can be sent together as one larger transmission unit, and this can be
+// critical for good performance over shared-medium networks (such as 802.11
+// WiFi). https://en.wikipedia.org/wiki/Frame-bursting
+class SenderPacketRouter : public BandwidthEstimator,
+                           public Environment::PacketConsumer {
+ public:
+  class Sender {
+   public:
+    // Called to provide the Sender with what looks like a RTCP packet meant for
+    // it specifically (among other Senders) to process. `arrival_time`
+    // indicates when the packet arrived (i.e., when it was received from the
+    // platform).
+    virtual void OnReceivedRtcpPacket(Clock::time_point arrival_time,
+                                      ByteView packet) = 0;
+
+    // Populates the given `buffer` with a RTCP/RTP packet that will be sent
+    // immediately. Returns the portion of `buffer` contaning the packet, or an
+    // empty Span if nothing is ready to send.
+    virtual ByteBuffer GetRtcpPacketForImmediateSend(
+        Clock::time_point send_time,
+        ByteBuffer buffer) = 0;
+    virtual ByteBuffer GetRtpPacketForImmediateSend(Clock::time_point send_time,
+                                                    ByteBuffer buffer) = 0;
+
+    // Returns the point-in-time at which RTP sending should resume, or kNever
+    // if it should be suspended until an explicit call to RequestRtpSend(). The
+    // implementation may return a value on or before "now" to indicate an
+    // immediate resume is desired.
+    virtual Clock::time_point GetRtpResumeTime() = 0;
+
+    // Returns the last logged RTP timestamp, for use in expanding truncated
+    // packet RTP timestamps for metrics purposes.
+    virtual RtpTimeTicks GetLastRtpTimestamp() const = 0;
+
+    // Returns the type of stream that this sender is providing.
+    virtual StreamType GetStreamType() const = 0;
+
+   protected:
+    virtual ~Sender();
+  };
+
+  // Constructs an instance with default burst parameters appropriate for the
+  // given `max_burst_bitrate`.
+  explicit SenderPacketRouter(Environment& environment,
+                              int max_burst_bitrate = kDefaultMaxBurstBitrate);
+
+  // Constructs an instance with specific burst parameters. The maximum bitrate
+  // will be computed based on these (and Environment::GetMaxPacketSize()).
+  SenderPacketRouter(Environment& environment,
+                     int max_packets_per_burst,
+                     std::chrono::milliseconds burst_interval);
+
+  ~SenderPacketRouter();
+
+  int max_packet_size() const { return packet_buffer_size_; }
+  int max_burst_bitrate() const { return max_burst_bitrate_; }
+
+  // Called from a Sender constructor/destructor to register/deregister a Sender
+  // instance that processes RTP/RTCP packets from a Receiver having the given
+  // SSRC.
+  void OnSenderCreated(Ssrc receiver_ssrc, Sender* client);
+  void OnSenderDestroyed(Ssrc receiver_ssrc);
+
+  // Requests an immediate send of a RTCP packet, and then RTCP sending will
+  // repeat at regular intervals (see kRtcpSendInterval) until the Sender is
+  // de-registered.
+  void RequestRtcpSend(Ssrc receiver_ssrc);
+
+  // Requests an immediate send of a RTP packet. RTP sending will continue until
+  // the Sender stops providing packet data.
+  //
+  // See also: Sender::GetRtpResumeTime().
+  void RequestRtpSend(Ssrc receiver_ssrc);
+
+  // A reasonable default maximum bitrate for bursting. Congestion control
+  // should always be employed to limit the Senders' sustained/average outbound
+  // data volume for "fair" use of the network.
+  static constexpr int kDefaultMaxBurstBitrate = 24 << 20;  // 24 megabits/sec
+
+  // The minimum amount of time between burst-sends. The methodology by which
+  // this value was determined is lost knowledge, but is likely the result of
+  // experimentation with various network and operating system configurations.
+  // This value came from the original Chrome Cast Streaming implementation.
+  static constexpr std::chrono::milliseconds kDefaultBurstInterval{10};
+
+  // A special time_point value representing "never."
+  static constexpr Clock::time_point kNever = Clock::time_point::max();
+
+ private:
+  struct SenderEntry {
+    Ssrc receiver_ssrc;
+    raw_ptr<Sender> sender;
+    Clock::time_point next_rtcp_send_time;
+    Clock::time_point next_rtp_send_time;
+
+    // Entries are ordered by the transmission priority (high→low), as implied
+    // by their SSRC. See ssrc.h for details.
+    bool operator<(const SenderEntry& other) const {
+      return ComparePriority(receiver_ssrc, other.receiver_ssrc) < 0;
+    }
+  };
+
+  using SenderEntries = std::vector<SenderEntry>;
+
+  // Environment::PacketConsumer implementation.
+  void OnReceivedPacket(const IPEndpoint& source,
+                        Clock::time_point arrival_time,
+                        std::vector<uint8_t> packet) final;
+
+  // Helper to return an iterator pointing to the entry corresponding to the
+  // given `receiver_ssrc`, or "end" if not found.
+  SenderEntries::iterator FindEntry(Ssrc receiver_ssrc);
+
+  // Examine the next send time for all Senders, and decide whether to schedule
+  // a burst-send.
+  void ScheduleNextBurst();
+
+  // Performs a burst-send of packets. This is called whenever the Alarm fires.
+  void SendBurstOfPackets();
+
+  // Send an RTCP packet from each Sender that has one ready, and return the
+  // number of packets sent.
+  int SendJustTheRtcpPackets(Clock::time_point send_time);
+
+  // Send zero or more RTP packets from each Sender, up to a maximum of
+  // `num_packets_to_send`, and return the number of packets sent.
+  int SendJustTheRtpPackets(Clock::time_point send_time,
+                            int num_packets_to_send);
+
+  // Returns the maximum number of packets to send in one burst, based on the
+  // given parameters.
+  static int ComputeMaxPacketsPerBurst(
+      int max_burst_bitrate,
+      int packet_size,
+      std::chrono::milliseconds burst_interval);
+
+  // Returns the maximum bitrate inferred by the given parameters.
+  static int ComputeMaxBurstBitrate(int packet_size,
+                                    int max_packets_per_burst,
+                                    std::chrono::milliseconds burst_interval);
+
+  const raw_ref<Environment> environment_;
+  const int packet_buffer_size_;
+  const std::unique_ptr<uint8_t[]> packet_buffer_;
+  const int max_packets_per_burst_;
+  const std::chrono::milliseconds burst_interval_;
+  const int max_burst_bitrate_;
+
+  // Schedules the task that calls back into this SenderPacketRouter at a later
+  // time to send the next burst of packets.
+  Alarm alarm_;
+
+  // The current list of Senders and their timing information. This is
+  // maintained in order of the priority implied by the Sender SSRC's.
+  SenderEntries senders_;
+
+  // The last time a burst of packets was sent. This is used to determine the
+  // next burst time.
+  Clock::time_point last_burst_time_ = Clock::time_point::min();
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_SENDER_PACKET_ROUTER_H_

breadcast-caststream-sys/vendor/openscreen/cast/streaming/ssrc.cc

@@ -0,0 +1,42 @@
+// Copyright 2019 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cast/streaming/ssrc.h"
+
+#include <random>
+
+#include "platform/api/time.h"
+
+namespace openscreen::cast {
+
+namespace {
+
+// These ranges are arbitrary, but have been used for several years (in prior
+// implementations of Cast Streaming).
+constexpr int kHigherPriorityMin = 1;
+constexpr int kHigherPriorityMax = 50000;
+constexpr int kNormalPriorityMin = 50001;
+constexpr int kNormalPriorityMax = 100000;
+
+}  // namespace
+
+Ssrc GenerateSsrc(bool higher_priority) {
+  // Use a statically-allocated generator, instantiated upon first use, and
+  // seeded with the current time tick count. This generator was chosen because
+  // it is light-weight and does not need to produce unguessable (nor
+  // crypto-secure) values.
+  static std::minstd_rand generator(static_cast<std::minstd_rand::result_type>(
+      Clock::now().time_since_epoch().count()));
+
+  std::uniform_int_distribution<int> distribution(
+      higher_priority ? kHigherPriorityMin : kNormalPriorityMin,
+      higher_priority ? kHigherPriorityMax : kNormalPriorityMax);
+  return static_cast<Ssrc>(distribution(generator));
+}
+
+int ComparePriority(Ssrc ssrc_a, Ssrc ssrc_b) {
+  return static_cast<int>(ssrc_a) - static_cast<int>(ssrc_b);
+}
+
+}  // namespace openscreen::cast