Playback and downloads
Playback crosses four repositories: Frontend owns the controls, Server owns the session and public media contract, Token supplies YouTube-specific session material, and Player owns the browser MSE pipeline. Downloader reuses the Server contract when a user asks for an offline artifact.
YouTube playback path
The browser does not receive the upstream SABR URL or talk to Token. Server keeps the stateful upstream session, format selection, playback position, cached segments, and recovery generation. Player requests only TypeType-owned manifest and media paths.
Responsibility by layer
Frontend
Frontend decides what the person asked for: quality, codec, audio track, captions, audio-only mode, seek position, autoplay, and player layout. It creates and destroys the Player engine and converts engine events into visible state.
Server
Server exposes the playback-session contract under /sabr/playback/.... It selects formats, creates an isolated session token, warms initialization and media data, tracks playback position, handles seeks and generations, and evicts idle sessions.
For live content, Server and Player follow a moving playback window rather than a fixed list of segments. A quality or audio-track change creates replacement playback state at the requested position. The replacement path exists, but issue #163 tracks a current failure where live playback freezes after a quality or codec change.
Token
Token creates the YouTube-side material needed before Server can build a session: visitor data, PO tokens, player URL decoding, adaptive format metadata, and the SABR streaming URL. Its /youtube/sabr/session response is internal and is converted into Server models before anything reaches the browser.
Token is required for current YouTube playback even when remote YouTube login is disabled. The optional setting controls only the interactive login flow, not the token and decoder service itself.
Player
@typetype/mse loads the TypeType manifest, initialization data, and segment windows. It owns MediaSource and SourceBuffer operations, request cancellation, forward and back-buffer limits, segment scheduling, seek generations, quality changes, live-edge following, and recovery from stale or interrupted requests.
The package intentionally contains no controls or application state. That boundary lets playback behavior be tested without the React interface.
Other media services
Server also wraps PipePipeExtractor for supported non-YouTube services. Depending on the extracted response, Frontend can use direct media, DASH, HLS, or a TypeType proxy. Provider-specific extraction stays in Server; Player's TypeType SABR session contract is specifically the browser pipeline for stateful TypeType playback.
Download path
The public route is /api/downloader/...; the Downloader service itself remains internal. Its job keeps the user's Authorization header so its later extraction request has the same access as the original browser request.
In the bundled stack, Downloader creates an internal Garage URL. Server recognises the garage host and proxies the artifact instead of sending that private hostname to the browser. A normal deployment therefore does not need to expose Garage or set a browser-facing S3 endpoint.
Diagnosing a deployed version
The bundled nginx exposes the revision of every application image:
curl -fsS https://watch.example.com/api/version
curl -fsS https://watch.example.com/api/version/server
curl -fsS https://watch.example.com/api/version/token
curl -fsS https://watch.example.com/api/version/downloaderInclude these four responses when a playback or download report may depend on a recent component change. Also include whether the instance follows main or beta.
Reports that informed this page
The current separation between playback, Token, and container boundaries was made clearer by hugoghx's Token deployment investigation. Livestream reports such as issue #145 and issue #163 also helped identify the live-session and quality-change concepts that need to be explicit here. See Community sources for the complete acknowledgements.