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Add optional WebTransport frame transport

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James Magahern
2026-06-24 21:28:15 -07:00
parent d37694e4d3
commit 3e2ca8057b
9 changed files with 829 additions and 31 deletions
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README.md
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@@ -3,7 +3,7 @@
A small web app that plays a remote video stream without using browser video decoding. The server uses `ffmpeg` to decode the input URL into:
- an MP3 audio stream served to a normal `<audio>` element
- timed JPEG image frames sent over a WebSocket and painted onto a `<canvas>`
- timed JPEG image frames sent over a WebSocket, or optionally WebTransport/QUIC, and painted onto a `<canvas>`
This is meant for machines where image and audio decoding work but browser video decoding is unavailable or unreliable.
@@ -58,6 +58,8 @@ YouTube URLs are resolved server-side with `yt-dlp` before they enter the existi
JPEG frames are dropped when the browser WebSocket falls behind instead of letting stale frames queue indefinitely. Tune the server-side backlog cap with `MAX_WS_BUFFER_BYTES`; the default is `2097152`.
WebSocket remains the default frame transport. To try WebTransport/QUIC for frame delivery, set `FRAME_TRANSPORT=webtransport` or `FRAME_TRANSPORT=auto` and expose the WebTransport UDP port. The default WebTransport port is `PORT + 1`; override it with `WEBTRANSPORT_PORT` and, when needed behind Docker or a proxy, `WEBTRANSPORT_PUBLIC_HOST` and `WEBTRANSPORT_PUBLIC_PORT`. The server generates a short-lived local ECDSA certificate under `data/` unless `WEBTRANSPORT_CERT_PATH` and `WEBTRANSPORT_KEY_PATH` are both set. Browser WebTransport requires a secure context: localhost is usually allowed, but plain HTTP over a LAN address may not expose the API. Browsers that cannot connect with WebTransport fall back to WebSocket.
In single mode, audio output from `ffmpeg` is buffered before it is written to the browser so short HTTP backpressure pauses are less likely to stall frame generation. Tune the cap with `MAX_AUDIO_QUEUE_BYTES`; the default is `4194304`.
Playback uses `PLAYBACK_CONNECTION_MODE=split` by default. The Docker Compose example sets `PLAYBACK_CONNECTION_MODE=relay` so IPTV-style streams can be tested with one upstream connection.