Record a single WebRTC track (not the full room) from a LiveKit session using Track Egress
domain: docs.livekit.io · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Call the LiveKit Egress service's StartTrackEgress via the Server SDK/Twirp API (https://<host>/twirp/livekit.Egress/StartTrackEgress) with an access token carrying the roomRecord grant
Specify room_name and track_id for the single track to export (audio or video, not both)
Set exactly one output: a file output (container is auto-selected — H.264 to MP4, VP8 to WebM, Opus to Ogg) or a websocket_url for raw PCM audio streaming
If streaming to a websocket, expect binary PCM (pcm_s16le) frames plus JSON text frames carrying mute state ({"muted": true/false})
Subscribe to egress webhooks to confirm the egress reaches EGRESS_ACTIVE/EGRESS_COMPLETE status
Known gotchas
StartTrackEgress exports only one track with no muxing/transcoding — use StartTrackCompositeEgress instead if you need synced audio+video in one file
If your app manages subscriptions manually, calling UpdateSubscriptions against the egress participant can silently switch which track is captured
websocket_url output is audio-only; video tracks can only go to a file output
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