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Add audio tracks to a video

The multi-track audio feature adds alternative audio tracks to a video — useful for multiple languages (dubs), accessibility, or offering viewers a choice such as a director's commentary. Viewers pick the track from the player's settings menu.

Uploading alternate audio tracks

Adding alternate audio tracks is not yet possible through the GUI.

Use the "Upload audio track" ⧉ endpoint — a multipart form with three fields:

Field Meaning
file The audio file, at most 100 MB. Any common audio format works — the file is probed, and rejected only if it contains no audio stream.
title The track's label shown to viewers in the player (up to 64 characters).
lang_code The track's language as a BCP 47 code (e.g. en, pt-BR).

Prerequisites and behavior

  • The video must already be playable (processed); otherwise the request fails with 422 video_not_ready. Audio tracks can't be added to a fast clip.
  • Upload audio that matches the video's duration: a longer file is cut to the video's length.
  • The track encodes asynchronously. Its status starts at queued, becomes ready when it's playable, or errored if the encode fails for good.
  • Uploaded tracks have type: alternate; the video's own audio is the embedded track. Alternate tracks keep a downloadable original_link.
  • Auto-generated captions are per audio track — a specific alternate track can be captioned by passing its id to the caption endpoint, and deleting an audio track also deletes the captions generated from it. See auto-generated captions.