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Arc XP

Video encoding fails resulting in invalid captions format error in playback

Symptoms

  • Video fails with Invalid captions format during playback.
  • Video Center clip failed to encode with error:
    transcoder.m3u8vtt.postprocess

Cause

There is an illegal character in your clip’s closed captions that causes the error. All XML reserved characters including " < > & ' should not be included in the .vtt file.

Solution

  1. Go to the video and confirm that the subtitle is failing. If you see the Invalid captions format error, this guide covers your scenario.

  2. Get the video UUID.

  3. Use curl to get the S3 subtitle path.

    • Remember to change “replace_with_uuid” in the URL.

    • The first time, you might need to install jq:

      Terminal window
      brew install jq

  4. Look for the WEB_VTT file (“url” is an S3 path).

  5. In the WEB_VTT file, look for any bad or illegal characters.

  6. If you cannot find any and are still having issues, please submit an ACS ticket.