Final Cut Pro convert closed captions: burn cues in Sume

Final Cut Pro 12.3 added a way to convert existing closed captions to subtitles. The Sume docs describe no closed-caption converter, but if you have the text and timings, POST /v1/video-captions burns them onto a video as cues or segments. SRT uploads are unsupported, so you map each line to text, start and end.

Apple's line is from its release notes; Sume's from Video captions, read 2026-10-01.

What did Apple add in 12.3?

Under workflow enhancements the notes list: easily convert existing closed captions to subtitles, quickly select all subtitles with a single command, and adjust position, rotation, scale and alignment for multiple selected subtitles from the inspector. All of that happens inside the editor.

How do I burn existing caption text with Sume?

Pass cues (or segments), each with text, start and end in seconds. The docs call this an authored overlay that skips speech-to-text. script_text, words, cues and segments are mutually exclusive, so send only one.

curl -X POST https://api.sume.com/v1/video-captions \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: cc-burn-001" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/example/clean.mp4",
    "cues": [
      { "text": "[door closes]", "start": 1.2, "end": 2.4 },
      { "text": "We start Monday.", "start": 2.4, "end": 4.8 }
    ]
  }'

Why not upload the caption file?

The docs state that SRT uploads and provider task ids are unsupported. The docs describe no reading of closed-caption tracks from your video, so send the text in the request.

Can I change the look afterwards?

Yes. To re-burn the same video under a different style, pass source_caption_id instead of video_url. The docs say Sume reuses that caption's source video and the word timings it already has, and billing is unchanged because a restyle is still a render. Standalone jobs reserve $0.20 USD for videos up to 60 seconds under the current fixed estimate.

What about silent clips?

A silent clip fails as caption_no_speech unless you pass cues, which is the usual route for existing text; see silent clips and overlay cues and captions vs subtitles.