H3 Max Recast file types: mp4, mov, webm, m4v or GIF?

What fal's page lists for the input video

Recast is MiniMax H3 Max's person swap: it recasts the people in a video using reference photos while keeping the source motion, camera, cuts and audio. fal's model page, read 2026-10-03, lists five accepted video file types and the two prices.

The same page does not state a maximum length or file size. Sume's own catalog does state limits, so the table puts the two side by side.

What Sume asks of the clip

Sume takes the source as a URL, not an upload. The Media inputs page says video URLs must be fetchable public HTTPS addresses, and that localhost, private-network, signed or private URLs and mismatched content types are rejected before the job is accepted.

Sume also needs a number from you. A Recast request must carry duration, the source length in seconds rounded up, and the value must land between 5 and 30. The request is refused without it, and because the output keeps the source length, the number is also what Sume uses to price the job.

• mp4 is the common choice; mov, webm and m4v are on fal's list, so a clip in one of them is in scope on the vendor side.
• A GIF has no soundtrack, so there is no audio for Recast to keep. Use a real video file when sound matters.
• A clip behind a login or an expiring signed link will fail the public-URL check even when the file type is right.

Probe it once, then submit

Sume's Video inspect reads one clip that already lives on media.sume.com and returns probe facts: duration, size, rotation, fps, codecs and audio. A clip from elsewhere is brought in first with POST /v1/media-imports.

Round the probed duration up, check it is 5 to 30 seconds, and send that as duration with the same video_url you probed. If the clip is over 30 seconds, trim it first.

curl -X POST https://api.sume.com/v1/video-inspect \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: probe-recast-source-001" \
  -d '{"video_url": "https://media.sume.com/artifacts/artf_demo/source.mp4"}'

Where this leaves you

The vendor lists the file types, Sume lists the limits, and neither promises that every codec inside a container works. Treat the probe as the cheap test: if inspect reads the clip, you have a duration to send, and a real 768p run on a short clip is the proof for anything unusual.