Change frame rate when compositing: output_fps_resamples_sources

Leave output.fps out of a Sume compose and the shot keeps the video layer's own frame rate, which is the only rate that repeats or drops no frame. Set an explicit output.fps that differs from the clip's rate and the job warns output_fps_resamples_sources.

This is from the Timeline compose docs, read 2026-10-01. Runway's changelog added a frame-rate converter on Sep 17, 2026; for that comparison see the Runway frame-rate post.

What is the default output?

1080x1920 MP4 at the video layer's own frame rate. Set output.width and output.height to the timeline you will assemble into, so the shot is not rescaled twice.

What does the warning mean?

The compose has two sources, a still and a clip, and an explicit rate that differs from the clip's means the clip is resampled. It is a warning, so the job still succeeds.

Should I set output.fps at all?

Only to match the timeline you will join the shot into. If every clip already shares a rate, omit it. A mismatch at assembly is a separate concern; see the frame-rate judder warning.

What does a request with a rate look like?

The sample sets 25 fps explicitly; if the clip is not 25 fps, expect the warning.

curl -X POST https://api.sume.com/v1/timeline-1.0/compose \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: compose-fps-001" \
  -d '{
    "operation": "stack",
    "image": { "url": "https://media.sume.com/artifacts/artf_demo/poster.png" },
    "video": { "url": "https://media.sume.com/artifacts/artf_demo/talk.mp4" },
    "output": { "width": 720, "height": 1280, "fps": 25 }
  }'