Seedance 2.5 secondary edit vs trim-and-regenerate on Sume

On Sume you cannot ask Seedance 2.5 to change a time range inside a finished clip. The BytePlus page describes timestamp-level and character-level secondary editing on its own platform, but the Sume video docs expose no equivalent field. The Sume route is to trim the parts you keep and generate only the part you want to replace.

What changes versus a vendor edit

Two things make this less clean than a true local edit. First, the generation endpoint documents no seed for any model, so a regenerated segment will not reproduce the original motion. Second, the join between the kept footage and the new segment is yours to manage.

Step 1: keep the good part

The video trim endpoint takes one Sume-hosted clip, a start, and exactly one of end or duration. It returns a new MP4 and leaves the source untouched. The default precision is exact, a frame-accurate re-encode, and the docs list the public rate as $0.02 per job and say to confirm it in the live catalog.

curl -X POST https://api.sume.com/v1/video-trim \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: keep-intro-001" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/artf_demo/clip.mp4",
    "start": 0,
    "duration": 12
  }'

Step 2: regenerate only the gap

Trim the tail the same way with a second job, then generate the middle as its own clip. If the model you choose lists first_frame in supported_frame_images, you can seed the new segment with a still taken from the last frame of the kept intro to keep the subject consistent. Check that field on GET /v1/videos/models first, since the docs say limits are not uniform across models.

Assemble the three pieces in order with the timeline workflow. The video trim docs say sequencing stays on Timeline 1.0, with the trimmed MP4 dropped in with source_in set to 0.

A worked example

Suppose a 30 second clip is right except for seconds 12 to 16, where a product label is unreadable. The vendor-edit route would target that range. On Sume you trim [0, 12) and [16, 30) into two new clips, which is two trim jobs at the listed $0.02 each, then generate a replacement for the gap.

The gap is 4 seconds, which is also the lower end of the documented seedance-2.5 range of 4 to 30 seconds, so a 4 second regeneration is allowed. Check supported_durations on the live catalog to be sure before you rely on it. Then assemble the three files in order and review the joins at full size, since a change in lighting or camera speed at a cut is the most common giveaway.

• Trim jobs: 2 at $0.02 each, per the docs' public rate.
• Generation: one 4 second job at the model's live price.
• Assembly: one timeline job; see the timeline docs for its rate.
• Review: watch each join at full resolution before sign-off.

When to skip the stitch

If the replaced span is short, ask whether a regenerated full clip is cheaper than three jobs plus a timeline. For a 30 second clip where one beat is wrong, regenerating the whole thing is often simpler. The related post on trim versus regenerate covers the shorter-clip case.