Omni 1.1 Flash extends to 40 s; Seedance 2.5 makes 30 s in one pass

Gemini Omni 1.1 Flash extends a scene by analyzing up to 10 seconds of prior context and adding more, up to 40 seconds total in 10-second steps (Google, read 2026-10-05). Seedance 2.5 instead generates up to 30 seconds in one pass and can extend over multiple rounds (ByteDance Seed, read 2026-10-05). If you want a 40-second video on Sume, the documented path is one Seedance job plus a short second clip, joined with Timeline 1.0, because Sume's Omni route is 3 to 10 seconds per job.

What each vendor says

What Sume exposes

Sume's Video Router docs list gemini-omni-flash-1.1 at 3 to 10 seconds, 360p to 4K, 16:9 or 9:16, with native audio always on. The Omni job takes a prompt, an image, references or a source video to edit. The docs describe no extension parameter, so on Sume each Omni job is one clip of up to 10 seconds. seedance-2.5 accepts 4 to 30 seconds at 480p, 720p or 1080p.

A 40-second plan

The seam is where a join can show. A hard cut at a natural beat looks better than a fade across a changing subject. Tune the second prompt to restate the subject and setting, since the model sees only the still, not the earlier motion.

• Job 1: seedance-2.5, duration 30, at 720p, for the main run.
• Job 2: a 10-second clip that continues the story. Use a model whose catalog entry lists a start image, and pass a still pulled from the end of job 1 (see the video frames route) as the first frame.
• Assemble: Timeline 1.0 with two video[] slots, start 0 and 30, an optional 0.25 s fade, and audio.duration_seconds of 40.
• Run POST /v1/timeline-1.0/plan first; it is unbilled and returns estimated_cost_usd_micros.

curl -X POST https://api.sume.com/v1/timeline-1.0/render \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: forty-seconds-001" \
  -d '{
    "audio": { "mode": "silence", "duration_seconds": 40 },
    "video": [
      { "source_url": "https://media.sume.com/artifacts/artf_demo/part1.mp4", "start": 0, "duration": 30 },
      { "source_url": "https://media.sume.com/artifacts/artf_demo/part2.mp4", "start": 30, "duration": 10 }
    ]
  }'

Which to choose for which video

Use Seedance for the long unbroken part and Omni for short, high-resolution inserts. A 30-second Seedance job is one request and has no seam inside the 30 seconds. Omni's strength on Sume is its resolution range (up to 4K for 3 to 10 seconds), native audio and video edit, so it suits a final insert, a product close-up or an edited version of an existing clip.

If you truly need one continuous 40-second scene from a single vendor-side extension chain, that is a Google surface, and the Sume docs do not describe it. Plan around two jobs and a good cut point instead.

• 30 seconds of one scene: seedance-2.5.
• Short 4K insert: gemini-omni-flash-1.1.
• Edit of existing footage: Omni with video_url.

Silence mode declares the length without a spine file; if you want the generated audio, detach it per clip and join it with the timeline audio route instead, then pass the result as audio.url. Vendor details: Google's Omni 1.1 Flash post and the Seed post.