Cold open with a recurring cast: Gemini Omni Flash with 10 image refs

Gemini Omni Flash 1.1 on Sume makes a 3 to 10 second cold open from up to 10 reference images and up to 3 reference clips of at most 3 seconds each, in 16:9 or 9:16, with synced audio always on. Put your recurring cast in the references and address them as <IMAGE_REF_0> in the prompt. It is a short-form tool; for 30 second shots use Seedance 2.5.

A cold open is the few seconds before the title, and episodic micro-dramas, which Metricool reports as gaining traction on TikTok, lean on it to hook the viewer.

Limits from the docs

Sume routes this model by the shape of the request, so you do not pick an endpoint. Read capabilities from GET /v1/video-router/models instead of assuming.

The request

Send reference_image_urls and, if you have motion to carry over, reference_video_urls. Reference media is addressed by its zero-based position in the list. Media must be on media.sume.com. The prompt below uses two cast images and one clip.

curl -X POST https://api.sume.com/v1/video-router/generate \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: s1e5-cold-open-v1" \
  -d '{"model":"gemini-omni-flash-1.1","aspect_ratio":"9:16","resolution":"720p","duration":8,
       "reference_image_urls":["https://media.sume.com/artifacts/artf_a/lead.png","https://media.sume.com/artifacts/artf_a/rival.png"],
       "prompt":"<IMAGE_REF_0> runs through a night market, <IMAGE_REF_1> watches from a rooftop, tense hush"}'

Rules you must respect

Native audio cannot be switched off: generate_audio set to false is rejected. There is no reference_audio_urls. A video_url edit source cannot be combined with image or reference lists. So a cold open with your own voice track needs the sound replaced afterwards in Timeline 1.0.

Keeping the cast stable

Reference images are the lever. Use a clean, front-facing image of each character on a plain background, name them in the prompt by ref, and reuse the same files in every episode. Our reference image guide covers building the set.

Sume does not promise identical faces from one render to the next. Check the first frame against your approved image before posting.