21:9 cinematic AI video API: which Sume models accept ultrawide

For 21:9 ultrawide video on Sume, use a Seedance row (seedance-2.5, seedance-2, seedance-2-fast, seedance-2-mini), minimax-h3 or minimax-h3-max. Kling 3, Wan 3.0, Gemini Omni Flash 1.1 and Grok Imagine Video 1.5 do not list it.

Send aspect_ratio: "21:9" in the request and check supported_aspect_ratios in GET /v1/videos/models first: a ratio a model does not advertise gets a 400, not a crop.

Which rows list 21:9

The ratios below come from the capability records in the Video Router catalog and the /v1/videos descriptor. The Router catalog also lists auto and adaptive for some rows, but those two are not in the /v1/videos ratio list.

Per-second prices for the MiniMax rows

The MiniMax rows are billed per second, so the cost of a 21:9 clip is easy to compute. Seedance rows are billed per video token and are not tabulated here.

Request

A 21:9 text-to-video job on H3 Max. There is no audio field; the model always makes stereo audio.

curl -X POST "https://api.sume.com/v1/videos" \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"minimax-h3-max","prompt":"A lone rider crosses a salt flat at dusk, wide anamorphic look","duration":5,"resolution":"768p","aspect_ratio":"21:9"}'

Choosing

For a longer ultrawide shot, Seedance 2.5 is the only 21:9 row that runs past 15 seconds, up to 30. For the lowest-priced test of a composition, run minimax-h3 at 480p first. If your final needs 1080p, use H3 Max or a Seedance row. Remember that the 1080p tier on H3 Max is a latent refinement from a native 768p render.

If you need a 21:9 look from a model without the ratio, generate 16:9 and crop on a timeline; the crop discards pixels, so shoot the subject centered.

• Longest 21:9: Seedance 2.5, 30 seconds.
• Lowest-priced 21:9 draft: MiniMax H3 at 480p.
• Not available: Kling 3, Wan 3.0, Omni Flash, Grok.