MiniMax H3 aspect ratios: 21:9 to 9:16, and when adaptive works

MiniMax H3 supports six aspect ratios: 21:9, 16:9, 4:3, 1:1, 3:4 and 9:16, which covers ultra-wide down to vertical. Sume accepts the same six on minimax-h3 and minimax-h3-max, and its code accepts adaptive only on reference-to-video.

Ratios are from MiniMax's model card and fal's guide; Sume's rules from the Video generation docs and code, read 2026-09-29.

Which ratio for which platform?

What does adaptive do?

fal's guide says that on reference-to-video you can set aspect ratio to adaptive and let H3 choose. In Sume's code adaptive is forwarded only for reference requests; on text-to-video it is refused with a message to use one of the six ratios.

What ratio does an image-to-video clip get?

fal's guide says first and last frame output follows the aspect ratio of the uploaded image. Sume's H3 image-to-video route does not forward aspect_ratio, so crop your frame to the ratio you want. See first and last frame to video.

Do 3:2 and 2:3 work?

They are in Sume's general ratio list for video, but not in this model's six. Each model advertises its own subset in supported_aspect_ratios; read it from GET /v1/videos/models before you submit.