AI game trailer generator: 4-30 s shots joined in Timeline

There is no single "trailer" endpoint. You generate each beat of the trailer as its own seedance-2.5 shot (4 to 30 seconds each), then cut the shots together with Timeline 1.0, which can put a fade, wipeleft or similar transition between slots.

ByteDance's launch post describes Seedance 2.5 as taking images, video clips and audio clips as references in one pass, which is how you keep a game's characters and look consistent across shots. Sume's side is from the video docs and Timeline docs, read 2026-10-01.

How long can each trailer shot be?

Sume's video docs say limits are not uniform across models: seedance-2.5 accepts 4 to 30 seconds. A trailer beat such as a logo reveal can be 4 seconds; a combat sequence can use up to 30. The docs name only a few models with ranges that long; check GET /v1/videos/models for the model you pick.

How do I keep the game's look the same across shots?

Send your key art, character sheets or a gameplay capture as input_references. The docs say audio and video references are honored by the Seedance 2.x models, so a gameplay clip can steer motion and a music file can steer rhythm. Only models whose supported_input_references lists a type accept it, so read the catalog entry first. For blocking out camera moves with a 3D model, see Seedance 2.5 clay render.

How do I join the shots with transitions?

Import each finished clip to media.sume.com with POST /v1/media-imports, then render a Timeline with one video[] slot per shot and an audio spine (audio.duration_seconds, 1 to 1800). Transitions go on slots after the first.

What should I do first?

Write the trailer as a shot list, generate the shots one request each, and run the unbilled Timeline /plan preflight before you pay for the render. Trailers usually want hard cuts on beats and a short transition only at tonal shifts; the 8-fade limit nudges you the same way.