# render_video_timeline

Compose assets the user already has into ONE finished video and return immediately with a handle.

This is the video editor: stitch or sequence clips, add transitions, overlay text/logos/CTAs, layer  
audio, arrange side-by-side or picture-in-picture, repeat a clip. Use it for any such edit — composing  
existing assets is distinct from generating new content with \`execute\_forge\` or a workflow.

Call \`estimate\_video\_timeline\_price\` with the same timeline first to learn the price, and confirm with  
the user before rendering when it is high. Do not ask the user about optional editing details (clip  
trimming, audio mixing, transition timing) — pick sensible defaults, render, and say what you chose.

Rendering is asynchronous and produces exactly one video. Check the returned \`generation\_id\` with  
\`get\_generation\_run\`.

## Parameters

| Parameter                  | Type                      | Default | Description                                                                                                                                                                       |
| -------------------------- | ------------------------- | ------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| workspace\_idrequired      | string (uuid)             | —       | The user's workspace id.                                                                                                                                                          |
| session\_id                | string (uuid)             | —       | The Session ID to attach the results to.                                                                                                                                          |
| session\_name              | string                    | —       | Creates a new session with this name. One of \`session\_name\` or \`session\_id\` must specified, but not both.                                                                   |
| templaterequired           | TimelineTemplate          | —       | Timeline layout designed in the editor. Tracks, items, timing, and slot references.                                                                                               |
| tracks                     | TimelineTemplateTrack\[\] | —       | Ordered list of tracks in the timeline. Composited in reverse order (Track 1 is on top). Do not overlap items within the same track; use multiple tracks for overlapping content. |
| idrequired                 | string                    | —       | Unique identifier for the track.                                                                                                                                                  |
| namerequired               | string                    | —       | User-facing name of the track.                                                                                                                                                    |
| itemsrequired              | any\[\]                   | —       | Ordered list of items on this track.                                                                                                                                              |
| transitions                | any\[\]                   | —       | Transitions on the seams between adjacent items on this track.                                                                                                                    |
| disabled                   | boolean                   | false   | Whether the track is excluded from rendering.                                                                                                                                     |
| fps                        | integer≤120, >0           | 30      | Frames per second of the output video.                                                                                                                                            |
| width                      | integer2–7680             | 1920    | Width of the output video, in pixels. Must be even.                                                                                                                               |
| height                     | integer2–4320             | 1080    | Height of the output video, in pixels. Must be even.                                                                                                                              |
| codec                      | string                    | h264    | Video codec for encoding the output. Only h264 is supported.                                                                                                                      |
| crf                        | integer0–51               | 18      | Constant Rate Factor controlling output quality. Lower values produce higher quality.                                                                                             |
| max\_duration\_in\_seconds | number≤120, >0            | —       | Maximum allowed duration of the rendered video, in seconds.                                                                                                                       |
| playback\_rate             | number≤4, >0              | 1       | Global playback speed multiplier. 1.0 = normal, 2.0 = double speed, 0.5 = half speed.                                                                                             |
| videos                     | object                    | —       | Slotted video assets. Each slot name matches a slot reference in the timeline template.                                                                                           |
| images                     | object                    | —       | Slotted image assets. Each slot name matches a slot reference in the timeline template.                                                                                           |
| audios                     | object                    | —       | Slotted audio assets. Each slot name matches a slot reference in the timeline template.                                                                                           |