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Compose API: render video from a JSON timeline

The compose job renders finished video from a declarative JSON timeline. Tracks, clips, transitions, text, per-clip effects, and scene-first authoring.

API Dashboard

The compose job renders finished video from a JSON timeline. Tracks hold clips. Clips reference video, image, audio, or text assets. Transitions sit between them. You POST the timeline and get an MP4 back, with progress streamed while it renders.

Rendered by compose from the JSON timeline below. No editor, no template.

What the timeline covers

The timeline covers real editing work, not a fixed template. Per-clip effects include color grading, seven look presets, chroma key, seven blend modes, Ken Burns motion, speed control, blur, sharpen, crop, flip, and keyframed opacity with easing. Text carries font, stroke, background, position, entrance animations, and a drop shadow. Output goes to MP4, WebM, GIF, MP3, or a JPG or PNG still of any frame.

import { createClient, outputUrl } from "@rendobar/sdk";


const client = createClient({ apiKey: "rb_YOUR_KEY" });


const job = await client.jobs.create({
  type: "compose",
  params: {
    schemaVersion: 1,
    output: { format: "mp4", resolution: { width: 1080, height: 1920 }, fps: 30 },
    timeline: {
      tracks: [{
        clips: [
          { asset: { type: "video", src: "https://cdn.rendobar.com/assets/examples/sea.mp4" }, start: 0, length: 4 },
          { type: "transition", transition: "crossfade", duration: 1 },
          { asset: { type: "video", src: "https://cdn.rendobar.com/assets/examples/sample.mp4" }, start: 3, length: 4 },
        ],
      }],
    },
  },
});


console.log(outputUrl(await client.jobs.wait(job.id)));
  • Two authoring shapes: primitive tracks for direct multi-track control, and scenes with global overlays for sequential editing. Both compile to the same engine.
  • A clip can hold a nested timeline, so a whole composition drops onto a track as one unit.
  • Live progress streams percent, fps, and render speed while the job runs.

See the Compose API page for a tour of every capability with real renders, or start from the compose reference.

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