Square YouTube Short at 1080x1080: set Timeline output size

YouTube's Shorts help page says a video needs "a square or vertical aspect ratio" to be classified as a Short up to three minutes, and that creators wanting long-form should use a wider ratio such as 16:9. Square is allowed, and it is a smaller canvas to fill.

Setting the size

Timeline 1.0 defaults to a 1080 by 1920 MP4. output.width and output.height accept even integers from 256 to 2160, so 1080 by 1080 is a valid square. Each slot has fit with cover (default), contain, stretch, or blur.

Pick the fit

A 9:16 clip on a square canvas loses its top and bottom under cover. Under contain it keeps the frame and leaves side bars. Under blur the bars are filled with a blurred copy. Decide which loss you accept before you batch.

Render body

A minimal square render body, ready to POST to the render route with an Idempotency-Key.

import json

body = {
    "audio": {"mode": "silence", "duration_seconds": 12},
    "video": [{
        "source_url": "https://media.sume.com/artifacts/example/vertical.mp4",
        "start": 0, "duration": 12, "fit": "blur",
    }],
    "output": {"width": 1080, "height": 1080},
}
print(json.dumps(body, indent=2))