Timeline renders 1080x1920 by default: set size for square or 16:9

You joined clips on Sume and the result is tall and narrow. That is the default: Timeline 1.0 outputs a 1080 by 1920 MP4 unless you say otherwise, which is 9:16 and suits Reels, Shorts and TikTok.

To change it, set output.width and output.height. Both must be even integers from 256 to 2160. video[].fit decides how a source fills the frame: cover (default), contain, stretch or blur.

Sizes that fit the limits

All four sizes use even numbers within range. A 4K width of 3840 does not fit, since the cap is 2160.

Set it in the request

import json
import os

sizes = {"square": (1080, 1080), "wide": (1920, 1080), "tall": (1080, 1920)}
w, h = sizes[os.environ.get("SHAPE", "square")]
body = {
    "audio": {"mode": "silence", "duration_seconds": 10},
    "video": [{"source_url": "https://media.sume.com/artifacts/artf_demo/a.mp4", "start": 0, "duration": 10, "fit": "blur"}],
    "output": {"width": w, "height": h},
}
print(json.dumps(body, indent=2))

Post the body to /v1/timeline-1.0/render with an Idempotency-Key. The rate is $0.10 per output minute, rounded up, whatever the size.