Product still 30%, clip 70%: compose stack ratio in pixels

In a Sume stack compose, layout.ratio is the still's share of the frame, from 0.1 to 0.9, and the video gets the exact remainder. On the default 1080x1920 output, ratio: 0.3 gives a 576-pixel product still above a 1344-pixel clip. The default 0.5 is the half-banner split.

The reason to care this week: product trends move quickly. Exploding Topics' September 21 update lists massage comb at +12,800%, egg weights at +4,300% and wireless meat thermometer at +2,500% (Exploding Topics, read 2026-10-04). A clip of someone using a gadget with the product photo pinned above it is a common way to show one; the ratio decides how much of the screen the photo gets.

The ratio table for 1080x1920

On a horizontal split the ratio applies to the 1920-pixel height. The still's region is ratio times the height and the video region is what is left. Both numbers below are straight multiplication from the timeline compose docs defaults; they do not include any encoder rounding.

Vertical splits use width

With split: "vertical" the still takes left or right and the ratio applies to the 1080-pixel width. A 0.4 ratio leaves 432 pixels for the still and 648 for the video, which is narrow for a landscape clip. Keep image_region on the matching axis or the request fails with compose_image_region_wrong_axis; top and bottom belong to a horizontal split.

Request with ratio 0.3

Both URLs must already be this workspace's media.sume.com artifacts. The still must probe as a still and the video as a video. Output length always comes from the video layer, and the still is held for the whole clip.

import os, requests

HEIGHT = 1920
for ratio in (0.2, 0.3, 0.4):
    still = round(HEIGHT * ratio)
    print(ratio, still, HEIGHT - still)

resp = requests.post(
    "https://api.sume.com/v1/timeline-1.0/compose",
    headers={
        "Authorization": f"Bearer {os.environ['SUME_API_KEY']}",
        "Idempotency-Key": "compose-ratio-0-3-001",
    },
    json={
        "operation": "stack",
        "image": {"url": "https://media.sume.com/artifacts/artf_demo/product.png"},
        "video": {"url": "https://media.sume.com/artifacts/artf_demo/demo.mp4"},
        "layout": {"split": "horizontal", "image_region": "top", "ratio": 0.3},
        "output": {"width": 1080, "height": 1920},
    },
    timeout=60,
)
print(resp.status_code, resp.json().get("request_id"))

Compose is flat $0.02 per job; confirm in GET /v1/catalog. Poll GET /v1/jobs/:id/status and read GET /v1/jobs/:id/result for video_url. Nothing here predicts which ratio performs better; test two ratios on the same clip.