Put a slide above an AI presenter with Timeline compose: $0.02 a shot

Use POST /v1/timeline-1.0/compose with operation 'stack': the slide goes on top and the avatar video below, in one MP4. The public rate is $0.02 flat per job, with no model inference, because it only runs ffmpeg on the worker.

What you need first

Compose takes one still and one video and returns one shot. Putting several shots in sequence is the job of Timeline 1.0.

• A still (the slide) and a video (the avatar clip), both already on media.sume.com for your workspace. Import files first with POST /v1/media-imports.
• An Idempotency-Key header, which is required.
• The slide must probe as a still and the clip as video, or the job fails with compose_image_not_still or compose_video_not_video.

The request

The field that picks stack or overlay is operation. The default layout is a half-banner: slide on the top half, video on the bottom half. ratio is the slide's share of the frame, from 0.1 to 0.9, and the video gets the remainder.

import json, os, urllib.request

body = {
    "operation": "stack",
    "image": {"url": os.environ["SLIDE_URL"]},
    "video": {"url": os.environ["CLIP_URL"]},
    "layout": {"split": "horizontal", "image_region": "top", "ratio": 0.4},
    "output": {"width": 720, "height": 1280, "fps": 25},
    "mode": "sync",
}
req = urllib.request.Request(
    "https://api.sume.com/v1/timeline-1.0/compose",
    data=json.dumps(body).encode(),
    method="POST",
    headers={
        "Authorization": f"Bearer {os.environ['SUME_API_KEY']}",
        "Content-Type": "application/json",
        "Idempotency-Key": "slide-presenter-001",
    },
)
with urllib.request.urlopen(req, timeout=40) as r:
    print(r.status, r.read().decode()[:300])

Layout choices

With mode sync, Sume waits up to 30 seconds for a finished job and returns 200; otherwise you get 202 and poll the job. The output length comes from the video: the still stays on screen for the whole clip.

Cost of a slide deck

A 10-slide explainer, one avatar clip per slide, is 10 compose jobs at $0.02 each, so 10 x $0.02 = $0.20 on top of the avatar render. Ten 12-second clips at standard quality are 10 x 12 x $0.184 = $22.08 before any per-job rounding. The total is about $22.28.

What to do

Start with one slide, one 8-second clip and ratio 0.4. If the presenter's face is too small, move ratio down to 0.3 or switch to the overlay operation. Put the finished shots into a Timeline 1.0 video array to assemble the deck.