Classroom projector lesson video in 4:3: set the avatar aspect ratio

For a classroom projector that still shows 4:3, set aspect_ratio to "4:3" on POST /v1/avatar-1.0/talking-video. If you omit it you get the default, 9:16, which is a tall phone-shaped video that will sit as a narrow strip on a projector. Resolution is currently 720p and the duration window is 4 to 60 seconds.

Source: Avatar videos, read 2026-10-04.

Supported ratios

The five supported ratios cover most classroom screens, phones and slide decks.

Request

Because lesson scripts are often over a minute, split them into several videos. The limit is 60 seconds per video, and inline captions are limited to videos of 60 seconds or less.

curl -X POST https://api.sume.com/v1/avatar-1.0/talking-video \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: fractions-lesson-1" \
  -d '{
    "avatar_handle": "mr_okafor",
    "aspect_ratio": "4:3",
    "quality": "standard",
    "script": "Today we compare fractions with different denominators. Start by finding a common denominator.",
    "scene": { "type": "prompt", "prompt": "A classroom whiteboard with a clean marker tray" },
    "captions": { "enabled": true, "style": "slam", "language": "en" }
  }\

Check the frame first

To see the framing before the full render, use Avatar video previews. The aspect ratio is part of the request and cannot be overridden at generate-video, so a wrong ratio means a new preview.

One idea per video

Split a long lesson into several clips of 60 seconds or less, one concept each, and reuse the same avatar_handle and scene so the teacher looks the same across the set. Name each video with title so the set stays in order in your workspace.