16:9 avatar video for slides and webinars: aspect ratio on Sume

For a landscape slide or webinar intro, set aspect_ratio to 16:9 on the avatar video request: Sume supports 1:1, 3:4, 9:16, 4:3 and 16:9, defaults to 9:16, and currently renders at 720p only (read 2026-10-03). A 45-second 16:9 clip on Plus costs about $11.025 at the listed no-product rate.

The default is vertical because most avatar clips go to phone feeds. If you forget the field when making a lesson intro, you will get a tall video that needs letterboxing.

Choosing the ratio

The avatar video docs list the five ratios without stating a price difference, and the pricing page I read lists per-second rates by tier and product, not by aspect ratio. So choose by destination, not cost.

Use 16:9 for slide decks, webinar intros and web hero embeds; 4:3 for older slide templates and some LMS players; 9:16 for Shorts, Reels and TikTok; 1:1 and 3:4 for feed posts. For a talking head over slides, you may want the avatar in a corner, which is a Timeline composition task rather than an avatar setting.

A landscape request

Set the ratio explicitly and keep your script within 4 to 60 seconds. If the scene should look like a studio rather than a bedroom, direct it with a scene prompt, and keep the same prompt across a series so every lesson shares one set.

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: webinar-intro-001" \
  -d '{
    "avatar_handle": "webinar_host",
    "aspect_ratio": "16:9",
    "quality": "plus",
    "scene": {"type": "prompt", "prompt": "Bright modern studio, soft key light, plain background"},
    "script": "Welcome to today\u0027s session. In the next forty minutes we will walk through three ways to cut onboarding time in half."
  }'

What 720p means for slides

Because the resolution is currently fixed at 720p, a full-screen 1080p slide deck will have an avatar that is sharper at small sizes than at full-screen. Use the avatar as an inset, not a full-frame background, and keep text-heavy slides as separate images. If you need higher resolution for a final deliverable, check the docs for the current upscaling options rather than assuming.

Run a preview first. A landscape preview shows you whether the framing leaves space on the side for slide content, before you pay for the full render.

• Keep a consistent scene prompt for all lessons in a course.
• Use captions for accessibility; the inline caption styles burn into the final MP4.
• Test one slide and one clip together before producing the series.

Cost for a webinar series

A six-part webinar series with a 45-second host intro each is 270 seconds, which costs $49.68 on Standard, $66.15 on Plus and $148.50 on Max at the listed no-product rates (read 2026-10-03), plus $0.95 for the host avatar once. Because the aspect ratio does not appear in the rate card, you can switch between 16:9 for the webinar page and 9:16 for the social cut without changing the unit price, though each is its own render and its own bill.

That last point is worth planning for. A 16:9 clip cannot be re-cropped to a good 9:16 clip, since the avatar is framed for the wide shot. If you need both formats, budget two renders per intro, or use a preview for each to confirm the framing before paying for the full video.

Two checks before you render

Read the script aloud with a timer. Sume estimates duration from the text, and the estimate has to land between 4 and 60 seconds, so a 45-second intro should be roughly 110 words at a calm webinar pace. If you are near 60 seconds, split the intro into two jobs.

Then check the scene prompt for anything that clashes with a wide frame. A prompt that describes a desk close-up will look odd in 16:9. Describe the room, the light and the camera distance instead, and keep the description identical across the series.