LinkedIn video ad under 30 FPS and 4:5: what to render

For a LinkedIn video ad at 4:5, render 720 by 900 at 24 or 25 frames per second, since the spec asks for under 30 FPS. Sume's video generation catalog lists no 4:5 ratio, so the clean route is to generate at 3:4 or 9:16 and let Timeline 1.0 fit it to 720 by 900, then check the finished file.

The spec

These come from LinkedIn's help page. Re-read it before you submit, since ad specs change.

Render 4:5 in Timeline

Timeline output width and height are even integers from 256 to 2160, so 720 by 900 is valid. output.fps accepts 24, 25, 30 or 60, so pick 24 or 25: 30 is not under 30. Each slot has a fit mode, and cover (the default) fills the frame by cropping, so a 3:4 source is trimmed slightly to 4:5.

Without an explicit output.fps the render follows the source rate, and a rate change repeats or drops frames and can look juddery, so set fps deliberately.

curl -X POST https://api.sume.com/v1/timeline-1.0/render \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: linkedin-45-001" \
  -d '{
    "audio": { "url": "https://media.sume.com/artifacts/artf_demo/vo.wav", "duration_seconds": 20 },
    "video": [
      { "source_url": "https://media.sume.com/artifacts/artf_demo/shot.mp4", "start": 0, "duration": 20, "fit": "cover" }
    ],
    "output": { "width": 720, "height": 900, "fps": 25 }
  }'

Check the result against the spec

Run video inspect on the render. With frames set to false you get probe facts only; read them for frame rate, size and audio. I do not assume the codec from the render docs, so confirm H.264 and AAC in the probe before upload, and check the file size against the 500 MB ceiling.

For the thumbnail, ask video inspect for one still as png or jpeg and check its size against the 2 MB limit.

curl -X POST https://api.sume.com/v1/video-inspect \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: linkedin-probe-001" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/artf_demo/render.mp4",
    "frames": { "at": [1], "format": "jpeg", "max_edge": 900 }
  }'