Instagram carousel crops to the first image: crop stills to match

Crop the clip once with POST /v1/video-filter, then take every still from the cropped file so all slides share the first slide's shape. Meta's guide says "Carousel images are all cropped based on the first image in the carousel, with the default being a 1:1 aspect ratio."

What does Meta's rule mean for stills?

The first image sets the crop for the rest, so a set of stills with mixed shapes will be cropped based on slide one. Frames from one video share the source's shape, which avoids the surprise, and a crop first lets you choose that shape.

How do I crop a 16:9 clip to a square?

A crop op takes fractional x, y, width and height. For a 1920 by 1080 source, a width fraction of 0.5625 with full height is 1080 by 1080, and x 0.21875 centers it. Sume rounds crop results to even numbers for yuv420p, and a check route (/v1/video-filter/check) is free.

curl -X POST https://api.sume.com/v1/video-filter \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: square-crop-001" \
  -d '{
    "video_url": "https://media.sume.com/artifacts/artf_demo/wide.mp4",
    "ops": [{ "op": "crop", "x": 0.21875, "y": 0, "width": 0.5625, "height": 1 }]
  }'

Then how do I get the stills?

Pass the filter result's video_url to POST /v1/video-frames with at[]. Every frame then has the cropped shape, and max_edge clamps the long edge if you want a smaller file. A video filter job costs $0.02.

What should I check?

Read width and height in frames[] and confirm they match. Sume's docs do not describe how Instagram crops when shapes differ, so that behavior stays Meta's; re-read the guide if it matters.

Which ratio should I pick?

Meta's default is 1:1, so a square is the case you do not have to think about. If your first slide is another shape, the rest are cropped to it. Keep the important content in the middle of each frame so a crop does not cut it, and choose the first slide deliberately since it decides the rest.

• Square: matches Meta's stated default.
• Other shapes: the first slide sets the crop for all.
• Crop before extracting, so the shape is decided by you and not by the carousel.