4:5 feed video on a 9:16 canvas: cover, contain or blur?

A 4:5 video, 1080x1350, sits inside Instagram's range for photos, 1.91:1 to 3:4, so it works as a feed post. Put it on a 9:16 Reel canvas of 1080x1920 and the shapes differ, so something has to give. Sume's Timeline has three ways to resolve that, and the numbers show what each costs you.

The ranges are from Instagram's photo resolution page and the Reel size page, both read 2026-10-03. The Reel page puts 9:16 at the tall end of its range, so a 1080x1920 canvas is the tallest shape a Reel can take.

The arithmetic

cover scales the clip to fill the canvas. 1920 / 1350 is 1.422, so the clip becomes 1536 wide and the crop keeps 1080 of 1536 columns, 70.3 percent of the width. contain scales the clip to the canvas width, 1080x1350, and pads the remaining 570 rows with black, 285 on top and 285 on the bottom. blur places the same 1080x1350 clip over a blurred copy that fills the canvas.

Choose by what is at the edges

If the subject is centred and nothing is written near the left or right edges, cover gives the fullest frame. If there is text near the edges, or a person at the side, use contain or blur. Blur is the usual choice for a Reel, and the compiler draws the foreground fitted to the canvas width over the blurred copy.

Render with blur

Timeline's default output is 1080x1920, so no output object is needed. A 30-second clip costs $0.10 at the public rate of $0.10 per started output minute.

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: feed-to-reel-001" \
  -d '{
    "audio": { "mode": "silence", "duration_seconds": 30 },
    "video": [{
      "source_url": "https://media.sume.com/artifacts/artf_demo/feed-4x5.mp4",
      "start": 0,
      "duration": 30,
      "fit": "blur"
    }]
  }'