Reframe 16:9 to 9:16: crop fractions for left, center, right

To turn a 16:9 clip into 9:16 with Sume video filter, crop a column that is 0.3164 of the frame wide and the full height. Set x to 0 for a subject on the left, 0.3418 for a centered subject, and 0.6836 for a subject on the right.

Luma lists a Reframe feature for Ray 3.2. Sume does not run Ray 3.2, but it can reframe any MP4 you import, as plain geometry.

Where 0.3164 comes from

A 9:16 window inside a 16:9 frame keeps the full height, so its width is (9/16) divided by (16/9) of the source width, which is 81/256 = 0.3164. The video filter docs take crop values as fractions of the source frame, with width and height in [0.05, 1], x and y in [0, 1], and x+width and y+height no more than 1. The compiler rounds to even values for yuv420p.

On a 1920 px wide source, 0.3164 is about 608 px. That is a narrow column, so expect a later enlargement to 1080x1920 to soften the picture by about 1.8x.

The three crop programs

Run the check first

POST /v1/video-filter/check validates the same program as the encode and is free. It creates no job and reserves nothing. The encode costs $0.02 per job and needs an Idempotency-Key.

curl -X POST https://api.sume.com/v1/video-filter \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: reframe-center-001" \
  -d '{"video_url":"https://media.sume.com/artifacts/artf_demo/wide.mp4",
       "ops":[{"op":"crop","x":0.3418,"y":0,"width":0.3164,"height":1}]}'

Then land it in 1080x1920

The filter result keeps the source frame rate and audio unless the program changes them, and returns a new MP4. The default Timeline 1.0 output is 1080x1920, so place the cropped clip in a one-slot render with the default cover fit. If you want to keep the full wide shot instead of cropping, blur fit is covered in a separate post.

A subject that moves across the frame

A single crop is a fixed window. Sume's filter crop does not follow a subject, and the docs do not describe a tracking or subject-aware reframe. If the subject crosses the frame, cut the clip with video trim into two ranges and crop each with its own x, then join them in Timeline. For a shot that stays in one place, one crop is enough.

Other source ratios

The same formula works for any source. For a 4:3 source, a 9:16 window is (9/16) divided by (4/3) of the width, which is 0.4219. For a 1:1 source it is 0.5625. For a 21:9 source it is 0.2411. The rule is the target ratio divided by the source ratio, with the full height kept. Always keep x + width at 1 or less, or the check returns video_filter_crop_out_of_bounds.

A 16:9 to 4:5 feed crop is (4/5) divided by (16/9) = 0.45 of the width.

Quality and the audio track

Cropping then enlarging trades resolution for framing. A 1080p wide clip gives about a 608 px wide column, which is enlarged about 1.8 times to reach 1080 px. If you can, generate the vertical version directly: Seedance 2 lists 9:16 and Omni Flash 1.1 accepts 16:9 or 9:16. Reframing is for footage that already exists.

The filter output keeps the geometry, frame rate and audio of the source unless the program changes them, so a cropped clip keeps its sound. The source must be 300 seconds or shorter.

Before you build

Before you build, read the linked Sume docs page for the exact request fields, limits and prices, because those pages are the source of truth and can change. Run one short, cheap test with your own material first, check the output in a player and in your editor, and only then scale to the full shot list. Keep every job id and file you approve, so a later change never forces you to regenerate work that was already signed off. Note that this post describes Sume's catalog and tools; Sume does not run Luma Ray 3.2, and nothing here claims HDR or EXR output.