Vidu Q4 Preview aspect ratios vs Sume video rows: who offers 21:9, 4:3

Vidu Q4 Preview's reference-to-video endpoint lists five aspect ratios: 1:1, 9:16, 16:9, 3:4 and 4:3. On Sume the set depends on the row. Seedance and the MiniMax H3 rows list those five plus 21:9, Wan 3.0 lists the five, Kling 3 offers 16:9, 9:16 and 1:1, and Gemini Omni Flash 1.1 offers only 16:9 and 9:16. None of the catalog rows lists 4:5, so a feed-portrait clip needs a crop from 3:4 or 1:1.

The comparison

Sume validates the aspect ratio against the row's advertised list, so a ratio that a model does not advertise returns a 400 instead of a quiet fallback. Several rows also accept auto or adaptive, which let the model follow the input image. Read the exact list from supported_aspect_ratios.

Pick a row by the delivery format

Work backwards from where the clip will be published. A phone feed or Shorts slot wants 9:16, which every row above offers. A square post wants 1:1, which excludes Omni. A cinematic banner at 21:9 is possible only on the Seedance and H3 rows.

Steps:

• List the ratios you need to deliver, for example 9:16, 1:1 and 16:9.
• Remove rows that do not list all of them.
• Among what remains, choose on price, duration and reference needs.
• Send aspect_ratio explicitly in the request instead of relying on a default.

curl -X POST https://api.sume.com/v1/videos \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"minimax-h3","prompt":"Wide skyline at dusk, slow drift","aspect_ratio":"21:9","resolution":"768p","duration":6}'

The 4:5 gap

Instagram's portrait format is 4:5, and neither Vidu's five ratios nor the Sume rows include it. The practical route is to generate 3:4 and crop the top and bottom edges slightly, or to generate 1:1 and accept the extra headroom. Keep the subject in the centre third so a crop does not clip it.

Costs do not change with ratio on the per-second rows, so the choice is about composition, not budget. Wan 3.0 at 720p is $0.125 a second whether the frame is 9:16 or 1:1.

Checking before you submit

A mismatch between ratio and row is the kind of error that is cheap to catch early and annoying to catch in a batch. If a script submits fifty jobs and the model rejects the ratio, the first 400 tells you, but only after you have queued work.

Add a pre-flight check to your submit script. Fetch the catalog once per run, look up the row, and compare your aspect_ratio, resolution and duration against supported_aspect_ratios, supported_resolutions and supported_durations. Fail the whole batch before the first POST if any shot is out of range. It adds one GET to the run and spares you partial batches.

What Sume does not do

Sume does not offer a custom pixel size on video: size returns 400 unsupported_parameter, so use resolution plus aspect_ratio. It also does not list a Vidu row.