LinkedIn video ad 360 to 1920 px range: downscale a 4K master

A 3840x2160 master is twice too wide for a LinkedIn video ad: the spec (read 2026-10-08) allows width and height from 360 to 1920 pixels. Scale it to 1920x1080 with Sume's video trim in exact mode by sending output: { width: 1920, height: 1080 } and a full-length range. The output stays 16:9, which is the widest ratio the ad allows (maximum 1.778).

What LinkedIn lists

The LinkedIn Video Ads Specifications page gives recommended dimensions by format, which also set the ceiling. Aspect ratios run from 9:16 (minimum, 0.563) to 16:9 (maximum, 1.778).

Scaling to the limit

The trim API accepts an optional output with width and height between 256 and 2160 and fps of 24, 25, 30 or 60. It works only with precision: "exact"; with keyframe you get video_trim_output_requires_exact. Match the ratio yourself: 1920 / 1080 is 16:9, so a 16:9 master does not distort. Pick a different pair for other ratios, such as 1080x1350 for 4:5. The docs describe the field as a conform and do not say whether a mismatched ratio is padded or stretched, so keep the ratio equal to the source.

{
  "video_url": "https://media.sume.com/artifacts/artf_demo/master-4k.mp4",
  "start": 0,
  "duration": 30,
  "precision": "exact",
  "output": { "width": 1920, "height": 1080, "fps": 30 }
}

Checks on the result

Poll GET /v1/jobs/:id/status and then read GET /v1/jobs/:id/result, which returns kind: video_trim with the new video_url, duration_seconds and actual_start_seconds. Run video inspect on the new file and compare width, height, fps and size_bytes with the table: both sides at 1920 or below, 30 fps, and under 500 MB.

A 30-second 1080p clip is far below 500 MB, so size is rarely the blocker for short ads. The more frequent failure is the sound rate or the length; see the related checks. Each trim is a $0.02 job.

Other masters

Scaling is half the story when the master is not exactly 16:9. A DCI 4K file at 4096x2160 has a ratio of 1.896, which is wider than the 1.778 maximum, so it needs a crop before the scale. Cropping the width to 2160 x 16 / 9 = 3,840 pixels is a width fraction of 3840 / 4096 = 0.9375, centered with x = 0.03125; that gives 3840x2160, which then scales to 1920x1080. Do the crop with video filter and the scale with video trim, in that order.

• 3840x2160 (16:9): trim output 1920x1080. That is 25% of the pixels (2,073,600 against 8,294,400).
• 2160x3840 (9:16): trim output 1080x1920, the recommended vertical size.
• 4096x2160 (1.896): filter crop with width 0.9375 and x 0.03125, then trim output 1920x1080.

Source limits

The trim source can be up to 1,800 seconds and the output up to 900. Anything longer than 15 minutes needs a split or a Timeline render, which takes up to 1,800 seconds of audio spine and 200 video slots. LinkedIn's ad length range is 3 seconds to 30 minutes, so a 30-minute ad is a Timeline job rather than a trim job.