LinkedIn video ad sound rate: under 64 kHz, read it with a probe

LinkedIn's video ad specification lists the sound format as AAC or MPEG4 and the sound rate as less than 64 kHz. Common 44.1 kHz and 48 kHz audio sits well under that line. To confirm instead of assuming, run Sume's video inspect on the file: the probe returns has_audio, audio_codec, audio_channels and audio_sample_rate.

The ad spec in one table

The LinkedIn Video Ads Specifications page (read 2026-10-08) gives the figures below. The Sume column names the probe field that lets you test each one on a file you host.

Run the probe

Video inspect reads one clip already on media.sume.com. The default mode is sync and waits up to 30 seconds, then returns 200 with the result or 202 with a queued job. Add frames: false to skip stills. The probe is billed by its Modal compute rather than at a flat rate, so the live cost is whatever your account shows.

curl -X POST https://api.sume.com/v1/video-inspect \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: li-ad-probe-001" \
  -d '{"video_url": "https://media.sume.com/artifacts/artf_demo/ad.mp4", "frames": false}'

If a value fails

There is no sample-rate field on Sume's video tools, so you cannot ask a render to resample. What you can do is route around it. Video trim in exact mode re-encodes the video and remuxes kept audio as AAC, and the Timeline render writes AAC audio. If the probe shows an odd codec such as a non-AAC track, an exact trim gives you AAC in an MP4.

A clip with has_audio: false carries no sound track at all. The page lists captions as optional and does not say sound is required, but a silent file has no rate to check. For a muted autoplay feed, burn captions in with the video captions API; it needs audible speech for speech-to-captions, or authored cues for a silent clip.

Length and size are the other two quick failures. The 500 MB cap is a file-size limit and Sume has no bitrate field, so trim to the shortest cut that carries the message and check size_bytes on the result.

Two numbers worth computing

Sound rate: 48 kHz is 75% of the 64 kHz ceiling and 44.1 kHz is about 69%, so the line only bites for unusual masters. Size: 500 MB is 4,000 megabits, so a 30-minute ad that fills the cap averages about 2.2 Mbps (4,000 / 1,800), while a 30-second ad could carry over 130 Mbps before reaching it. The size cap matters for the long end of the 3 second to 30 minute window, and for nothing else.

A sensible pre-flight order is: container, then codec and sound rate, then duration, then dimensions and ratio, then size. The first three come from one probe, the last two from the same probe, so one call covers the list.

Scope

This post covers file checks. It does not submit an ad to LinkedIn, and it does not cover targeting or the campaign API. LinkedIn can change the figures; confirm on the page before a production run.