Snapchat Commercials need H.264: trim keyframe copies the source codec

Snapchat lists mp4 or mov files that are H.264 encoded for Commercials. In Sume's video trim, precision exact re-encodes with libx264 and yuv420p, so its output is H.264. Precision keyframe is a stream copy, so it keeps whatever codec the source had. If your source might be HEVC, as some phone recordings are, use exact or probe the result first.

What each side says

The Snapchat figures come from its ad format page and the Sume figures from the video trim and video inspect docs.

Choosing the precision

Keyframe is faster in principle and does not re-encode, but it gives up two things for this use. The codec stays as it was, and the start can land a GOP early, so the cut can be longer than you asked for. For a Commercial that must stay inside 3 to 6 seconds or start at a precise point, neither is a good trade.

Exact costs the same $0.02 per job as keyframe (Sume catalog, read 2026-10-08), so there is no price reason to prefer the copy. Use keyframe only when you have already confirmed the codec is H.264 and the exact start is not important.

A short routine

Run video inspect with frames set to false on the source and read video_codec. If it reads h264, either precision gives an H.264 file. If it reads anything else, use exact. After trimming, probe the result once more and check three fields: video_codec, width and height, and duration_seconds.

Remember the size. Snapchat lists 720x1280, and a trim with exact precision can conform the output width, height and fps in the same job, so one exact job can both cut and resize. Width and height must be 256 to 2160 and fps one of 24, 25, 30 or 60.

Do not read more into the Snapchat line than it says. The page lists H.264 for Commercials, and it lists mp4 or mov as the containers. Other formats on the same page list file types without naming the codec, so only apply the codec check to Commercials.

If the probe shows a pixel format other than yuv420p, exact trimming also converts it, because the docs name yuv420p for the exact output. That is another reason to prefer exact when the source came from an unknown camera or app.

• Cost: $0.02 per trim job, plus the probe's Modal compute.
• The conform option is exact only; sending it with keyframe returns video_trim_output_requires_exact.