Video trim end past the clip: trim_clamped_to_source and a short ad

If end is after the end of the source, Sume video trim does not fail. It clamps the range to the source and puts the warning trim_clamped_to_source in the result. So a request for start: 0, end: 20 on a 15-second clip returns a 15-second MP4 as a successful job, and a script that only checks for errors would pass it on. If your target is a 20-second spot, read duration_seconds in the result.

What the API does with a range

Video trim 1.0 takes one Sume-hosted clip and exactly one of end or duration. The output is a new MP4 and costs $0.02 a job. The limits from the docs (read 2026-10-08) are below.

Why it matters for ad specs

Platform specs have both a floor and a ceiling. The TikTok page (read 2026-10-08) allows up to 10 minutes for non-Spark ads, and it sets 540x960 and 516 kbps as minimums. The page facts used here give no minimum length, but a creative brief often does. A clamp silently turns a 20-second brief into a 15-second file. The fix is a check in your code, and it is two lines: compare duration_seconds with what you asked for, and compare the list of warnings.

import math

def trim_ok(result: dict, asked_seconds: float) -> bool:
    warned = any("trim_clamped_to_source" in str(w) for w in result.get("warnings", []))
    return not warned and math.isclose(
        result["duration_seconds"], asked_seconds, abs_tol=0.1
    )

print(trim_ok({"duration_seconds": 15.0, "warnings": [{"code": "trim_clamped_to_source"}]}, 20))
print(trim_ok({"duration_seconds": 20.0}, 20))

Reading the result

A finished trim returns kind: video_trim with video_url, duration_seconds, actual_start_seconds, precision, audio, output and the optional warnings[]. Three fields tell you whether the file is the one you asked for. duration_seconds is the real length. actual_start_seconds is the real in-point, which can differ from start under precision: keyframe. warnings[] lists soft problems such as the clamp. A job that carries a warning is still a finished job, billed at $0.02, so a retry costs another $0.02. Fix the request before you retry, or you will pay twice for the same short file.

• Asked 20 s, got 15 s: the source was 15 s. Check the clip, not the API.
• Asked 20 s from start: 10, source 15 s: the cut is 5 s long, so the clamp is larger than it looks.
• The check costs nothing: a probe with frames: false reads the duration first.

Use `duration` when you want a length

With duration you state the length you want, and with end you state a point in the source. For a fixed-length cutdown, duration reads more clearly. Combine it with video_inspect first if you do not know the source length: a probe with frames: false is enough, and it gives the duration before you pay the $0.02. The warnings[] field is optional, so treat a missing field as no warnings.