Problem
In src/lib/ffmpeg.ts, the buildVideoFilter function uses a fallback of
999999 when trimEnd is null:
const end = recipe.trimEnd !== null ? recipe.trimEnd : 999999;
filters.push(`trim=start=${recipe.trimStart}:end=${end}`);The FFmpeg trim filter with an explicit end timestamp must decode the video
up to that timestamp to find the end point. When trimEnd is null (meaning
no trim is needed), the filter is still applied with end=999999, forcing
FFmpeg to decode and scan through the entire video duration rather than
treating it as pass-through.
For a 2-hour video (7,200 seconds), this is harmless for the content but
wastes processing time. For unusual container formats that require full seek
to determine duration, this can add significant overhead.
Additionally, if a user sets trimEnd to a value beyond the actual video
duration, FFmpeg silently outputs a shorter video with no warning to the user.
Suggested Fix
- Only add the
trim filter when trimStart > 0 or trimEnd !== null:
if (recipe.trimStart > 0 || recipe.trimEnd !== null) {
const endVal = recipe.trimEnd ?? Number.MAX_SAFE_INTEGER;
filters.push(`trim=start=${recipe.trimStart}:end=${endVal}`);
filters.push("setpts=PTS-STARTPTS");
}-ss and -to input/output flags for faster
seeking instead of the trim video filter.
- When
trimEnd exceeds the video duration, clamp it to the actual duration
and show a warning in the UI.
Problem
In
src/lib/ffmpeg.ts, thebuildVideoFilterfunction uses a fallback of999999whentrimEndisnull:The FFmpeg
trimfilter with an explicit end timestamp must decode the videoup to that timestamp to find the end point. When
trimEndisnull(meaningno trim is needed), the filter is still applied with
end=999999, forcingFFmpeg to decode and scan through the entire video duration rather than
treating it as pass-through.
For a 2-hour video (7,200 seconds), this is harmless for the content but
wastes processing time. For unusual container formats that require full seek
to determine duration, this can add significant overhead.
Additionally, if a user sets
trimEndto a value beyond the actual videoduration, FFmpeg silently outputs a shorter video with no warning to the user.
Suggested Fix
trimfilter whentrimStart > 0ortrimEnd !== null:-ssand-toinput/output flags for fasterseeking instead of the
trimvideo filter.trimEndexceeds the video duration, clamp it to the actual durationand show a warning in the UI.