When I record a movie on TV, I sometimes wish to archive the movie on my NAS. In that case, I want to remove (at least) the beginning and the end of the recording if the movie was broadcast on a advertisment free channel, or even worse I may have to split it in numerous parts so as to remove the advertisments. And I do not want to reencode the entire movie since it's a really slow process (on my NAS) and the movie is already broadcast using H264 (DVB-T).

Doing this by hand is really painful, because most tools like ffmpeg, or mkvmerge are only able to cut a movie (without reencoding) at a boundary within the video stream that corresponds to a reference frame (so called I-frames). These frames are only present roughly every 10-20 frames which corresponds to quite long duration (in the order of a second).

I really want to cut the movie with a better precision. So I have written a Python script that leverages ffmpeg, ffprobe and mkvmerge to do the job with the required precision.

Parameters

How does it work ?

How to determine where to cuts

Use mpv --osd-fractions --osd-level=3 ./movie.ts