Remove a section from the middle of a video without concat

user_3310334 0
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How do I cut a section out of a video with ffmpeg?

Imagine I have a 60 second mp4 A.

I want to remove all the stuff from 0:15 to 0:45.

The result should be a 30-second mp4, which is composed of the first 15 seconds of A directly followed by the last 15 seconds of A.

How can I do this without using concat?

I know how I could do it by creating two intermediary files and then using ffmpeg to concat them. I don't want to have to perform so much manual work for this (simple?) operation.

I have also seen the trim filder used for removing multiple parts from a video. All the usages I've found show that it seems to be very verbose, and I haven't found an example for a case as simple as I would like (just a single section removed).

Do I have to use trim for this operation? Or are there other less verbose solutions?

The ideal would of course be something at least simple as -ss 0:15 -to 0:45 which removes the ends of a video (-cut 0:15-0:45 for example).

ffmpeg
2 Answers

I started from https://stackoverflow.com/a/54192662/3499840 (currently the only answer to "FFmpeg remove 2 sec from middle of video and concat the parts. Single line solution").

Working from that example, the following works for me:

# In order to keep <start-15s> and <45s-end>, you need to 
# keep all the frames which are "not between 15s and 45s":

ffmpeg -i input.mp4 \
  -vf  "select='not(between(t,15,45))',  setpts=N/FRAME_RATE/TB" \
  -af "aselect='not(between(t,15,45))', asetpts=N/SR/TB" \
  output.mp4

This is a one-line linux command, but I've used the bash line-continuation character ('\') so that I can vertically align the equals-signs as this helps me to understand what is going on.

I had never seen ffmpeg's not and between operators before, but I found their documentation here.

Regarding the usual ffmpeg "copy vs re-encode" dichotomy, I was hoping to be able to use ffmpeg's "copy" "codec" (yeah, I know that it's not really a codec) so that ffmpeg would not re-encode my video, but if I specify "copy", then ffmpeg starts and stops at the nearest keyframes which are not sufficiently close to my desired start and stop points. (I want to remove a piece of video that is approximately 20 seconds long, but my source video only has one keyframe every 45 seconds!). Hence I am obliged to re-encode. See https://trac.ffmpeg.org/wiki/Seeking#Seekingwhiledoingacodeccopy for more info.

The setpts/asetpts filters set the timestamps on each frame to the correct values so that your media player will play each frame at the correct time.

HTH.

user_34998400

If you want to use the copy "codec", consider the following approach:

ffmpeg -i input.mp4 -t "$start_cut_section" -c copy part1.mp4&
ffmpeg -i input.mp4 -ss "$end_cut_section" -c copy part2.mp4&
echo "file 'part1.mp4'" > filelist;
echo "file 'part2.mp4'" >> filelist;
wait;

ffmpeg -f concat -i filelist -c copy output.mp4;
rm filelist;

This creates two now files from before and after the cut, then combines them into a new trimmed final video. Obviously, this can be used to create as many cuts as you like. It may seem like a longer approach than the accepted answer, but it likely will execute much faster because of the use of the copy "codex".

user_2009850
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