Accurately cut video files from command line

FFmpeg will do this for you.

Your command might look something like this:

Code: ffmpeg -i input.mpg -ss 00:00:10 -t 00:00:30 out1.mpg -ss is the start point in hh:mm:ss from the beginning of your video file

-t is the length of time in hh:mm:ss of your new segment.

So, in the above example, you're starting 10 seconds in from the beginning of the original file and ending 30 seconds later.

If you want to create multiple parts in one pass then the following should work:

Code: ffmpeg -i input.mpg -ss 00:00:10 -t 00:00:30 out1.mpg -ss 00:00:35 -t 00:00:30 out2.mpg In this example, the first segment is the same as the first example, but you're also creating a second file starting at 35 seconds in and being 30 seconds long.

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timecode_frame_start does not work like this.

Seeking based on frame numbers is not possible. The only way to start at specific frames is to convert a number of frames to ss.ms syntax, or hh:mm:ss.ms. So, if your video is at 25 fps, and you want to start at 133 frames, you would need to first calculate the timestamp:

133 / 25 = 5.32

Then run:

ffmpeg -ss 5.32 -i input.mp4 -c:v libx264 -c:a aac out.mp4

Note that cutting on exact frames with bitstream copy (-c:v copy) is not possible, since not all frames are intra-coded ("keyframes"). A video must begin with a keyframe to be decoded properly. You will therefore have to re-encode the video, e.g. to H.264 using -c:v libx264 as shown above. You can also choose a lossless codec like -c:v ffv1 which preserves the quality of the input video.

To summarize, -ss will always be frame-accurate when performing re-encoding.

If you further want to encode a specific number of frames, use -frames:v, for example:

ffmpeg -ss 5.32 -i input.mp4 -c:v libx264 -c:a aac -frames:v 60 out.mp4

Note that you you also have the choice to use the select/aselect filters to select frames/audio samples.

ffmpeg -i input.mp4 -vf 'select=gte(n\,100)' -c:v libx264 -c:a aac out.mp4

This, however, is slower than the -ss option shown above, since the entire video will be decoded.