swinsey/avcut

Frame-accurate video cutting with only small quality loss

avcut

avcut is a ffmpeg-based video cutter that is able to do frame-accurate cuts of h264 streams (and possibly other codecs with or without inter-frame prediction) without reencoding the complete stream.

avcut always buffers a so-called group of pictures (GOP) and either copies all of the packets, if no cutting point lies in the corresponding time interval, or reencodes the frames of the GOP before or after the cutting point in order to resolve dependencies on frames that will be removed from the stream. Please see this blog article for a detailed description.

Please note:

• This is an experimental version. Please check any resulting video if everything worked as intended. If you need a more mature solution, check avidemux.
• You can specify an arbitrary output container that is supported by ffmpeg. However, avcut has only been tested with the Matroska (.mkv) container.

Dependencies

• ffmpeg

avcut also compiles with libav if you enable the flag in the Makefile but it has not been tested much.

Compilation

Install dependencies:

• For Ubuntu versions with libav as default, e.g., 15.04:

  • apt-get install libavcodec-ffmpeg-dev libavformat-ffmpeg-dev libavutil-ffmpeg-dev

• For Ubuntu with ffmpeg:

  • apt-get install libavcodec-dev libavformat-dev libavutil-dev

• Gentoo:

  • emerge media-video/ffmpeg

Execute make to start building avcut. Execute make debug to build avcut with verbose output and debug symbols.

Usage

Usage: avcut [options] [<drop_from_ts> <continue_with_ts> ...]

Options:

  -c            Create a shell script to check cutpoints with mpv
  -d <diff>     Accept this difference in packet sizes during packet matching
  -i <file>     Input file
  -o <file>     Output file
  -p <profile>  Use this encoding profile. If <profile> ends with ".profile",
                <profile> is used as a path to the profile file. If not, the profile
                is loaded from the default profile directory:
                   /usr/share/avcut/profiles/
  -s <index>    Skip stream with this index
  -v <level>    Set verbosity level (see https://www.ffmpeg.org/doxygen/2.8/log_8h.html)

Besides the input and output file, avcut expects a "blacklist", i.e. what should be dropped, as argument. This blacklist consists of timestamps that denote from where to where frames have to be dropped. The last argument can be a hyphen to indicate that all remaining frames shall be dropped.

For example, to drop the frames of the first 10 seconds, the frames between 55.5s and 130s and all frames after 140s in input.avi and write the result to output.mkv, the following command can be used:

avcut -i input.avi -o output.mkv 0 10 55.5 130 140 -

The option -c causes avcut to create a shell script in the current working directory that will call mpv to play the video from 10 seconds before to 10 seconds after each cutting point.