How do I split an audio file into multiple?

This worked for me when I tried it on a mp3 file.

$ ffmpeg -i somefile.mp3 -f segment -segment_time 3 -c copy out%03d.mp3

Where -segment_time is the amount of time you want per each file (in seconds).

References

• Splitting an audio file into chunks of a specified length
• 4.22 segment, stream_segment, ssegment - ffmpeg documentation

To split a big audio file into a set of tracks with varying lengths, you can use the following command:

# -to is the end time of the sub-file
ffmpeg -i BIG_FILE -acodec copy -ss START_TIME -to END_TIME LITTLE_FILE

For example, I broke up a single .opus file of the Inception Original Soundtrack into sub-files using this text file containing start, end, name:

00:00:00 00:01:11 01_half_remembered_dream
00:01:11 00:03:07 02_we_built_our_own_world
00:03:07 00:05:31 03_dream_is_collapsing
00:05:31 00:09:14 04_radical_notion
00:09:14 00:16:58 05_old_souls
00:16:58 00:19:22 06
00:19:22 00:24:16 07_mombasa
00:24:16 00:26:44 08_one_simple_idea
00:26:44 00:31:49 09_dream_within_a_dream
00:31:49 00:41:19 10_waiting_for_a_train
00:41:19 00:44:44 11_paradox
00:44:44 00:49:20 12_time

I wrote this short awk program to read the text file and create ffmpeg commands from each line:

{
    # make ffmpeg command string using sprintf
    cmd = sprintf("ffmpeg -i inception_ost.opus -acodec copy -ss %s -to %s %s.opus", $1, $2, $3)

    # execute ffmpeg command with awk's system function
    system(cmd)
}

Here is a more detailed python version of the program called split.py, where now both the original track file and the text file specifying sub-tracks are read from the command line:

import subprocess
import sys


def main():
    """split a music track into specified sub-tracks by calling ffmpeg from the shell"""

    # check command line for original file and track list file
    if len(sys.argv) != 3:
        print 'usage: split <original_track> <track_list>'
        exit(1)

    # record command line args
    original_track = sys.argv[1]
    track_list = sys.argv[2]

    # create a template of the ffmpeg call in advance
    cmd_string = 'ffmpeg -i {tr} -acodec copy -ss {st} -to {en} {nm}.opus'

    # read each line of the track list and split into start, end, name
    with open(track_list, 'r') as f:
        for line in f:
            # skip comment and empty lines
            if line.startswith('#') or len(line) <= 1:
                continue

            # create command string for a given track
            start, end, name = line.strip().split()
            command = cmd_string.format(tr=original_track, st=start, en=end, nm=name)

            # use subprocess to execute the command in the shell
            subprocess.call(command, shell=True)

    return None


if __name__ == '__main__':
    main()

You can easily build up more and more complicated ffmpeg calls by modifying the command template and/or adding more fields to each line of the track_list file.

The following line will split an audio file into multiple files each with 30 sec duration.

ffmpeg -i file.wav -f segment -segment_time 30 -c copy parts/output%09d.wav

Change 30 (which is the number of seconds) to any number you want.