CUE splitter using ffmpeg

ffcuesplit.py

#!/usr/bin/env python

import os
import subprocess
import sys

if len(sys.argv) != 2:
    sys.exit("Usage:\n\t%s <%s>" % (sys.argv[0], 'input_cuesheet'))

cuesheet_fname = sys.argv[1]
global_metadata = {}
media_fname = ""
tracks = []

if not os.path.exists(cuesheet_fname):
    sys.exit("Cuesheet '%s' was not found." % cuesheet_fname)

with open(cuesheet_fname) as f:
    for line in f.readlines():
        line = line.strip('\n')
        if line.startswith('REM GENRE '):
            global_metadata['genre'] = ' '.join(line.split(' ')[2:])
        if line.startswith('REM DATE '):
            global_metadata['date'] = ' '.join(line.split(' ')[2:])
        if line.startswith('PERFORMER '):
            global_metadata['artist'] = ' '.join(line.split(' ')[1:]).replace('"', '')
        if line.startswith('TITLE '):
            global_metadata['album'] = ' '.join(line.split(' ')[1:]).replace('"', '')
        if line.startswith('FILE '):
            media_fname = ' '.join(line.split(' ')[1:-1]).replace('"', '')
        if line.startswith('  TRACK '):
            track = global_metadata.copy()
            track['track'] = int(line.strip().split(' ')[1], 10)
            tracks.append(track)
        if line.startswith('    TITLE '):
            tracks[-1]['title'] = ' '.join(line.strip().split(' ')[1:]).replace('"', '')
        if line.startswith('    PERFORMER '):
            tracks[-1]['artist'] = ' '.join(line.strip().split(' ')[1:]).replace('"', '')
        if line.startswith('    INDEX 01 '):
            t = list(map(int, ' '.join(line.strip().split(' ')[2:]).replace('"', '').split(':')))
            tracks[-1]['start'] = 60 * t[0] + t[1] + t[2] / 100.0

if not os.path.exists(media_fname):
    sys.exit("Media file '%s' referenced in cue sheet could not be found." % media_fname)

for i in range(len(tracks)):
    if i != len(tracks) - 1:
        tracks[i]['duration'] = tracks[i + 1]['start'] - tracks[i]['start']

for track in tracks:
    track_metadata = {
        'artist': track['artist'],
        'title': track['title'],
        'album': track['album'],
        'track': str(track['track']) + '/' + str(len(tracks))
    }
    if 'genre' in track:
        track_metadata['genre'] = track['genre']
    if 'date' in track:
        track_metadata['date'] = track['date']
    cmd, args = ['ffmpeg'], []
    args.extend(['-i',media_fname])
    args.extend(['-c','copy'])
    args.extend(['-ss','%.2d:%.2d:%.2d' % (track['start'] / 60 / 60, track['start'] / 60 % 60, int(track['start'] % 60))])
    if 'duration' in track:
        args.extend(['-t','%.2d:%.2d:%.2d' % (track['duration'] / 60 / 60, track['duration'] / 60 % 60, int(track['duration'] % 60))])
    for (k, v) in list(track_metadata.items()):
        args.extend(['-metadata','%s=%s' % (k, v) ])
    args.append('%.2d - %s - %s%s' % (track['track'], track['artist'], track['title'], os.path.splitext(media_fname)[1]))
    cmd.extend(args)
    subprocess.call(cmd)
    

Line 18:

with open(cuesheet_fname) as f:

Maybe it would be better to allow users to choose a file encoding via an argument or add some auto detection. I got decoding exceptions from some of my cuesheets with non-UTF encodings like JIS.

Line 20:

if line.startswith('FILE '):
    media_fname = ' '.join(line.split(' ')[1:-1]).replace('"', '')

You might want to consider adding the containing directory of the cuesheet to form a path rather than using the media filename directly. People may run this script from a different working directory than the one containing the cuesheet and the media file. In that case, the script wouldn't be able to find the media file with only its name. Something like this should be fine:

if line.startswith('FILE '):
    media_fname = ' '.join(line.split(' ')[1:-1]).replace('"', '')
    media_fname = os.path.join(os.path.dirname(cuesheet_fname), media_fname)

A command line argument can also be added to allow users to choose where their media files are. But I would say assuming the cuesheet and the media sit in the same directory should be okay, since that seems to be a convention for most media players.

Line 69:

args.append('%.2d - %s - %s%s' % (track['track'], track['artist'], track['title'], os.path.splitext(media_fname)[1]))

• The previous path suggestion also applies here.
• Some tracks may not have a performer attribute so the script will crash here.
• Joining track ID, performer, and title directly together to form a filename means that the resulting name can be invalid on some OS or filesystems (e.g. contains : on Windows). However, after some Googling it seems that Python has not provided a convenient way to escape these invalid names. I might try to come up with some platform-dependent regexes to handle these cases without introducing any 3rd party dependencies.

I ended up changing as follows to address the first two points:

if 'artist' in track:
    output_track_fname = format('%.2d - %s - %s%s' % (track['track'], track['artist'], track['title'], os.path.splitext(media_fname)[1]))
else:
    output_track_fname = format('%.2d - %s%s' % (track['track'], track['title'], os.path.splitext(media_fname)[1]))
output_track_path = os.path.join(os.path.dirname(cuesheet_fname), output_track_fname)
args.append(output_track_path)

By the way, ffmpeg seems to have a 7-year bug tracked at https://trac.ffmpeg.org/ticket/4905 that produces split FLAC files with wrong durations. I have yet to find a way to circumvent this issue.