flac2aac.py

#!/usr/bin/env python

'''
===============================================================================
                   ______   ___  _____  ___    ___   ___  _____
                  / __/ /  / _ |/ ___/ |_  |  / _ | / _ |/ ___/
                 / _// /__/ __ / /__  / __/  / __ |/ __ / /__  
                /_/ /____/_/ |_\___/ /____/ /_/ |_/_/ |_\___/
                                   
                                   FLAC 2 AAC
===============================================================================

Script:         flac2aac.py 
Author:         Sebastian Weigand   www.sw-dd.com
Email:          sab@sw-dd.com
Current:        July, 2012
Copyright:      2012, Sebastian Weigand
License:        BSD
Description:    A script which converts FLAC files to MPEG4/AAC files and
                copies over song metadata, utilizing Apple's CoreAudio
                framework for better AAC support.
Version:        1.2
Requirements:
    OS:         Mac OS X, v10.5+    [afconvert]
    Platform:   Python 2.6+         [multiprocessing]
    Binaries:   flac                [decoding]
    Python Lib: mutagen             [metadata]

===============================================================================
'''

import os, sys

# =============================================================================
# Sanity Checking:
# =============================================================================

try:
    import mutagen, fnmatch, argparse

    from subprocess import call, Popen, PIPE
    from multiprocessing import Pool, cpu_count

except ImportError, e:
    print >> sys.stderr, 'Error: Unable to import requisite modules:', e
    exit(1)

def isProgramValid(program):
    paths = os.environ["PATH"].split(os.pathsep)

    for path in paths:
        if os.access(os.path.join(path, program), os.X_OK):
            return True
    return False

for program in ['flac', 'afconvert']:
    if not isProgramValid(program):
        print >> sys.stderr, 'Error: Unable to execute/find "%s" from your PATH.' % program
        exit(1)

afconvertFormatHelp = Popen('afconvert -hf', shell=True, stderr=PIPE).communicate()[1]
afconvertFormats = [format for format in ['aac', 'aach', 'aacp'] if format in afconvertFormatHelp]

# =============================================================================
# Library Methods:
# =============================================================================

def getRealPath(path):
    return os.path.realpath(os.path.expanduser(path))

def getWorkingDirectory():
    # curdir does not support ~ expansion:
    return getRealPath(os.curdir)

def findMatchingFiles(pattern, root = getWorkingDirectory()):
    root = getRealPath(root)

    if not os.path.isdir(root):
        raise IOError('"' + root + '" is not a directory to search within.')
    elif not os.access(root, os.R_OK):
        raise IOError('"' + root + '" is not readable by "' + getpass.getuser() + '".')

    results = []

    try:
        for path, dirs, files in os.walk(getRealPath(root)):
            for filename in fnmatch.filter(files, pattern):
                if '/.' not in path:
                    results.append(os.path.join(path, filename))

    except (KeyboardInterrupt, EOFError):
        print >> sys.stderr, 'Session cancelled via break or EOF.'

    if len(results) == 0:
        print >> sys.stderr, 'No files were found which matched the pattern "' + pattern + '" within "' + root + '", or its subdirectories.'
        return []
    else:
        return results

# =============================================================================
# Argument Parsing:
# =============================================================================

parser = argparse.ArgumentParser(description = 'Converts FLAC to MPEG4/AAC via CoreAudio and transfers metadata using Mutagen.', epilog = 'Note: Mac OS X v10.5+ is required for HE AAC (aach), and 10.7 is required for HE AAC v2 (aacp).')
parser.add_argument('location', metavar = 'location', type = str, nargs = 1, help = 'the location to search for media files [.]')
parser.add_argument('-q', '--quality', type = int, default = 75, help = 'VBR quality, in percent (overrides bitrate)')
parser.add_argument('-v', '--no-vbr', action = "store_true", default = False, help = 'disable variable bitrate [no]')
parser.add_argument('-b', '--bitrate', type = int, default = 256, help = 'bitrate, in KB/s [256]')
parser.add_argument('-c', '--codec', choices = afconvertFormats, default = 'aac', help = 'codec to use, if available on your platform [aac]')

args = parser.parse_args()

# Reset the arguments:
bitrate = args.bitrate * 1000
quality = str(int(args.quality / 100.0 * 127))
args.location = args.location[0]

# See `afconvert -h`:
if args.no_vbr:
    vbrMode = 0
else:
    vbrMode = 3

# =============================================================================
# Transcoding Methods:
# =============================================================================

def convertFLACtoAAC(mediaFileLocation):
    try:
        metadata = mutagen.File(mediaFileLocation, easy = True)
        
        validKeys = ['title', 'album', 'artist', 'albumartist', 'date', 'comment', 'description', 'grouping', 'genre', 'copyright', 'albumsort', 'albumartistsort', 'artistsort', 'titlesort', 'composersort', 'tracknumber', 'discnumber']

        # Sometimes extraneous data will be stored within FLAC's metadata, and that
        #   confuses the direct key updating methods of the Easy-branch of Mutagen.

        for key in metadata.keys():
            if key not in validKeys:
                del metadata[key]

        print 'Parsed:', mediaFileLocation
        
        call(['flac', '-s', '-d', mediaFileLocation])
        print 'Decoded:', mediaFileLocation

        intermediateFile = mediaFileLocation.replace(mediaFileLocation.split('.')[-1], 'wav')

        call(['afconvert', '-f', 'm4af', '-d', args.codec, '-b', str(bitrate), '-s', str(vbrMode), '-u', 'vbrq', quality, '--soundcheck-generate', intermediateFile])
        print 'Encoded:', intermediateFile

        finalFile = mediaFileLocation.replace(mediaFileLocation.split('.')[-1], 'm4a')

        m4aData = mutagen.File(finalFile, easy = True)
        m4aData.update(metadata)
        m4aData.save()
        print 'Applied metadata:', finalFile

        os.remove(intermediateFile)
        print 'Removed intermediate file:', intermediateFile

        print 'Converted', mediaFileLocation, 'to:', finalFile
        
    except:
        exit(2)

# =============================================================================
# Main:
# =============================================================================

# The path to a directory (and its subdirectories) which contain media files:
mediaLocation = getRealPath(args.location)

print 'Searching:', mediaLocation

mediaFileLocations = findMatchingFiles('*.flac', mediaLocation)

print 'Found', len(mediaFileLocations), 'files.'

if len(mediaFileLocations) < 1:
    print >> sys.stderr, 'Could not find any files.'
    exit(1)

print '=' * 80

# Multi-core goodness (N-simultaneous processes, where N = core count):
if __name__ == '__main__':
    try:
        pool = Pool(cpu_count())
        p = pool.map_async(convertFLACtoAAC, mediaFileLocations)
        p.get(0xFFFF)   # needed for KeyboardInterrupt

    except:
        exit(2)

    print 'Done.\n'

#EOF