transcode.py 文件源码

 复制代码def transcode(flac_file, output_dir, output_format):
    '''
    Transcodes a FLAC file into another format.
    '''
    # gather metadata from the flac file
    flac_info = mutagen.flac.FLAC(flac_file)
    sample_rate = flac_info.info.sample_rate
    bits_per_sample = flac_info.info.bits_per_sample
    resample = sample_rate > 48000 or bits_per_sample > 16

    # if resampling isn't needed then needed_sample_rate will not be used.
    needed_sample_rate = resample_rate(os.path.dirname(flac_file))

    if resample and needed_sample_rate is None:
        raise UnknownSampleRateException(
            'FLAC file "{0}" has a sample rate {1}, which is not 88.2,',
            '176.4, or 96kHz, but needs resampling. This is unsupported.'.format(flac_file, sample_rate)
        )

    if flac_info.info.channels > 2:
        raise TranscodeDownmixException('FLAC file "%s" has more than 2 channels, unsupported' % flac_file)

    # determine the new filename
    transcode_basename = os.path.splitext(os.path.basename(flac_file))[0]
    transcode_basename = re.sub(r'[\?<>\\*\|"]', '_', transcode_basename)
    transcode_file = os.path.join(output_dir, transcode_basename)
    transcode_file += ENCODERS[output_format]['ext']

    if not os.path.exists(os.path.dirname(transcode_file)):
        try:
            os.makedirs(os.path.dirname(transcode_file))
        except OSError as e:
            if e.errno == errno.EEXIST:
                # Harmless race condition -- another transcode process
                # beat us here.
                pass
            else:
                raise e

    commands = transcode_commands(output_format, resample, needed_sample_rate, flac_file, transcode_file)
    results = run_pipeline(commands)

    # Check for problems. Because it's a pipeline, the earliest one is
    # usually the source. The exception is -SIGPIPE, which is caused
    # by "backpressure" due to a later command failing: ignore those
    # unless no other problem is found.
    last_sigpipe = None
    for (cmd, (code, stderr)) in zip(commands, results):
        if code:
            if code == -signal.SIGPIPE:
                last_sigpipe = (cmd, (code, stderr))
            else:
                raise TranscodeException('Transcode of file "%s" failed: %s' % (flac_file, stderr))
    if last_sigpipe:
        # XXX: this should probably never happen....
        raise TranscodeException('Transcode of file "%s" failed: SIGPIPE' % flac_file)

    return transcode_file