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#!/usr/bin/python3

"""

audiotranscode

Sources on github:

http://github.com/devsnd/audiotranscode/

licensed under GNU GPL version 3 (or later)

This program is free software: you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation, either version 3 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

GNU General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program. If not, see <http://www.gnu.org/licenses/>

"""

__version__ = '0.2'

import subprocess

import re

import os

import time

from distutils.spawn import find_executable

MIMETYPES = {

'mp3': 'audio/mpeg',

'ogg': 'audio/ogg',

'flac': 'audio/flac',

'aac': 'audio/aac',

'm4a': 'audio/m4a',

'wav': 'audio/wav',

}

class Transcoder(object):

"""super class for encoders and decoders"""

devnull = open(os.devnull, 'w')

def __init__(self):

self.command = ['']

def available(self):

"""checks if the command defined in the encoder or decoder is

available by calling it once"""

return bool(find_executable(self.command[0]))

class Encoder(Transcoder):

"""encoder"""

def __init__(self, filetype, command):

Transcoder.__init__(self)

self.filetype = filetype

self.mimetype = MIMETYPES[filetype]

self.command = command

def encode(self, decoder_process, bitrate):

"""encodes the raw audio stream coming from the decoder_process

using the spedcified command"""

# get the absolute path under which the executable is found

cmd = [find_executable(self.command[0])] + self.command[1:]

if 'BITRATE' in cmd:

cmd[cmd.index('BITRATE')] = str(bitrate)

return subprocess.Popen(cmd,

stdin=decoder_process.stdout,

stdout=subprocess.PIPE,

stderr=Transcoder.devnull

)

def __str__(self):

return "<Encoder type='%s' cmd='%s'>" % (self.filetype,

str(' '.join(self.command)))

def __repr__(self):

return self.__str__()

class Decoder(Transcoder):

"""decoder"""

def __init__(self, filetype, command):

Transcoder.__init__(self)

self.filetype = filetype

self.mimetype = MIMETYPES[filetype]

self.command = command

def decode(self, filepath):

"""returns the process the decodes the file to a raw audio stream"""

# get the absolute path under which the executable is found

cmd = [find_executable(self.command[0])] + self.command[1:]

if 'INPUT' in cmd:

cmd[cmd.index('INPUT')] = filepath

return subprocess.Popen(cmd,

stdout=subprocess.PIPE,

stderr=Transcoder.devnull

)

def __str__(self):

return "<Decoder type='%s' cmd='%s'>" % (self.filetype,

str(' '.join(self.command)))

def __repr__(self):

return self.__str__()

class TranscodeError(Exception):

"""exception for if either a decoder or encoder error has occurred"""

def __init__(self, value):

Exception.__init__(self, value)

self.value = value

def __str__(self):

return repr(self.value)

class EncodeError(TranscodeError):

"""exception if an encoder is missing"""

def __init__(self, value):

TranscodeError.__init__(self, value)

self.value = value

def __str__(self):

return repr(self.value)

class DecodeError(TranscodeError):

"""exception if a decoder is missing"""

def __init__(self, value):

TranscodeError.__init__(self, value)

self.value = value

def __str__(self):

return repr(self.value)

def _filetype(filepath):

"""returns the file extension of a file"""

if '.' in filepath:

return filepath.lower()[filepath.rindex('.')+1:]

def mime_type(file_extension):

"""return a mimetype based on the file extension"""

return MIMETYPES.get(file_extension)

class AudioTranscode:

"""main class that manages encoders and decoders

call transcode(infile, outfile) for file transformations

or transcode_stream to get a generator of the encoded stream"""

READ_BUFFER = 1024

Encoders = [

#encoders take input from stdin and write output to stout

Encoder('ogg', ['oggenc', '-b', 'BITRATE', '-']),

#doesn't work yet

#Encoder('ogg', ['ffmpeg', '-i', '-', '-f', 'ogg',

# '-acodec', 'vorbis', '-']),

Encoder('mp3', ['lame', '-b', 'BITRATE', '-', '-']),

Encoder('aac', ['faac', '-b', 'BITRATE', '-P', '-X', '-o', '-', '-']),

Encoder('m4a', ['faac', '-b', 'BITRATE', '-P', '-X', '-o', '-', '-']),

Encoder('flac', ['flac', '--force-raw-format', '--endian=little',

'--channels=2', '--bps=16', '--sample-rate=44100',

'--sign=signed', '-o', '-', '-']),

Encoder('wav', ['cat']),

]

Decoders = [

#INPUT is replaced with filepath

Decoder('mp3', ['mpg123', '-w', '-', 'INPUT']),

Decoder('mp3', ['ffmpeg', '-i', 'INPUT', '-f', 'wav',

'-acodec', 'pcm_s16le', '-']),

Decoder('ogg', ['oggdec', '-Q', '-b', '16', '-o', '-', 'INPUT']),

Decoder('ogg', ['ffmpeg', '-i', 'INPUT', '-f', 'wav',

'-acodec', 'pcm_s16le', '-']),

Decoder('flac', ['flac', '-F', '-d', '-c', 'INPUT']),

Decoder('aac', ['faad', '-w', 'INPUT']),

Decoder('m4a', ['faad', '-w', 'INPUT']),

Decoder('wav', ['cat', 'INPUT']),

]

def __init__(self, debug=False):

self.debug = debug

self.available_encoders = [enc for enc in AudioTranscode.Encoders

if enc.available()]

self.available_decoders = [dec for dec in AudioTranscode.Decoders

if dec.available()]

self.bitrate = {'mp3': 160, 'ogg': 128, 'aac': 128}

def available_encoder_formats(self):

"""returns the names of all available encoder formats"""

return set(enc.filetype for enc in self.available_encoders)

def available_decoder_formats(self):

"""returns the names of all available decoder formats"""

return set(dec.filetype for dec in self.available_decoders)

def _decode(self, filepath, decoder=None):

"""find the correct decoder and return a decoder process"""

if not os.path.exists(filepath):

filepath = os.path.abspath(filepath)

errmsg = 'File not Found! Cannot decode "file" %s'

raise IOError(errmsg % filepath)

filetype = _filetype(filepath)

if not filetype in self.available_decoder_formats():

errmsg = 'No decoder available to handle filetype %s'

raise DecodeError(errmsg % filetype)

elif not decoder:

for dec in self.available_decoders:

if dec.filetype == filetype:

decoder = dec

break

if self.debug:

print(decoder)

return decoder.decode(filepath)

def _encode(self, audio_format, decoder_process,

bitrate=None, encoder=None):

"""find the correct encoder and pass in the decoder process,

returns the encoder process"""

if not bitrate:

bitrate = self.bitrate.get(audio_format)

if not bitrate:

bitrate = 128

if not encoder:

for enc in self.available_encoders:

if enc.filetype == audio_format:

encoder = enc

break

if self.debug:

print(encoder)

return encoder.encode(decoder_process, bitrate)

def check_encoder_available(self, audio_format):

"""checks if an encoder for this audio format is available"""

if not audio_format in self.available_encoder_formats():

errmsg = 'No encoder available to handle audio format %s'

raise EncodeError(errmsg % audio_format)

def transcode(self, in_file, out_file, bitrate=None):

"""transcodes one file into another format. the filetype is

determined using the file extension of those files"""

audioformat = _filetype(out_file)

self.check_encoder_available(audioformat)

with open(out_file, 'wb') as fhandler:

for data in self.transcode_stream(in_file, audioformat, bitrate):

fhandler.write(data)

fhandler.close()

def transcode_stream(self, filepath, newformat, bitrate=None,

encoder=None, decoder=None):

"""returns a generator wih the bytestream of the encoded audio

stream"""

self.check_encoder_available(newformat)

decoder_process = None

encoder_process = None

try:

decoder_process = self._decode(filepath, decoder)

encoder_process = self._encode(newformat, decoder_process,

bitrate=bitrate, encoder=encoder)

while encoder_process.poll() is None:

data = encoder_process.stdout.read(AudioTranscode.READ_BUFFER)

if data is None:

time.sleep(0.1) # wait for new data...

break

yield data

except Exception as exc:

#pass on exception, but clean up

raise exc

finally:

if decoder_process and decoder_process.poll() is None:

if decoder_process.stderr:

decoder_process.stderr.close()

if decoder_process.stdout:

decoder_process.stdout.close()

if decoder_process.stdin:

decoder_process.stdin.close()

decoder_process.terminate()

if encoder_process:

encoder_process.stdout.read()

encoder_process.stdout.close()

if encoder_process.stdin:

encoder_process.stdin.close()

if encoder_process.stderr:

encoder_process.stderr.close()

encoder_process.wait()