"""Stuff to parse Sun and NeXT audio files.
An audio file consists of a header followed by the data. The structure
of the header is as follows.
The magic word consists of the 4 characters '.snd'. Apart from the
info field, all header fields are 4 bytes in size. They are all
32-bit unsigned integers encoded in big-endian byte order.
The header size really gives the start of the data.
The data size is the physical size of the data. From the other
parameters the number of frames can be calculated.
The encoding gives the way in which audio samples are encoded.
Possible values are listed below.
The info field currently consists of an ASCII string giving a
human-readable description of the audio file. The info field is
padded with NUL bytes to the header size.
f = sunau.open(file, 'r')
where file is either the name of a file or an open file pointer.
The open file pointer must have methods read(), seek(), and close().
When the setpos() and rewind() methods are not used, the seek()
This returns an instance of a class with the following public methods:
getnchannels() -- returns number of audio channels (1 for
getsampwidth() -- returns sample width in bytes
getframerate() -- returns sampling frequency
getnframes() -- returns number of audio frames
getcomptype() -- returns compression type ('NONE' or 'ULAW')
getcompname() -- returns human-readable version of
compression type ('not compressed' matches 'NONE')
getparams() -- returns a namedtuple consisting of all of the
getmarkers() -- returns None (for compatibility with the
getmark(id) -- raises an error since the mark does not
exist (for compatibility with the aifc module)
readframes(n) -- returns at most n frames of audio
rewind() -- rewind to the beginning of the audio stream
setpos(pos) -- seek to the specified position
tell() -- return the current position
close() -- close the instance (make it unusable)
The position returned by tell() and the position given to setpos()
are compatible and have nothing to do with the actual position in the
The close() method is called automatically when the class instance
f = sunau.open(file, 'w')
where file is either the name of a file or an open file pointer.
The open file pointer must have methods write(), tell(), seek(), and
This returns an instance of a class with the following public methods:
setnchannels(n) -- set the number of channels
setsampwidth(n) -- set the sample width
setframerate(n) -- set the frame rate
setnframes(n) -- set the number of frames
-- set the compression type and the
human-readable compression type
setparams(tuple)-- set all parameters at once
tell() -- return current position in output file
-- write audio frames without pathing up the
-- write audio frames and patch up the file header
close() -- patch up the file header and close the
You should set the parameters before the first writeframesraw or
writeframes. The total number of frames does not need to be set,
but when it is set to the correct value, the header does not have to
It is best to first set all parameters, perhaps possibly the
compression type, and then write audio frames using writeframesraw.
When all frames have been written, either call writeframes(b'') or
close() to patch up the sizes in the header.
The close() method is called automatically when the class instance
from collections import namedtuple
_sunau_params = namedtuple('_sunau_params',
'nchannels sampwidth framerate nframes comptype compname')
# from <multimedia/audio_filehdr.h>
AUDIO_FILE_MAGIC = 0x2e736e64
AUDIO_FILE_ENCODING_MULAW_8 = 1
AUDIO_FILE_ENCODING_LINEAR_8 = 2
AUDIO_FILE_ENCODING_LINEAR_16 = 3
AUDIO_FILE_ENCODING_LINEAR_24 = 4
AUDIO_FILE_ENCODING_LINEAR_32 = 5
AUDIO_FILE_ENCODING_FLOAT = 6
AUDIO_FILE_ENCODING_DOUBLE = 7
AUDIO_FILE_ENCODING_ADPCM_G721 = 23
AUDIO_FILE_ENCODING_ADPCM_G722 = 24
AUDIO_FILE_ENCODING_ADPCM_G723_3 = 25
AUDIO_FILE_ENCODING_ADPCM_G723_5 = 26
AUDIO_FILE_ENCODING_ALAW_8 = 27
# from <multimedia/audio_hdr.h>
AUDIO_UNKNOWN_SIZE = 0xFFFFFFFF # ((unsigned)(~0))
_simple_encodings = [AUDIO_FILE_ENCODING_MULAW_8,
AUDIO_FILE_ENCODING_LINEAR_8,
AUDIO_FILE_ENCODING_LINEAR_16,
AUDIO_FILE_ENCODING_LINEAR_24,
AUDIO_FILE_ENCODING_LINEAR_32,
AUDIO_FILE_ENCODING_ALAW_8]
f = builtins.open(f, 'rb')
def __exit__(self, *args):
magic = int(_read_u32(file))
if magic != AUDIO_FILE_MAGIC:
raise Error('bad magic number')
self._hdr_size = int(_read_u32(file))
raise Error('header size too small')
raise Error('header size ridiculously large')
self._data_size = _read_u32(file)
if self._data_size != AUDIO_UNKNOWN_SIZE:
self._data_size = int(self._data_size)
self._encoding = int(_read_u32(file))
if self._encoding not in _simple_encodings:
raise Error('encoding not (yet) supported')
if self._encoding in (AUDIO_FILE_ENCODING_MULAW_8,
AUDIO_FILE_ENCODING_ALAW_8):
elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_8:
self._framesize = self._sampwidth = 1
elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_16:
self._framesize = self._sampwidth = 2
elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_24:
self._framesize = self._sampwidth = 3
elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_32:
self._framesize = self._sampwidth = 4
raise Error('unknown encoding')
self._framerate = int(_read_u32(file))
self._nchannels = int(_read_u32(file))
self._framesize = self._framesize * self._nchannels
self._info = file.read(self._hdr_size - 24)
self._info, _, _ = self._info.partition(b'\0')
self._data_pos = file.tell()
except (AttributeError, OSError):
if self._data_size == AUDIO_UNKNOWN_SIZE:
return AUDIO_UNKNOWN_SIZE
if self._encoding in _simple_encodings:
return self._data_size // self._framesize
return 0 # XXX--must do some arithmetic here
if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
elif self._encoding == AUDIO_FILE_ENCODING_ALAW_8:
if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
return 'CCITT G.711 u-law'
elif self._encoding == AUDIO_FILE_ENCODING_ALAW_8:
return 'CCITT G.711 A-law'
return _sunau_params(self.getnchannels(), self.getsampwidth(),
self.getframerate(), self.getnframes(),
self.getcomptype(), self.getcompname())
def readframes(self, nframes):
if self._encoding in _simple_encodings:
if nframes == AUDIO_UNKNOWN_SIZE:
data = self._file.read(nframes * self._framesize)
self._soundpos += len(data) // self._framesize
if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
data = audioop.ulaw2lin(data, self._sampwidth)
return None # XXX--not implemented yet
if self._data_pos is None:
raise OSError('cannot seek')
self._file.seek(self._data_pos)
if pos < 0 or pos > self.getnframes():
raise Error('position not in range')
if self._data_pos is None:
raise OSError('cannot seek')
self._file.seek(self._data_pos + pos * self._framesize)
f = builtins.open(f, 'wb')
def __exit__(self, *args):
self._nframes = AUDIO_UNKNOWN_SIZE
self._comptype = 'ULAW' # default is U-law
def setnchannels(self, nchannels):
raise Error('cannot change parameters after starting to write')
if nchannels not in (1, 2, 4):
raise Error('only 1, 2, or 4 channels supported')
self._nchannels = nchannels
raise Error('number of channels not set')
def setsampwidth(self, sampwidth):
raise Error('cannot change parameters after starting to write')
if sampwidth not in (1, 2, 3, 4):
raise Error('bad sample width')
self._sampwidth = sampwidth
raise Error('sample width not specified')
def setframerate(self, framerate):
raise Error('cannot change parameters after starting to write')
self._framerate = framerate
raise Error('frame rate not set')
def setnframes(self, nframes):
raise Error('cannot change parameters after starting to write')
raise Error('# of frames cannot be negative')
return self._nframeswritten
def setcomptype(self, type, name):
if type in ('NONE', 'ULAW'):
raise Error('unknown compression type')
if self._comptype == 'ULAW':
return 'CCITT G.711 u-law'
elif self._comptype == 'ALAW':
return 'CCITT G.711 A-law'
def setparams(self, params):
nchannels, sampwidth, framerate, nframes, comptype, compname = params
self.setnchannels(nchannels)
self.setsampwidth(sampwidth)
self.setframerate(framerate)
self.setcomptype(comptype, compname)
return _sunau_params(self.getnchannels(), self.getsampwidth(),
self.getframerate(), self.getnframes(),
self.getcomptype(), self.getcompname())
return self._nframeswritten
def writeframesraw(self, data):
if not isinstance(data, (bytes, bytearray)):
data = memoryview(data).cast('B')
self._ensure_header_written()
if self._comptype == 'ULAW':
data = audioop.lin2ulaw(data, self._sampwidth)
nframes = len(data) // self._framesize
self._nframeswritten = self._nframeswritten + nframes
self._datawritten = self._datawritten + len(data)
def writeframes(self, data):
self.writeframesraw(data)
if self._nframeswritten != self._nframes or \
self._datalength != self._datawritten:
self._ensure_header_written()
if self._nframeswritten != self._nframes or \
self._datalength != self._datawritten:
def _ensure_header_written(self):
if not self._nframeswritten:
raise Error('# of channels not specified')
raise Error('sample width not specified')
raise Error('frame rate not specified')
if self._comptype == 'NONE':
encoding = AUDIO_FILE_ENCODING_LINEAR_8
elif self._sampwidth == 2:
encoding = AUDIO_FILE_ENCODING_LINEAR_16
elif self._sampwidth == 3:
encoding = AUDIO_FILE_ENCODING_LINEAR_24
elif self._sampwidth == 4:
encoding = AUDIO_FILE_ENCODING_LINEAR_32
raise Error('internal error')
elif self._comptype == 'ULAW':
encoding = AUDIO_FILE_ENCODING_MULAW_8
raise Error('internal error')
self._framesize = self._framesize * self._nchannels
_write_u32(self._file, AUDIO_FILE_MAGIC)
header_size = 25 + len(self._info)
header_size = (header_size + 7) & ~7
_write_u32(self._file, header_size)
if self._nframes == AUDIO_UNKNOWN_SIZE:
length = AUDIO_UNKNOWN_SIZE
length = self._nframes * self._framesize
self._form_length_pos = self._file.tell()
except (AttributeError, OSError):
self._form_length_pos = None
_write_u32(self._file, length)
self._datalength = length
_write_u32(self._file, encoding)
_write_u32(self._file, self._framerate)
_write_u32(self._file, self._nchannels)
It is recommended that you Edit text format, this type of Fix handles quite a lot in one request
