"""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.
+---------------+
| magic word |
+---------------+
| header size |
+---------------+
| data size |
+---------------+
| encoding |
+---------------+
| sample rate |
+---------------+
| # of channels |
+---------------+
| info |
| |
+---------------+
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.
Usage.
Reading audio files:
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()
method is not necessary.
This returns an instance of a class with the following public methods:
getnchannels() -- returns number of audio channels (1 for
mono, 2 for stereo)
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
above in the above order
getmarkers() -- returns None (for compatibility with the
aifc module)
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
file.
The close() method is called automatically when the class instance
is destroyed.
Writing audio files:
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
close().
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
setcomptype(type, name)
-- set the compression type and the
human-readable compression type
setparams(tuple)-- set all parameters at once
tell() -- return current position in output file
writeframesraw(data)
-- write audio frames without pathing up the
file header
writeframes(data)
-- write audio frames and patch up the file header
close() -- patch up the file header and close the
output file
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
be patched up.
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
is destroyed.
"""
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]
class Error(Exception):
pass
def _read_u32(file):
x = 0
for i in range(4):
byte = file.read(1)
if not byte:
raise EOFError
x = x*256 + ord(byte)
return x
def _write_u32(file, x):
data = []
for i in range(4):
d, m = divmod(x, 256)
data.insert(0, int(m))
x = d
file.write(bytes(data))
class Au_read:
def __init__(self, f):
if type(f) == type(''):
import builtins
f = builtins.open(f, 'rb')
self._opened = True
else:
self._opened = False
self.initfp(f)
def __del__(self):
if self._file:
self.close()
def __enter__(self):
return self
def __exit__(self, *args):
self.close()
def initfp(self, file):
self._file = file
self._soundpos = 0
magic = int(_read_u32(file))
if magic != AUDIO_FILE_MAGIC:
raise Error('bad magic number')
self._hdr_size = int(_read_u32(file))
if self._hdr_size < 24:
raise Error('header size too small')
if self._hdr_size > 100:
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):
self._sampwidth = 2
self._framesize = 1
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
else:
raise Error('unknown encoding')
self._framerate = int(_read_u32(file))
self._nchannels = int(_read_u32(file))
if not self._nchannels:
raise Error('bad # of channels')
self._framesize = self._framesize * self._nchannels
if self._hdr_size > 24:
self._info = file.read(self._hdr_size - 24)
self._info, _, _ = self._info.partition(b'\0')
else:
self._info = b''
try:
self._data_pos = file.tell()
except (AttributeError, OSError):
self._data_pos = None
def getfp(self):
return self._file
def getnchannels(self):
return self._nchannels
def getsampwidth(self):
return self._sampwidth
def getframerate(self):
return self._framerate
def getnframes(self):
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
def getcomptype(self):
if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
return 'ULAW'
elif self._encoding == AUDIO_FILE_ENCODING_ALAW_8:
return 'ALAW'
else:
return 'NONE'
def getcompname(self):
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'
else:
return 'not compressed'
def getparams(self):
return _sunau_params(self.getnchannels(), self.getsampwidth(),
self.getframerate(), self.getnframes(),
self.getcomptype(), self.getcompname())
def getmarkers(self):
return None
def getmark(self, id):
raise Error('no marks')
def readframes(self, nframes):
if self._encoding in _simple_encodings:
if nframes == AUDIO_UNKNOWN_SIZE:
data = self._file.read()
else:
data = self._file.read(nframes * self._framesize)
self._soundpos += len(data) // self._framesize
if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
import audioop
data = audioop.ulaw2lin(data, self._sampwidth)
return data
return None # XXX--not implemented yet
def rewind(self):
if self._data_pos is None:
raise OSError('cannot seek')
self._file.seek(self._data_pos)
self._soundpos = 0
def tell(self):
return self._soundpos
def setpos(self, 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)
self._soundpos = pos
def close(self):
file = self._file
if file:
self._file = None
if self._opened:
file.close()
class Au_write:
def __init__(self, f):
if type(f) == type(''):
import builtins
f = builtins.open(f, 'wb')
self._opened = True
else:
self._opened = False
self.initfp(f)
def __del__(self):
if self._file:
self.close()
self._file = None
def __enter__(self):
return self
def __exit__(self, *args):
self.close()
def initfp(self, file):
self._file = file
self._framerate = 0
self._nchannels = 0
self._sampwidth = 0
self._framesize = 0
self._nframes = AUDIO_UNKNOWN_SIZE
self._nframeswritten = 0
self._datawritten = 0
self._datalength = 0
self._info = b''
self._comptype = 'ULAW' # default is U-law
def setnchannels(self, nchannels):
if self._nframeswritten:
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
def getnchannels(self):
if not self._nchannels:
raise Error('number of channels not set')
return self._nchannels
def setsampwidth(self, sampwidth):
if self._nframeswritten:
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
def getsampwidth(self):
if not self._framerate:
raise Error('sample width not specified')
return self._sampwidth
def setframerate(self, framerate):
if self._nframeswritten:
raise Error('cannot change parameters after starting to write')
self._framerate = framerate
def getframerate(self):
if not self._framerate:
raise Error('frame rate not set')
return self._framerate
def setnframes(self, nframes):
if self._nframeswritten:
raise Error('cannot change parameters after starting to write')
if nframes < 0:
raise Error('# of frames cannot be negative')
self._nframes = nframes
def getnframes(self):
return self._nframeswritten
def setcomptype(self, type, name):
if type in ('NONE', 'ULAW'):
self._comptype = type
else:
raise Error('unknown compression type')
def getcomptype(self):
return self._comptype
def getcompname(self):
if self._comptype == 'ULAW':
return 'CCITT G.711 u-law'
elif self._comptype == 'ALAW':
return 'CCITT G.711 A-law'
else:
return 'not compressed'
def setparams(self, params):
nchannels, sampwidth, framerate, nframes, comptype, compname = params
self.setnchannels(nchannels)
self.setsampwidth(sampwidth)
self.setframerate(framerate)
self.setnframes(nframes)
self.setcomptype(comptype, compname)
def getparams(self):
return _sunau_params(self.getnchannels(), self.getsampwidth(),
self.getframerate(), self.getnframes(),
self.getcomptype(), self.getcompname())
def tell(self):
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':
import audioop
data = audioop.lin2ulaw(data, self._sampwidth)
nframes = len(data) // self._framesize
self._file.write(data)
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._patchheader()
def close(self):
if self._file:
try:
self._ensure_header_written()
if self._nframeswritten != self._nframes or \
self._datalength != self._datawritten:
self._patchheader()
self._file.flush()
finally:
file = self._file
self._file = None
if self._opened:
file.close()
#
# private methods
#
def _ensure_header_written(self):
if not self._nframeswritten:
if not self._nchannels:
raise Error('# of channels not specified')
if not self._sampwidth:
raise Error('sample width not specified')
if not self._framerate:
raise Error('frame rate not specified')
self._write_header()
def _write_header(self):
if self._comptype == 'NONE':
if self._sampwidth == 1:
encoding = AUDIO_FILE_ENCODING_LINEAR_8
self._framesize = 1
elif self._sampwidth == 2:
encoding = AUDIO_FILE_ENCODING_LINEAR_16
self._framesize = 2
elif self._sampwidth == 3:
encoding = AUDIO_FILE_ENCODING_LINEAR_24
self._framesize = 3
elif self._sampwidth == 4:
encoding = AUDIO_FILE_ENCODING_LINEAR_32
self._framesize = 4
else:
raise Error('internal error')
elif self._comptype == 'ULAW':
encoding = AUDIO_FILE_ENCODING_MULAW_8
self._framesize = 1
else:
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
else:
length = self._nframes * self._framesize
try:
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)
self._file.write(self._info)
self._file.write(b'\0'*(header_size - len(self._info) - 24))
def _patchheader(self):
if self._form_length_pos is None:
raise OSError('cannot seek')
self._file.seek(self._form_length_pos)
_write_u32(self._file, self._datawritten)
self._datalength = self._datawritten
self._file.seek(0, 2)
def open(f, mode=None):
if mode is None:
if hasattr(f, 'mode'):
mode = f.mode
else:
mode = 'rb'
if mode in ('r', 'rb'):
return Au_read(f)
elif mode in ('w', 'wb'):
return Au_write(f)
else:
raise Error("mode must be 'r', 'rb', 'w', or 'wb'")
Mini Shell