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|
# Stuff to parse Sun and NeXT audio files.
#
# An audio 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
# parameter 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 = au.open(file, 'r')
# or
# f = au.openfp(filep, 'r')
# where file is the name of a file and filep is 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' for AIFF files)
# getcompname() -- returns human-readable version of
# compression type ('not compressed' for AIFF files)
# getparams() -- returns a tuple 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 postion in the
# file.
# The close() method is called automatically when the class instance
# is destroyed.
#
# Writing audio files:
# f = au.open(file, 'w')
# or
# f = au.openfp(filep, 'w')
# where file is the name of a file and filep is 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(nchannels, sampwidth, framerate, nframes, comptype, compname)
# -- 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('') or
# close() to patch up the sizes in the header.
# The close() method is called automatically when the class instance
# is destroyed.
# 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 = 0xFFFFFFFFL # ((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]
def _read_u32(file):
x = 0L
for i in range(4):
byte = file.read(1)
if 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, m)
x = d
for i in range(4):
file.write(chr(int(data[i])))
class Au_read:
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 rediculously 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_LINEAR_8,
AUDIO_FILE_ENCODING_ALAW_8):
self._sampwidth = 2
self._framesize = 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))
self._framesize = self._framesize * self._nchannels
if self._hdr_size > 24:
self._info = file.read(self._hdr_size - 24)
for i in range(len(self._info)):
if self._info[i] == '\0':
self._info = self._info[:i]
break
else:
self._info = ''
return self
def init(self, filename):
import builtin
return self.initfp(builtin.open(filename, 'r'))
def __del__(self):
if self._file:
self.close()
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 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._sampwidth * self._nchannels)
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):
self._soundpos = 0
self._file.seek(self._hdr_size)
def tell(self):
return self._soundpos
def setpos(self, pos):
if pos < 0 or pos > self.getnframes():
raise Error, 'position not in range'
self._file.seek(pos * self._framesize + self._hdr_size)
self._soundpos = pos
def close(self):
self._file = None
class Au_write:
def init(self, filename):
import builtin
return self.initfp(builtin.open(filename, 'w'))
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 = ''
self._comptype = 'ULAW' # default is U-law
return self
def __del__(self):
if self._file:
self.close()
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, 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, (nchannels, sampwidth, framerate, nframes, comptype, compname)):
self.setnchannels(nchannels)
self.setsampwidth(sampwidth)
self.setframerate(framerate)
self.setnframes(nframes)
self.setcomptype(comptype, compname)
def getparams(self):
return self.getnchannels(), self.getsampwidth(), \
self.getframerate(), self.getnframes(), \
self.getcomptype(), self.getcompname()
def tell(self):
return self._nframeswritten
def writeframesraw(self, data):
self._ensure_header_written()
nframes = len(data) / self._framesize
if self._comptype == 'ULAW':
import audioop
data = audioop.lin2ulaw(data, self._sampwidth)
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):
self._ensure_header_written()
if self._nframeswritten != self._nframes or \
self._datalength != self._datawritten:
self._patchheader()
self._file.flush()
self._file = None
#
# 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 == 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
_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('\0'*(header_size - len(self._info) - 24))
def _patchheader(self):
self._file.seek(8)
_write_u32(self._file, self._datawritten)
self._datalength = self._datawritten
self._file.seek(0, 2)
def open(filename, mode):
if mode == 'r':
return Au_read().init(filename)
elif mode == 'w':
return Au_write().init(filename)
else:
raise Error, "mode must be 'r' or 'w'"
def openfp(filep, mode):
if mode == 'r':
return Au_read().initfp(filep)
elif mode == 'w':
return Au_write().initfp(filep)
else:
raise Error, "mode must be 'r' or 'w'"
|