cpython/Lib/wave.py

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# Stuff to parse WAVE files.
#
# Usage.
#
# Reading WAVE files:
# f = wave.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' 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 WAVE files:
# f = wave.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(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.
import __builtin__
Error = 'wave.Error'
WAVE_FORMAT_PCM = 0x0001
_array_fmts = None, 'b', 'h', None, 'l'
def _read_long(file):
x = 0L
for i in range(4):
byte = file.read(1)
if byte == '':
raise EOFError
x = x + (ord(byte) << (8 * i))
if x >= 0x80000000L:
x = x - 0x100000000L
return int(x)
def _read_ulong(file):
x = 0L
for i in range(4):
byte = file.read(1)
if byte == '':
raise EOFError
x = x + (ord(byte) << (8 * i))
return x
def _read_short(file):
x = 0
for i in range(2):
byte = file.read(1)
if byte == '':
raise EOFError
x = x + (ord(byte) << (8 * i))
if x >= 0x8000:
x = x - 0x10000
return x
def _write_short(f, x):
d, m = divmod(x, 256)
f.write(chr(m))
f.write(chr(d))
def _write_long(f, x):
if x < 0:
x = x + 0x100000000L
for i in range(4):
d, m = divmod(x, 256)
f.write(chr(int(m)))
x = d
class Chunk:
def __init__(self, file):
self.file = file
self.chunkname = self.file.read(4)
if len(self.chunkname) < 4:
raise EOFError
self.chunksize = _read_long(self.file)
self.size_read = 0
self.offset = self.file.tell()
def rewind(self):
self.file.seek(self.offset, 0)
self.size_read = 0
def setpos(self, pos):
if pos < 0 or pos > self.chunksize:
raise RuntimeError
self.file.seek(self.offset + pos, 0)
self.size_read = pos
def read(self, length):
if self.size_read >= self.chunksize:
return ''
if length > self.chunksize - self.size_read:
length = self.chunksize - self.size_read
data = self.file.read(length)
self.size_read = self.size_read + len(data)
return data
def skip(self):
try:
self.file.seek(self.chunksize - self.size_read, 1)
except RuntimeError:
while self.size_read < self.chunksize:
dummy = self.read(8192)
if not dummy:
raise EOFError
class Wave_read:
# Variables used in this class:
#
# These variables are available to the user though appropriate
# methods of this class:
# _file -- the open file with methods read(), close(), and seek()
# set through the __init__() method
# _nchannels -- the number of audio channels
# available through the getnchannels() method
# _nframes -- the number of audio frames
# available through the getnframes() method
# _sampwidth -- the number of bytes per audio sample
# available through the getsampwidth() method
# _framerate -- the sampling frequency
# available through the getframerate() method
# _comptype -- the AIFF-C compression type ('NONE' if AIFF)
# available through the getcomptype() method
# _compname -- the human-readable AIFF-C compression type
# available through the getcomptype() method
# _soundpos -- the position in the audio stream
# available through the tell() method, set through the
# setpos() method
#
# These variables are used internally only:
# _fmt_chunk_read -- 1 iff the FMT chunk has been read
# _data_seek_needed -- 1 iff positioned correctly in audio
# file for readframes()
# _data_chunk -- instantiation of a chunk class for the DATA chunk
# _framesize -- size of one frame in the file
access _file, _nchannels, _nframes, _sampwidth, _framerate, \
_comptype, _compname, _soundpos, \
_fmt_chunk_read, _data_seek_needed, \
_data_chunk, _framesize: private
def initfp(self, file):
self._file = file
self._convert = None
self._soundpos = 0
form = self._file.read(4)
if form != 'RIFF':
raise Error, 'file does not start with RIFF id'
formlength = _read_long(self._file)
if formlength <= 0:
raise Error, 'invalid FORM chunk data size'
formdata = self._file.read(4)
formlength = formlength - 4
if formdata != 'WAVE':
raise Error, 'not a WAVE file'
self._fmt_chunk_read = 0
while formlength > 0:
self._data_seek_needed = 1
chunk = Chunk(self._file)
if chunk.chunkname == 'fmt ':
self._read_fmt_chunk(chunk)
self._fmt_chunk_read = 1
elif chunk.chunkname == 'data':
if not self._fmt_chunk_read:
raise Error, 'data chunk before fmt chunk'
self._data_chunk = chunk
self._nframes = chunk.chunksize / self._framesize
self._data_seek_needed = 0
formlength = formlength - 8 - chunk.chunksize
if formlength > 0:
chunk.skip()
if not self._fmt_chunk_read or not self._data_chunk:
raise Error, 'fmt chunk and/or data chunk missing'
def __init__(self, f):
if type(f) == type(''):
f = __builtin__.open(f, 'r')
# else, assume it is an open file object already
self.initfp(f)
def __del__(self):
if self._file:
self.close()
#
# User visible methods.
#
def getfp(self):
return self._file
def rewind(self):
self._data_seek_needed = 1
self._soundpos = 0
def close(self):
self._file = None
def tell(self):
return self._soundpos
def getnchannels(self):
return self._nchannels
def getnframes(self):
return self._nframes
def getsampwidth(self):
return self._sampwidth
def getframerate(self):
return self._framerate
def getcomptype(self):
return self._comptype
def getcompname(self):
return self._compname
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 setpos(self, pos):
if pos < 0 or pos > self._nframes:
raise Error, 'position not in range'
self._soundpos = pos
self._data_seek_needed = 1
def readframes(self, nframes):
if self._data_seek_needed:
self._data_chunk.rewind()
pos = self._soundpos * self._framesize
if pos:
self._data_chunk.setpos(pos)
self._data_seek_needed = 0
if nframes == 0:
return ''
if self._sampwidth > 1:
# unfortunately the fromfile() method does not take
# something that only looks like a file object, so
# we have to reach into the innards of the chunk object
import array
data = array.array(_array_fmts[self._sampwidth])
nitems = nframes * self._nchannels
if nitems * self._sampwidth > self._data_chunk.chunksize - self._data_chunk.size_read:
nitems = (self._data_chunk.chunksize - self._data_chunk.size_read) / self._sampwidth
data.fromfile(self._data_chunk.file, nitems)
self._data_chunk.size_read = self._data_chunk.size_read + nitems * self._sampwidth
data.byteswap()
data = data.tostring()
else:
data = self._data_chunk.read(nframes * self._framesize)
if self._convert and data:
data = self._convert(data)
self._soundpos = self._soundpos + len(data) / (self._nchannels * self._sampwidth)
return data
#
# Internal methods.
#
access *: private
def _read_fmt_chunk(self, chunk):
wFormatTag = _read_short(chunk)
self._nchannels = _read_short(chunk)
self._framerate = _read_long(chunk)
dwAvgBytesPerSec = _read_long(chunk)
wBlockAlign = _read_short(chunk)
if wFormatTag == WAVE_FORMAT_PCM:
self._sampwidth = (_read_short(chunk) + 7) / 8
else:
raise Error, 'unknown format'
self._framesize = self._nchannels * self._sampwidth
self._comptype = 'NONE'
self._compname = 'not compressed'
class Wave_write:
# Variables used in this class:
#
# These variables are user settable through appropriate methods
# of this class:
# _file -- the open file with methods write(), close(), tell(), seek()
# set through the __init__() method
# _comptype -- the AIFF-C compression type ('NONE' in AIFF)
# set through the setcomptype() or setparams() method
# _compname -- the human-readable AIFF-C compression type
# set through the setcomptype() or setparams() method
# _nchannels -- the number of audio channels
# set through the setnchannels() or setparams() method
# _sampwidth -- the number of bytes per audio sample
# set through the setsampwidth() or setparams() method
# _framerate -- the sampling frequency
# set through the setframerate() or setparams() method
# _nframes -- the number of audio frames written to the header
# set through the setnframes() or setparams() method
#
# These variables are used internally only:
# _datalength -- the size of the audio samples written to the header
# _nframeswritten -- the number of frames actually written
# _datawritten -- the size of the audio samples actually written
access _file, _comptype, _compname, _nchannels, _sampwidth, \
_framerate, _nframes, _nframeswritten, \
_datalength, _datawritten: private
def __init__(self, f):
if type(f) == type(''):
f = __builtin__.open(f, 'w')
self.initfp(f)
def initfp(self, file):
self._file = file
self._convert = None
self._nchannels = 0
self._sampwidth = 0
self._framerate = 0
self._nframes = 0
self._nframeswritten = 0
self._datawritten = 0
self._datalength = 0
def __del__(self):
if self._file:
self.close()
#
# User visible methods.
#
def setnchannels(self, nchannels):
if self._datawritten:
raise Error, 'cannot change parameters after starting to write'
if nchannels < 1:
raise Error, 'bad # of channels'
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._datawritten:
raise Error, 'cannot change parameters after starting to write'
if sampwidth < 1 or sampwidth > 4:
raise Error, 'bad sample width'
self._sampwidth = sampwidth
def getsampwidth(self):
if not self._sampwidth:
raise Error, 'sample width not set'
return self._sampwidth
def setframerate(self, framerate):
if self._datawritten:
raise Error, 'cannot change parameters after starting to write'
if framerate <= 0:
raise Error, 'bad frame rate'
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._datawritten:
raise Error, 'cannot change parameters after starting to write'
self._nframes = nframes
def getnframes(self):
return self._nframeswritten
def setcomptype(self, comptype, compname):
if self._datawritten:
raise Error, 'cannot change parameters after starting to write'
if comptype not in ('NONE',):
raise Error, 'unsupported compression type'
self._comptype = comptype
self._compname = compname
def getcomptype(self):
return self._comptype
def getcompname(self):
return self._compname
def setparams(self, (nchannels, sampwidth, framerate, nframes, comptype, compname)):
if self._datawritten:
raise Error, 'cannot change parameters after starting to write'
self.setnchannels(nchannels)
self.setsampwidth(sampwidth)
self.setframerate(framerate)
self.setnframes(nframes)
self.setcomptype(comptype, compname)
def getparams(self):
if not self._nchannels or not self._sampwidth or not self._framerate:
raise Error, 'not all parameters set'
return self._nchannels, self._sampwidth, self._framerate, \
self._nframes, self._comptype, self._compname
def setmark(self, id, pos, name):
raise Error, 'setmark() not supported'
def getmark(self, id):
raise Error, 'no marks'
def getmarkers(self):
return None
def tell(self):
return self._nframeswritten
def writeframesraw(self, data):
self._ensure_header_written(len(data))
nframes = len(data) / (self._sampwidth * self._nchannels)
if self._convert:
data = self._convert(data)
if self._sampwidth > 1:
import array
data = array.array(_array_fmts[self._sampwidth], data)
data.byteswap()
data.tofile(self._file)
self._datawritten = self._datawritten + len(data) * self._sampwidth
else:
self._file.write(data)
self._datawritten = self._datawritten + len(data)
self._nframeswritten = self._nframeswritten + nframes
def writeframes(self, data):
self.writeframesraw(data)
if self._datalength != self._datawritten:
self._patchheader()
def close(self):
self._ensure_header_written(0)
if self._datalength != self._datawritten:
self._patchheader()
self._file.flush()
self._file = None
#
# Internal methods.
#
access *: private
def _ensure_header_written(self, datasize):
if not self._datawritten:
if not self._nchannels:
raise Error, '# channels not specified'
if not self._sampwidth:
raise Error, 'sample width not specified'
if not self._framerate:
raise Error, 'sampling rate not specified'
self._write_header(datasize)
def _write_header(self, initlength):
self._file.write('RIFF')
if not self._nframes:
self._nframes = initlength / (self._nchannels * self._sampwidth)
self._datalength = self._nframes * self._nchannels * self._sampwidth
self._form_length_pos = self._file.tell()
_write_long(self._file, 36 + self._datalength)
self._file.write('WAVE')
self._file.write('fmt ')
_write_long(self._file, 16)
_write_short(self._file, WAVE_FORMAT_PCM)
_write_short(self._file, self._nchannels)
_write_long(self._file, self._framerate)
_write_long(self._file, self._nchannels * self._framerate * self._sampwidth)
_write_short(self._file, self._nchannels * self._sampwidth)
_write_short(self._file, self._sampwidth * 8)
self._file.write('data')
self._data_length_pos = self._file.tell()
_write_long(self._file, self._datalength)
def _patchheader(self):
if self._datawritten == self._datalength:
return
curpos = self._file.tell()
self._file.seek(self._form_length_pos, 0)
_write_long(36 + self._datawritten)
self._file.seek(self._data_length_pos, 0)
_write_long(self._file, self._datawritten)
self._file.seek(curpos, 0)
self._datalength = self._datawritten
def open(f, mode):
if mode == 'r':
return Wave_read(f)
elif mode == 'w':
return Wave_write(f)
else:
raise Error, "mode must be 'r' or 'w'"
openfp = open # B/W compatibility