"""Stuff to parse WAVE files.
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' for linear samples)
getcompname() -- returns human-readable version of
compression type ('not compressed' linear samples)
getparams() -- returns a tuple 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
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
-- 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('') or
close() to patch up the sizes in the header.
The close() method is called automatically when the class instance
__all__ = ["open", "openfp", "Error"]
_array_fmts = None, 'b', 'h', None, 'i'
"""Variables used in this class:
These variables are available to the user though appropriate
_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
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
_data_chunk -- instantiation of a chunk class for the DATA chunk
_framesize -- size of one frame in the file
self._file = Chunk(file, bigendian = 0)
if self._file.getname() != 'RIFF':
raise Error, 'file does not start with RIFF id'
if self._file.read(4) != 'WAVE':
raise Error, 'not a WAVE file'
self._data_seek_needed = 1
chunk = Chunk(self._file, bigendian = 0)
chunkname = chunk.getname()
self._read_fmt_chunk(chunk)
elif chunkname == 'data':
if not self._fmt_chunk_read:
raise Error, 'data chunk before fmt chunk'
self._nframes = chunk.chunksize // self._framesize
self._data_seek_needed = 0
if not self._fmt_chunk_read or not self._data_chunk:
raise Error, 'fmt chunk and/or data chunk missing'
self._i_opened_the_file = None
if isinstance(f, basestring):
f = __builtin__.open(f, 'rb')
self._i_opened_the_file = f
# else, assume it is an open file object already
if self._i_opened_the_file:
self._data_seek_needed = 1
file = self._i_opened_the_file
self._i_opened_the_file = None
return self.getnchannels(), self.getsampwidth(), \
self.getframerate(), self.getnframes(), \
self.getcomptype(), self.getcompname()
if pos < 0 or pos > self._nframes:
raise Error, 'position not in range'
self._data_seek_needed = 1
def readframes(self, nframes):
if self._data_seek_needed:
self._data_chunk.seek(0, 0)
pos = self._soundpos * self._framesize
self._data_chunk.seek(pos, 0)
self._data_seek_needed = 0
if self._sampwidth in (2, 4) and sys.byteorder == 'big':
# 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
data = array.array(_array_fmts[self._sampwidth])
assert data.itemsize == self._sampwidth
nitems = nframes * self._nchannels
if nitems * self._sampwidth > chunk.chunksize - chunk.size_read:
nitems = (chunk.chunksize - chunk.size_read) // self._sampwidth
data.fromfile(chunk.file.file, nitems)
# "tell" data chunk how much was read
chunk.size_read = chunk.size_read + nitems * self._sampwidth
# do the same for the outermost chunk
chunk.size_read = chunk.size_read + nitems * self._sampwidth
data = self._data_chunk.read(nframes * self._framesize)
if self._sampwidth == 3 and sys.byteorder == 'big':
if self._convert and data:
data = self._convert(data)
self._soundpos = self._soundpos + len(data) // (self._nchannels * self._sampwidth)
def _read_fmt_chunk(self, chunk):
wFormatTag, self._nchannels, self._framerate, dwAvgBytesPerSec, wBlockAlign = struct.unpack('<HHLLH', chunk.read(14))
if wFormatTag == WAVE_FORMAT_PCM:
sampwidth = struct.unpack('<H', chunk.read(2))[0]
self._sampwidth = (sampwidth + 7) // 8
raise Error, 'unknown format: %r' % (wFormatTag,)
self._framesize = self._nchannels * self._sampwidth
self._compname = 'not compressed'
"""Variables used in this class:
These variables are user settable through appropriate methods
_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
self._i_opened_the_file = None
if isinstance(f, basestring):
f = __builtin__.open(f, 'wb')
self._i_opened_the_file = f
if self._i_opened_the_file:
self._headerwritten = False
def setnchannels(self, nchannels):
raise Error, 'cannot change parameters after starting to write'
raise Error, 'bad # of channels'
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 < 1 or sampwidth > 4:
raise Error, 'bad sample width'
self._sampwidth = sampwidth
raise Error, 'sample width not set'
def setframerate(self, framerate):
raise Error, 'cannot change parameters after starting to write'
raise Error, 'bad frame rate'
self._framerate = framerate
raise Error, 'frame rate not set'
def setnframes(self, nframes):
raise Error, 'cannot change parameters after starting to write'
return self._nframeswritten
def setcomptype(self, comptype, compname):
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 setparams(self, params):
nchannels, sampwidth, framerate, nframes, comptype, compname = params
raise Error, 'cannot change parameters after starting to write'
self.setnchannels(nchannels)
self.setsampwidth(sampwidth)
self.setframerate(framerate)
self.setcomptype(comptype, compname)
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'
return self._nframeswritten
def writeframesraw(self, data):
self._ensure_header_written(len(data))
nframes = len(data) // (self._sampwidth * self._nchannels)
data = self._convert(data)
if self._sampwidth in (2, 4) and sys.byteorder == 'big':
a = array.array(_array_fmts[self._sampwidth])
assert data.itemsize == self._sampwidth
self._datawritten = self._datawritten + len(data) * self._sampwidth
if self._sampwidth == 3 and sys.byteorder == 'big':
self._datawritten = self._datawritten + len(data)
self._nframeswritten = self._nframeswritten + nframes
def writeframes(self, data):
self.writeframesraw(data)
if self._datalength != self._datawritten:
self._ensure_header_written(0)
if self._datalength != self._datawritten:
file = self._i_opened_the_file
self._i_opened_the_file = None
def _ensure_header_written(self, datasize):
if not self._headerwritten:
raise Error, '# channels not specified'
raise Error, 'sample width not specified'
raise Error, 'sampling rate not specified'
self._write_header(datasize)
def _write_header(self, initlength):
assert not self._headerwritten
self._nframes = initlength / (self._nchannels * self._sampwidth)
self._datalength = self._nframes * self._nchannels * self._sampwidth
self._form_length_pos = self._file.tell()
self._file.write(struct.pack('<L4s4sLHHLLHH4s',
36 + self._datalength, 'WAVE', 'fmt ', 16,
WAVE_FORMAT_PCM, self._nchannels, self._framerate,
self._nchannels * self._framerate * self._sampwidth,
self._nchannels * self._sampwidth,
self._sampwidth * 8, 'data'))
self._data_length_pos = self._file.tell()
self._file.write(struct.pack('<L', self._datalength))
self._headerwritten = True
assert self._headerwritten
if self._datawritten == self._datalength:
curpos = self._file.tell()
self._file.seek(self._form_length_pos, 0)
self._file.write(struct.pack('<L', 36 + self._datawritten))
self._file.seek(self._data_length_pos, 0)
self._file.write(struct.pack('<L', self._datawritten))
It is recommended that you Edit text format, this type of Fix handles quite a lot in one request
