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Editing: wave.py
"""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 linear samples) getcompname() -- returns human-readable version of compression type ('not compressed' linear samples) 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 position 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(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('') or close() to patch up the sizes in the header. The close() method is called automatically when the class instance is destroyed. """ import __builtin__ __all__ = ["open", "openfp", "Error"] class Error(Exception): pass WAVE_FORMAT_PCM = 0x0001 _array_fmts = None, 'b', 'h', None, 'i' import struct import sys from chunk import Chunk def _byteswap3(data): ba = bytearray(data) ba[::3] = data[2::3] ba[2::3] = data[::3] return bytes(ba) 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 """ def initfp(self, file): self._convert = None self._soundpos = 0 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._fmt_chunk_read = 0 self._data_chunk = None while 1: self._data_seek_needed = 1 try: chunk = Chunk(self._file, bigendian = 0) except EOFError: break chunkname = chunk.getname() if chunkname == 'fmt ': self._read_fmt_chunk(chunk) self._fmt_chunk_read = 1 elif 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 break 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): 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 try: self.initfp(f) except: if self._i_opened_the_file: f.close() raise def __del__(self): 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 file = self._i_opened_the_file if file: self._i_opened_the_file = None file.close() 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.seek(0, 0) pos = self._soundpos * self._framesize if pos: self._data_chunk.seek(pos, 0) self._data_seek_needed = 0 if nframes == 0: return '' 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 import array chunk = self._data_chunk 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 = chunk.file chunk.size_read = chunk.size_read + nitems * self._sampwidth data.byteswap() data = data.tostring() else: data = self._data_chunk.read(nframes * self._framesize) if self._sampwidth == 3 and sys.byteorder == 'big': data = _byteswap3(data) if self._convert and data: data = self._convert(data) self._soundpos = self._soundpos + len(data) // (self._nchannels * self._sampwidth) return data # # Internal methods. # 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 else: raise Error, 'unknown format: %r' % (wFormatTag,) 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 """ def __init__(self, f): self._i_opened_the_file = None if isinstance(f, basestring): f = __builtin__.open(f, 'wb') self._i_opened_the_file = f try: self.initfp(f) except: if self._i_opened_the_file: f.close() raise 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 self._headerwritten = False def __del__(self): 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, params): nchannels, sampwidth, framerate, nframes, comptype, compname = params 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 in (2, 4) and sys.byteorder == 'big': import array a = array.array(_array_fmts[self._sampwidth]) a.fromstring(data) data = a assert data.itemsize == self._sampwidth data.byteswap() data.tofile(self._file) self._datawritten = self._datawritten + len(data) * self._sampwidth else: if self._sampwidth == 3 and sys.byteorder == 'big': data = _byteswap3(data) 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): try: if self._file: self._ensure_header_written(0) if self._datalength != self._datawritten: self._patchheader() self._file.flush() finally: self._file = None file = self._i_opened_the_file if file: self._i_opened_the_file = None file.close() # # Internal methods. # def _ensure_header_written(self, datasize): if not self._headerwritten: 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): assert not self._headerwritten 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() 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 def _patchheader(self): assert self._headerwritten if self._datawritten == self._datalength: return 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)) self._file.seek(curpos, 0) self._datalength = self._datawritten 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 Wave_read(f) elif mode in ('w', 'wb'): return Wave_write(f) else: raise Error, "mode must be 'r', 'rb', 'w', or 'wb'" openfp = open # B/W compatibility
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