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aifc.py
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"""Stuff to parse AIFF-C and AIFF files. Unless explicitly stated otherwise, the description below is true both for AIFF-C files and AIFF files. An AIFF-C file has the following structure. +-----------------+ | FORM | +-----------------+ | <size> | +----+------------+ | | AIFC | | +------------+ | | <chunks> | | | . | | | . | | | . | +----+------------+ An AIFF file has the string "AIFF" instead of "AIFC". A chunk consists of an identifier (4 bytes) followed by a size (4 bytes, big endian order), followed by the data. The size field does not include the size of the 8 byte header. The following chunk types are recognized. FVER <version number of AIFF-C defining document> (AIFF-C only). MARK <# of markers> (2 bytes) list of markers: <marker ID> (2 bytes, must be > 0) <position> (4 bytes) <marker name> ("pstring") COMM <# of channels> (2 bytes) <# of sound frames> (4 bytes) <size of the samples> (2 bytes) <sampling frequency> (10 bytes, IEEE 80-bit extended floating point) in AIFF-C files only: <compression type> (4 bytes) <human-readable version of compression type> ("pstring") SSND <offset> (4 bytes, not used by this program) <blocksize> (4 bytes, not used by this program) <sound data> A pstring consists of 1 byte length, a string of characters, and 0 or 1 byte pad to make the total length even. Usage. Reading AIFF files: f = aifc.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(). In some types of audio files, if the setpos() method is 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 namedtuple consisting of all of the above in the above order getmarkers() -- get the list of marks in the audio file or None if there are no marks getmark(id) -- get mark with the specified id (raises an error if the mark does not exist) 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(), the position given to setpos() and the position of marks are all 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 AIFF files: f = aifc.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: aiff() -- create an AIFF file (AIFF-C default) aifc() -- create an AIFF-C file 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 setmark(id, pos, name) -- add specified mark to the list of marks tell() -- return current position in output file (useful in combination with setmark()) 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. Marks can be added anytime. If there are any marks, you must call close() after all frames have been written. The close() method is called automatically when the class instance is destroyed. When a file is opened with the extension '.aiff', an AIFF file is written, otherwise an AIFF-C file is written. This default can be changed by calling aiff() or aifc() before the first writeframes or writeframesraw. """ import struct import builtins import warnings __all__ = ["Error", "open", "openfp"] class Error(Exception): pass _AIFC_version = 0xA2805140 # Version 1 of AIFF-C def _read_long(file): try: return struct.unpack('>l', file.read(4))[0] except struct.error: raise EOFError def _read_ulong(file): try: return struct.unpack('>L', file.read(4))[0] except struct.error: raise EOFError def _read_short(file): try: return struct.unpack('>h', file.read(2))[0] except struct.error: raise EOFError def _read_ushort(file): try: return struct.unpack('>H', file.read(2))[0] except struct.error: raise EOFError def _read_string(file): length = ord(file.read(1)) if length == 0: data = b'' else: data = file.read(length) if length & 1 == 0: dummy = file.read(1) return data _HUGE_VAL = 1.79769313486231e+308 # See <limits.h> def _read_float(f): # 10 bytes expon = _read_short(f) # 2 bytes sign = 1 if expon < 0: sign = -1 expon = expon + 0x8000 himant = _read_ulong(f) # 4 bytes lomant = _read_ulong(f) # 4 bytes if expon == himant == lomant == 0: f = 0.0 elif expon == 0x7FFF: f = _HUGE_VAL else: expon = expon - 16383 f = (himant * 0x100000000 + lomant) * pow(2.0, expon - 63) return sign * f def _write_short(f, x): f.write(struct.pack('>h', x)) def _write_ushort(f, x): f.write(struct.pack('>H', x)) def _write_long(f, x): f.write(struct.pack('>l', x)) def _write_ulong(f, x): f.write(struct.pack('>L', x)) def _write_string(f, s): if len(s) > 255: raise ValueError("string exceeds maximum pstring length") f.write(struct.pack('B', len(s))) f.write(s) if len(s) & 1 == 0: f.write(b'\x00') def _write_float(f, x): import math if x < 0: sign = 0x8000 x = x * -1 else: sign = 0 if x == 0: expon = 0 himant = 0 lomant = 0 else: fmant, expon = math.frexp(x) if expon > 16384 or fmant >= 1 or fmant != fmant: # Infinity or NaN expon = sign|0x7FFF himant = 0 lomant = 0 else: # Finite expon = expon + 16382 if expon < 0: # denormalized fmant = math.ldexp(fmant, expon) expon = 0 expon = expon | sign fmant = math.ldexp(fmant, 32) fsmant = math.floor(fmant) himant = int(fsmant) fmant = math.ldexp(fmant - fsmant, 32) fsmant = math.floor(fmant) lomant = int(fsmant) _write_ushort(f, expon) _write_ulong(f, himant) _write_ulong(f, lomant) from chunk import Chunk from collections import namedtuple _aifc_params = namedtuple('_aifc_params', 'nchannels sampwidth framerate nframes comptype compname') class Aifc_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 # _markers -- the marks in the audio file # available through the getmarkers() and getmark() # methods # _soundpos -- the position in the audio stream # available through the tell() method, set through the # setpos() method # # These variables are used internally only: # _version -- the AIFF-C version number # _decomp -- the decompressor from builtin module cl # _comm_chunk_read -- 1 iff the COMM chunk has been read # _aifc -- 1 iff reading an AIFF-C file # _ssnd_seek_needed -- 1 iff positioned correctly in audio # file for readframes() # _ssnd_chunk -- instantiation of a chunk class for the SSND chunk # _framesize -- size of one frame in the file def initfp(self, file): self._version = 0 self._convert = None self._markers = [] self._soundpos = 0 self._file = file chunk = Chunk(file) if chunk.getname() != b'FORM': raise Error('file does not start with FORM id') formdata = chunk.read(4) if formdata == b'AIFF': self._aifc = 0 elif formdata == b'AIFC': self._aifc = 1 else: raise Error('not an AIFF or AIFF-C file') self._comm_chunk_read = 0 while 1: self._ssnd_seek_needed = 1 try: chunk = Chunk(self._file) except EOFError: break chunkname = chunk.getname() if chunkname == b'COMM': self._read_comm_chunk(chunk) self._comm_chunk_read = 1 elif chunkname == b'SSND': self._ssnd_chunk = chunk dummy = chunk.read(8) self._ssnd_seek_needed = 0 elif chunkname == b'FVER': self._version = _read_ulong(chunk) elif chunkname == b'MARK': self._readmark(chunk) chunk.skip() if not self._comm_chunk_read or not self._ssnd_chunk: raise Error('COMM chunk and/or SSND chunk missing') def __init__(self, f): if isinstance(f, str): f = builtins.open(f, 'rb') # else, assume it is an open file object already self.initfp(f) def __enter__(self): return self def __exit__(self, *args): self.close() # # User visible methods. # def getfp(self): return self._file def rewind(self): self._ssnd_seek_needed = 1 self._soundpos = 0 def close(self): file = self._file if file is not None: self._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 getversion(self): ## return self._version def getparams(self): return _aifc_params(self.getnchannels(), self.getsampwidth(), self.getframerate(), self.getnframes(), self.getcomptype(), self.getcompname()) def getmarkers(self): if len(self._markers) == 0: return None return self._markers def getmark(self, id): for marker in self._markers: if id == marker[0]: return marker raise Error('marker {0!r} does not exist'.format(id)) def setpos(self, pos): if pos < 0 or pos > self._nframes: raise Error('position not in range') self._soundpos = pos self._ssnd_seek_needed = 1 def readframes(self, nframes): if self._ssnd_seek_needed: self._ssnd_chunk.seek(0) dummy = self._ssnd_chunk.read(8) pos = self._soundpos * self._framesize if pos: self._ssnd_chunk.seek(pos + 8) self._ssnd_seek_needed = 0 if nframes == 0: return b'' data = self._ssnd_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. # def _alaw2lin(self, data): import audioop return audioop.alaw2lin(data, 2) def _ulaw2lin(self, data): import audioop return audioop.ulaw2lin(data, 2) def _adpcm2lin(self, data): import audioop if not hasattr(self, '_adpcmstate'): # first time self._adpcmstate = None data, self._adpcmstate = audioop.adpcm2lin(data, 2, self._adpcmstate) return data def _read_comm_chunk(self, chunk): self._nchannels = _read_short(chunk) self._nframes = _read_long(chunk) self._sampwidth = (_read_short(chunk) + 7) // 8 self._framerate = int(_read_float(chunk)) self._framesize = self._nchannels * self._sampwidth if self._aifc: #DEBUG: SGI's soundeditor produces a bad size :-( kludge = 0 if chunk.chunksize == 18: kludge = 1 warnings.warn('Warning: bad COMM chunk size') chunk.chunksize = 23 #DEBUG end self._comptype = chunk.read(4) #DEBUG start if kludge: length = ord(chunk.file.read(1)) if length & 1 == 0: length = length + 1 chunk.chunksize = chunk.chunksize + length chunk.file.seek(-1, 1) #DEBUG end self._compname = _read_string(chunk) if self._comptype != b'NONE': if self._comptype == b'G722': self._convert = self._adpcm2lin elif self._comptype in (b'ulaw', b'ULAW'): self._convert = self._ulaw2lin elif self._comptype in (b'alaw', b'ALAW'): self._convert = self._alaw2lin else: raise Error('unsupported compression type') self._sampwidth = 2 else: self._comptype = b'NONE' self._compname = b'not compressed' def _readmark(self, chunk): nmarkers = _read_short(chunk) # Some files appear to contain invalid counts. # Cope with this by testing for EOF. try: for i in range(nmarkers): id = _read_short(chunk) pos = _read_long(chunk) name = _read_string(chunk) if pos or name: # some files appear to have # dummy markers consisting of # a position 0 and name '' self._markers.append((id, pos, name)) except EOFError: w = ('Warning: MARK chunk contains only %s marker%s instead of %s' % (len(self._markers), '' if len(self._markers) == 1 else 's', nmarkers)) warnings.warn(w) class Aifc_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 # _aifc -- whether we're writing an AIFF-C file or an AIFF file # set through the aifc() method, reset through the # aiff() method # # These variables are used internally only: # _version -- the AIFF-C version number # _comp -- the compressor from builtin module cl # _nframeswritten -- the number of audio frames actually written # _datalength -- the size of the audio samples written to the header # _datawritten -- the size of the audio samples actually written def __init__(self, f): if isinstance(f, str): filename = f f = builtins.open(f, 'wb') else: # else, assume it is an open file object already filename = '???' self.initfp(f) if filename[-5:] == '.aiff': self._aifc = 0 else: self._aifc = 1 def initfp(self, file): self._file = file self._version = _AIFC_version self._comptype = b'NONE' self._compname = b'not compressed' 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._markers = [] self._marklength = 0 self._aifc = 1 # AIFF-C is default def __del__(self): self.close() def __enter__(self): return self def __exit__(self, *args): self.close() # # User visible methods. # def aiff(self): if self._nframeswritten: raise Error('cannot change parameters after starting to write') self._aifc = 0 def aifc(self): if self._nframeswritten: raise Error('cannot change parameters after starting to write') self._aifc = 1 def setnchannels(self, nchannels): if self._nframeswritten: 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._nframeswritten: 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._nframeswritten: 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._nframeswritten: 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._nframeswritten: raise Error('cannot change parameters after starting to write') if comptype not in (b'NONE', b'ulaw', b'ULAW', b'alaw', b'ALAW', b'G722'): raise Error('unsupported compression type') self._comptype = comptype self._compname = compname def getcomptype(self): return self._comptype def getcompname(self): return self._compname ## def setversion(self, version): ## if self._nframeswritten: ## raise Error, 'cannot change parameters after starting to write' ## self._version = version def setparams(self, params): nchannels, sampwidth, framerate, nframes, comptype, compname = params if self._nframeswritten: raise Error('cannot change parameters after starting to write') if comptype not in (b'NONE', b'ulaw', b'ULAW', b'alaw', b'ALAW', b'G722'): raise Error('unsupported compression type') 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 _aifc_params(self._nchannels, self._sampwidth, self._framerate, self._nframes, self._comptype, self._compname) def setmark(self, id, pos, name): if id <= 0: raise Error('marker ID must be > 0') if pos < 0: raise Error('marker position must be >= 0') if not isinstance(name, bytes): raise Error('marker name must be bytes') for i in range(len(self._markers)): if id == self._markers[i][0]: self._markers[i] = id, pos, name return self._markers.append((id, pos, name)) def getmark(self, id): for marker in self._markers: if id == marker[0]: return marker raise Error('marker {0!r} does not exist'.format(id)) def getmarkers(self): if len(self._markers) == 0: return None return self._markers 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(len(data)) nframes = len(data) // (self._sampwidth * self._nchannels) if self._convert: data = self._convert(data) 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 is None: return try: self._ensure_header_written(0) if self._datawritten & 1: # quick pad to even size self._file.write(b'\x00') self._datawritten = self._datawritten + 1 self._writemarkers() if self._nframeswritten != self._nframes or \ self._datalength != self._datawritten or \ self._marklength: self._patchheader() finally: # Prevent ref cycles self._convert = None f = self._file self._file = None f.close() # # Internal methods. # def _lin2alaw(self, data): import audioop return audioop.lin2alaw(data, 2) def _lin2ulaw(self, data): import audioop return audioop.lin2ulaw(data, 2) def _lin2adpcm(self, data): import audioop if not hasattr(self, '_adpcmstate'): self._adpcmstate = None data, self._adpcmstate = audioop.lin2adpcm(data, 2, self._adpcmstate) return data def _ensure_header_written(self, datasize): if not self._nframeswritten: if self._comptype in (b'ULAW', b'ulaw', b'ALAW', b'alaw', b'G722'): if not self._sampwidth: self._sampwidth = 2 if self._sampwidth != 2: raise Error('sample width must be 2 when compressing ' 'with ulaw/ULAW, alaw/ALAW or G7.22 (ADPCM)') 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 _init_compression(self): if self._comptype == b'G722': self._convert = self._lin2adpcm elif self._comptype in (b'ulaw', b'ULAW'): self._convert = self._lin2ulaw elif self._comptype in (b'alaw', b'ALAW'): self._convert = self._lin2alaw def _write_header(self, initlength): if self._aifc and self._comptype != b'NONE': self._init_compression() self._file.write(b'FORM') if not self._nframes: self._nframes = initlength // (self._nchannels * self._sampwidth) self._datalength = self._nframes * self._nchannels * self._sampwidth if self._datalength & 1: self._datalength = self._datalength + 1 if self._aifc: if self._comptype in (b'ulaw', b'ULAW', b'alaw', b'ALAW'): self._datalength = self._datalength // 2 if self._datalength & 1: self._datalength = self._datalength + 1 elif self._comptype == b'G722': self._datalength = (self._datalength + 3) // 4 if self._datalength & 1: self._datalength = self._datalength + 1 try: self._form_length_pos = self._file.tell() except (AttributeError, OSError): self._form_length_pos = None commlength = self._write_form_length(self._datalength) if self._aifc: self._file.write(b'AIFC') self._file.write(b'FVER') _write_ulong(self._file, 4) _write_ulong(self._file, self._version) else: self._file.write(b'AIFF') self._file.write(b'COMM') _write_ulong(self._file, commlength) _write_short(self._file, self._nchannels) if self._form_length_pos is not None: self._nframes_pos = self._file.tell() _write_ulong(self._file, self._nframes) if self._comptype in (b'ULAW', b'ulaw', b'ALAW', b'alaw', b'G722'): _write_short(self._file, 8) else: _write_short(self._file, self._sampwidth * 8) _write_float(self._file, self._framerate) if self._aifc: self._file.write(self._comptype) _write_string(self._file, self._compname) self._file.write(b'SSND') if self._form_length_pos is not None: self._ssnd_length_pos = self._file.tell() _write_ulong(self._file, self._datalength + 8) _write_ulong(self._file, 0) _write_ulong(self._file, 0) def _write_form_length(self, datalength): if self._aifc: commlength = 18 + 5 + len(self._compname) if commlength & 1: commlength = commlength + 1 verslength = 12 else: commlength = 18 verslength = 0 _write_ulong(self._file, 4 + verslength + self._marklength + \ 8 + commlength + 16 + datalength) return commlength def _patchheader(self): curpos = self._file.tell() if self._datawritten & 1: datalength = self._datawritten + 1 self._file.write(b'\x00') else: datalength = self._datawritten if datalength == self._datalength and \ self._nframes == self._nframeswritten and \ self._marklength == 0: self._file.seek(curpos, 0) return self._file.seek(self._form_length_pos, 0) dummy = self._write_form_length(datalength) self._file.seek(self._nframes_pos, 0) _write_ulong(self._file, self._nframeswritten) self._file.seek(self._ssnd_length_pos, 0) _write_ulong(self._file, datalength + 8) self._file.seek(curpos, 0) self._nframes = self._nframeswritten self._datalength = datalength def _writemarkers(self): if len(self._markers) == 0: return self._file.write(b'MARK') length = 2 for marker in self._markers: id, pos, name = marker length = length + len(name) + 1 + 6 if len(name) & 1 == 0: length = length + 1 _write_ulong(self._file, length) self._marklength = length + 8 _write_short(self._file, len(self._markers)) for marker in self._markers: id, pos, name = marker _write_short(self._file, id) _write_ulong(self._file, pos) _write_string(self._file, name) 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 Aifc_read(f) elif mode in ('w', 'wb'): return Aifc_write(f) else: raise Error("mode must be 'r', 'rb', 'w', or 'wb'") openfp = open # B/W compatibility if __name__ == '__main__': import sys if not sys.argv[1:]: sys.argv.append('/usr/demos/data/audio/bach.aiff') fn = sys.argv[1] with open(fn, 'r') as f: print("Reading", fn) print("nchannels =", f.getnchannels()) print("nframes =", f.getnframes()) print("sampwidth =", f.getsampwidth()) print("framerate =", f.getframerate()) print("comptype =", f.getcomptype()) print("compname =", f.getcompname()) if sys.argv[2:]: gn = sys.argv[2] print("Writing", gn) with open(gn, 'w') as g: g.setparams(f.getparams()) while 1: data = f.readframes(1024) if not data: break g.writeframes(data) print("Done.")