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sunau.py
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"""Stuff to parse Sun and NeXT audio files. An audio file 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 parameters 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 = sunau.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' or 'ULAW') getcompname() -- returns human-readable version of compression type ('not compressed' matches 'NONE') getparams() -- returns a namedtuple 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 audio files: f = sunau.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(b'') or close() to patch up the sizes in the header. The close() method is called automatically when the class instance is destroyed. """ from collections import namedtuple import warnings _sunau_params = namedtuple('_sunau_params', 'nchannels sampwidth framerate nframes comptype compname') # 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 = 0xFFFFFFFF # ((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] class Error(Exception): pass def _read_u32(file): x = 0 for i in range(4): byte = file.read(1) if not 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, int(m)) x = d file.write(bytes(data)) class Au_read: def __init__(self, f): if type(f) == type(''): import builtins f = builtins.open(f, 'rb') self._opened = True else: self._opened = False self.initfp(f) def __del__(self): if self._file: self.close() def __enter__(self): return self def __exit__(self, *args): self.close() 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 ridiculously 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_ALAW_8): self._sampwidth = 2 self._framesize = 1 elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_8: self._framesize = self._sampwidth = 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)) if not self._nchannels: raise Error('bad # of channels') self._framesize = self._framesize * self._nchannels if self._hdr_size > 24: self._info = file.read(self._hdr_size - 24) self._info, _, _ = self._info.partition(b'\0') else: self._info = b'' try: self._data_pos = file.tell() except (AttributeError, OSError): self._data_pos = None 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 _sunau_params(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._framesize) self._soundpos += len(data) // self._framesize 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): if self._data_pos is None: raise OSError('cannot seek') self._file.seek(self._data_pos) self._soundpos = 0 def tell(self): return self._soundpos def setpos(self, pos): if pos < 0 or pos > self.getnframes(): raise Error('position not in range') if self._data_pos is None: raise OSError('cannot seek') self._file.seek(self._data_pos + pos * self._framesize) self._soundpos = pos def close(self): file = self._file if file: self._file = None if self._opened: file.close() class Au_write: def __init__(self, f): if type(f) == type(''): import builtins f = builtins.open(f, 'wb') self._opened = True else: self._opened = False self.initfp(f) def __del__(self): if self._file: self.close() self._file = None def __enter__(self): return self def __exit__(self, *args): self.close() 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 = b'' self._comptype = 'ULAW' # default is U-law 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, 3, 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, params): nchannels, sampwidth, framerate, nframes, comptype, compname = params self.setnchannels(nchannels) self.setsampwidth(sampwidth) self.setframerate(framerate) self.setnframes(nframes) self.setcomptype(comptype, compname) def getparams(self): return _sunau_params(self.getnchannels(), self.getsampwidth(), self.getframerate(), self.getnframes(), self.getcomptype(), self.getcompname()) 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() if self._comptype == 'ULAW': import audioop data = audioop.lin2ulaw(data, self._sampwidth) nframes = len(data) // self._framesize 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: try: self._ensure_header_written() if self._nframeswritten != self._nframes or \ self._datalength != self._datawritten: self._patchheader() self._file.flush() finally: file = self._file self._file = None if self._opened: file.close() # # 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 == 3: encoding = AUDIO_FILE_ENCODING_LINEAR_24 self._framesize = 3 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 try: self._form_length_pos = self._file.tell() except (AttributeError, OSError): self._form_length_pos = None _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(b'\0'*(header_size - len(self._info) - 24)) def _patchheader(self): if self._form_length_pos is None: raise OSError('cannot seek') self._file.seek(self._form_length_pos) _write_u32(self._file, self._datawritten) self._datalength = self._datawritten self._file.seek(0, 2) 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 Au_read(f) elif mode in ('w', 'wb'): return Au_write(f) else: raise Error("mode must be 'r', 'rb', 'w', or 'wb'") def openfp(f, mode=None): warnings.warn("sunau.openfp is deprecated since Python 3.7. " "Use sunau.open instead.", DeprecationWarning, stacklevel=2) return open(f, mode=mode)