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474 lines
16 KiB
Python
474 lines
16 KiB
Python
"""Stuff to parse Sun and NeXT audio files.
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An audio file consists of a header followed by the data. The structure
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of the header is as follows.
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+---------------+
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| magic word |
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+---------------+
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| header size |
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+---------------+
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| data size |
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+---------------+
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| encoding |
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+---------------+
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| sample rate |
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+---------------+
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| # of channels |
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+---------------+
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| info |
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+---------------+
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The magic word consists of the 4 characters '.snd'. Apart from the
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info field, all header fields are 4 bytes in size. They are all
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32-bit unsigned integers encoded in big-endian byte order.
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The header size really gives the start of the data.
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The data size is the physical size of the data. From the other
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parameters the number of frames can be calculated.
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The encoding gives the way in which audio samples are encoded.
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Possible values are listed below.
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The info field currently consists of an ASCII string giving a
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human-readable description of the audio file. The info field is
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padded with NUL bytes to the header size.
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Usage.
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Reading audio files:
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f = sunau.open(file, 'r')
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where file is either the name of a file or an open file pointer.
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The open file pointer must have methods read(), seek(), and close().
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When the setpos() and rewind() methods are not used, the seek()
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method is not necessary.
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This returns an instance of a class with the following public methods:
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getnchannels() -- returns number of audio channels (1 for
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mono, 2 for stereo)
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getsampwidth() -- returns sample width in bytes
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getframerate() -- returns sampling frequency
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getnframes() -- returns number of audio frames
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getcomptype() -- returns compression type ('NONE' or 'ULAW')
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getcompname() -- returns human-readable version of
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compression type ('not compressed' matches 'NONE')
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getparams() -- returns a tuple consisting of all of the
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above in the above order
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getmarkers() -- returns None (for compatibility with the
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aifc module)
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getmark(id) -- raises an error since the mark does not
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exist (for compatibility with the aifc module)
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readframes(n) -- returns at most n frames of audio
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rewind() -- rewind to the beginning of the audio stream
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setpos(pos) -- seek to the specified position
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tell() -- return the current position
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close() -- close the instance (make it unusable)
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The position returned by tell() and the position given to setpos()
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are compatible and have nothing to do with the actual position in the
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file.
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The close() method is called automatically when the class instance
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is destroyed.
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Writing audio files:
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f = sunau.open(file, 'w')
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where file is either the name of a file or an open file pointer.
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The open file pointer must have methods write(), tell(), seek(), and
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close().
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This returns an instance of a class with the following public methods:
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setnchannels(n) -- set the number of channels
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setsampwidth(n) -- set the sample width
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setframerate(n) -- set the frame rate
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setnframes(n) -- set the number of frames
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setcomptype(type, name)
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-- set the compression type and the
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human-readable compression type
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setparams(tuple)-- set all parameters at once
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tell() -- return current position in output file
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writeframesraw(data)
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-- write audio frames without pathing up the
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file header
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writeframes(data)
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-- write audio frames and patch up the file header
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close() -- patch up the file header and close the
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output file
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You should set the parameters before the first writeframesraw or
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writeframes. The total number of frames does not need to be set,
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but when it is set to the correct value, the header does not have to
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be patched up.
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It is best to first set all parameters, perhaps possibly the
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compression type, and then write audio frames using writeframesraw.
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When all frames have been written, either call writeframes('') or
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close() to patch up the sizes in the header.
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The close() method is called automatically when the class instance
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is destroyed.
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"""
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# from <multimedia/audio_filehdr.h>
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AUDIO_FILE_MAGIC = 0x2e736e64
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AUDIO_FILE_ENCODING_MULAW_8 = 1
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AUDIO_FILE_ENCODING_LINEAR_8 = 2
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AUDIO_FILE_ENCODING_LINEAR_16 = 3
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AUDIO_FILE_ENCODING_LINEAR_24 = 4
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AUDIO_FILE_ENCODING_LINEAR_32 = 5
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AUDIO_FILE_ENCODING_FLOAT = 6
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AUDIO_FILE_ENCODING_DOUBLE = 7
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AUDIO_FILE_ENCODING_ADPCM_G721 = 23
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AUDIO_FILE_ENCODING_ADPCM_G722 = 24
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AUDIO_FILE_ENCODING_ADPCM_G723_3 = 25
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AUDIO_FILE_ENCODING_ADPCM_G723_5 = 26
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AUDIO_FILE_ENCODING_ALAW_8 = 27
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# from <multimedia/audio_hdr.h>
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AUDIO_UNKNOWN_SIZE = 0xFFFFFFFFL # ((unsigned)(~0))
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_simple_encodings = [AUDIO_FILE_ENCODING_MULAW_8,
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AUDIO_FILE_ENCODING_LINEAR_8,
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AUDIO_FILE_ENCODING_LINEAR_16,
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AUDIO_FILE_ENCODING_LINEAR_24,
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AUDIO_FILE_ENCODING_LINEAR_32,
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AUDIO_FILE_ENCODING_ALAW_8]
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class Error(Exception):
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pass
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def _read_u32(file):
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x = 0L
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for i in range(4):
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byte = file.read(1)
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if byte == '':
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raise EOFError
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x = x*256 + ord(byte)
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return x
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def _write_u32(file, x):
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data = []
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for i in range(4):
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d, m = divmod(x, 256)
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data.insert(0, m)
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x = d
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for i in range(4):
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file.write(chr(int(data[i])))
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class Au_read:
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def __init__(self, f):
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if type(f) == type(''):
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import __builtin__
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f = __builtin__.open(f, 'rb')
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self.initfp(f)
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def __del__(self):
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if self._file:
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self.close()
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def initfp(self, file):
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self._file = file
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self._soundpos = 0
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magic = int(_read_u32(file))
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if magic != AUDIO_FILE_MAGIC:
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raise Error, 'bad magic number'
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self._hdr_size = int(_read_u32(file))
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if self._hdr_size < 24:
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raise Error, 'header size too small'
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if self._hdr_size > 100:
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raise Error, 'header size ridiculously large'
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self._data_size = _read_u32(file)
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if self._data_size != AUDIO_UNKNOWN_SIZE:
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self._data_size = int(self._data_size)
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self._encoding = int(_read_u32(file))
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if self._encoding not in _simple_encodings:
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raise Error, 'encoding not (yet) supported'
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if self._encoding in (AUDIO_FILE_ENCODING_MULAW_8,
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AUDIO_FILE_ENCODING_ALAW_8):
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self._sampwidth = 2
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self._framesize = 1
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elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_8:
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self._framesize = self._sampwidth = 1
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elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_16:
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self._framesize = self._sampwidth = 2
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elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_24:
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self._framesize = self._sampwidth = 3
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elif self._encoding == AUDIO_FILE_ENCODING_LINEAR_32:
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self._framesize = self._sampwidth = 4
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else:
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raise Error, 'unknown encoding'
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self._framerate = int(_read_u32(file))
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self._nchannels = int(_read_u32(file))
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self._framesize = self._framesize * self._nchannels
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if self._hdr_size > 24:
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self._info = file.read(self._hdr_size - 24)
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for i in range(len(self._info)):
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if self._info[i] == '\0':
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self._info = self._info[:i]
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break
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else:
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self._info = ''
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def getfp(self):
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return self._file
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def getnchannels(self):
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return self._nchannels
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def getsampwidth(self):
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return self._sampwidth
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def getframerate(self):
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return self._framerate
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def getnframes(self):
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if self._data_size == AUDIO_UNKNOWN_SIZE:
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return AUDIO_UNKNOWN_SIZE
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if self._encoding in _simple_encodings:
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return self._data_size / self._framesize
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return 0 # XXX--must do some arithmetic here
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def getcomptype(self):
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if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
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return 'ULAW'
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elif self._encoding == AUDIO_FILE_ENCODING_ALAW_8:
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return 'ALAW'
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else:
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return 'NONE'
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def getcompname(self):
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if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
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return 'CCITT G.711 u-law'
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elif self._encoding == AUDIO_FILE_ENCODING_ALAW_8:
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return 'CCITT G.711 A-law'
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else:
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return 'not compressed'
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def getparams(self):
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return self.getnchannels(), self.getsampwidth(), \
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self.getframerate(), self.getnframes(), \
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self.getcomptype(), self.getcompname()
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def getmarkers(self):
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return None
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def getmark(self, id):
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raise Error, 'no marks'
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def readframes(self, nframes):
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if self._encoding in _simple_encodings:
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if nframes == AUDIO_UNKNOWN_SIZE:
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data = self._file.read()
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else:
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data = self._file.read(nframes * self._framesize * self._nchannels)
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if self._encoding == AUDIO_FILE_ENCODING_MULAW_8:
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import audioop
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data = audioop.ulaw2lin(data, self._sampwidth)
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return data
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return None # XXX--not implemented yet
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def rewind(self):
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self._soundpos = 0
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self._file.seek(self._hdr_size)
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def tell(self):
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return self._soundpos
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def setpos(self, pos):
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if pos < 0 or pos > self.getnframes():
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raise Error, 'position not in range'
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self._file.seek(pos * self._framesize + self._hdr_size)
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self._soundpos = pos
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def close(self):
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self._file = None
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class Au_write:
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def __init__(self, f):
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if type(f) == type(''):
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import __builtin__
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f = __builtin__.open(f, 'wb')
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self.initfp(f)
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def __del__(self):
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if self._file:
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self.close()
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def initfp(self, file):
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self._file = file
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self._framerate = 0
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self._nchannels = 0
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self._sampwidth = 0
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self._framesize = 0
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self._nframes = AUDIO_UNKNOWN_SIZE
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self._nframeswritten = 0
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self._datawritten = 0
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self._datalength = 0
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self._info = ''
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self._comptype = 'ULAW' # default is U-law
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def setnchannels(self, nchannels):
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if self._nframeswritten:
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raise Error, 'cannot change parameters after starting to write'
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if nchannels not in (1, 2, 4):
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raise Error, 'only 1, 2, or 4 channels supported'
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self._nchannels = nchannels
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def getnchannels(self):
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if not self._nchannels:
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raise Error, 'number of channels not set'
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return self._nchannels
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def setsampwidth(self, sampwidth):
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if self._nframeswritten:
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raise Error, 'cannot change parameters after starting to write'
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if sampwidth not in (1, 2, 4):
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raise Error, 'bad sample width'
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self._sampwidth = sampwidth
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def getsampwidth(self):
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if not self._framerate:
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raise Error, 'sample width not specified'
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return self._sampwidth
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def setframerate(self, framerate):
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if self._nframeswritten:
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raise Error, 'cannot change parameters after starting to write'
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self._framerate = framerate
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def getframerate(self):
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if not self._framerate:
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raise Error, 'frame rate not set'
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return self._framerate
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def setnframes(self, nframes):
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if self._nframeswritten:
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raise Error, 'cannot change parameters after starting to write'
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if nframes < 0:
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raise Error, '# of frames cannot be negative'
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self._nframes = nframes
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def getnframes(self):
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return self._nframeswritten
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def setcomptype(self, type, name):
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if type in ('NONE', 'ULAW'):
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self._comptype = type
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else:
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raise Error, 'unknown compression type'
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def getcomptype(self):
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return self._comptype
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def getcompname(self):
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if self._comptype == 'ULAW':
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return 'CCITT G.711 u-law'
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elif self._comptype == 'ALAW':
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return 'CCITT G.711 A-law'
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else:
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return 'not compressed'
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def setparams(self, (nchannels, sampwidth, framerate, nframes, comptype, compname)):
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self.setnchannels(nchannels)
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self.setsampwidth(sampwidth)
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self.setframerate(framerate)
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self.setnframes(nframes)
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self.setcomptype(comptype, compname)
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def getparams(self):
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return self.getnchannels(), self.getsampwidth(), \
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self.getframerate(), self.getnframes(), \
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self.getcomptype(), self.getcompname()
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def tell(self):
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return self._nframeswritten
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def writeframesraw(self, data):
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self._ensure_header_written()
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nframes = len(data) / self._framesize
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if self._comptype == 'ULAW':
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import audioop
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data = audioop.lin2ulaw(data, self._sampwidth)
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self._file.write(data)
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self._nframeswritten = self._nframeswritten + nframes
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self._datawritten = self._datawritten + len(data)
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def writeframes(self, data):
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self.writeframesraw(data)
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if self._nframeswritten != self._nframes or \
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self._datalength != self._datawritten:
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self._patchheader()
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def close(self):
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self._ensure_header_written()
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if self._nframeswritten != self._nframes or \
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self._datalength != self._datawritten:
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self._patchheader()
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self._file.flush()
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self._file = None
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#
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# private methods
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#
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def _ensure_header_written(self):
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if not self._nframeswritten:
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if not self._nchannels:
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raise Error, '# of channels not specified'
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if not self._sampwidth:
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raise Error, 'sample width not specified'
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if not self._framerate:
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raise Error, 'frame rate not specified'
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self._write_header()
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def _write_header(self):
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if self._comptype == 'NONE':
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if self._sampwidth == 1:
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encoding = AUDIO_FILE_ENCODING_LINEAR_8
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self._framesize = 1
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elif self._sampwidth == 2:
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encoding = AUDIO_FILE_ENCODING_LINEAR_16
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self._framesize = 2
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elif self._sampwidth == 4:
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encoding = AUDIO_FILE_ENCODING_LINEAR_32
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self._framesize = 4
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else:
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raise Error, 'internal error'
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elif self._comptype == 'ULAW':
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encoding = AUDIO_FILE_ENCODING_MULAW_8
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self._framesize = 1
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else:
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raise Error, 'internal error'
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self._framesize = self._framesize * self._nchannels
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_write_u32(self._file, AUDIO_FILE_MAGIC)
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header_size = 25 + len(self._info)
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header_size = (header_size + 7) & ~7
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_write_u32(self._file, header_size)
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if self._nframes == AUDIO_UNKNOWN_SIZE:
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length = AUDIO_UNKNOWN_SIZE
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else:
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length = self._nframes * self._framesize
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_write_u32(self._file, length)
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self._datalength = length
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_write_u32(self._file, encoding)
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_write_u32(self._file, self._framerate)
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_write_u32(self._file, self._nchannels)
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self._file.write(self._info)
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self._file.write('\0'*(header_size - len(self._info) - 24))
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def _patchheader(self):
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self._file.seek(8)
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_write_u32(self._file, self._datawritten)
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self._datalength = self._datawritten
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self._file.seek(0, 2)
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def open(f, mode=None):
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if mode is None:
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if hasattr(f, 'mode'):
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mode = f.mode
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else:
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mode = 'rb'
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if mode in ('r', 'rb'):
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return Au_read(f)
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elif mode in ('w', 'wb'):
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return Au_write(f)
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else:
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raise Error, "mode must be 'r', 'rb', 'w', or 'wb'"
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openfp = open
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