]> git.ipfire.org Git - thirdparty/Python/cpython.git/commitdiff
New module aifc to read and write AIFF-C and AIFF files. See
authorSjoerd Mullender <sjoerd@acm.org>
Fri, 22 Jan 1993 12:53:11 +0000 (12:53 +0000)
committerSjoerd Mullender <sjoerd@acm.org>
Fri, 22 Jan 1993 12:53:11 +0000 (12:53 +0000)
(extensive) comments in the file for usage.

Lib/aifc.py [new file with mode: 0644]

diff --git a/Lib/aifc.py b/Lib/aifc.py
new file mode 100644 (file)
index 0000000..72c1b23
--- /dev/null
@@ -0,0 +1,912 @@
+# 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)
+#              if 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')
+# or
+#      f = aifc.openfp(filep, 'r')
+# where file is the name of a file and filep is 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 tuple 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
+# 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 postion in the file.
+#
+# Writing AIFF files:
+#      f = aifc.open(file, 'w')
+# or
+#      f = aifc.openfp(filep, 'w')
+# where file is the name of a file and filep is 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(nchannels, sampwidth, framerate, nframes, comptype, compname)
+#                      -- 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 the write audio frames using writeframesraw.
+# When all frames have been written, either call writeframes('') or
+# close() to patch up the sizes in the header.
+# Marks can be added anytime.  If there are any marks, ypu must call
+# close() after all frames have been written.
+#
+# 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 builtin
+import AL
+try:
+       import CL
+except ImportError:
+       pass
+
+Error = 'aifc.Error'
+
+_AIFC_version = 0xA2805140             # Version 1 of AIFF-C
+
+_skiplist = 'COMT', 'INST', 'MIDI', 'AESD', \
+         'APPL', 'NAME', 'AUTH', '(c) ', 'ANNO'
+
+_nchannelslist = [(1, AL.MONO), (2, AL.STEREO)]
+_sampwidthlist = [(8, AL.SAMPLE_8), (16, AL.SAMPLE_16), (24, AL.SAMPLE_24)]
+_frameratelist = [(48000, AL.RATE_48000), \
+                 (44100, AL.RATE_44100), \
+                 (32000, AL.RATE_32000), \
+                 (22050, AL.RATE_22050), \
+                 (16000, AL.RATE_16000), \
+                 (11025, AL.RATE_11025), \
+                 ( 8000,  AL.RATE_8000)]
+
+def _convert1(value, list):
+       for t in list:
+               if value == t[0]:
+                       return t[1]
+       raise Error, 'unknown parameter value'
+
+def _convert2(value, list):
+       for t in list:
+               if value == t[1]:
+                       return t[0]
+       raise Error, 'unknown parameter value'
+
+def _read_long(file):
+       x = 0L
+       for i in range(4):
+               byte = file.read(1)
+               if byte == '':
+                       raise EOFError
+               x = x*256 + ord(byte)
+       if x >= 0x80000000L:
+               x = x - 0x100000000L
+       return int(x)
+
+def _read_ulong(file):
+       x = 0L
+       for i in range(4):
+               byte = file.read(1)
+               if byte == '':
+                       raise EOFError
+               x = x*256 + ord(byte)
+       return x
+
+def _read_short(file):
+       x = 0
+       for i in range(2):
+               byte = file.read(1)
+               if byte == '':
+                       raise EOFError
+               x = x*256 + ord(byte)
+       if x >= 0x8000:
+               x = x - 0x10000
+       return x
+
+def _read_string(file):
+       length = ord(file.read(1))
+       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
+       import math
+       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 * 0x100000000L + lomant) * pow(2.0, expon - 63)
+       return sign * f
+
+def _write_short(f, x):
+       d, m = divmod(x, 256)
+       f.write(chr(d))
+       f.write(chr(m))
+
+def _write_long(f, x):
+       if x < 0:
+               x = x + 0x100000000L
+       data = []
+       for i in range(4):
+               d, m = divmod(x, 256)
+               data.insert(0, m)
+               x = d
+       for i in range(4):
+               f.write(chr(int(data[i])))
+
+def _write_string(f, s):
+       f.write(chr(len(s)))
+       f.write(s)
+       if len(s) & 1 == 0:
+               f.write(chr(0))
+
+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:         # 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 = long(fsmant)
+                       fmant = math.ldexp(fmant - fsmant, 32)
+                       fsmant = math.floor(fmant)
+                       lomant = long(fsmant)
+       _write_short(f, expon)
+       _write_long(f, himant)
+       _write_long(f, lomant)
+
+class Chunk():
+       def init(self, file):
+               self.file = file
+               self.chunkname = self.file.read(4)
+               if len(self.chunkname) < 4:
+                       raise EOFError
+               self.chunksize = _read_long(self.file)
+               self.size_read = 0
+               self.offset = self.file.tell()
+               return self
+
+       def rewind(self):
+               self.file.seek(self.offset, 0)
+               self.size_read = 0
+
+       def setpos(self, pos):
+               if pos < 0 or pos > self.chunksize:
+                       raise RuntimeError
+               self.file.seek(self.offset + pos, 0)
+               self.size_read = pos
+               
+       def read(self, length):
+               if self.size_read >= self.chunksize:
+                       return ''
+               if length > self.chunksize - self.size_read:
+                       length = self.chunksize - self.size_read
+               data = self.file.read(length)
+               self.size_read = self.size_read + len(data)
+               return data
+
+       def skip(self):
+               try:
+                       self.file.seek(self.chunksize - self.size_read, 1)
+               except RuntimeError:
+                       while self.size_read < self.chunksize:
+                               dummy = self.read(8192)
+                               if not dummy:
+                                       raise EOFError
+               if self.chunksize & 1:
+                       dummy = self.read(1)
+
+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() ir initfp() 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
+       #               tell() 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
+       def initfp(self, file):
+               self._file = file
+               self._version = 0
+               self._decomp = None
+               self._markers = []
+               self._soundpos = 0
+               form = self._file.read(4)
+               if form != 'FORM':
+                       raise Error, 'file does not start with FORM id'
+               formlength = _read_long(self._file)
+               if formlength <= 0:
+                       raise Error, 'invalid FORM chunk data size'
+               formdata = self._file.read(4)
+               formlength = formlength - 4
+               if formdata == 'AIFF':
+                       self._aifc = 0
+               elif formdata == '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().init(self._file)
+                       except EOFError:
+                               raise Error, 'COMM chunk and/or SSND chunk missing'
+                       formlength = formlength - 8 - chunk.chunksize
+                       if chunk.chunksize & 1:
+                               formlength = formlength - 1
+                       if chunk.chunkname == 'COMM':
+                               self._read_comm_chunk(chunk)
+                               self._comm_chunk_read = 1
+                       elif chunk.chunkname == 'SSND':
+                               self._ssnd_chunk = chunk
+                               dummy = chunk.read(8)
+                               self._ssnd_seek_needed = 0
+                               if formlength <= 0:
+                                       if not self._comm_chunk_read:
+                                               raise Error, 'COMM chunk missing'
+                                       break
+                       elif chunk.chunkname == 'FVER':
+                               self._version = _read_long(chunk)
+                       elif chunk.chunkname == 'MARK':
+                               self._readmark(chunk)
+                       elif chunk.chunkname in _skiplist:
+                               pass
+                       else:
+                               raise Error, 'unrecognized chunk type '+chunk.chunkname
+                       chunk.skip()
+               if self._aifc and self._decomp:
+                       params = [CL.ORIGINAL_FORMAT, 0, \
+                                 CL.BITS_PER_COMPONENT, 0, \
+                                 CL.FRAME_RATE, self._framerate]
+                       if self._nchannels == AL.MONO:
+                               params[1] = CL.MONO
+                       else:
+                               params[1] = CL.STEREO_INTERLEAVED
+                       if self._sampwidth == AL.SAMPLE_8:
+                               params[3] = 8
+                       elif self._sampwidth == AL.SAMPLE_16:
+                               params[3] = 16
+                       else:
+                               params[3] = 24
+                       self._decomp.SetParams(params)
+               return self
+
+       def init(self, filename):
+               return self.initfp(builtin.open(filename, 'r'))
+
+       #
+       # User visible methods.
+       #
+       def getfp(self):
+               return self._file
+
+       def rewind(self):
+               self._ssnd_seek_needed = 1
+               self._soundpos = 0
+
+       def close(self):
+               if self._decomp:
+                       self._decomp.CloseDecompressor()
+                       self._decomp = None
+               self._file.close()
+               self._file = None
+
+       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 self._nchannels, self._sampwidth, self._framerate, \
+                         self._nframes, self._comptype, self._compname
+
+       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 ' + `id` + ' does not exist'
+
+       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.rewind()
+                       dummy = self._ssnd_chunk.read(8)
+                       pos = self._soundpos * self._nchannels * self._sampwidth
+                       if self._decomp:
+                               if self._comptype in ('ULAW', 'ALAW'):
+                                       pos = pos / 2
+                       if pos:
+                               self._ssnd_chunk.setpos(pos + 8)
+                       self._ssnd_seek_needed = 0
+               size = nframes * self._nchannels * self._sampwidth
+               if self._decomp:
+                       if self._comptype in ('ULAW', 'ALAW'):
+                               size = size / 2
+               data = self._ssnd_chunk.read(size)
+               if self._decomp and data:
+                       params = [CL.FRAME_BUFFER_SIZE, len(data) * 2]
+                       self._decomp.SetParams(params)
+                       data = self._decomp.Decompress(len(data) / self._nchannels, data)
+               self._soundpos = self._soundpos + len(data) / (self._nchannels * self._sampwidth)
+               return data
+
+       #
+       # Internal methods.
+       #
+       def _read_comm_chunk(self, chunk):
+               nchannels = _read_short(chunk)
+               self._nchannels = _convert1(nchannels, _nchannelslist)
+               self._nframes = _read_long(chunk)
+               sampwidth = _read_short(chunk)
+               self._sampwidth = _convert1(sampwidth, _sampwidthlist)
+               framerate = _read_float(chunk)
+               self._framerate = _convert1(framerate, _frameratelist)
+               if self._aifc:
+                       #DEBUG: SGI's soundeditor produces a bad size :-(
+                       kludge = 0
+                       if chunk.chunksize == 18:
+                               kludge = 1
+                               print '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 != 'NONE':
+                               try:
+                                       import cl, CL
+                               except ImportError:
+                                       raise Error, 'cannot read compressed AIFF-C files'
+                               if self._comptype == 'ULAW':
+                                       scheme = CL.G711_ULAW
+                               elif self._comptype == 'ALAW':
+                                       scheme = CL.G711_ALAW
+                               else:
+                                       raise Error, 'unsupported compression type'
+                               self._decomp = cl.OpenDecompressor(scheme)
+               else:
+                       self._comptype = 'NONE'
+                       self._compname = 'not compressed'
+
+       def _readmark(self, chunk):
+               nmarkers = _read_short(chunk)
+               for i in range(nmarkers):
+                       id = _read_short(chunk)
+                       pos = _read_long(chunk)
+                       name = _read_string(chunk)
+                       self._markers.append((id, pos, name))
+
+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() or initfp() 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, filename):
+               self = self.initfp(builtin.open(filename, 'w'))
+               if filename[-5:] == '.aiff':
+                       self._aifc = 0
+               else:
+                       self._aifc = 1
+               return self
+
+       def initfp(self, file):
+               self._file = file
+               self._version = _AIFC_version
+               self._comptype = 'NONE'
+               self._compname = 'not compressed'
+               self._comp = None
+               self._nchannels = 0
+               self._sampwidth = 0
+               self._framerate = 0
+               self._nframes = 0
+               self._nframeswritten = 0
+               self._datawritten = 0
+               self._markers = []
+               self._marklength = 0
+               self._aifc = 1          # AIFF-C is default
+               return self
+
+       #
+       # 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'
+               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'
+               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'
+               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 ('NONE', 'ULAW', 'ALAW'):
+                       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, (nchannels, sampwidth, framerate, nframes, comptype, compname)):
+               if self._nframeswritten:
+                       raise Error, 'cannot change parameters after starting to write'
+               if comptype not in ('NONE', 'ULAW', 'ALAW'):
+                       raise Error, 'unsupported compression type'
+               self._nchannels = nchannels
+               self._sampwidth = sampwidth
+               self._framerate = framerate
+               self._nframes = nframes
+               self._comptype = comptype
+               self._compname = 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)):
+               if id <= 0:
+                       raise Error, 'marker ID must be > 0'
+               if pos < 0:
+                       raise Error, 'marker position must be >= 0'
+               if type(name) != type(''):
+                       raise Error, 'marker name must be a string'
+               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 ' + `id` + ' does not exist'
+
+       def getmarkers(self):
+               if len(self._markers) == 0:
+                       return None
+               return self._markers
+                               
+       def writeframesraw(self, data):
+               if not self._nframeswritten:
+                       if self._comptype in ('ULAW', 'ALAW'):
+                               if not self._sampwidth:
+                                       self._sampwidth = AL.SAMPLE_16
+                               if self._sampwidth != AL.SAMPLE_16:
+                                       raise Error, 'sample width must be 2 when compressing with ULAW or ALAW'
+                       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(len(data))
+               nframes = len(data) / (self._sampwidth * self._nchannels)
+               if self._comp:
+                       params = [CL.FRAME_BUFFER_SIZE, len(data), \
+                                 CL.COMPRESSED_BUFFER_SIZE, len(data)]
+                       self._comp.SetParams(params)
+                       data = self._comp.Compress(nframes, 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._datawritten & 1:
+                       # quick pad to even size
+                       self._file.write(chr(0))
+                       self._datawritten = self._datawritten + 1
+               self._writemarkers()
+               if self._nframeswritten != self._nframes or \
+                         self._datalength != self._datawritten or \
+                         self._marklength:
+                       self._patchheader()
+               if self._comp:
+                       self._comp.CloseCompressor()
+                       self._comp = None
+               self._file.close()
+               self._file = None
+
+       #
+       # Internal methods.
+       #
+       def _write_header(self, initlength):
+               if self._aifc and self._comptype != 'NONE':
+                       try:
+                               import cl, CL
+                       except ImportError:
+                               raise Error, 'cannot write compressed AIFF-C files'
+                       if self._comptype == 'ULAW':
+                               scheme = CL.G711_ULAW
+                       elif self._comptype == 'ALAW':
+                               scheme = CL.G711_ALAW
+                       else:
+                               raise Error, 'unsupported compression type'
+                       self._comp = cl.OpenCompressor(scheme)
+                       params = [CL.ORIGINAL_FORMAT, 0, \
+                                 CL.BITS_PER_COMPONENT, 0, \
+                                 CL.FRAME_RATE, self._framerate]
+                       if self._nchannels == AL.MONO:
+                               params[1] = CL.MONO
+                       else:
+                               params[1] = CL.STEREO_INTERLEAVED
+                       if self._sampwidth == AL.SAMPLE_8:
+                               params[3] = 8
+                       elif self._sampwidth == AL.SAMPLE_16:
+                               params[3] = 16
+                       else:
+                               params[3] = 24
+                       self._comp.SetParams(params)
+               self._file.write('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 and self._comptype in ('ULAW', 'ALAW'):
+                       self._datalength = self._datalength / 2
+                       if self._datalength & 1:
+                               self._datalength = self._datalength + 1
+               self._form_length_pos = self._file.tell()
+               commlength = self._write_form_length(self._datalength)
+               if self._aifc:
+                       self._file.write('AIFC')
+                       self._file.write('FVER')
+                       _write_long(self._file, 4)
+                       _write_long(self._file, self._version)
+               else:
+                       self._file.write('AIFF')
+               self._file.write('COMM')
+               _write_long(self._file, commlength)
+               _write_short(self._file, self._nchannels)
+               self._nframes_pos = self._file.tell()
+               _write_long(self._file, self._nframes)
+               _write_short(self._file, _convert2(self._sampwidth, _sampwidthlist))
+               _write_float(self._file, _convert2(self._framerate, _frameratelist))
+               if self._aifc:
+                       self._file.write(self._comptype)
+                       _write_string(self._file, self._compname)
+               self._file.write('SSND')
+               self._ssnd_length_pos = self._file.tell()
+               _write_long(self._file, self._datalength + 8)
+               _write_long(self._file, 0)
+               _write_long(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_long(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(chr(0))
+               else:
+                       datalength = self._datawritten
+               if datalength == self._datalength and \
+                         self._nframes == self._nframeswritten:
+                       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_long(self._file, self._nframeswritten)
+               self._file.seek(self._ssnd_length_pos, 0)
+               _write_long(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('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_long(self._file, length)
+               self._marklength = length + 8
+               _write_short(len(self._file, markers))
+               for marker in self._markers:
+                       id, pos, name = marker
+                       _write_short(self._file, id)
+                       _write_long(self._file, pos)
+                       _write_string(self._file, name)
+
+def open(filename, mode):
+       if mode == 'r':
+               return Aifc_read().init(filename)
+       elif mode == 'w':
+               return Aifc_write().init(filename)
+       else:
+               raise Error, 'mode must be \'r\' or \'w\''
+
+def openfp(filep, mode):
+       if mode == 'r':
+               return Aifc_read().initfp(filep)
+       elif mode == 'w':
+               return Aifc_write().initfp(filep)
+       else:
+               raise Error, 'mode must be \'r\' or \'w\''