Lib/plat-mac/Carbon/MediaDescr.py

   1 # Parsers/generators for QuickTime media descriptions
   2 import struct
   3
   4 Error = 'MediaDescr.Error'
   5
   6 class _MediaDescriptionCodec:
   7     def __init__(self, trunc, size, names, fmt):
   8         self.trunc = trunc
   9         self.size = size
  10         self.names = names
  11         self.fmt = fmt
  12
  13     def decode(self, data):
  14         if self.trunc:
  15             data = data[:self.size]
  16         values = struct.unpack(self.fmt, data)
  17         if len(values) != len(self.names):
  18             raise Error, ('Format length does not match number of names', descr)
  19         rv = {}
  20         for i in range(len(values)):
  21             name = self.names[i]
  22             value = values[i]
  23             if type(name) == type(()):
  24                 name, cod, dec = name
  25                 value = dec(value)
  26             rv[name] = value
  27         return rv
  28
  29     def encode(dict):
  30         list = [self.fmt]
  31         for name in self.names:
  32             if type(name) == type(()):
  33                 name, cod, dec = name
  34             else:
  35                 cod = dec = None
  36             value = dict[name]
  37             if cod:
  38                 value = cod(value)
  39             list.append(value)
  40         rv = struct.pack(*list)
  41         return rv
  42
  43 # Helper functions
  44 def _tofixed(float):
  45     hi = int(float)
  46     lo = int(float*0x10000) & 0xffff
  47     return (hi<<16)|lo
  48
  49 def _fromfixed(fixed):
  50     hi = (fixed >> 16) & 0xffff
  51     lo = (fixed & 0xffff)
  52     return hi + (lo / float(0x10000))
  53
  54 def _tostr31(str):
  55     return chr(len(str)) + str + '\0'*(31-len(str))
  56
  57 def _fromstr31(str31):
  58     return str31[1:1+ord(str31[0])]
  59
  60 SampleDescription = _MediaDescriptionCodec(
  61         1,      # May be longer, truncate
  62         16,     # size
  63         ('descSize', 'dataFormat', 'resvd1', 'resvd2', 'dataRefIndex'), # Attributes
  64         "l4slhh"        # Format
  65 )
  66
  67 SoundDescription = _MediaDescriptionCodec(
  68         1,
  69         36,
  70         ('descSize', 'dataFormat', 'resvd1', 'resvd2', 'dataRefIndex',
  71         'version', 'revlevel', 'vendor', 'numChannels', 'sampleSize',
  72         'compressionID', 'packetSize', ('sampleRate', _tofixed, _fromfixed)),
  73         "l4slhhhh4shhhhl"       # Format
  74 )
  75
  76 SoundDescriptionV1 = _MediaDescriptionCodec(
  77         1,
  78         52,
  79         ('descSize', 'dataFormat', 'resvd1', 'resvd2', 'dataRefIndex',
  80         'version', 'revlevel', 'vendor', 'numChannels', 'sampleSize',
  81         'compressionID', 'packetSize', ('sampleRate', _tofixed, _fromfixed), 'samplesPerPacket',
  82         'bytesPerPacket', 'bytesPerFrame', 'bytesPerSample'),
  83         "l4slhhhh4shhhhlllll"   # Format
  84 )
  85
  86 ImageDescription = _MediaDescriptionCodec(
  87         1,      # May be longer, truncate
  88         86,     # size
  89         ('idSize', 'cType', 'resvd1', 'resvd2', 'dataRefIndex', 'version',
  90          'revisionLevel', 'vendor', 'temporalQuality', 'spatialQuality',
  91          'width', 'height', ('hRes', _tofixed, _fromfixed), ('vRes', _tofixed, _fromfixed),
  92         'dataSize', 'frameCount', ('name', _tostr31, _fromstr31),
  93          'depth', 'clutID'),
  94         'l4slhhhh4sllhhlllh32shh',
  95 )
  96
  97 # XXXX Others, like TextDescription and such, remain to be done.