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97 lines
3 KiB
Python
97 lines
3 KiB
Python
# Parsers/generators for QuickTime media descriptions
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import struct
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Error = 'MediaDescr.Error'
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class _MediaDescriptionCodec:
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def __init__(self, trunc, size, names, fmt):
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self.trunc = trunc
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self.size = size
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self.names = names
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self.fmt = fmt
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def decode(self, data):
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if self.trunc:
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data = data[:self.size]
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values = struct.unpack(self.fmt, data)
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if len(values) != len(self.names):
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raise Error, ('Format length does not match number of names', descr)
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rv = {}
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for i in range(len(values)):
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name = self.names[i]
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value = values[i]
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if type(name) == type(()):
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name, cod, dec = name
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value = dec(value)
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rv[name] = value
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return rv
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def encode(dict):
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list = [self.fmt]
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for name in self.names:
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if type(name) == type(()):
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name, cod, dec = name
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else:
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cod = dec = None
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value = dict[name]
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if cod:
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value = cod(value)
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list.append(value)
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rv = struct.pack(*list)
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return rv
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# Helper functions
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def _tofixed(float):
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hi = int(float)
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lo = int(float*0x10000) & 0xffff
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return (hi<<16)|lo
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def _fromfixed(fixed):
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hi = (fixed >> 16) & 0xffff
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lo = (fixed & 0xffff)
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return hi + (lo / float(0x10000))
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def _tostr31(str):
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return chr(len(str)) + str + '\0'*(31-len(str))
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def _fromstr31(str31):
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return str31[1:1+ord(str31[0])]
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SampleDescription = _MediaDescriptionCodec(
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1, # May be longer, truncate
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16, # size
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('descSize', 'dataFormat', 'resvd1', 'resvd2', 'dataRefIndex'), # Attributes
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"l4slhh" # Format
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)
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SoundDescription = _MediaDescriptionCodec(
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1,
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36,
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('descSize', 'dataFormat', 'resvd1', 'resvd2', 'dataRefIndex',
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'version', 'revlevel', 'vendor', 'numChannels', 'sampleSize',
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'compressionID', 'packetSize', ('sampleRate', _tofixed, _fromfixed)),
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"l4slhhhh4shhhhl" # Format
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)
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SoundDescriptionV1 = _MediaDescriptionCodec(
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1,
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52,
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('descSize', 'dataFormat', 'resvd1', 'resvd2', 'dataRefIndex',
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'version', 'revlevel', 'vendor', 'numChannels', 'sampleSize',
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'compressionID', 'packetSize', ('sampleRate', _tofixed, _fromfixed), 'samplesPerPacket',
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'bytesPerPacket', 'bytesPerFrame', 'bytesPerSample'),
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"l4slhhhh4shhhhlllll" # Format
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)
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ImageDescription = _MediaDescriptionCodec(
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1, # May be longer, truncate
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86, # size
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('idSize', 'cType', 'resvd1', 'resvd2', 'dataRefIndex', 'version',
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'revisionLevel', 'vendor', 'temporalQuality', 'spatialQuality',
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'width', 'height', ('hRes', _tofixed, _fromfixed), ('vRes', _tofixed, _fromfixed),
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'dataSize', 'frameCount', ('name', _tostr31, _fromstr31),
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'depth', 'clutID'),
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'l4slhhhh4sllhhlllh32shh',
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)
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# XXXX Others, like TextDescription and such, remain to be done.
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