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