A module to parse/generate MediaDescription handles as used by QuickTime. Only

generic, video and audio implemented for now.

diff --git a/Mac/Lib/lib-toolbox/MediaDescr.py b/Mac/Lib/lib-toolbox/MediaDescr.py
new file mode 100644 (file)
index 0000000..3c73820
--- /dev/null
+++ b/Mac/Lib/lib-toolbox/MediaDescr.py
@@ -0,0 +1,97 @@
+# 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 = apply(struct.pack, tuple(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.