| Jack Jansen | ab98ae9 | 2001-08-19 22:13:00 +0000 | [diff] [blame] | 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 = apply(struct.pack, tuple(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. |