private void DecodeElementaryStream(BitSplitter bs)
{
int marker = (int)bs.GetInteger(2);
if (marker != 2) throw new DemuxException("Invalid PES: first marker missing");
ReadFlags(bs);
if (bs.BitOffset != 0) throw new DemuxException("Alignment problem in PES (internal)");
HeaderLength = (int)bs.GetInteger(8);
int head_start = bs.ByteOffset;
if (HasPTS && HasDTS) {
ReadDTS_PTS(bs);
} else if (HasPTS) {
ReadPTS(bs);
}
if (HasESCR) bs.SkipBytes(6); // not currently used.
if (HasEsRate) bs.SkipBits(24); // not currently used.
if (UsesTrickMode) bs.SkipBytes(1); // ignored
if (MoreCopyright) bs.SkipBytes(1); // ignored
if (HasPesCRC) bs.SkipBytes(2); // ignored
if (HasPesExtension) ReadExtendedHeader(bs);
// skip anything that's left
int head_end = bs.ByteOffset;
int to_skip = HeaderLength - (head_end - head_start);
if (to_skip < 0) throw new DemuxException("Invalid PES: declared header length did not match measured length");
bs.SkipBytes(to_skip);
// Now, the remaining bytes are data and padding
int data_length = PacketLength - (HeaderLength + to_skip) - 3; // no idea where the '3' is coming from...
byte[] data = bs.RemainingBytes();
if (data.Length < data_length)
throw new DemuxException("Invalid PES: packet shorter than described");
/*if (data.Length != data_length)
throw new DemuxException("Possible issue: expect length != real length");*/
MemoryStream ms = new MemoryStream(data, 0, data_length);
FrameData = ms.ToArray();
}
/// <summary>
/// Digest a packet payload into structured table. Payload should be from the pointer field onward.
/// Does not yet handle multi-packet tables
/// </summary>
public PMT(byte[] RawPayload)
{
BitSplitter bs = new BitSplitter(RawPayload);
Map = new Dictionary<int, int>();
ReverseMap = new Dictionary<StreamType, int>();
ValidateTable(bs);
bs.SkipBits(2);
SectionLength = (int)bs.GetInteger(12); // total length after this, in bytes; includes 4 byte CRC.
ProgramNumber = (int)bs.GetInteger(16);
bs.SkipBits(2);
Version = (int)bs.GetInteger(5);
IsCurrent = bs.GetFlag();
SectionNumber = (int)bs.GetInteger(8);
LastSection = (int)bs.GetInteger(8);
bs.SkipBits(3);
PCR_PID = (int)bs.GetInteger(13); // Either the PID of a channel timecode stream, or 0x1FFF for none.
bs.SkipBits(4);
ProgInfoLength = (int)bs.GetInteger(12); // number of bytes of descriptors.
if (bs.BitOffset != 0) throw new DemuxException("Byte alignment error (internal)");
bs.SkipBytes(ProgInfoLength); // ignore descriptors.
int info_bytes = (SectionLength - ProgInfoLength) - 13; // bytes of descriptor.
while (info_bytes > 0) { // descriptions can be variable length
int stream_type = (int)bs.GetInteger(8);
bs.SkipBits(3);
int pid = (int)bs.GetInteger(13);
bs.SkipBits(4);
if (!Map.ContainsKey(pid)) Map.Add(pid, stream_type); // more complete map of pid types
else throw new DemuxException("Invalid PMT: PID specified more than once");
StreamType st = DecodeStreamType(stream_type);
if (!ReverseMap.ContainsKey(st)) ReverseMap.Add(st, pid); // store first pid of each type
int es_info_length = (int)bs.GetInteger(12);
bs.SkipBytes(es_info_length);
info_bytes -= 5 + es_info_length;
}
if (bs.BitOffset != 0) throw new DemuxException("Invalid PMT: program info length didn't match data");
// ignoring CRC.
}
private void CheckAdaptionField(BitSplitter bs)
{
if (HasAdaptionField) {
int adaption_end = (int)bs.GetInteger(8);
adaption_end += bs.ByteOffset;
Discont = bs.GetFlag();
KeyFrame = bs.GetFlag();
ES_Prio = bs.GetFlag();
HasPCR = bs.GetFlag();
HasOPCR = bs.GetFlag();
HasSplice = bs.GetFlag();
PrivateFlag = bs.GetFlag();
AdapExtFlag = bs.GetFlag();
if (bs.BitOffset != 0) throw new Exception("bit align problem");
if (HasPCR) {
PCR = (long)bs.GetInteger(33);
bs.SkipBits(15); // throw away useless sync stuff.
}
if (HasOPCR) bs.SkipBits(48); // throw away useless "old" timecode
if (HasSplice) bs.SkipBits(8); // throw away splice counter
if (PrivateFlag) {
int priv_len = (int)bs.GetInteger(8);
bs.SkipBytes(priv_len); // skip private data
}
// ignore the rest of the adaption field (it's mostly to support stuff we ignore)
int skip_len = adaption_end - bs.ByteOffset;
bs.SkipBytes(skip_len);
}
}
