/// <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 ValidateTable(BitSplitter bs)
{
int pointer = (int)bs.GetInteger(8);
if (pointer != 0) throw new DemuxException("Non-zero pointers are not currently supported");
int table_id = (int)bs.GetInteger(8);
if (table_id != 0x02) throw new DemuxException("Wrong table ID for PMT");
SectionSyntax = bs.GetFlag();
if (!SectionSyntax) throw new DemuxException("Invalid PMT: incorrect section syntax");
bool zero = bs.GetFlag();
if (zero) throw new DemuxException("Invalid PMT: zero bit wasn't zero");
}
/// <summary>
/// Decode the bizzare PTS format
/// </summary>
private void ReadPTS(BitSplitter bs)
{
int marker = (int)bs.GetInteger(4);
if (marker != 2) throw new DemuxException("Invalid PES: PTS marker incorrect");
long part_1 = (long)bs.GetInteger(3);
bs.SkipBits(1);
long part_2 = (long)bs.GetInteger(15);
bs.SkipBits(1);
long part_3 = (long)bs.GetInteger(15);
bs.SkipBits(1);
PTS = part_3 + (part_2 << 15) + (part_1 << 30);
}
private void ReadSpecialForm(BitSplitter bs)
{
byte[] data = bs.RemainingBytes();
if (data.Length < PacketLength) throw new DemuxException("Invalid PES: packet shorter than described");
MemoryStream ms = new MemoryStream(data, 0, PacketLength);
FrameData = ms.ToArray();
}
private void ReadExtendedHeader(BitSplitter bs)
{
throw new NotImplementedException();
}
/// <summary>
/// Reads the long list of flags in the default PES header.
/// </summary>
private void ReadFlags(BitSplitter bs)
{
ScrambleControl = (int)bs.GetInteger(2);
HighPriority = bs.GetFlag();
HasAlignment = bs.GetFlag();
IsCopyright = bs.GetFlag();
IsOriginal = bs.GetFlag();
HasPTS = bs.GetFlag();
HasDTS = bs.GetFlag();
if (HasDTS && !HasPTS) throw new DemuxException("Invalid PES: DTS without PTS is not allowed");
HasESCR = bs.GetFlag();
HasEsRate = bs.GetFlag();
UsesTrickMode = bs.GetFlag();
MoreCopyright = bs.GetFlag();
HasPesCRC = bs.GetFlag();
HasPesExtension = bs.GetFlag();
}
/// <summary>
/// Digest a PES payload into structured table.
/// Does not handle split-payloads -- agregate payloads before calling
/// </summary>
public PES(byte[] RawPayload)
{
BitSplitter bs = new BitSplitter(RawPayload);
int start_code = (int)bs.GetInteger(24);
if (start_code != 1) throw new DemuxException("Invalid PES: start code prefix missing");
PTS = DTS = -1;
StreamId = (int)bs.GetInteger(8);
PacketLength = (int)bs.GetInteger(16);
// Both these methods set 'FrameData'
if (SpecialStream(StreamId)) {
ReadSpecialForm(bs);
} else {
DecodeElementaryStream(bs);
}
}
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();
}
private void ReadTransportHeader(BitSplitter bs)
{
bs.SkipToNextByte(); // Sync byte
Error = bs.GetFlag();
StartIndicator = bs.GetFlag();
HighPriority = bs.GetFlag();
PID = (int)bs.GetInteger(13);
ScrambleCode = (int)bs.GetInteger(2);
HasAdaptionField = bs.GetFlag();
HasPayload = bs.GetFlag();
Counter = (int)bs.GetInteger(4);
}
/// <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 PAT(byte[] RawPayload)
{
Map = new Dictionary<int, int>();
BitSplitter bs = new BitSplitter(RawPayload);
ValidateTable(bs);
bs.SkipBits(2); // reserved;
SectionLength = (int)bs.GetInteger(12);
TransportID = (int)bs.GetInteger(16);
bs.SkipBits(2); // reserved
Version = (int)bs.GetInteger(5);
IsCurrent = bs.GetFlag();
SectionNumber = (int)bs.GetInteger(8);
LastSection = (int)bs.GetInteger(8);
int bits_left = (SectionLength - 5) - 4; // remaining length in bytes, excluding CRC
int items = bits_left / 4;
for (int i = 0; i < items; i++) {
int prog = (int)bs.GetInteger(16);
bs.SkipBits(3);
int pid = (int)bs.GetInteger(13);
if (!Map.ContainsKey(prog))
Map.Add(prog, pid);
else throw new DemuxException("Invalid PAT: program number specified more than once (" + prog + ")");
}
// Ignoring CRC.
}
private void CheckPayloadType(BitSplitter bs)
{
if (payload.Length > 4) {
if (payload[0] == 0 && payload[1] == 0 && payload[2] == 0x01) {
PayloadIs_PES = true;
}
}
if (!PayloadIs_PES && HasPayload && StartIndicator) {
if (payload[0] != 0x00) throw new DemuxException("Non-zero pointer values are not yet supported!");
TableId = payload[1];
}
}
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);
}
}
/// <summary>Digest data into structured packet</summary>
public Packet(byte[] RawPacket)
{
if (RawPacket[0] != 0x47) throw new DemuxException("Sync byte missing");
PCR = -1; TableId = -1; PayloadIs_PES = false;
BitSplitter bs = new BitSplitter(RawPacket);
ReadTransportHeader(bs);
if (PID == 0x1FFF) return; // null packet
CheckAdaptionField(bs);
payload = bs.RemainingBytes();
CheckPayloadType(bs);
}
/// <summary>
/// Decode the bizzare PTS format
/// </summary>
private void ReadPTS(BitSplitter bs)
{
int marker = (int)bs.GetInteger(4);
if (marker != 2) throw new DemuxException("Invalid PES: PTS marker incorrect");
long part_1 = (long)bs.GetInteger(3);
bs.SkipBits(1);
long part_2 = (long)bs.GetInteger(15);
bs.SkipBits(1);
long part_3 = (long)bs.GetInteger(15);
bs.SkipBits(1);
unchecked { // allow overflow so we can catch it later:
PTS = (UInt32)(part_3 + (part_2 << 15) + (part_1 << 30));
}
}
private void ReadExtendedHeader(BitSplitter bs)
{
// not yet implemented
}
