#include "mpegts/mpegts.h" #include "log.h" #include "bitstream.h" namespace mpegts { Header Header::Parse(BufferReader& reader) { if (reader.GetLeft()<4) throw std::runtime_error("Not enought data to read mpegts packet header"); //Get the MPEG TS header bytes BitReader bitreader(reader.GetData(4), 4); //The hceader Header header = {}; /* Sync Byte 8 0xff000000 Bit pattern of 0x47 (ASCII char 'G') Transport error indicator (TEI) 1 0x800000 Set when a demodulator can't correct errors from FEC data; indicating the packet is corrupt.[9] Payload unit start indicator (PUSI) 1 0x400000 Set when this packet contains the first uint8_t of a new payload unit. The first uint8_t of the payload will indicate where this new payload unit starts. This field allows a receiver that started reading mid transmission to know when it can start extracting data. Transport priority 1 0x200000 Set when the current packet has a higher priority than other packets with the same PID. PID 13 0x1fff00 Packet Identifier, describing the payload data. Transport scrambling control (TSC) 2 0xc0 '00' = Not scrambled. For DVB-CSA and ATSC DES only:[10] '01' (0x40) = Reserved for future use '10' (0x80) = Scrambled with even key '11' (0xC0) = Scrambled with odd key Adaptation field control 2 0x30 01 – no adaptation field, payload only, 10 – adaptation field only, no payload, 11 – adaptation field followed by payload, 00 – RESERVED for future use [11] Continuity counter 4 0xf Sequence number of payload packets (0x00 to 0x0F) within each stream (except PID 8191) Incremented per-PID, only when a payload flag is set. */ header.syncByte = bitreader.Get(8); header.transportErrorIndication = bitreader.Get(1); header.payloadUnitStartIndication = bitreader.Get(1); header.transportPriority = bitreader.Get(1); header.packetIdentifier = bitreader.Get(13); header.transportScramblingControl = bitreader.Get(2); header.adaptationFieldControl = (AdaptationFieldControl)bitreader.Get(2); header.continuityCounter = bitreader.Get(4); //Done return header; } void Header::Dump() const { //Dump Debug("[Header sync=%x,tei=%d,pusi=%d,prio=%d,pid=%d,tsc=%d,afc=%d,cc=%d/]\n", syncByte, transportErrorIndication, payloadUnitStartIndication, transportPriority, packetIdentifier, transportScramblingControl, adaptationFieldControl, continuityCounter ); } AdaptationField AdaptationField::Parse(BufferReader& reader) { if (reader.GetLeft() < 1) throw std::runtime_error("Not enought data to read mpegts adaptation field length"); /* Adaptation field length 8 Number of uint8_ts in the adaptation field immediately following this uint8_t Discontinuity indicator 1 0x80 Set if current TS packet is in a discontinuity state with respect to either the continuity counter or the program clock reference Random access indicator 1 0x40 Set when the stream may be decoded without errors from this point Elementary stream priority indicator 1 0x20 Set when this stream should be considered "high priority" PCR flag 1 0x10 Set when PCR field is present OPCR flag 1 0x08 Set when OPCR field is present Splicing point flag 1 0x04 Set when splice countdown field is present Transport private data flag 1 0x02 Set when transport private data is present Adaptation field extension flag 1 0x01 Set when adaptation extension data is present */ uint8_t adaptationFieldLength = reader.Get1(); //Ensure we have enough if (adaptationFieldLength > reader.GetLeft()) throw std::runtime_error("Not enought data to read mpegts adaptation field"); //Get current position uint32_t start = reader.Mark(); AdaptationField adaptationField = {}; //Get bit reader BitReader bitreader(reader.GetData(1), 1); adaptationField.discontinuityIndicator = bitreader.Get(1); adaptationField.randomAccessIndicator = bitreader.Get(1); adaptationField.elementaryStreamPriorityIndicator = bitreader.Get(1); adaptationField.pcrFlag = bitreader.Get(1); adaptationField.opcrFlag = bitreader.Get(1); adaptationField.splicingPointFlag = bitreader.Get(1); adaptationField.transportPrivateDataFlag = bitreader.Get(1); adaptationField.adaptationFieldExtensionFlag = bitreader.Get(1); //Go to the end of the adaptation field reader.GoTo(start + adaptationFieldLength); //Done return adaptationField; } Packet Packet::Parse(BufferReader& reader) { //Get packet header Packet packet = { mpegts::Header::Parse(reader)}; //Check if it has adaptation field if (packet.header.adaptationFieldControl == AdaptationFieldOnly || packet.header.adaptationFieldControl == AdaptationFiedlAndPayload) //Parse Adaptation field packet.adaptationField = mpegts::AdaptationField::Parse(reader); //If it has payload if (packet.header.adaptationFieldControl == PayloadOnly || packet.header.adaptationFieldControl == AdaptationFiedlAndPayload) { /* Payload Pointer (optional) 8 0xff Present only if the Payload Unit Start Indicator (PUSI) flag is set. It gives the index after this uint8_t at which the new payload unit starts. Any payload uint8_t before the index is part of the previous payload unit. Actual Payload variable The content of the payload. */ packet.payloadPointer = 0; //If we have a new payload unit if (packet.header.payloadUnitStartIndication) { //Ensure we have at least 1 uint8_t if (!reader.GetLeft()) throw std::runtime_error("Not enought data to read mpegts payload pointer"); //Get optional payload pointer packet.payloadPointer = reader.Peek1(); //If we have any if (*packet.payloadPointer) //Consume it reader.Skip(1); } } return packet; } namespace pes { Header Header::Parse(BufferReader& reader) { if (reader.GetLeft() < 6) throw std::runtime_error("Not enought data to read mpegtsp pes header"); /* PES packet header Packet start code prefix 3 uint8_ts 0x000001 Stream id 1 uint8_t Examples: Audio streams (0xC0-0xDF), Video streams (0xE0-0xEF) [4][5] Note: The above 4 uint8_ts is called the 32 bit start code. PES Packet length 2 uint8_ts Specifies the number of uint8_ts remaining in the packet after this field. Can be zero. If the PES packet length is set to zero, the PES packet can be of any length. A value of zero for the PES packet length can be used only when the PES packet payload is a video elementary stream.[6] Optional PES header variable length (length >= 3) not present in case of Padding stream & Private stream 2 (navigation data) */ Header header = {}; header.packetStartCodePrefix = reader.Get3(); header.streamId = reader.Get1(); header.packetLength = reader.Get2(); return header; } HeaderExtension HeaderExtension::Parse(BufferReader& reader) { if (reader.GetLeft() < 3) throw std::runtime_error("Not enought data to read mpegtsp pes extension header"); /* Marker bits 2 10 binary or 0x2 hex Scrambling control 2 00 implies not scrambled Priority 1 Data alignment indicator 1 1 indicates that the PES packet header is immediately followed by the video start code or audio syncword Copyright 1 1 implies copyrighted Original or Copy 1 1 implies original PTS DTS indicator 2 11 = both present, 01 is forbidden, 10 = only PTS, 00 = no PTS or DTS ESCR flag 1 ES rate flag 1 DSM trick mode flag 1 Additional copy info flag 1 CRC flag 1 extension flag 1 PES header length 8 gives the length of the remainder of the PES header in uint8_ts Optional fields variable length presence is determined by flag bits above Stuffing uint8_ts variable length 0xff */ //Get extended header BitReader bitreader(reader.GetData(3), 3); //Parse packet header HeaderExtension headerExtension = {}; headerExtension.markerBits = bitreader.Get(2); headerExtension.scramblingControl = bitreader.Get(2); headerExtension.priority = bitreader.Get(1); headerExtension.dataAlignmentIndicator = bitreader.Get(1); headerExtension.copyrigth = bitreader.Get(1); headerExtension.original = bitreader.Get(1); headerExtension.ptsdtsIndicator = (PTSDTSIndicator)bitreader.Get(2); headerExtension.escrFlag = bitreader.Get(1); headerExtension.rateFlag = bitreader.Get(1); headerExtension.trickModeFlag = bitreader.Get(1); headerExtension.aditionalInfoFlag = bitreader.Get(1); headerExtension.crcFlag = bitreader.Get(1); headerExtension.extensionFlag = bitreader.Get(1); headerExtension.remainderHeaderLength = bitreader.Get(8); //Get current postition auto pos = reader.Mark(); //Read PTS if (headerExtension.ptsdtsIndicator == Both || headerExtension.ptsdtsIndicator == OnlyPTS) { if (reader.GetLeft() < 5) throw std::runtime_error("Not enought data to read mpegtsp pes extension header PTS"); //PTS is 33 bits BitReader ptsreader(reader.GetData(5), 5); //Read parts ptsreader.Skip(4); uint64_t pts32_30 = ptsreader.Get(3); ptsreader.Skip(1); uint64_t pts29_15 = ptsreader.Get(15); ptsreader.Skip(1); uint64_t pts14_0 = ptsreader.Get(15); //Get PTS headerExtension.pts = (pts32_30 << 30) | (pts29_15 << 15) | pts14_0; } //Read DTS if (headerExtension.ptsdtsIndicator == Both) { if (reader.GetLeft() < 5) throw std::runtime_error("Not enought data to read mpegtsp pes extension header DTS"); //PTS is 33 bits BitReader ptsreader(reader.GetData(5), 5); //Read parts ptsreader.Skip(4); uint64_t dts32_30 = ptsreader.Get(3); ptsreader.Skip(1); uint64_t dts29_15 = ptsreader.Get(15); ptsreader.Skip(1); uint64_t dts14_0 = ptsreader.Get(15); //Get PTS headerExtension.dts = (dts32_30 << 30) | (dts29_15 << 15) | dts14_0; } //Skip the rest of the header reader.GoTo(pos + headerExtension.remainderHeaderLength); return headerExtension; } /* Stream ID Stream type extension present? 1011 1101 0xBD Private stream 1 (non MPEG audio, subpictures) Yes 1011 1110 0xBE Padding stream No 1011 1111 0xBF Private stream 2 (navigation data) No 110x xxxx 0xC0 - 0xDF MPEG-1 or MPEG-2 audio stream number x xxxx Yes 1110 xxxx 0xE0 - 0xEF MPEG-1 or MPEG-2 video stream number xxxx Yes */ StreamType GetStreamType(const uint8_t& streamId) { if (streamId == 0xBD) return PrivateStream1; else if (streamId == 0xBE) return PaddingStream; else if (streamId == 0xBF) return PrivateStream2; else if (streamId >= 0xC0 && streamId <= 0xDF) return AudioStream; else if (streamId >= 0xE0 && streamId <= 0xEF) return VideoStream; else return Invalid; } Packet Packet::Parse(BufferReader& reader) { //Parse header Packet packet = {Header::Parse(reader)}; //Check stream type switch (mpegts::pes::GetStreamType(packet.header.streamId)) { case PrivateStream1: [[fallthrough]]; case AudioStream: [[fallthrough]]; case VideoStream: //parse packet extesion packet.headerExtension = HeaderExtension::Parse(reader); break; default: //Do nothing ; } //Done return packet; } namespace adts { Header Header::Parse(BufferReader& reader) { //Ensure we have enought data for the header if (reader.GetLeft() < 7) throw std::runtime_error("Not enought data to read mpegtsp pes adts header"); /* ADTS header Letter Length (bits) Description A 12 Syncword, all bits must be set to 1. B 1 MPEG Version, set to 0 for MPEG-4 and 1 for MPEG-2. C 2 Layer, always set to 0. D 1 Protection absence, set to 1 if there is no CRC and 0 if there is CRC. E 2 Profile, the MPEG-4 Audio Object Type minus 1. F 4 MPEG-4 Sampling Frequency Index (15 is forbidden). G 1 Private bit, guaranteed never to be used by MPEG, set to 0 when encoding, ignore when decoding. H 3 MPEG-4 Channel Configuration (in the case of 0, the channel configuration is sent via an inband PCE (Program Config Element)). I 1 Originality, set to 1 to signal originality of the audio and 0 otherwise. J 1 Home, set to 1 to signal home usage of the audio and 0 otherwise. K 1 Copyright ID bit, the next bit of a centrally registered copyright identifier. This is transmitted by sliding over the bit-string in LSB-first order and putting the current bit value in this field and wrapping to start if reached end (circular buffer). L 1 Copyright ID start, signals that this frame's Copyright ID bit is the first one by setting 1 and 0 otherwise. M 13 Frame length, length of the ADTS frame including headers and CRC check. O 11 Buffer fullness, states the bit-reservoir per frame. P 2 Number of AAC frames (RDBs (Raw Data Blocks)) in ADTS frame minus 1. For maximum compatibility always use one AAC frame per ADTS frame. Q 16 CRC check (as of ISO/IEC 11172-3, subclause 2.4.3.1), if Protection absent is 0. */ //Get header BitReader bitreader(reader.GetData(7), 7); Header header = {}; header.syncWord = bitreader.Get(12); header.version = bitreader.Get(1); header.layer = bitreader.Get(2); header.protectionAbsence = bitreader.Get(1); header.objectType = bitreader.Get(2) + 1; header.samplingFrequency = bitreader.Get(4); header.priv = bitreader.Get(1); header.channelConfiguration = bitreader.Get(3); header.originality = bitreader.Get(1); header.home = bitreader.Get(1); header.copyrigth = bitreader.Get(1); header.copyrigthStart = bitreader.Get(1); header.frameLength = bitreader.Get(13); header.bufferFullness = bitreader.Get(11); header.numberOfFrames = bitreader.Get(2) + 1; if (!header.protectionAbsence) header.crc = reader.Get2(); //Done return header; } }; //namespace mpegts::pes::adts }; //namespace mpegts::pes }; //namespace mpegts