mpeg2indexfromtransportstream.cpp

H.264 RTSP 串流(live 555)視窗版本

  u_int16_t section_length = ((pkt[2]&0x0F)<<8) | pkt[3];
  if ((unsigned)(4+section_length) < size) size = (4+section_length);

  // Then, skip any descriptors following the "program_info_length":
  if (size < 22) return; // not enough data
  unsigned program_info_length = ((pkt[11]&0x0F)<<8) | pkt[12];
  pkt += 13; size -= 13;
  if (size < program_info_length) return; // not enough data
  pkt += program_info_length; size -= program_info_length;

  // Look at each ("stream_type","elementary_PID") pair, looking for a video stream
  // ("stream_type" == 1 or 2):
  while (size >= 9) {
    u_int8_t stream_type = pkt[0];
    u_int16_t elementary_PID = ((pkt[1]&0x1F)<<8) | pkt[2];
    if (stream_type == 1 || stream_type == 2) {
      fVideo_PID = elementary_PID;
      return;
    }

    u_int16_t ES_info_length = ((pkt[3]&0x0F)<<8) | pkt[4];
    pkt += 5; size -= 5;
    if (size < ES_info_length) return; // not enough data
    pkt += ES_info_length; size -= ES_info_length;
  }
}

Boolean MPEG2IFrameIndexFromTransportStream::deliverIndexRecord() {
  IndexRecord* head = fHeadIndexRecord;
  if (head == NULL) return False;

  // Check whether the head record has been parsed yet:
  if (head->recordType() == RECORD_UNPARSED) return False;

  // Remove the head record (the one whose data we'll be delivering):
  IndexRecord* next = head->next();
  head->unlink();
  if (next == head) {
    fHeadIndexRecord = fTailIndexRecord = NULL;
  } else {
    fHeadIndexRecord = next;
  }

  if (head->recordType() == RECORD_JUNK) {
    // Don't actually deliver the data to the client:
    delete head;
    return True;
  }

  // Deliver data from the head record:
#ifdef DEBUG
  envir() << "delivering: " << *head << "\n";
#endif
  if (fMaxSize < 11) {
    fFrameSize = 0;
  } else {
    fTo[0] = (u_int8_t)(head->recordType());
    fTo[1] = head->startOffset();
    fTo[2] = head->size();
    // Deliver the PCR, as 24 bits (integer part; little endian) + 8 bits (fractional part)
    float pcr = head->pcr();
    unsigned pcr_int = (unsigned)pcr;
    u_int8_t pcr_frac = (u_int8_t)(256*(pcr-pcr_int));
    fTo[3] = (unsigned char)(pcr_int);
    fTo[4] = (unsigned char)(pcr_int>>8);
    fTo[5] = (unsigned char)(pcr_int>>16);
    fTo[6] = (unsigned char)(pcr_frac);
    // Deliver the transport packet number (in little-endian order):
    unsigned long tpn = head->transportPacketNumber();
    fTo[7] = (unsigned char)(tpn);
    fTo[8] = (unsigned char)(tpn>>8);
    fTo[9] = (unsigned char)(tpn>>16);
    fTo[10] = (unsigned char)(tpn>>24);
    fFrameSize = 11;
  }

  // Free the (former) head record (as we're now done with it):
  delete head;

  // Complete delivery to the client:
  afterGetting(this);
  return True;
}

Boolean MPEG2IFrameIndexFromTransportStream::parseFrame() {
  // At this point, we have a queue of >=0 (unparsed) index records, representing
  // the data in the parse buffer from "fParseBufferFrameStart"
  // to "fParseBufferDataEnd".  We now parse through this data, looking for
  // a complete 'frame' (where a 'frame', in this case, means
  // a Video Sequence Header, GOP Header, Picture Header, or Slice).

  // Inspect the frame's initial 4-byte code, to make sure it starts with a system code:
  if (fParseBufferDataEnd-fParseBufferFrameStart < 4) return False; // not enough data
  unsigned numInitialBadBytes = 0;
  unsigned char const* p = &fParseBuffer[fParseBufferFrameStart];
  if (!(p[0] == 0 && p[1] == 0 && p[2] == 1)) {
    // There's no system code at the beginning.  Parse until we find one:
    if (fParseBufferParseEnd == fParseBufferFrameStart + 4) {
      // Start parsing from the beginning of the frame data:
      fParseBufferParseEnd = fParseBufferFrameStart;
    }
    unsigned char nextCode;
    if (!parseToNextCode(nextCode)) return False;

    numInitialBadBytes = fParseBufferParseEnd - fParseBufferFrameStart;
    //fprintf(stderr, "#####numInitialBadBytes: 0x%x\n", numInitialBadBytes);
    fParseBufferFrameStart = fParseBufferParseEnd;
    fParseBufferParseEnd += 4; // skip over the code that we just saw
    p = &fParseBuffer[fParseBufferFrameStart];
  }

  unsigned char curCode = p[3];
  RecordType curRecordType;
  unsigned char nextCode;
  switch (curCode) {
  case VIDEO_SEQUENCE_START_CODE:
  case VISUAL_OBJECT_SEQUENCE_START_CODE: {
    curRecordType = RECORD_VSH;
    while (1) {
      if (!parseToNextCode(nextCode)) return False;
      if (nextCode == GROUP_START_CODE || /*nextCode == GROUP_VOP_START_CODE ||*/
	  nextCode == PICTURE_START_CODE || nextCode == VOP_START_CODE) break;
      fParseBufferParseEnd += 4; // skip over the code that we just saw
    }
    break;
  }
  case GROUP_START_CODE:
    /*case GROUP_VOP_START_CODE:*/ {
    curRecordType = RECORD_GOP;
    while (1) {
      if (!parseToNextCode(nextCode)) return False;
      if (nextCode == PICTURE_START_CODE || nextCode == VOP_START_CODE) break;
      fParseBufferParseEnd += 4; // skip over the code that we just saw
    }
    break;
  }
  default: { // picture (including slices)
    curRecordType = RECORD_PIC_NON_IFRAME; // may get changed to IFRAME later
    while (1) {
      if (!parseToNextCode(nextCode)) return False;
      if (nextCode == VIDEO_SEQUENCE_START_CODE || nextCode == VISUAL_OBJECT_SEQUENCE_START_CODE ||
	  nextCode == GROUP_START_CODE || nextCode == GROUP_VOP_START_CODE ||
	  nextCode == PICTURE_START_CODE || nextCode == VOP_START_CODE) break;
      fParseBufferParseEnd += 4; // skip over the code that we just saw
    }
    break;
  }
  }

  if (curRecordType == RECORD_PIC_NON_IFRAME) {
    if (curCode == VOP_START_CODE) { // MPEG-4
      //fprintf(stderr, "#####parseFrame()1(4): 0x%x, 0x%x\n", curCode, fParseBuffer[fParseBufferFrameStart+4]&0xC0);
      if ((fParseBuffer[fParseBufferFrameStart+4]&0xC0) == 0) {
	// This is actually an I-frame.  Note it as such:
	curRecordType = RECORD_PIC_IFRAME;
      }
    } else { // MPEG-1 or 2
      //fprintf(stderr, "#####parseFrame()1(!4): 0x%x, 0x%x\n", curCode, fParseBuffer[fParseBufferFrameStart+5]&0x38);
      if ((fParseBuffer[fParseBufferFrameStart+5]&0x38) == 0x08) {
	// This is actually an I-frame.  Note it as such:
	curRecordType = RECORD_PIC_IFRAME;
      }
    }
  }

  // There is now a parsed 'frame', from "fParseBufferFrameStart"
  // to "fParseBufferParseEnd". Tag the corresponding index records to note this:
  unsigned frameSize = fParseBufferParseEnd - fParseBufferFrameStart + numInitialBadBytes;
#ifdef DEBUG
  envir() << "parsed " << recordTypeStr[curRecordType] << "; length "
	  << frameSize << "\n";
#endif
  for (IndexRecord* r = fHeadIndexRecord; ; r = r->next()) {
    if (numInitialBadBytes >= r->size()) {
      r->recordType() = RECORD_JUNK;
      numInitialBadBytes -= r->size();
    } else {
      r->recordType() = curRecordType;
    }
    if (r == fHeadIndexRecord) r->setFirstFlag();
    // indicates that this is the first record for this frame

    if (r->size() > frameSize) {
      // This record contains extra data that's not part of the frame.
      // Shorten this record, and move the extra data to a new record
      // that comes afterwards:
      u_int8_t newOffset = r->startOffset() + frameSize;
      u_int8_t newSize = r->size() - frameSize;
      r->size() = frameSize;
#ifdef DEBUG
      envir() << "tagged record (modified): " << *r << "\n";
#endif

      IndexRecord* newRecord
	= new IndexRecord(newOffset, newSize, r->transportPacketNumber(), r->pcr());
      newRecord->addAfter(r);
      if (fTailIndexRecord == r) fTailIndexRecord = newRecord;
#ifdef DEBUG
      envir() << "added extra record: " << *newRecord << "\n";
#endif
    } else {
#ifdef DEBUG
      envir() << "tagged record: " << *r << "\n";
#endif
    }
    frameSize -= r->size();
    if (frameSize == 0) break;
    if (r == fTailIndexRecord) { // this shouldn't happen
      envir() << "!!!!!Internal consistency error!!!!!\n";
      return False;
    }
  }

  // Finally, update our parse state (to skip over the now-parsed data):
  fParseBufferFrameStart = fParseBufferParseEnd;
  fParseBufferParseEnd += 4; // to skip over the next code (that we found)

  return True;
}

Boolean MPEG2IFrameIndexFromTransportStream
::parseToNextCode(unsigned char& nextCode) {
  unsigned char const* p = &fParseBuffer[fParseBufferParseEnd];
  unsigned char const* end = &fParseBuffer[fParseBufferDataEnd];
  while (p <= end-4) {
    if (p[2] > 1) p += 3; // common case (optimized)
    else if (p[2] == 0) ++p;
    else if (p[0] == 0 && p[1] == 0) { // && p[2] == 1
      // We found a code here:
      nextCode = p[3];
      fParseBufferParseEnd = p - &fParseBuffer[0]; // where we've gotten to
      return True;
    } else p += 3;
  }

  fParseBufferParseEnd = p - &fParseBuffer[0]; // where we've gotten to
  return False; // no luck this time
}

void MPEG2IFrameIndexFromTransportStream::compactParseBuffer() {
#ifdef DEBUG
  envir() << "Compacting parse buffer: [" << fParseBufferFrameStart
	  << "," << fParseBufferParseEnd << "," << fParseBufferDataEnd << "]";
#endif
  memmove(&fParseBuffer[0], &fParseBuffer[fParseBufferFrameStart],
	  fParseBufferDataEnd - fParseBufferFrameStart);
  fParseBufferDataEnd -= fParseBufferFrameStart;
  fParseBufferParseEnd -= fParseBufferFrameStart;
  fParseBufferFrameStart = 0;
#ifdef DEBUG
  envir() << "-> [" << fParseBufferFrameStart
	  << "," << fParseBufferParseEnd << "," << fParseBufferDataEnd << "]\n";
#endif
}

void MPEG2IFrameIndexFromTransportStream::addToTail(IndexRecord* newIndexRecord) {
#ifdef DEBUG
  envir() << "adding new: " << *newIndexRecord << "\n";
#endif
  if (fTailIndexRecord == NULL) {
    fHeadIndexRecord = fTailIndexRecord = newIndexRecord;
  } else {
    newIndexRecord->addAfter(fTailIndexRecord);
    fTailIndexRecord = newIndexRecord;
  }
}

////////// IndexRecord implementation //////////

IndexRecord::IndexRecord(u_int8_t startOffset, u_int8_t size,
			 unsigned long transportPacketNumber, float pcr)
  : fNext(this), fPrev(this), fRecordType(RECORD_UNPARSED),
    fStartOffset(startOffset), fSize(size),
    fPCR(pcr), fTransportPacketNumber(transportPacketNumber) {
}

IndexRecord::~IndexRecord() {
  IndexRecord* nextRecord = next();
  unlink();
  if (nextRecord != this) delete nextRecord;
}

void IndexRecord::addAfter(IndexRecord* prev) {
  fNext = prev->fNext;
  fPrev = prev;
  prev->fNext->fPrev = this;
  prev->fNext = this;
}

void IndexRecord::unlink() {
  fNext->fPrev = fPrev;
  fPrev->fNext = fNext;
  fNext = fPrev = this;
}