jpegvideortpsource.cpp

流媒体传输协议的实现代码,非常有用.可以支持rtsp mms等流媒体传输协议

  *ptr++ = (BYTE)(h); // number of lines (must be a multiple of 8)
  *ptr++ = (BYTE)(w >> 8);
  *ptr++ = (BYTE)(w); // number of columns (must be a multiple of 8)
  *ptr++ = 0x03; // number of components
  *ptr++ = 0x01; // id of component
  *ptr++ = type ? 0x22 : 0x21; // sampling ratio (h,v)
  *ptr++ = 0x00; // quant table id
  *ptr++ = 0x02; // id of component
  *ptr++ = 0x11; // sampling ratio (h,v)
  *ptr++ = numQtables == 1 ? 0x00 : 0x01; // quant table id
  *ptr++ = 0x03; // id of component
  *ptr++ = 0x11; // sampling ratio (h,v)
  *ptr++ = 0x01; // quant table id
  
  createHuffmanHeader(ptr, lum_dc_codelens, sizeof lum_dc_codelens,
		      lum_dc_symbols, sizeof lum_dc_symbols, 0, 0);
  createHuffmanHeader(ptr, lum_ac_codelens, sizeof lum_ac_codelens,
		      lum_ac_symbols, sizeof lum_ac_symbols, 0, 1);
  createHuffmanHeader(ptr, chm_dc_codelens, sizeof chm_dc_codelens,
		      chm_dc_symbols, sizeof chm_dc_symbols, 1, 0);
  createHuffmanHeader(ptr, chm_ac_codelens, sizeof chm_ac_codelens,
		      chm_ac_symbols, sizeof chm_ac_symbols, 1, 1);

  // MARKER_SOS:
  *ptr++ = 0xFF;  *ptr++ = MARKER_SOS;
  *ptr++ = 0x00; *ptr++ = 0x0C; // size of chunk
  *ptr++ = 0x03; // number of components
  *ptr++ = 0x01; // id of component
  *ptr++ = 0x00; // huffman table id (DC, AC)
  *ptr++ = 0x02; // id of component
  *ptr++ = 0x11; // huffman table id (DC, AC)
  *ptr++ = 0x03; // id of component
  *ptr++ = 0x11; // huffman table id (DC, AC)
  *ptr++ = 0x00; // start of spectral
  *ptr++ = 0x3F; // end of spectral
  *ptr++ = 0x00; // successive approximation bit position (high, low)
}

// The default 'luma' and 'chroma' quantizer tables, in zigzag order:
static unsigned char const defaultQuantizers[128] = {
  // luma table:
  16, 11, 12, 14, 12, 10, 16, 14,
  13, 14, 18, 17, 16, 19, 24, 40,
  26, 24, 22, 22, 24, 49, 35, 37,
  29, 40, 58, 51, 61, 60, 57, 51,
  56, 55, 64, 72, 92, 78, 64, 68,
  87, 69, 55, 56, 80, 109, 81, 87,
  95, 98, 103, 104, 103, 62, 77, 113,
  121, 112, 100, 120, 92, 101, 103, 99,
  // chroma table:
  17, 18, 18, 24, 21, 24, 47, 26,
  26, 47, 99, 66, 56, 66, 99, 99,
  99, 99, 99, 99, 99, 99, 99, 99,
  99, 99, 99, 99, 99, 99, 99, 99,
  99, 99, 99, 99, 99, 99, 99, 99,
  99, 99, 99, 99, 99, 99, 99, 99,
  99, 99, 99, 99, 99, 99, 99, 99,
  99, 99, 99, 99, 99, 99, 99, 99
};

static void makeDefaultQtables(unsigned char* resultTables, unsigned Q) {
  int factor = Q;
  int q;

  if (Q < 1) factor = 1;
  else if (Q > 99) factor = 99;

  if (Q < 50) {
    q = 5000 / factor;
  } else {
    q = 200 - factor*2;
  }

  for (int i = 0; i < 128; ++i) {
    int newVal = (defaultQuantizers[i]*q + 50)/100;
    if (newVal < 1) newVal = 1;
    else if (newVal > 255) newVal = 255;
    resultTables[i] = newVal;
  }
}

Boolean JPEGVideoRTPSource
::processSpecialHeader(BufferedPacket* packet,
		       unsigned& resultSpecialHeaderSize) {
  unsigned char* headerStart = packet->data();
  unsigned packetSize = packet->dataSize();

  unsigned char* qtables = NULL;
  unsigned qtlen = 0;
  unsigned dri = 0;

  // There's at least 8-byte video-specific header
  /*
0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type-specific |              Fragment Offset                  |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Type     |       Q       |     Width     |     Height    |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  */
  if (packetSize < 8) return False;

  resultSpecialHeaderSize = 8;

  unsigned Offset = (unsigned)((DWORD)headerStart[1] << 16 | (DWORD)headerStart[2] << 8 | (DWORD)headerStart[3]);
  unsigned Type = (unsigned)headerStart[4];
  unsigned type = Type & 1;
  unsigned Q = (unsigned)headerStart[5];
  unsigned width = (unsigned)headerStart[6] * 8;
  if (width == 0) width = 256*8; // special case
  unsigned height = (unsigned)headerStart[7] * 8;
  if (height == 0) height = 256*8; // special case

  if (Type > 63) {
    // Restart Marker header present
    /*
0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|       Restart Interval        |F|L|       Restart Count       |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    */
    if (packetSize < resultSpecialHeaderSize + 4) return False;

    unsigned RestartInterval = (unsigned)((WORD)headerStart[resultSpecialHeaderSize] << 8 | (WORD)headerStart[resultSpecialHeaderSize + 1]);
    dri = RestartInterval;
    resultSpecialHeaderSize += 4;
  }

  if (Offset == 0) {
    if (Q > 127) {
      // Quantization Table header present
/*
0                   1                   2                   3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MBZ      |   Precision   |             Length            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                    Quantization Table Data                    |
|                              ...                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
      if (packetSize < resultSpecialHeaderSize + 4) return False;

      unsigned MBZ = (unsigned)headerStart[resultSpecialHeaderSize];
      if (MBZ == 0) {
	// unsigned Precision = (unsigned)headerStart[resultSpecialHeaderSize + 1];
	unsigned Length = (unsigned)((WORD)headerStart[resultSpecialHeaderSize + 2] << 8 | (WORD)headerStart[resultSpecialHeaderSize + 3]);

	//ASSERT(Length == 128);

	resultSpecialHeaderSize += 4;

	if (packetSize < resultSpecialHeaderSize + Length) return False;

	if (qtables) delete [] qtables;

	qtlen = Length;
	qtables = &headerStart[resultSpecialHeaderSize];
	
	resultSpecialHeaderSize += Length;
      }
    }
  }

  // If this is the first (or only) fragment of a JPEG frame, then we need
  // to synthesize a JPEG header, and prepend it to the incoming data.
  // Hack: We can do this because we allowed space for it in
  // our special "JPEGBufferedPacket" subclass.  We also adjust
  // "resultSpecialHeaderSize" to compensate for this, by subtracting
  // the size of the synthesized header.  Note that this will cause
  // "resultSpecialHeaderSize" to become negative, but the code that called
  // us (in "MultiFramedRTPSource") will handle this properly.
  if (Offset == 0) {
    unsigned char newQtables[128];
    if (qtlen == 0) {
      // A quantization table was not present in the RTP JPEG header,
      // so use the default tables, scaled according to the "Q" factor:
      makeDefaultQtables(newQtables, Q);
      qtables = newQtables;
      qtlen = sizeof newQtables;
    }

    unsigned hdrlen = computeJPEGHeaderSize(qtlen, dri);
    resultSpecialHeaderSize -= hdrlen; // goes negative
    headerStart += (int)resultSpecialHeaderSize; // goes backward
    createJPEGHeader(headerStart, type, width, height, qtables, qtlen, dri);
  }

  fCurrentPacketBeginsFrame = (Offset == 0);

  // The RTP "M" (marker) bit indicates the last fragment of a frame:
  ((JPEGBufferedPacket*)packet)->completesFrame
   = fCurrentPacketCompletesFrame = packet->rtpMarkerBit();

  return True;
}    

char const* JPEGVideoRTPSource::MIMEtype() const {
  return "video/JPEG";
}

////////// JPEGBufferedPacket and JPEGBufferedPacketFactory implementation

void JPEGBufferedPacket::reset() {
  BufferedPacket::reset();

  // Move our "fHead" and "fTail" forward, to allow space for a synthesized
  // JPEG header to precede the RTP data that comes in over the network.
  unsigned offset = MAX_JPEG_HEADER_SIZE;
  if (offset > fPacketSize) offset = fPacketSize; // shouldn't happen
  fHead = fTail = offset;
}

unsigned JPEGBufferedPacket
::nextEnclosedFrameSize(unsigned char*& framePtr, unsigned dataSize) {
  // Normally, the enclosed frame size is just "dataSize".  If, however,
  // the frame does not end with the "EOI" marker, then add this now:
  if (completesFrame && dataSize >= 2 &&
      !(framePtr[dataSize-2] == 0xFF && framePtr[dataSize-1] == MARKER_EOI)) {
    framePtr[dataSize++] = 0xFF;
    framePtr[dataSize++] = MARKER_EOI;
  }
  return dataSize;
}

BufferedPacket* JPEGBufferedPacketFactory
::createNewPacket(MultiFramedRTPSource* /*ourSource*/) {
  return new JPEGBufferedPacket;
}