mpeg4videostreamframer.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

/**********
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the terms of the GNU Lesser General Public License as published by the
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option) any later version. (See <http://www.gnu.org/copyleft/lesser.html>.)

This library is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for
more details.

You should have received a copy of the GNU Lesser General Public License
along with this library; if not, write to the Free Software Foundation, Inc.,
59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
**********/
// "liveMedia"
// Copyright (c) 1996-2004 Live Networks, Inc.  All rights reserved.
// A filter that breaks up an MPEG-4 video elementary stream into
//   frames for:
// - Visual Object Sequence (VS) Header + Visual Object (VO) Header
//   + Video Object Layer (VOL) Header
// - Group of VOP (GOV) Header
// - VOP frame
// Implementation

#include "MPEG4VideoStreamFramer.hh"
#include "MPEGVideoStreamParser.hh"
#include <string.h>

////////// MPEG4VideoStreamParser definition //////////

// An enum representing the current state of the parser:
enum MPEGParseState {
  PARSING_VISUAL_OBJECT_SEQUENCE,
  PARSING_VISUAL_OBJECT_SEQUENCE_SEEN_CODE,
  PARSING_VISUAL_OBJECT,
  PARSING_VIDEO_OBJECT_LAYER,
  PARSING_GROUP_OF_VIDEO_OBJECT_PLANE,
  PARSING_VIDEO_OBJECT_PLANE,
  PARSING_VISUAL_OBJECT_SEQUENCE_END_CODE
}; 

class MPEG4VideoStreamParser: public MPEGVideoStreamParser {
public:
  MPEG4VideoStreamParser(MPEG4VideoStreamFramer* usingSource,
			 FramedSource* inputSource);
  virtual ~MPEG4VideoStreamParser();

private: // redefined virtual functions:
  virtual void flushInput();
  virtual unsigned parse();

private:
  MPEG4VideoStreamFramer* usingSource() {
    return (MPEG4VideoStreamFramer*)fUsingSource;
  }
  void setParseState(MPEGParseState parseState);

  unsigned parseVisualObjectSequence(Boolean haveSeenStartCode = False);
  unsigned parseVisualObject();
  unsigned parseVideoObjectLayer();
  unsigned parseGroupOfVideoObjectPlane();
  unsigned parseVideoObjectPlane();
  unsigned parseVisualObjectSequenceEndCode();

  // These are used for parsing within an already-read frame:
  Boolean getNextFrameBit(u_int8_t& result);
  Boolean getNextFrameBits(unsigned numBits, u_int32_t& result);

  // Which are used by:
  void analyzeVOLHeader();

private:
  MPEGParseState fCurrentParseState;
  unsigned fNumBitsSeenSoFar; // used by the getNextFrameBit*() routines 
  u_int32_t vop_time_increment_resolution;
  unsigned fNumVTIRBits;
      // # of bits needed to count to "vop_time_increment_resolution"
  u_int8_t fixed_vop_rate;
  unsigned fixed_vop_time_increment; // used if 'fixed_vop_rate' is set
  unsigned fSecondsSinceLastTimeCode, fTotalTicksSinceLastTimeCode, fPrevNewTotalTicks; 
  unsigned fPrevPictureCountDelta;
};


////////// MPEG4VideoStreamFramer implementation //////////

MPEG4VideoStreamFramer*
MPEG4VideoStreamFramer::createNew(UsageEnvironment& env,
				  FramedSource* inputSource) {
  // Need to add source type checking here???  #####
  return new MPEG4VideoStreamFramer(env, inputSource);
}

unsigned char* MPEG4VideoStreamFramer
::getConfigBytes(unsigned& numBytes) const {
  numBytes = fNumConfigBytes;
  return fConfigBytes;
}

MPEG4VideoStreamFramer::MPEG4VideoStreamFramer(UsageEnvironment& env,
					       FramedSource* inputSource,
					       Boolean createParser)
  : MPEGVideoStreamFramer(env, inputSource),
    fProfileAndLevelIndication(0),
    fConfigBytes(NULL), fNumConfigBytes(0),
    fNewConfigBytes(NULL), fNumNewConfigBytes(0) {
  fParser = createParser
    ? new MPEG4VideoStreamParser(this, inputSource)
    : NULL;
}

MPEG4VideoStreamFramer::~MPEG4VideoStreamFramer() {
  delete[] fConfigBytes; delete[] fNewConfigBytes;
}

void MPEG4VideoStreamFramer::startNewConfig() {
  delete[] fNewConfigBytes; fNewConfigBytes = NULL;
  fNumNewConfigBytes = 0;
}

void MPEG4VideoStreamFramer
::appendToNewConfig(unsigned char* newConfigBytes, unsigned numNewBytes) {
  // Allocate a new block of memory for the new config bytes:
  unsigned char* configNew
    = new unsigned char[fNumNewConfigBytes + numNewBytes];

  // Copy the old, then the new, config bytes there:
  memmove(configNew, fNewConfigBytes, fNumNewConfigBytes);
  memmove(&configNew[fNumNewConfigBytes], newConfigBytes, numNewBytes);
  
  delete[] fNewConfigBytes; fNewConfigBytes = configNew;
  fNumNewConfigBytes += numNewBytes;
}

void MPEG4VideoStreamFramer::completeNewConfig() {
  delete fConfigBytes; fConfigBytes = fNewConfigBytes;
  fNewConfigBytes = NULL;
  fNumConfigBytes = fNumNewConfigBytes;
  fNumNewConfigBytes = 0;
}

Boolean MPEG4VideoStreamFramer::isMPEG4VideoStreamFramer() const {
  return True;
}

////////// MPEG4VideoStreamParser implementation //////////

MPEG4VideoStreamParser
::MPEG4VideoStreamParser(MPEG4VideoStreamFramer* usingSource,
			 FramedSource* inputSource)
  : MPEGVideoStreamParser(usingSource, inputSource),
    fCurrentParseState(PARSING_VISUAL_OBJECT_SEQUENCE),
    vop_time_increment_resolution(0), fNumVTIRBits(0),
    fixed_vop_rate(0), fixed_vop_time_increment(0),
    fSecondsSinceLastTimeCode(0), fTotalTicksSinceLastTimeCode(0),
    fPrevNewTotalTicks(0), fPrevPictureCountDelta(1) {
}

MPEG4VideoStreamParser::~MPEG4VideoStreamParser() {
}

void MPEG4VideoStreamParser::setParseState(MPEGParseState parseState) {
  fCurrentParseState = parseState;
  MPEGVideoStreamParser::setParseState();
}

void MPEG4VideoStreamParser::flushInput() {
  fSecondsSinceLastTimeCode = 0;
  fTotalTicksSinceLastTimeCode = 0;
  fPrevNewTotalTicks = 0;
  fPrevPictureCountDelta = 1;

  StreamParser::flushInput();
  if (fCurrentParseState != PARSING_VISUAL_OBJECT_SEQUENCE) {
    setParseState(PARSING_VISUAL_OBJECT_SEQUENCE); // later, change to GOV or VOP? #####
  }
}


unsigned MPEG4VideoStreamParser::parse() {
  try {
    switch (fCurrentParseState) {
    case PARSING_VISUAL_OBJECT_SEQUENCE: {
      return parseVisualObjectSequence();
    }
    case PARSING_VISUAL_OBJECT_SEQUENCE_SEEN_CODE: {
      return parseVisualObjectSequence(True);
    }
    case PARSING_VISUAL_OBJECT: {
      return parseVisualObject();
    }
    case PARSING_VIDEO_OBJECT_LAYER: {
      return parseVideoObjectLayer();
    }
    case PARSING_GROUP_OF_VIDEO_OBJECT_PLANE: {
      return parseGroupOfVideoObjectPlane();
    }
    case PARSING_VIDEO_OBJECT_PLANE: {
      return parseVideoObjectPlane();
    }
    case PARSING_VISUAL_OBJECT_SEQUENCE_END_CODE: {
      return parseVisualObjectSequenceEndCode();
    }
    default: {
      return 0; // shouldn't happen
    }
    }
  } catch (int /*e*/) {
#ifdef DEBUG
    fprintf(stderr, "MPEG4VideoStreamParser::parse() EXCEPTION (This is normal behavior - *not* an error)\n");
#endif
    return 0;  // the parsing got interrupted
  }
}

#define VISUAL_OBJECT_SEQUENCE_START_CODE 0x000001B0
#define VISUAL_OBJECT_SEQUENCE_END_CODE   0x000001B1
#define GROUP_VOP_START_CODE              0x000001B3
#define VISUAL_OBJECT_START_CODE          0x000001B5
#define VOP_START_CODE                    0x000001B6

unsigned MPEG4VideoStreamParser
::parseVisualObjectSequence(Boolean haveSeenStartCode) {
#ifdef DEBUG
  fprintf(stderr, "parsing VisualObjectSequence\n");
#endif
  usingSource()->startNewConfig();
  u_int32_t first4Bytes;
  if (!haveSeenStartCode) {
    while ((first4Bytes = test4Bytes()) != VISUAL_OBJECT_SEQUENCE_START_CODE) {
#ifdef DEBUG
      fprintf(stderr, "ignoring non VS header: 0x%08x\n", first4Bytes);
#endif
      get1Byte(); setParseState(PARSING_VISUAL_OBJECT_SEQUENCE);
          // ensures we progress over bad data
    }
    first4Bytes = get4Bytes();
  } else {
    // We've already seen the start code
    first4Bytes = VISUAL_OBJECT_SEQUENCE_START_CODE;
  }
  save4Bytes(first4Bytes);

  // The next byte is the "profile_and_level_indication":
  u_int8_t pali = get1Byte();
#ifdef DEBUG
  fprintf(stderr, "profile_and_level_indication: %02x\n", pali);
#endif
  saveByte(pali);
  usingSource()->fProfileAndLevelIndication = pali;

  // Now, copy all bytes that we see, up until we reach
  // a VISUAL_OBJECT_START_CODE:
  u_int32_t next4Bytes = get4Bytes();
  while (next4Bytes != VISUAL_OBJECT_START_CODE) {
    saveToNextCode(next4Bytes);
  }
  
  setParseState(PARSING_VISUAL_OBJECT);

  // Compute this frame's presentation time:
  usingSource()->computePresentationTime(fTotalTicksSinceLastTimeCode);

  // This header forms part of the 'configuration' information:
  usingSource()->appendToNewConfig(fStartOfFrame, curFrameSize());

  return curFrameSize();
}

static inline Boolean isVideoObjectStartCode(u_int32_t code) {
  return code >= 0x00000100 && code <= 0x0000011F;
}

unsigned MPEG4VideoStreamParser::parseVisualObject() {
#ifdef DEBUG
  fprintf(stderr, "parsing VisualObject\n");
#endif
  // Note that we've already read the VISUAL_OBJECT_START_CODE
  save4Bytes(VISUAL_OBJECT_START_CODE);

  // Next, extract the "visual_object_type" from the next 1 or 2 bytes:
  u_int8_t nextByte = get1Byte(); saveByte(nextByte);
  Boolean is_visual_object_identifier = (nextByte&0x80) != 0;
  u_int8_t visual_object_type;
  if (is_visual_object_identifier) {
#ifdef DEBUG
    fprintf(stderr, "visual_object_verid: 0x%x; visual_object_priority: 0x%x\n", (nextByte&0x78)>>3, (nextByte&0x07));
#endif
    nextByte = get1Byte(); saveByte(nextByte);
    visual_object_type = (nextByte&0xF0)>>4;
  } else {
    visual_object_type = (nextByte&0x78)>>3;
  }
#ifdef DEBUG
  fprintf(stderr, "visual_object_type: 0x%x\n", visual_object_type);
#endif
  // At present, we support only the "Video ID" "visual_object_type" (1)
  if (visual_object_type != 1) {
    usingSource()->envir() << "MPEG4VideoStreamParser::parseVisualObject(): Warning: We don't handle visual_object_type " << visual_object_type << "\n";
  }
  
  // Now, copy all bytes that we see, up until we reach
  // a video_object_start_code
  u_int32_t next4Bytes = get4Bytes();
  while (!isVideoObjectStartCode(next4Bytes)) {
    saveToNextCode(next4Bytes);
  }
  save4Bytes(next4Bytes);
#ifdef DEBUG
  fprintf(stderr, "saw a video_object_start_code: 0x%08x\n", next4Bytes);
#endif

  setParseState(PARSING_VIDEO_OBJECT_LAYER);

  // Compute this frame's presentation time:
  usingSource()->computePresentationTime(fTotalTicksSinceLastTimeCode);

  // This header forms part of the 'configuration' information:
  usingSource()->appendToNewConfig(fStartOfFrame, curFrameSize());

  return curFrameSize();
}

static inline Boolean isVideoObjectLayerStartCode(u_int32_t code) {
  return code >= 0x00000120 && code <= 0x0000012F;
}