mp3aduinterleaving.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

	// (this works only if the source can be read synchronously)
	fInputSource->syncGetNextFrame(dummyBuf, sizeof dummyBuf,
				       numBytesRead, presentationTime);
      } else {
	break; // from while (1)
      }
    }
#endif
    unsigned char* dataPtr;
    unsigned bytesAvailable;
    fFrames->getIncomingFrameParams(dataPtr, bytesAvailable);

    // Read the next incoming frame (asynchronously)
    fInputSource->getNextFrame(dataPtr, bytesAvailable,
			       &MP3ADUinterleaverBase::afterGettingFrame, this,
			       handleClosure, this);
  }
}

void MP3ADUdeinterleaver::afterGettingFrame(unsigned numBytesRead,
					    struct timeval presentationTime,
					    unsigned durationInMicroseconds) {
  // Get the (icc,ii) and set the frame size of the newly-read frame:
  unsigned char icc, ii;
  fFrames->getIncomingFrameParamsAfter(numBytesRead,
				       presentationTime, durationInMicroseconds,
				       icc, ii);

  // Compare these to the values we saw last:
  if (icc != fICClastSeen || ii == fIIlastSeen) { 
    // We've started a new interleave cycle
    // (or interleaving was not used).  Release all
    // pending ADU frames to the ADU->MP3 conversion step:
    fFrames->startNewCycle();
  } else {
    // We're still in the same cycle as before.
    // Move the newly-read frame into place, so it can be used:
    fFrames->moveIncomingFrameIntoPlace();
  }

  fICClastSeen = icc;
  fIIlastSeen = ii;
}

void MP3ADUdeinterleaver::releaseOutgoingFrame() {
  unsigned char* fromPtr;
  fFrames->getReleasingFrameParams(fromPtr, fFrameSize,
				   fPresentationTime, fDurationInMicroseconds);

  if (fFrameSize > fMaxSize) {
    fNumTruncatedBytes = fFrameSize - fMaxSize;
    fFrameSize = fMaxSize;
  }
  memmove(fTo, fromPtr, fFrameSize);

  fFrames->releaseNext();
}

////////// InterleavingFrames (implementation) //////////

#define MAX_FRAME_SIZE 2000 /* conservatively high */

class InterleavingFrameDescriptor {
public:
  InterleavingFrameDescriptor() {frameDataSize = 0;}

  unsigned frameDataSize; // includes ADU descriptor and (modified) MPEG hdr
  struct timeval presentationTime;
  unsigned durationInMicroseconds;
  unsigned char frameData[MAX_FRAME_SIZE]; // ditto
};

InterleavingFrames::InterleavingFrames(unsigned maxCycleSize)
  : fMaxCycleSize(maxCycleSize), fNextIndexToRelease(0),
    fDescriptors(new InterleavingFrameDescriptor[maxCycleSize]) {
}
InterleavingFrames::~InterleavingFrames() {
  delete[] fDescriptors;
}

Boolean InterleavingFrames::haveReleaseableFrame() {
  return fDescriptors[fNextIndexToRelease].frameDataSize > 0;
}

void InterleavingFrames::getIncomingFrameParams(unsigned char index,
						unsigned char*& dataPtr,
						unsigned& bytesAvailable) {
  InterleavingFrameDescriptor& desc = fDescriptors[index];
  dataPtr = &desc.frameData[0];
  bytesAvailable = MAX_FRAME_SIZE;
}

void InterleavingFrames::getReleasingFrameParams(unsigned char index,
						 unsigned char*& dataPtr,
						 unsigned& bytesInUse,
						 struct timeval& presentationTime,
						 unsigned& durationInMicroseconds) {
  InterleavingFrameDescriptor& desc = fDescriptors[index];
  dataPtr = &desc.frameData[0];
  bytesInUse = desc.frameDataSize;
  presentationTime = desc.presentationTime;
  durationInMicroseconds = desc.durationInMicroseconds;
}

void InterleavingFrames::setFrameParams(unsigned char index,
					unsigned char icc,
					unsigned char ii,
					unsigned frameSize,
					struct timeval presentationTime,
					unsigned durationInMicroseconds) {
  InterleavingFrameDescriptor& desc = fDescriptors[index];
  desc.frameDataSize = frameSize;
  desc.presentationTime = presentationTime;
  desc.durationInMicroseconds = durationInMicroseconds;

  // Advance over the ADU descriptor, to get to the MPEG 'syncword':
  unsigned char* ptr = &desc.frameData[0];
  (void)ADUdescriptor::getRemainingFrameSize(ptr);

  // Replace the next 11 bits with (ii,icc):
  *ptr++ = ii;
  *ptr &=~ 0xE0;
  *ptr |= (icc<<5);
}

void InterleavingFrames::releaseNext() {
  fDescriptors[fNextIndexToRelease].frameDataSize = 0;
  fNextIndexToRelease = (fNextIndexToRelease+1)%fMaxCycleSize;
}

////////// DeinterleavingFrames (implementation) //////////

class DeinterleavingFrameDescriptor {
public:
  DeinterleavingFrameDescriptor() {frameDataSize = 0; frameData = NULL;}
  virtual ~DeinterleavingFrameDescriptor() {delete[] frameData;}

  unsigned frameDataSize; // includes ADU descriptor and (modified) MPEG hdr
  struct timeval presentationTime;
  unsigned durationInMicroseconds;
  unsigned char* frameData;
};

DeinterleavingFrames::DeinterleavingFrames()
  : fNextIndexToRelease(0), fHaveEndedCycle(False),
    fMinIndexSeen(MAX_CYCLE_SIZE), fMaxIndexSeen(0),
    fDescriptors(new DeinterleavingFrameDescriptor[MAX_CYCLE_SIZE+1]) {
}
DeinterleavingFrames::~DeinterleavingFrames() {
  delete[] fDescriptors;
}

Boolean DeinterleavingFrames::haveReleaseableFrame() {
  if (!fHaveEndedCycle) {
    // Check just the next frame in the sequence
    return fDescriptors[fNextIndexToRelease].frameDataSize > 0;
  } else {
    // We've just ended a cycle, so we can skip over frames that didn't
    // get filled in (due to packet loss):
    if (fNextIndexToRelease < fMinIndexSeen) {
      fNextIndexToRelease = fMinIndexSeen;
    }
    while (fNextIndexToRelease < fMaxIndexSeen
	   && fDescriptors[fNextIndexToRelease].frameDataSize == 0) {
      ++fNextIndexToRelease;
    }
    if (fNextIndexToRelease >= fMaxIndexSeen) {
      // No more frames are available from the cycle that we just ended, so
      // clear out all previously stored frames, then make available
      // the last-read frame, and return false for now:
      for (unsigned i = fMinIndexSeen; i < fMaxIndexSeen; ++i) {
	fDescriptors[i].frameDataSize = 0;
      }

      fMinIndexSeen = MAX_CYCLE_SIZE; fMaxIndexSeen = 0;
      moveIncomingFrameIntoPlace();

      fHaveEndedCycle = False;
      fNextIndexToRelease = 0;
      return False;
    }

    return True;
  }
}

void DeinterleavingFrames::getIncomingFrameParams(unsigned char*& dataPtr,
						  unsigned& bytesAvailable) {
  // Use fDescriptors[MAX_CYCLE_SIZE] to store the incoming frame,
  // prior to figuring out its real position:
  DeinterleavingFrameDescriptor& desc = fDescriptors[MAX_CYCLE_SIZE];
  if (desc.frameData == NULL) {
    // There's no buffer yet, so allocate a new one:
    desc.frameData = new unsigned char[MAX_FRAME_SIZE];
  }
  dataPtr = desc.frameData;
  bytesAvailable = MAX_FRAME_SIZE;
}

void DeinterleavingFrames
::getIncomingFrameParamsAfter(unsigned frameSize,
			      struct timeval presentationTime,
			      unsigned durationInMicroseconds,
			      unsigned char& icc, unsigned char& ii) {
  DeinterleavingFrameDescriptor& desc = fDescriptors[MAX_CYCLE_SIZE];
  desc.frameDataSize = frameSize;
  desc.presentationTime = presentationTime;
  desc.durationInMicroseconds = durationInMicroseconds;
  
  // Advance over the ADU descriptor, to get to the MPEG 'syncword':
  unsigned char* ptr = desc.frameData;
  (void)ADUdescriptor::getRemainingFrameSize(ptr);

  // Read the next 11 bits into (ii,icc), and replace them with all-1s:
  fIIlastSeen = ii = *ptr; *ptr++ = 0xFF;
  icc = (*ptr&0xE0)>>5; *ptr |= 0xE0;
}

void DeinterleavingFrames::getReleasingFrameParams(unsigned char*& dataPtr,
						   unsigned& bytesInUse,
						   struct timeval& presentationTime,
						   unsigned& durationInMicroseconds) {
  DeinterleavingFrameDescriptor& desc = fDescriptors[fNextIndexToRelease];
  dataPtr = desc.frameData;
  bytesInUse = desc.frameDataSize;
  presentationTime = desc.presentationTime;
  durationInMicroseconds = desc.durationInMicroseconds;
}

void DeinterleavingFrames::moveIncomingFrameIntoPlace() {
  DeinterleavingFrameDescriptor& fromDesc = fDescriptors[MAX_CYCLE_SIZE];
  DeinterleavingFrameDescriptor& toDesc = fDescriptors[fIIlastSeen];

  toDesc.frameDataSize = fromDesc.frameDataSize;
  toDesc.presentationTime = fromDesc.presentationTime;

  // Move the data pointer into place by swapping the data pointers:
  unsigned char* tmp = toDesc.frameData;
  toDesc.frameData = fromDesc.frameData;
  fromDesc.frameData = tmp;

  if (fIIlastSeen < fMinIndexSeen) {
    fMinIndexSeen = fIIlastSeen;
  }
  if (fIIlastSeen + 1 > fMaxIndexSeen) {
    fMaxIndexSeen = fIIlastSeen + 1;
  }
}

void DeinterleavingFrames::releaseNext() {
  fDescriptors[fNextIndexToRelease].frameDataSize = 0;
  fNextIndexToRelease = (fNextIndexToRelease+1)%MAX_CYCLE_SIZE;
}

void DeinterleavingFrames::startNewCycle() {
  fHaveEndedCycle = True;
}