mp3adu.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 library is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the
Free Software Foundation; either version 2.1 of the License, or (at your
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.
// 'ADU' MP3 streams (for improved loss-tolerance)
// Implementation

#include "MP3ADU.hh"
#include "MP3ADUdescriptor.hh"
#include "MP3Internals.hh"
#include <string.h>

#ifdef TEST_LOSS
#include "GroupsockHelper.hh"
#endif

// Segment data structures, used in the implementation below:

#define SegmentBufSize 2000	/* conservatively high */

class Segment {
public:
  unsigned char buf[SegmentBufSize];
  unsigned char* dataStart() { return &buf[descriptorSize]; }
  unsigned frameSize; // if it's a non-ADU frame
  unsigned dataHere(); // if it's a non-ADU frame

  unsigned descriptorSize;
  static unsigned const headerSize;
  unsigned sideInfoSize, aduSize;
  unsigned backpointer;

  struct timeval presentationTime;
  unsigned durationInMicroseconds;
};

unsigned const Segment::headerSize = 4;

#define SegmentQueueSize 10

class SegmentQueue {
public:
  SegmentQueue(Boolean directionIsToADU, Boolean includeADUdescriptors)
    : fDirectionIsToADU(directionIsToADU),
      fIncludeADUdescriptors(includeADUdescriptors) {
    reset();
  }

  Segment s[SegmentQueueSize];

  unsigned headIndex() {return fHeadIndex;}
  Segment& headSegment() {return s[fHeadIndex];}

  unsigned nextFreeIndex() {return fNextFreeIndex;}
  Segment& nextFreeSegment() {return s[fNextFreeIndex];}
  Boolean isEmpty() {return isEmptyOrFull() && totalDataSize() == 0;}
  Boolean isFull() {return isEmptyOrFull() && totalDataSize() > 0;}

  static unsigned nextIndex(unsigned ix) {return (ix+1)%SegmentQueueSize;}
  static unsigned prevIndex(unsigned ix) {return (ix+SegmentQueueSize-1)%SegmentQueueSize;}

  unsigned totalDataSize() {return fTotalDataSize;}

  void enqueueNewSegment(FramedSource* inputSource, FramedSource* usingSource);

  Boolean dequeue();

  Boolean insertDummyBeforeTail(unsigned backpointer);

  void reset() { fHeadIndex = fNextFreeIndex = fTotalDataSize = 0; }

private:
  static void sqAfterGettingSegment(void* clientData,
				    unsigned numBytesRead,
				    unsigned numTruncatedBytes,
				    struct timeval presentationTime,
				    unsigned durationInMicroseconds);

  Boolean sqAfterGettingCommon(Segment& seg, unsigned numBytesRead); 
  Boolean isEmptyOrFull() {return headIndex() == nextFreeIndex();}

  unsigned fHeadIndex, fNextFreeIndex, fTotalDataSize;

  // The following is used for asynchronous reads:
  FramedSource* fUsingSource;

  // This tells us whether the direction in which we're being used
  // is MP3->ADU, or vice-versa.  (This flag is used for debugging output.)
  Boolean fDirectionIsToADU;

  // The following is true iff we're used to enqueue incoming
  // ADU frames, and these have an ADU descriptor in front
  Boolean fIncludeADUdescriptors;
};

////////// ADUFromMP3Source //////////

ADUFromMP3Source::ADUFromMP3Source(UsageEnvironment& env,
				   FramedSource* inputSource,
				   Boolean includeADUdescriptors)
  : FramedFilter(env, inputSource),
    fAreEnqueueingMP3Frame(False),
    fSegments(new SegmentQueue(True /* because we're MP3->ADU */,
			       False /*no descriptors in incoming frames*/)),
    fIncludeADUdescriptors(includeADUdescriptors),
    fTotalDataSizeBeforePreviousRead(0), fScale(1), fFrameCounter(0) {
}

ADUFromMP3Source::~ADUFromMP3Source() {
  delete fSegments;
}


char const* ADUFromMP3Source::MIMEtype() const {
  return "audio/MPA-ROBUST";
}

ADUFromMP3Source* ADUFromMP3Source::createNew(UsageEnvironment& env,
                                              FramedSource* inputSource,
                                              Boolean includeADUdescriptors) {
  // The source must be a MPEG audio source:
  if (strcmp(inputSource->MIMEtype(), "audio/MPEG") != 0) {
    env.setResultMsg(inputSource->name(), " is not an MPEG audio source");
    return NULL;
  }

  return new ADUFromMP3Source(env, inputSource, includeADUdescriptors);
}

void ADUFromMP3Source::resetInput() {
  fSegments->reset();
}

Boolean ADUFromMP3Source::setScaleFactor(int scale) {
  if (scale < 1) return False;
  fScale = scale;
  return True;
}

void ADUFromMP3Source::doGetNextFrame() {
  if (!fAreEnqueueingMP3Frame) {
    // Arrange to enqueue a new MP3 frame:
    fTotalDataSizeBeforePreviousRead = fSegments->totalDataSize();
    fAreEnqueueingMP3Frame = True;
    fSegments->enqueueNewSegment(fInputSource, this);
  } else {
    // Deliver an ADU from a previously-read MP3 frame:
    fAreEnqueueingMP3Frame = False;

    if (!doGetNextFrame1()) {
      // An internal error occurred; act as if our source went away:
      FramedSource::handleClosure(this);
    }
  }
}

Boolean ADUFromMP3Source::doGetNextFrame1() {
  // First, check whether we have enough previously-read data to output an
  // ADU for the last-read MP3 frame:
  unsigned tailIndex;
  Segment* tailSeg;
  Boolean needMoreData;

  if (fSegments->isEmpty()) {
    needMoreData = True;
    tailSeg = NULL; tailIndex = 0; // unneeded, but stops compiler warnings
  } else {
    tailIndex = SegmentQueue::prevIndex(fSegments->nextFreeIndex());
    tailSeg = &(fSegments->s[tailIndex]);

    needMoreData
	  = fTotalDataSizeBeforePreviousRead < tailSeg->backpointer // bp points back too far
      || tailSeg->backpointer + tailSeg->dataHere() < tailSeg->aduSize; // not enough data
  }

  if (needMoreData) {
    // We don't have enough data to output an ADU from the last-read MP3
    // frame, so need to read another one and try again:
    doGetNextFrame();
    return True;
  }

  // Output an ADU from the tail segment:
  fFrameSize = tailSeg->headerSize+tailSeg->sideInfoSize+tailSeg->aduSize;
  fPresentationTime = tailSeg->presentationTime;
  fDurationInMicroseconds = tailSeg->durationInMicroseconds;
  unsigned descriptorSize
    = fIncludeADUdescriptors ? ADUdescriptor::computeSize(fFrameSize) : 0;
#ifdef DEBUG
  fprintf(stderr, "m->a:outputting ADU %d<-%d, nbr:%d, sis:%d, dh:%d, (descriptor size: %d)\n", tailSeg->aduSize, tailSeg->backpointer, fFrameSize, tailSeg->sideInfoSize, tailSeg->dataHere(), descriptorSize);
#endif
  if (descriptorSize + fFrameSize > fMaxSize) {
    envir() << "ADUFromMP3Source::doGetNextFrame1(): not enough room ("
	    << descriptorSize + fFrameSize << ">"
	    << fMaxSize << ")\n";
    fFrameSize = 0;
    return False;
  }

  unsigned char* toPtr = fTo;
  // output the ADU descriptor:
  if (fIncludeADUdescriptors) {
    fFrameSize += ADUdescriptor::generateDescriptor(toPtr, fFrameSize);
  }

  // output header and side info:
  memmove(toPtr, tailSeg->dataStart(),
	  tailSeg->headerSize + tailSeg->sideInfoSize);
  toPtr += tailSeg->headerSize + tailSeg->sideInfoSize;

  // go back to the frame that contains the start of our data:
  unsigned offset = 0;
  unsigned i = tailIndex;
  unsigned prevBytes = tailSeg->backpointer;
  while (prevBytes > 0) {
    i = SegmentQueue::prevIndex(i);
    unsigned dataHere = fSegments->s[i].dataHere();
    if (dataHere < prevBytes) {
      prevBytes -= dataHere;
    } else {
      offset = dataHere - prevBytes;
      break;
    }
  }

  // dequeue any segments that we no longer need:
  while (fSegments->headIndex() != i) {
    fSegments->dequeue(); // we're done with it
  }

  unsigned bytesToUse = tailSeg->aduSize;
  while (bytesToUse > 0) {
    Segment& seg = fSegments->s[i];
    unsigned char* fromPtr
      = &seg.dataStart()[seg.headerSize + seg.sideInfoSize + offset];
    unsigned dataHere = seg.dataHere() - offset;
    unsigned bytesUsedHere = dataHere < bytesToUse ? dataHere : bytesToUse;
    memmove(toPtr, fromPtr, bytesUsedHere);
    bytesToUse -= bytesUsedHere;
    toPtr += bytesUsedHere;
    offset = 0;
    i = SegmentQueue::nextIndex(i);
  }


  if (fFrameCounter++%fScale == 0) {
    // Call our own 'after getting' function.  Because we're not a 'leaf'
    // source, we can call this directly, without risking infinite recursion.
    afterGetting(this);
  } else {
    // Don't use this frame; get another one:
    doGetNextFrame();
  }

  return True;
}


////////// MP3FromADUSource //////////

MP3FromADUSource::MP3FromADUSource(UsageEnvironment& env,
				   FramedSource* inputSource,
				   Boolean includeADUdescriptors)
  : FramedFilter(env, inputSource),
    fAreEnqueueingADU(False),
    fSegments(new SegmentQueue(False /* because we're ADU->MP3 */,
			       includeADUdescriptors)),
    fIncludeADUdescriptors(includeADUdescriptors) {
}

MP3FromADUSource::~MP3FromADUSource() {
  delete fSegments;
}

char const* MP3FromADUSource::MIMEtype() const {
  return "audio/MPEG";
}

MP3FromADUSource* MP3FromADUSource::createNew(UsageEnvironment& env,
					      FramedSource* inputSource,
					      Boolean includeADUdescriptors) {
  // The source must be an MP3 ADU source:
  if (strcmp(inputSource->MIMEtype(), "audio/MPA-ROBUST") != 0) {
    env.setResultMsg(inputSource->name(), " is not an MP3 ADU source");
    return NULL;
  }

  return new MP3FromADUSource(env, inputSource, includeADUdescriptors);
}


void MP3FromADUSource::doGetNextFrame() {
  if (fAreEnqueueingADU) insertDummyADUsIfNecessary();
  fAreEnqueueingADU = False;

  if (needToGetAnADU()) {
    // Before returning a frame, we must enqueue at least one ADU:
#ifdef TEST_LOSS
  NOTE: This code no longer works, because it uses synchronous reads,
  which are no longer supported.
    static unsigned const framesPerPacket = 10;
    static unsigned const frameCount = 0;
    static Boolean packetIsLost;
    while (1) {
      if ((frameCount++)%framesPerPacket == 0) {