mpegvideostreamframer.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.
// A filter that breaks up an MPEG video elementary stream into
//   headers and frames
// Implementation

#include "MPEGVideoStreamParser.hh"
#include <GroupsockHelper.hh>

////////// TimeCode implementation //////////

TimeCode::TimeCode()
  : days(0), hours(0), minutes(0), seconds(0), pictures(0) {
}

TimeCode::~TimeCode() {
}

int TimeCode::operator==(TimeCode const& arg2) {
  return pictures == arg2.pictures && seconds == arg2.seconds
    && minutes == arg2.minutes && hours == arg2.hours && days == arg2.days;
}

////////// MPEGVideoStreamFramer implementation //////////

MPEGVideoStreamFramer::MPEGVideoStreamFramer(UsageEnvironment& env,
					     FramedSource* inputSource)
  : FramedFilter(env, inputSource),
    fFrameRate(0.0) /* until we learn otherwise */,
    fParser(NULL) {
  reset();
}

MPEGVideoStreamFramer::~MPEGVideoStreamFramer() {
  delete fParser;
}

void MPEGVideoStreamFramer::flushInput() {
  reset();
  if (fParser != NULL) fParser->flushInput();
}

void MPEGVideoStreamFramer::reset() {
  fPictureCount = 0;
  fPictureEndMarker = False;
  fPicturesAdjustment = 0;
  fPictureTimeBase = 0.0;
  fTcSecsBase = 0;
  fHaveSeenFirstTimeCode = False;

  // Use the current wallclock time as the base 'presentation time':
  gettimeofday(&fPresentationTimeBase, NULL);
}

#ifdef DEBUG
static struct timeval firstPT;
#endif
void MPEGVideoStreamFramer
::computePresentationTime(unsigned numAdditionalPictures) {
  // Computes "fPresentationTime" from the most recent GOP's
  // time_code, along with the "numAdditionalPictures" parameter:
  TimeCode& tc = fCurGOPTimeCode;

  double pictureTime = fFrameRate == 0.0 ? 0.0
    : (tc.pictures + fPicturesAdjustment + numAdditionalPictures)/fFrameRate
    - fPictureTimeBase;
  if (pictureTime < 0.0) pictureTime = 0.0; // sanity check
  unsigned pictureSeconds = (unsigned)pictureTime;
  double pictureFractionOfSecond = pictureTime - (double)pictureSeconds;

  unsigned tcSecs
    = (((tc.days*24)+tc.hours)*60+tc.minutes)*60+tc.seconds - fTcSecsBase;
  fPresentationTime = fPresentationTimeBase;
  fPresentationTime.tv_sec += tcSecs + pictureSeconds;
  fPresentationTime.tv_usec += (long)(pictureFractionOfSecond*1000000.0);
  if (fPresentationTime.tv_usec >= 1000000) {
    fPresentationTime.tv_usec -= 1000000;
    ++fPresentationTime.tv_sec;
  }
#ifdef DEBUG
  if (firstPT.tv_sec == 0 && firstPT.tv_usec == 0) firstPT = fPresentationTime;
  struct timeval diffPT;
  diffPT.tv_sec = fPresentationTime.tv_sec - firstPT.tv_sec; 
  diffPT.tv_usec = fPresentationTime.tv_usec - firstPT.tv_usec; 
  if (fPresentationTime.tv_usec < firstPT.tv_usec) {
    --diffPT.tv_sec;
    diffPT.tv_usec += 1000000;
  }
  fprintf(stderr, "MPEGVideoStreamFramer::computePresentationTime(%d) -> %lu.%06ld [%lu.%06ld]\n", numAdditionalPictures, fPresentationTime.tv_sec, fPresentationTime.tv_usec, diffPT.tv_sec, diffPT.tv_usec);
#endif
}

void MPEGVideoStreamFramer
::setTimeCode(unsigned hours, unsigned minutes, unsigned seconds,
	      unsigned pictures, unsigned picturesSinceLastGOP) {
  TimeCode& tc = fCurGOPTimeCode; // abbrev
  unsigned days = tc.days;
  if (hours < tc.hours) {
    // Assume that the 'day' has wrapped around:
    ++days;
  }
  tc.days = days;
  tc.hours = hours;
  tc.minutes = minutes;
  tc.seconds = seconds;
  tc.pictures = pictures;
  if (!fHaveSeenFirstTimeCode) {
    fPictureTimeBase = fFrameRate == 0.0 ? 0.0 : tc.pictures/fFrameRate;
    fTcSecsBase = (((tc.days*24)+tc.hours)*60+tc.minutes)*60+tc.seconds;
    fHaveSeenFirstTimeCode = True;
  } else if (fCurGOPTimeCode == fPrevGOPTimeCode) {
    // The time code has not changed since last time.  Adjust for this:
    fPicturesAdjustment += picturesSinceLastGOP;
  } else {
    // Normal case: The time code changed since last time.
    fPrevGOPTimeCode = tc;
    fPicturesAdjustment = 0;
  }
}

void MPEGVideoStreamFramer::doGetNextFrame() {
  fParser->registerReadInterest(fTo, fMaxSize);
  continueReadProcessing();
}

void MPEGVideoStreamFramer
::continueReadProcessing(void* clientData,
			 unsigned char* /*ptr*/, unsigned /*size*/,
			 struct timeval /*presentationTime*/) {
  MPEGVideoStreamFramer* framer = (MPEGVideoStreamFramer*)clientData;
  framer->continueReadProcessing();
}

void MPEGVideoStreamFramer::continueReadProcessing() {
  unsigned acquiredFrameSize = fParser->parse();
  if (acquiredFrameSize > 0) {
    // We were able to acquire a frame from the input.
    // It has already been copied to the reader's space.
    fFrameSize = acquiredFrameSize;
    fNumTruncatedBytes = fParser->numTruncatedBytes();
    
    // "fPresentationTime" should have already been computed.

    // Compute "fDurationInMicroseconds" now:
    fDurationInMicroseconds
      = (fFrameRate == 0.0 || ((int)fPictureCount) < 0) ? 0
      : (unsigned)((fPictureCount*1000000)/fFrameRate);
#ifdef DEBUG
    fprintf(stderr, "fDurationInMicroseconds: %d ((%d*1000000)/%f)\n", fDurationInMicroseconds, fPictureCount, fFrameRate);
#endif
    fPictureCount = 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 {
    // We were unable to parse a complete frame from the input, because:
    // - we had to read more data from the source stream, or
    // - the source stream has ended.
  }
}