live555 h264 videostream 数据流和时间戳的分析

rtsp客户端发送播放请求后,rtsp服务器调用流程如下

h264 video rtsp

1.ServerMediaSubsession::startStream -> OnDemandServerMediaSubsession::startStream

2.startStream -> StreamState::startPlaying

3.MediaSink::startPlaying

4.MediaSink::continuePlaying->MultiFramedRTPSink::continuePlaying

5.MultiFramedRTPSink::buildAndSendPacket

6.MultiFramedRTPSink::packFrame()  fSource->getNextFrame fSource type is H264FUAFragmenter

7.FramedSource::getNextFrame

8.FramedSource::doGetNextFrame ->H264FUAFragmenter::doGetNextFrame  ->  fInputSource->getNextFrame fInputSource type is H264VideoStreamFramer

9.H264VideoStreamFramer::getNextFrame -> MPEGVideoStreamFramer::doGetNextFrame

10.MPEGVideoStreamFramer::continueReadProcessing -> fParser->parse()   fParser type is H264VideoStreamParser

11.H264VideoStreamParser::parse()   -> ByteStreamFileSource::doGetNextFrame -> ByteStreamFileSource::doReadFromFile

时间戳生成流程

1.MultiFramedRTPSink::buildAndSendPacket 中组建rtp包头时，获取时间戳的位置fTimestampPosition，然后等待获取数据与时间戳后写入

2.MultiFramedRTPSink::afterGettingFrame1 ->H264VideoRTPSink::doSpecialFrameHandling->MultiFramedRTPSink::setTimestamp 将时间戳写入到rtp包中

3.H264VideoStreamParser::parse 中调用H264VideoStreamFramer::setPresentationTime { fPresentationTime = fNextPresentationTime; } 此fPresentationTime最终将传到步骤2中

4.fNextPresentationTime 初始化由构造函数获取当前时间戳 ，后续在H264VideoStreamParser::parse 当thisNALUnitEndsAccessUnit=TRUE后，根据帧率计算帧duration，然后计算下一帧的时间戳