live555 server 数据流发送流程和时间戳的分析

来源：互联网发布：黑客技术软件编辑：程序博客网时间：2024/06/12 01:30

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 isH264FUAFragmenter

7.FramedSource::getNextFrame

8.FramedSource::doGetNextFrame->H264FUAFragmenter::doGetNextFrame -> fInputSource->getNextFrame fInputSource typeis H264VideoStreamFramer

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

10.MPEGVideoStreamFramer::continueReadProcessing ->fParser->parse() fParser type isH264VideoStreamParser

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

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