[live555] 从testRTSPClient.cpp PLAY 请求四-优快云博客

本文链接：https://blog.youkuaiyun.com/engineer_james/article/details/82498227

本文深入剖析RTSP协议中的PLAY请求流程，包括从SETUP请求后如何触发PLAY请求，以及PLAY请求后的响应处理过程。文章详细介绍了live555源码中testRTSPClient.cpp的PLAY请求实现细节。

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前言

因为play 流程和DESCRIBE 和SETUP一样，所以，已经需要分析的内容很少，除了RTCP
[live555] 从testRTSPClient.cpp DESCRIBE 发起请求一
 [live555] testRTSPClient.cpp DESCRIBE （后续处理）二
 [live555] 从testRTSPClient.cpp SETUP请求三

PLAY 请求

对比 SETUP 请求大部分流程是一样的，在SETUP，发送请求后,continueAfterSETUP中发起PLAY请求

void continueAfterSETUP(RTSPClient* rtspClient, int resultCode
            , char* resultString) {
//....
setupNextSubsession(rtspClient);
}

setupNextSubsession 处理

// We have a "m=" line, representing a new sub-session:
MediaSubsession* subsession = createNewMediaSubsession();


void setupNextSubsession(RTSPClient* rtspClient) {
    scs.subsession = scs.iter->next();
    if (scs.subsession != NULL){...}//因为iter 只有一个subsession所以为null

    if (scs.session->absStartTime() != NULL) {
        rtspClient->sendPlayCommand(*scs.session, continueAfterPLAY
        , scs.session->absStartTime(), scs.session->absEndTime());
     } else {
        scs.duration = scs.session->playEndTime() - scs.session->playStartTime();
        rtspClient->sendPlayCommand(*scs.session, continueAfterPLAY);
     }
}

absStartTime 是播放开始时间，PLAY之前都为NULL，发送PLAY请求

continueAfterPLAY

发送完请求，会通过轮询回调continueAfterPLAY

接收response 消息

void RTSPClient::handleResponseBytes(int newBytesRead) {

    if (responseCode == 200) {
      // Do special-case response handling for some commands:
      if (strcmp(foundRequest->commandName(), "SETUP") == 0) {
        if (!handleSETUPResponse(*foundRequest->subsession(), sessionParamsStr, transportParamsStr, foundRequest->booleanFlags()&0x1)) break;
      } else if (strcmp(foundRequest->commandName(), "PLAY") == 0) {
        if (!handlePLAYResponse(foundRequest->session(), foundRequest->subsession(), scaleParamsStr, speedParamsStr, rangeParamsStr, rtpInfoParamsStr)) break;
      } else if (strcmp(foundRequest->commandName(), "TEARDOWN") == 0) {
        if (!handleTEARDOWNResponse(*foundRequest->session(), *foundRequest->subsession())) break;
      } else if (strcmp(foundRequest->commandName(), "GET_PARAMETER") == 0) {
        if (!handleGET_PARAMETERResponse(foundRequest->contentStr(), bodyStart, responseEnd)) break;
      }
    } 

}