最近在做项目的过程中遇到一个问题，在用DarwinStreamingServer中的QTSSReflectorModule模块做为流转发和分发服务，用live555的DarwinInjector类做为模拟设备进行流推送时，如果按照正常RTSP推送流程:Announce、Setup、Play…、Teardown，Darwin能较好地完成流的转发，但是假如设备在不正常工作，例如网络异常断开，设备断电等中断了数据流的推送，而缺少了<设备->服务器>的Teardown过程，这样与此路推送相关的RTSPSession、RTPSession以及ReflectorSession等都需要等到配置的“rtp_timeout”时间后、RTPSession超时才能析构所有相关转发对象。先分析下原因：RTSPSession在创建RTPSession时[cpp]viewplaincopyprint?1.//SetthecurrentRTSPsessionforthisRTPsession.2.//WedothisherebecauseweneedtomakesuretheSessionMutex3.//isgrabbedwhilewedothis.OnlydothisiftheRTSPsession4.//isstillalive,ofcourse.5.if(this->IsLiveSession())6.fRTPSession->UpdateRTSPSession(this);[cpp]viewplaincopyprint?1.voidRTPSessionInterface::UpdateRTSPSession(RTSPSessionInterface*inNewRTSPSession)2.{3.if(inNewRTSPSession!=fRTSPSession)4.{5.//Iftherewasanoldsession,letitknowthatwearedone6.if(fRTSPSession!=NULL)7.fRTSPSession->DecrementObjectHolderCount();8.9.//IncrementthiscounttopreventtheRTSPsessionfrombeingdeleted10.fRTSPSession=inNewRTSPSession;11.fRTSPSession->IncrementObjectHolderCount();12.}13.}IncrementObjectHolderCount()增加了fRTPSession对RTSPSession的引用，而对应的DecrementObjectHolderCount()在RTPSession::Teardown()中执行，由于RTSPSession拥有很好的对象保护机制，只有当对当前RTSPSession的引用数为0时[cpp]viewplaincopyprint?1.//Onlydeleteifitisoktodelete!2.if(fObjectHolders==0)3.return-1;RTSPSession自身才能调用Task::Run(){return-1;}delete，所以在RTSPSession注销之前，必须等待RTPSession注销，而且RTPSession没有等到Teardown命令，就只能等超时，而这个超时时间不能定，及时几秒钟对于转发实时流来说也是不合理的。解决办法：在RTSPSession:Run()函数中的[cpp]viewplaincopyprint?1.while(IsLiveSession())2.{3.switch(){case:}4.}状态机外加入代码及时析构RTPSession[cpp]viewplaincopyprint?1.//Makeabsolutelysuretherearenoresourcesbeingoccupiedbythesession2.//atthispoint.3.this->CleanupRequest();4.5.6.//Kill与RTSPSession相关的RTPSession7.if(!IsLiveSession()){8.OSRefTable*theMap=QTSServerInterface::GetServer()->GetRTPSessionMap();9.OSRef*theRef=theMap->Resolve(&fLastRTPSessionIDPtr);10.if(theRef!=NULL){11.fRTPSession=(RTPSession*)theRef->GetObject();12.if(fRTPSession)fRTPSession->Teardown();13.theMap->Release(fRTPSession->GetRef());14.fRTPSession=NULL;15.}16.}17.//Onlydeleteifitisoktodelete!18.if(fObjectHolders==0)return-1;19.//Ifweareherebecauseofatimeout,butwecan'tdeletebecausesomeone20.//isholdingontoareferencetothissession,justreschedulethetimeout.21.//Atthispoint,however,thesessionisDEAD.22.return0;注意this->CleanupRequest();在前,这样就能在RTSPSession判断fObjectHolders之前将附属的RTPSession析构，进而析构RTSPSession.由于工作比较忙，写的可能在思路上不是很清楚，欢迎指正！/--------------------------------------割了------------------------------------/在上段代码中可以加入一个补充条件进行代码的优化，并且CleanupRequest()必须在此之后！[cpp]viewplaincopyprint?1.//fObjectHolders--2.if(!IsLiveSession()&&fObjectHolders>0){3.OSRefTable*theMap=QTSServerInterface::GetServer()->GetRTPSessionMap();4.OSRef*theRef=theMap->Resolve(&fLastRTPSessionIDPtr);5.if(theRef!=NULL){6.fRTPSession=(RTPSession*)theRef->GetObject();7.if(fRTPSession)fRTPSession->Teardown();8.theMap->Release(fRTPSession->GetRef());9.fRTPSession=NULL;10.}11.}12.13.//Makeabsolutelysuretherearenoresourcesbeingoccupiedbythesession14.//atthispoint.15.this->CleanupRequest();16.17.//Onlydeleteifitisoktodelete!18.if(fObjectHolders==0)19.return-1;
