ZLMedia中RTSP协议的处理简要分析（2）--setup

setup要接收两次，指明流媒体的传输方式 。

 

 

 

 代码如下

void RtspSession::handleReq_Setup(const Parser &parser) {
    //处理setup命令，该函数可能进入多次
    int trackIdx = getTrackIndexByControlUrl(parser.FullUrl());
    SdpTrack::Ptr &trackRef = _sdp_track[trackIdx];
    if (trackRef->_inited) {
        //已经初始化过该Track
        throw SockException(Err_shutdown, "can not setup one track twice");
    }
    trackRef->_inited = true; //现在初始化

    if(_rtp_type == Rtsp::RTP_Invalid){
        auto &strTransport = parser["Transport"];
        if(strTransport.find("TCP") != string::npos){
            _rtp_type = Rtsp::RTP_TCP;
        }else if(strTransport.find("multicast") != string::npos){
            _rtp_type = Rtsp::RTP_MULTICAST;
        }else{
            _rtp_type = Rtsp::RTP_UDP;
        }
    }

    //允许接收rtp、rtcp包
    RtspSplitter::enableRecvRtp(_rtp_type == Rtsp::RTP_TCP);

    switch (_rtp_type) {
    case Rtsp::RTP_TCP: {
        if(_push_src){
            //rtsp推流时，interleaved由推流者决定
            auto key_values =  Parser::parseArgs(parser["Transport"],";","=");
            int interleaved_rtp = -1 , interleaved_rtcp = -1;
            if(2 == sscanf(key_values["interleaved"].data(),"%d-%d",&interleaved_rtp,&interleaved_rtcp)){
                trackRef->_interleaved = interleaved_rtp;
            }else{
                throw SockException(Err_shutdown, "can not find interleaved when setup of rtp over tcp");
            }
        }else{
            //rtsp播放时，由于数据共享分发，所以interleaved必须由服务器决定
            trackRef->_interleaved = 2 * trackRef->_type;
        }
        sendRtspResponse("200 OK",
                         {"Transport", StrPrinter << "RTP/AVP/TCP;unicast;"
                                                  << "interleaved=" << (int) trackRef->_interleaved << "-"
                                                  << (int) trackRef->_interleaved + 1 << ";"
                                                  << "ssrc=" << printSSRC(trackRef->_ssrc),
                          "x-Transport-Options", "late-tolerance=1.400000",
                          "x-Dynamic-Rate", "1"
                         });
    }
        break;

    case Rtsp::RTP_UDP: {
        std::pair<Socket::Ptr, Socket::Ptr> pr = std::make_pair(createSocket(),createSocket());
        try {
            makeSockPair(pr, get_local_ip());
        } catch (std::exception &ex) {
            //分配端口失败
            send_NotAcceptable();
            throw SockException(Err_shutdown, ex.what());
        }

        _rtp_socks[trackIdx] = pr.first;
        _rtcp_socks[trackIdx] = pr.second;

        //设置客户端内网端口信息
        string strClientPort = FindField(parser["Transport"].data(), "client_port=", NULL);
        uint16_t ui16RtpPort = atoi(FindField(strClientPort.data(), NULL, "-").data());
        uint16_t ui16RtcpPort = atoi(FindField(strClientPort.data(), "-", NULL).data());

        auto peerAddr = SockUtil::make_sockaddr(get_peer_ip().data(), ui16RtpPort);
        //设置rtp发送目标地址
        pr.first->bindPeerAddr((struct sockaddr *) (&peerAddr));

        //设置rtcp发送目标地址
        peerAddr = SockUtil::make_sockaddr(get_peer_ip().data(), ui16RtcpPort);
        pr.second->bindPeerAddr((struct sockaddr *) (&peerAddr));

        //尝试获取客户端nat映射地址
        startListenPeerUdpData(trackIdx);
        //InfoP(this) << "分配端口:" << srv_port;

        sendRtspResponse("200 OK",
                         {"Transport", StrPrinter << "RTP/AVP/UDP;unicast;"
                                                  << "client_port=" << strClientPort << ";"
                                                  << "server_port=" << pr.first->get_local_port() << "-"
                                                  << pr.second->get_local_port() << ";"
                                                  << "ssrc=" << printSSRC(trackRef->_ssrc)
                         });
    }
        break;
    case Rtsp::RTP_MULTICAST: {
        if(!_multicaster){
            _multicaster = RtpMultiCaster::get(*this, get_local_ip(), _media_info._vhost, _media_info._app, _media_info._streamid);
            if (!_multicaster) {
                send_NotAcceptable();
                throw SockException(Err_shutdown, "can not get a available udp multicast socket");
            }
            weak_ptr<RtspSession> weakSelf = dynamic_pointer_cast<RtspSession>(shared_from_this());
            _multicaster->setDetachCB(this, [weakSelf]() {
                auto strongSelf = weakSelf.lock();
                if(!strongSelf) {
                    return;
                }
                strongSelf->safeShutdown(SockException(Err_shutdown,"ring buffer detached"));
            });
        }
        int iSrvPort = _multicaster->getMultiCasterPort(trackRef->_type);
        //我们用trackIdx区分rtp和rtcp包
        //由于组播udp端口是共享的，而rtcp端口为组播udp端口+1，所以rtcp端口需要改成共享端口
        auto pSockRtcp = UDPServer::Instance().getSock(*this, get_local_ip().data(), 2 * trackIdx + 1, iSrvPort + 1);
        if (!pSockRtcp) {
            //分配端口失败
            send_NotAcceptable();
            throw SockException(Err_shutdown, "open shared rtcp socket failed");
        }
        startListenPeerUdpData(trackIdx);
        GET_CONFIG(uint32_t,udpTTL,MultiCast::kUdpTTL);

        sendRtspResponse("200 OK",
                         {"Transport", StrPrinter << "RTP/AVP;multicast;"
                                                  << "destination=" << _multicaster->getMultiCasterIP() << ";"
                                                  << "source=" << get_local_ip() << ";"
                                                  << "port=" << iSrvPort << "-" << pSockRtcp->get_local_port() << ";"
                                                  << "ttl=" << udpTTL << ";"
                                                  << "ssrc=" << printSSRC(trackRef->_ssrc)
                         });
    }
        break;
    default:
        break;
    }
}

1.首先得到SdpTrack信息。

2. auto &strTransport = parser["Transport"];得到要解析的传输信息。

3. auto key_values =  Parser::parseArgs(parser["Transport"],";","=");对Transport进行解析。

4. if(2 == sscanf(key_values["interleaved"].data(),"%d-%d",&interleaved_rtp,&interleaved_rtcp)解析interleaved，回复时使用。

5.回复时x-Transport-Options，x-Dynamic-Rate写了固定值，不知什么意思。