一、函数调用关系

Thread::PreRun

-->ProcessMessages

-->Dispatch

-->Thread::QueuedTaskHandler::OnMessage

-->BaseChannel::SetRemoteContent

-->VoiceChannel::SetRemoteContent_w

1)ProcessMessages

2)Dispatch

3) Thread::QueuedTaskHandler::OnMessage

4) BaseChannel::SetRemoteContent

 5)VoiceChannel::SetRemoteContent_w

----video.streams通过MediaContentDescription获取，MediaContentDescription通过sdp获取

->BaseChannel::UpdateRemoteStreams_w
->WebRtcVideoChannel::AddRecvStream

1）BaseChannel::UpdateRemoteStreams_w 

2）WebRtcVideoChannel::AddRecvStream 

-----调用ConfigureReceiverRtp配置远端ssrc

        WebRtcVideoChannel::WebRtcVideoReceiveStream::WebRtcVideoReceiveStream

        WebRtcVideoChannel::WebRtcVideoReceiveStream::RecreateWebRtcVideoStream

        webrtc::VideoReceiveStream* Call::CreateVideoReceiveStream

 ----将远端ssrc,emplace到receive_rtp_config_，后续收包时做合法性判断。、

        1）internal::VideoReceiveStream2::VideoReceiveStream2

        2）RtpVideoStreamReceiver2::RtpVideoStreamReceiver2

        ----生效远端ssrc

二、具体函数实现 

• CreateTracksFromSsrcInfos解析sdp命令行，构造StreamParams参数

• ConfigureReceiverRtp配置远端ssrc

• Call::CreateVideoReceiveStream，将远端ssrc,emplace到receive_rtp_config_

• DeliveryStatus Call::DeliverRtp对收到报文的ssrc进行合法性判断 

  

 ​

• RtpVideoStreamReceiver2::RtpVideoStreamReceiver2函数生效远端ssrc

• RtpVideoStreamReceiver2::RtpVideoStreamReceiver2函数生效远端ssrc 

        接收RTCP报文时，使用该值做合法性判断 

        SDP命令行 

        参考：webrtc代码走读二(视频数据处理流程)_EveryDayOneHour的博客-CSDN博客

        SDP有SSRC的协商  ：