WebRTC Peer ontrack 已调用但视频未播放

Question

我有远程对等方将视频发送到本地对等方。我在哪里使用自己的信令服务器。

流程就像，

1. 远程对等通过信令服务器向本地对等发送报价。

2. 本地节点接受提议并创建应答，然后通过信令服务器将其发送给远程节点。

3. 远程点对点接受应答并开始发送视频，点对点。

   我在本地同行的 createAnswer 部分遇到了一些问题。如果我通过单击按钮手动将答案发送给远程对等方，则视频播放正常。但是从pc.onicecandidate 内部发送答案是行不通的。

下面是代码

 var answer;
 async function createAnswer(offer) {
   
   if (pc.signalingState != "stable") return;
   await pc.setRemoteDescription({type: "offer", sdp: offer});
   await pc.setLocalDescription(await pc.createAnswer());
   pc.onicecandidate = ({candidate}) => {
     if (candidate) return;
      answer = pc.localDescription.sdp;
      sendAnswerToSignalingServer({ peer_type: "web",remote_peer: "RPi_Dev", type: "answer",  name: userLoggedIn, sdp:answer }); 

   };
 }

使用上面的代码，除了播放视频之外，所有的事情都可以正常工作，甚至是事件

pc.ontrack = function (event) {
  remoteVideo.srcObject =event.streams[0];
  //alert('new stream added! ' + event.streams[0]);
}

接到电话，但视频没有播放。

但如果我在上面评论 sendAnswerToSignalingServer 并通过按钮单击发送答案，那么一切正常，

function sendSignalButtonClick(){
   sendAnswerToSignalingServer({ peer_type: "web",remote_peer: "RPi_Dev", type: "answer",  name: userLoggedIn, sdp:answer }); 
}

我认为 createAnswer 部分存在一些编码问题。

我指的是这里的代码WebRTC datachannel with manual signaling, example please?。

谁能帮我解决这个问题。

编辑：完整代码

var userLoggedIn = "userWeb";
const config = {iceServers: [{urls: "stun:stun.l.google.com:19302"}]};
const pc = new RTCPeerConnection(config);

const dc = pc.createDataChannel("chat", {negotiated: true, id: 0});


pc.ontrack = function (event) {
  remoteVideo.srcObject = event.streams[0];

}

 
 var SDP;
 async function createAnswer(offer) {
   
   if (pc.signalingState != "stable") return;
   await pc.setRemoteDescription({type: "offer", sdp: offer});
   const answer = await pc.createAnswer();
   await pc.setLocalDescription(answer);
    pc.onicecandidate = async ({candidate}) => {
    if (candidate) return;
       SDP = await pc.localDescription.sdp;
       sendToWebSocket({ peer_type: "web",remote_peer: "RPi_Dev", type: "answer",  name: userLoggedIn, sdp:SDP }); 
     
   };
 

 }

async function sendSignalButtonClick() {
   SDP = await pc.localDescription.sdp;
   sendToWebSocket({ peer_type: "web",remote_peer: "RPi_Dev", type: "answer",  name: userLoggedIn, sdp:SDP }); 
}
 

function SendMessage(message) {
   dc.send(message);

 };


//********************************Signaling server part***************************/

var webSockConn = new WebSocket('wss://220.168.551.150:7000');

webSockConn.onopen = function () { 
    console.log("Connected to the signaling server"); 
    sendToWebSocket({ peer_type: "web",remote_peer: "RPi_Dev", type: "login",  name: userLoggedIn }); 
};


//when we got a message from a signaling server 
webSockConn.onmessage = function (msg) { 
   console.log("Got message", msg.data);
    
   var data = JSON.parse(msg.data);
    
   switch(data.type) { 
      case "offer": 
     console.log(data);
         createAnswer(data.offer, data.name); 
         break; 
      case "leave": 
         handleLeave(); 
         break; 
      default: 
         break; 
   } 
};
  
webSockConn.onerror = function (err) { 
   console.log("webSockConn----Got error", err); 
};

function handleLeave(){

   console.log("Leaving ......................"); 
}
  
//alias for sending JSON encoded messages 
function sendToWebSocket(message) { 
   //attach the other peer username to our messages 
   if (userLoggedIn) { 
      message.name = userLoggedIn; 
   } 
    
   webSockConn.send(JSON.stringify(message)); 
};



/*********************************************************************************/

Answer 1

尝试使用 await 创建答案：

answer = await pc.localDescription.sdp;

要将函数更改为异步：

pc.onicecandidate = async ({candidate}) => {