WebRTC - how to switch between getUserMedia and getDisplayMedia tracks inside RTCPeerConnection - stream

Question

I'm trying to develop an app where users can can video call to each other and share their screens using WebRTC technology. I have succeed with either video call or screen sharing app and now I'm trying to make it to be able to switch between getUserMedia and getDisplayMedia on button click during a call inside the same RTCPeerConnection but it doesn't work.
This is how I thought it could work:
function onLogin(success) {
var configuration = { offerToReceiveAudio: true, offerToReceiveVideo: true, "iceServers" : [ { "url" : "stun:stun.1.google.com:19302" } ] };
myConnection = window.RTCPeerConnection ? new RTCPeerConnection(configuration, { optional: [] }) : new RTCPeerConnection(configuration, { optional: [] });
myConnection.onicecandidate = function (event) {
console.log("onicecandidate");
if (event.candidate) send({ type: "candidate", candidate: event.candidate });
};
myConnection.ontrack=function(e){
try{remoteVideo.src = window.webkitURL?window.webkitURL.createObjectURL(e.streams[0]):window.URL.createObjectURL(e.streams[0])}
catch(err){remoteVideo.srcObject=e.streams[0]}
}
myConnection.ondatachannel=openDataChannel
openDataChannel();
startAVStream();
//startSStream()
};
function startAVStream(enable){
if(sStream)sStream.getTracks().forEach( function (track) {
try{myConnection.removeTrack( track, sStream );}
catch(e){}
} );
navigator.mediaDevices.getUserMedia({ video: true, audio: true }).then(s => {
if(!avStream){
avStream = s;
avStream.getTracks().forEach( function (track) {
myConnection.addTrack( track, avStream );
} );
}
}, function (error) { console.log(error); });
}
function startSStream(enable){
if(avStream)avStream.getTracks().forEach( function (track) {
try{myConnection.removeTrack( track, avStream );}
catch(e){}
} );
navigator.mediaDevices.getDisplayMedia({ video: true }).then(s => {
if(!sStream){
sStream = s;
sStream.getTracks().forEach( function (track) {
myConnection.addTrack( track, sStream );
} );
}
}, function (error) { console.log(error); });
}
Can anyone tell me how I can switch between tracks inside the same RTCPeerConnection or should I create 2 separate RTCPeerConnection - one for video/audio streaming and another for screen sharing?
Any help appreciated! Thanks!

Answer 1

You could use RTCRtpSender.replaceTrack to splice the screen capture track. This doesn't require renegotiation, and therefore has very low latency.
let newstream = navigator.mediaDevices.getDisplayMedia({});
let newtrack = newstream.getTracks()[1];
if(newtrack.kind !== 'video')
throw new Error('Eek!?');
pc.getSenders().forEach(async s => {
if(s.track && s.track.kind === 'video')
await s.replaceTrack(newtrack);
});
The test for s.track not being null deals with the case where you previously called replaceTrack(..., null).

Answer 2

shareScreen = () =>{
const success = (stream) => {
window.localStream = stream
// this.localVideoref.current.srcObject = stream
// localStream.replaceStream(stream);
this.setState({
localStream: stream
})
Object.values(this.state.peerConnections).forEach(pc => {
pc.getSenders().forEach(async s => {
console.log("s.track ",s.track);
if(s.track && s.track.kind === 'video'){
stream.getTracks().forEach(track => {
// pc.addTrack(track, this.state.localStream)
s.replaceTrack(track);
});
}
});
});
}
const failure = (e) => {
console.log('getUserMedia Error: ', e)
}
navigator.mediaDevices.getDisplayMedia({ cursor: true }).then(success).catch(failure)}