cordova-plugin-iosrtc: Problem with change camera during video call (replaceTrack is not a function)

@abardik I will see what I can do after #508 and #494 is released

@hthetiot

I can confirm that this feature will tremendously improve user experience, because replaceTrack allows to switch between front/rear cameras, screen capture (which you already implemented via getDisplayMedia) or any other potential video sources, as well as between audio sources (for example, microphone and system sound) with no renegotiation at all - the replaced track just appears on the other side immediately, so remote user should not wait for renegotiation (which usualy takes 2-5 seconds) every time you switch your camera/screen/etc.

Speaking of compatibility, replaceTrack is already supported by all browsers, including Safari 13.1+: https://caniuse.com/#search=replacetrack

And I can confirm - it really works like a charm, with no failure at all (for comparison, renegotiation used to fail often enough to start annoying users).

So if, in any case, it’s possible to implement replaceTrack without spending enormous amount of time, it would be great to have this feature on iOS devices.

Thank you.

Hi @hthetiot,

I have a quick clarification regarding current ‘replaceTrack’ implementation

Is it intended to have it work via ‘negotiationneeded’?

I just checked the MDM documentation and it says the method works without additional negotiation - it just replaces a track and the receiver party started to get new track immediately, w/o additional logic

Could you please clarify it. Thanks

@Christina05

If you need a workaround for replaceTrack, you can use the following code (place it after cordova.plugins.iosrtc.registerGlobals). But it’s not a native replaceTrack, so it will require a renegotiation. And it’s based on outdated addStream/removeStream, so please, use it on your own risk, because with ‘unified-plan’ addStream/removeStream creates new tracks, but doesn’t really remove old tracks, just mutes and marks them disabled.

Source: https://blog.mozilla.org/webrtc/warm-up-with-replacetrack/

  let orgRTCPeerConnection = window.RTCPeerConnection;
  window.RTCPeerConnection = function(config) {
    let pc = new orgRTCPeerConnection(config);
    pc._senders = [];
    pc.getSenders = () => pc._senders;
    pc._orgAddStream = pc.addStream;
    pc.addStream = stream => {
      pc._orgAddStream(stream);
      stream.getTracks().forEach(track => pc._senders.push({ track,
        replaceTrack: function (withTrack) {
          return new Promise(resolve => {
            stream.removeTrack(track);
            stream.addTrack(withTrack);
            let onn = pc.onnegotiationneeded;
            pc.onnegotiationneeded = null;
            pc.removeStream(stream);
            pc._orgAddStream(stream);
            if (onn) {
              Promise.resolve().then(onn);
              pc.addEventListener("signalingstatechange", function listener() {
                if (pc.signalingState != "stable") return;
                pc.removeEventListener("signalingstatechange", listener);
                pc.onnegotiationneeded = onn;
                resolve();
              });
            }
          });
        }
      }));
    };
    return pc;
  }