WebRTC set simulcast streams

HTML

<video id="v1" height="120" width="160" autoplay muted></video>
<video id="v2" height="120" width="160" autoplay></video>
<br>
<button onclick="start()">Start!</button>
<div id="div"></div>
<script src="https://webrtc.github.io/adapter/adapter-latest.js"></script>

JavaScript

var pc1 = new RTCPeerConnection(),
  pc2 = new RTCPeerConnection();

var add = (pc, can) => can && pc.addIceCandidate(can).catch(failed);
pc1.onicecandidate = e => add(pc2, e.candidate);
pc2.onicecandidate = e => add(pc1, e.candidate);
pc2.onaddstream = e => v2.srcObject = e.stream;
pc1.oniceconnectionstatechange = e => log(pc1.iceConnectionState);

function start() {
  navigator.mediaDevices.getUserMedia({
      video: {
        width: {
          ideal: 1280
        },
        height: {
          idesl: 720
        }
      }
    })
    .then(stream => {
      var sender = pc1.addTrack(stream.getVideoTracks()[0],
        v1.srcObject = stream);
      var parameters = {
        encodings: [{
          rid: "720"
        }, {
          rid: "360",
          scaleResolutionDownBy: 2
        }, {
          rid: "180",
          scaleResolutionDownBy: 4
        }, ]
      };
      sender.setParameters(parameters);
      
    })
    .then(() => pc1.createOffer())
    .then(offer => pc1.setLocalDescription(offer))
    .then(() => pc2.setRemoteDescription(pc1.localDescription))
    .then(() => pc2.createAnswer())
    .then(answer => pc2.setLocalDescription(answer))
    .then(() => pc1.setRemoteDescription(pc2.localDescription))
    .catch(failed);
}

var log = msg => div.innerHTML += "<p>" + msg + "</p>";
var failed = e => log(e + ", line " + e.lineNumber);