var audioMixer = new MultiStreamsMixer([microphone1, microphone2]);

// record using MediaRecorder API
var recorder = new MediaRecorder(audioMixer.getMixedStream());

// or share using WebRTC
rtcPeerConnection.addStream(audioMixer.getMixedStream());

screenStream.fullcanvas = true;
screenStream.width = screen.width; // or 3840
screenStream.height = screen.height; // or 2160 

cameraStream.width = parseInt((20 / 100) * screenStream.width);
cameraStream.height = parseInt((20 / 100) * screenStream.height);
cameraStream.top = screenStream.height - cameraStream.height;
cameraStream.left = screenStream.width - cameraStream.width;

var mixer = new MultiStreamsMixer([screenStream, cameraStream]);

rtcPeerConnection.addStream(audioMixer.getMixedStream());

mixer.frameInterval = 1;
mixer.startDrawingFrames();

btnStopStreams.onclick = function() {
    mixer.releaseStreams();
};

btnAppendNewStreams.onclick = function() {
    mixer.appendStreams([anotherStream]);
};

btnStopScreenSharing.onclick = function() {
    // replace all old streams with this one
    // it will replace only video tracks
    mixer.replaceStreams([cameraStreamOnly]);
};

var mixer = new MultiStreamsMixer([camera1, camera2]);

rtcPeerConnection.addStream(audioMixer.getMixedStream());

mixer.frameInterval = 1;
mixer.startDrawingFrames();