javascript video capture tinkering

var startR=document.createElement("button"),stopR=startR.cloneNode();

document.body.appendChild(startR);
document.body.appendChild(stopR);
startR.innerText="start capture";
stopR.innerText="stop capture";


self.auc=new AudioContext();
var mes=auc.createMediaElementSource(document.getElementsByTagName("video")[0]);
self.audio_merge=auc.createMediaStreamDestination();
mes.connect(audio_merge);

startR.onclick=function(){
navigator.mediaDevices.getDisplayMedia({ video: true }).then(function(disp){



var mediaRecorder1 = new MediaRecorder(disp,{"mimeType":"video/webm"/* , "audioBitsPerSecond":128*1024 */ }),
 mediaRecorder2 = new MediaRecorder(audio_merge.stream,{"mimeType":"audio/ogg"/* , "audioBitsPerSecond":128*1024 */ });

self.Rchunks = []; self.Rchunks2=[];
mediaRecorder1.ondataavailable = function(e) {
  Rchunks.push(e.data);
},
mediaRecorder2.ondataavailable = function(e) {
  Rchunks2.push(e.data);
};

setTimeout(function(){
  mediaRecorder1.start();
  mediaRecorder2.start();
},1000);


stopR.onclick=function(){
mediaRecorder1.stop();mediaRecorder2.stop();
};

});

};