<html>
<head>
<script>
async function boom() {
  const canvas = document.createElement("canvas");
  canvas.getContext("2d");
  const recorder = new MediaRecorder(new MediaStream([
    ...canvas.captureStream().getTracks(),
    ...canvas.captureStream().getTracks(),
  ]));
  recorder.start();
  recorder.requestData();
}
</script>
</head>
<body onload="boom()">
</body>
</html>

