html5转换成mp4,将HTML5 blob视频导出为MP4

我试图使用Chrome的屏幕共享功能制作屏幕录像机并将视频保存为MP4格式。但是，我不知道我是如何做到这一点的。该演示是在https://figgycity50.kd.io/screencap.html(包括HTTPS！)，代码为：将HTML5 blob视频导出为MP4

start

navigator.getUserMedia = navigator.webkitGetUserMedia || navigator.getUserMedia;

var stream = null;

button = document.querySelector("button");

function start(e) {

// Seems to only work over SSL.

navigator.getUserMedia({

video: {

mandatory: {

chromeMediaSource: 'screen',

maxWidth: 1280,

maxHeight: 720

}

}

}, function(s) {

stream = s;

button.textContent = 'Stop';

button.removeEventListener('click', start);

button.addEventListener('click', stop);

var video = document.querySelector('video');

video.src = window.URL.createObjectURL(stream);

video.autoplay = true;

stream.onended = function(e) {

//The save code should go here.

};

//document.body.appendChild(video);

}, function(e) {

});

}

function stop() {

stream.stop();

button.addEventListener('click', start);

button.textContent = 'Capture your screen';

}

button.addEventListener('click', start);

我该怎么办呢？