var context = canvas.getContext('2d');
var video = document.createElement('video');
video.src = '吔屎吧梁非凡_x264压制.mp4';
video.preload = 'preload';
video.autoplay = 'autoplay';
video.height = context.canvas.height;
video.width = context.canvas.width;

setInterval(function  () {
    var pattern = context.createPattern(video, 'no-repeat');
    context.fillStyle = pattern;
    context.fillRect(0, 0, context.canvas.width, context.canvas.height);
    pattern = null;

    //drowStar...这里执行其他绘画步骤

}, 100);

测试可用，setInterval的时间间隔尽量调大，不然电脑风扇会狂飙...

楼上的方法应该更高效吧 XD

var can = document.getElementById('canvas');

var ctx = canvas.getContext('2d');

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

video.addEventListener('play', function(){

    can.width = video.clientWidth;

    can.height = video.clientHeight;

    var ths = $(this);

    (function loop(){        

        if(!ths.paused && !ths.ended){

            ctx.drawImage(ths, 0, 0);

            setTimeout(loop, 1000/30);

        }

    })();    

}, false)