暂不支持chrom 。支持safari .其他未测试 
先引用 jquery 地址。选用新浪的 
 
<script type="text/javascript" src="http://lib.sinaapp.com/js/jquery/1.6/jquery.js"></script> 
加一个video标签 
 
<video id="video" controls="controls"> 
<source src="1.mp4" /> 
</video> 
然后js 
 
<script type="text/javascript"> 
$().ready(function(){ 
var video, output; 
var scale = 0.25; 
var initialize = function() { 
output = $("#output"); 
video = $("#video").get(0); 
$("#capture").click(captureImage); 
}; 
var captureImage = function() { 
var canvas = document.createElement("canvas"); 
canvas.width = video.videoWidth * scale; 
canvas.height = video.videoHeight * scale; 
canvas.getContext('2d') 
.drawImage(video, 0, 0, canvas.width, canvas.height); 
var img = document.createElement("img"); 
img.src = canvas.toDataURL(); 
output.prepend(img); 
}; 
$(initialize); 
}); 
</script> 
效果图就不贴了。