title: How can I get the html5 video element's width and height
body: <p>I have a simple html5 video tag:</p>
  
  <pre><code> &lt;video autobuffer="true" id="video" controls="true"&gt;
          &lt;source src="some_url"&gt;&lt;/scource&gt;
    &lt;/video&gt;
  </code></pre>
  
  <p>I have not define a obvious width and height in video tag or in css,the video wrapper would adjust according to the source video size,the problem is, how can I get the video current width and height?
  I have tried jquery </p>
  
  <pre><code>$('video').css('width');
  </code></pre>
  
  <p>but it return me the origin size :300px</p>
  
  <p>what I see in the page is 800px!</p>
  
  <p>How can I solve this problem?</p>