title: Preview image not work in Jw Player 6
body: <p>I'm using the following source code to display a video file using Jw Player 6.</p>
  
  <pre><code>&lt;script&gt;
          jwplayer('video-front').setup({
            height: 540,
            width: 980,
            image: "&lt;?php echo $base_url; ?&gt;/sites/default/files/video-front/thumbnail-223_0002.png",
            playlist: [{
              sources: [
                { file: "&lt;?php echo $base_url; ?&gt;/sites/default/files/video-front/1380575675.mp4" },
                { file: "&lt;?php echo $base_url; ?&gt;/sites/default/files/video-front/1380575748.webm" },
                { file: "&lt;?php echo $base_url; ?&gt;/sites/default/files/video-front/1380575648.flv" }
              ]
            }]
          });
        &lt;/script&gt;
  </code></pre>
  
  <p>But the image not display in my video. Only I can see a black background. What's wrong here?
  Thanks in advance.</p>