jwplayer不能播放七牛外链?

Question

七牛外链:http://7xrjj0.com1.z0.glb.clouddn.com/%40%2Fvideo/2047/f72a4e11-d0c1-42e9-bbff-aab2ee9958c1
jwplayer本地视频能播放：

    <script type = "text/javascript" >

       jwplayer ( "container" ). setup ({

                          flashplayer : "/jwplayer/player.swf" ,

                          file : "./band.mp4" ,

                          height : 270 ,

                          width : 480

      });

   </script>

上面file :变更为外链地址，视频不能播放,错误信息如下：
Error loading player:
No playable sources found

请教各位大牛，什么原因？