title: AVAsset duration is not correct
body: <p>I have video in Mac player duration of video is 31 seconds. When I'm using it in my app and loading that file the duration of AVAsset is '28.03'.</p>
  
  <pre><code>AVAsset *videoAsset = [AVAsset assetWithURL:videoUrl];
  Float64 time = CMTimeGetSeconds(videoAsset.duration);
  </code></pre>