title: How to get the size (KB) of a Video AVAsset
body: <p>I would like to get an <code>AVAsset</code> video file size, not the video's resolution, but the file weight in KB.</p>
  
  <p>A solution would be to calculate an estimated filesize from the duration and the estimatedDataRate, but this seems to be a lot just to get a filesize.</p>
  
  <p>I have checked all data embedded in <code>AVAssetTrack</code> it doesn't seems to be in there. Even an estimated filesize would be nice.</p>