title: AVCaptureVideoPreviewLayer doesn't fill up whole iPhone 4S Screen
body: <pre><code>AVCaptureVideoPreviewLayer *avLayer = 
                  [AVCaptureVideoPreviewLayer layerWithSession:session];
  avLayer.frame = self.view.frame;
  [self.view.layer addSublayer:avLayer];
  </code></pre>
  
  <p>I use AVCaptureVideoPreviewLayer to display video on the view.
  But the video's view didn't fill up the full iPhone4's screen.(two grey bar at the right&amp;left side)</p>
  
  <p>I want the video fills up full screen.
  How can I deal with it? Thank you very much!</p>
  
  <p><img src="https://i.stack.imgur.com/9fkW9.png" alt="enter image description here"></p>