title: Need to modify image before displaying on AVCaptureVideoPreviewLayer
body: <p>I'm using <code>AVCaptureSession</code> to capture video from my iPhone 3G and I need to capture the image and change it before displaying on my <code>AVCaptureVideoPreviewLayer</code>. In my current implementation, I am simply implementing the <code>captureOutput:</code> method and displaying the <code>UIImage</code> in a <code>UIImageView</code>, but that does not work for some reason.</p>
  
  <p>Any ideas? Subclass <code>AVCaptureSession</code> somehow?</p>
  
  <p>Thanks!</p>