ios - AVCaptureVideoPreviewLayer landscape orientation

Question

How can I get 'AVCaptureVideoPreviewLayer' to display properly in landscape orientation? It works fine in portrait but doesn't rotate, and shows a rotated camera capture when the parent view controller is in landscape orientation.

Answer 1

First, the answer

- (void)viewWillLayoutSubviews {
  _captureVideoPreviewLayer.frame = self.view.bounds;
  if (_captureVideoPreviewLayer.connection.supportsVideoOrientation) {
    _captureVideoPreviewLayer.connection.videoOrientation = [self interfaceOrientationToVideoOrientation:[UIApplication sharedApplication].statusBarOrientation];
  }
}

- (AVCaptureVideoOrientation)interfaceOrientationToVideoOrientation:(UIInterfaceOrientation)orientation {
  switch (orientation) {
    case UIInterfaceOrientationPortrait:
        return AVCaptureVideoOrientationPortrait;
    case UIInterfaceOrientationPortraitUpsideDown:
        return AVCaptureVideoOrientationPortraitUpsideDown;
    case UIInterfaceOrientationLandscapeLeft:
        return AVCaptureVideoOrientationLandscapeLeft;
    case UIInterfaceOrientationLandscapeRight:
        return AVCaptureVideoOrientationLandscapeRight;
    default:
        break;
  }
  NSLog(@"Warning - Didn't recognise interface orientation (%d)",orientation);
  return AVCaptureVideoOrientationPortrait;
}

I've come across several SO posts on this matter, and couldn't find any simple explanation so I thought I'd share my own.

If you follow Apple's sample on the matter, you'll run into two potential problems when you rotate your iOS device to landscape

1. Capture will appear rotated (as if you're holding the camera 90 degrees off)
2. It won't span its set bounds entirely

The problem here is that 'CALayer' doesn't support autorotation hence, unlike a 'UIView' you'd add as a subview, it won't rotate when its parent 'UIView' rotates. Therefore, you have to manually update its frame every time the parent view's bounds changes (not parent view's frame since frame stays the same after rotation). This is achieved by overriding 'viewWillLayoutSubviews' in the container view controller.

Secondly, you should use 'videoOrientation' property to inform AVFoundation about the orientation so it does the preview properly.

Hope this helps.