AVAssetWriter ignores transform value
I record in portrait mode only and i was able to avoid this issue by getting rotated pixel data directly from the camera using setVideoOrientation on the AVCaptureConnection to pass to AVAssetWriter (see https://developer.apple.com/library/ios/qa/qa1744/_index.html)
for (AVCaptureConnection *connection in [videoOutput connections] ) { for ( AVCaptureInputPort *port in [connection inputPorts] ) { if ( [[port mediaType] isEqual:AVMediaTypeVideo] ) { [connection setVideoOrientation:AVCaptureVideoOrientationPortrait]; } }}