When showing the Camera viewfinder in VideoOutput the image is shortly flipped when recording is started and stopped, or when the camera position (frontface/backface) is changed. It looks like this happens always, but due to timing and other processing it is not always visible. The recorded file is correct - it doesn't contain flipped image at any point.
When changing the camera position e.g. from frontface to backface, it is the frontface image that is flipped right before the backface viewfinder is shown. Thus the image is flipped around the time when the old camera/viewfinder is released. Interestingly on Nexus 7 the frontface camera image was flipped over horizontal axis while the backface image was flipped over vertical axis.
This has been seen on Nexus 7, Moto G and Samsung Galaxy Alpha, but there are also devices where this hasn't been seen (not happening or not visible?).
This can be reproduce on Qt declarative-camera Example when changing camera position. The attached example reproduces this also when recording is stopped.