Impress plays videos not according to ratio

My video is full HD (1920x1080). I inserted that FHD video into a 4:3 Impress slide. On the slide, the dimensions are OK (e.g. 10 inches x 5.62 inches). But when I presented the 4:3 slide to a 4:3 projector or monitor, it seems the width of the video will be squeezed to the screen it’s presented on while the height is full screen, which means the ratio is not maintained. Could this be a bug?