A:Answer Per the manufacturer this receiver is 4K pass through, not upscaling. Yes you must use a 4K blu ray to watch 4K movies, however, usually included with the 4K movie is a standard 1080p version. A 4K blu ray will play 1080p movies. Usually, only the high end 4K tvs have upscaling, most 4K tvs don't have upscaling. Plus, the difference in picture quality from a 1080p movie to a 1080p movie upscaled to 4K is not that much difference.