(1) A Blu-ray player that supports native 4K (2160p) content, which emerged in late 2015. See
Ultra HD Blu-ray.
(2) A Blu-ray player that upscales 2K (1080p) content to 4k resolution for rendering on 4K TV sets. Such devices were introduced in the 2011 time frame. See
4K TV,
4K pass-through and
4K resolution.