Comcast promises to deliver UHD programming with its new Xi4 set-top box, without extra cost to its subscribers. But it sounds as though such content may be limited at first to on-demand streaming, rather than live television, which is still being broadcast in HD. But it's possible, even probable perhaps, that the box will also some day be able to receive live 4K TV channels. Comcast will also be offering a library of films shot in large formats like IMAX. Furthermore, starting in 2016, the cable company will roll out another set-top box that adds support for high dynamic range (HDR) content, providing video with even more vibrant colors, contrast, and brightness.