I also recently purchased C800 4K HD (I91BM) and it hard to find info about this. I'm still new with camera 4k as well. My other cameras has fewer option compare to this camera.
Resolution: 1280x720, 1920x1080, 2688x1520, 2592x1944, 3840x2160
Video Quality: Lowest, Lower, Low, Medium, Higher...