For now, the only source of True4K video is a commercial streaming with heavy compression and (few) HDD-based pre-recorded multimedia players. True4K optical disc, for now, does not exist. 4K BD format has not yet been
defined (officially), and it should be a three-layer or even four-layer (BDXL). The current BD players are optimized for reading a double-layer discs and decode AVC/MPEG2/H264 video codec, so that will not be compatible with the three or
more-layer BDXL discs, recorded with the new HEVC/H265 video codec. The only consolation in this whole UHD circus is fact that we have PC optical BD drives that can read / write multi-layer BDXL discs. The whole "problem" about 4K
video, was created by the premature launch of UHD TV sets ("Money, money, money") without logistical support in the optical and other media and devices. Unlike HD, which was supported with HDDVD, Blu-ray Disc and HD streaming - immediately
after the launch of HD television sets. For now, with "new and glorious UHD", people are cheating with "4K remastered" 1080p discs and BD players with upscaling options FHD to false 4K video (sorry for my bad english I'm from Neptun).