Specifications
Ultra HD Blu-ray discs support both high dynamic range by increasing the color depth to 10-bit per color and a greater color gamut than supported by conventional Blu-ray video by using the Rec. 2020 color space. Ultra HD Blu-Ray discs also support a 12-bit per color container via Dolby Vision.[17] Moreover, Dolby Vision makes use of dynamic metadata, which adjusts the brightness and tone mapping per scene. In contrast, standard HDR10 only makes use of static metadata, which sets the same brightness and tone mapping for the entirety of the content.[18]
The specification for 4K Blu-ray allows for three disc capacities, each with its own data rate: 50 GB at 72 or 92 Mbit/s, and 66 GB and 100 GB at 92, 123, or 144 Mbit/s. On 66 GB and 100 GB discs, the pits and lands are not narrower than those of a standard Blu-ray Disc, but shorter, which increases the capacity of each layer from 25 GB to 33 1/3 GB (this structure is similar to the one used by BDXL discs). This also means that each revolution of such a disc transfers more data than that of a standard Blu-ray Disc, which means the transfer rate is higher with the same linear velocity. In addition, the disc can be encoded to have the drive hold the full 5,000 rpm until it reaches a point largely away from the innermost part of the disc if an even higher transfer rate is needed. 50 and 66 GB use two layers, and 100 GB uses three layers.[19][4]
Unlike conventional DVDs and Blu-rays, the 4K format does not officially have region coding,[20] although some releases have been reported to conditionally prevent playback based on player region.[21][22] Ultra HD Blu-ray uses a new revision of AACS DRM: AACS 2. AACS 2.1 is used on certain releases such as Stand by Me, Fury, The Patriot, and Zombieland.
Most retail Ultra HD Blu-ray discs are encoded with Ateme TITAN.[23] Ultra HD Blu-ray discs use HDMV or BD-J for menus. Subtitles use Presentation Graphic Stream, which is the same format as normal Blu-ray discs.
Even though a specification was defined for 8K, no commercial products using it have been released. The executive director of the 8K Association said 8K discs being developed had "a low probability."[15]
Advanced HDR by Technicolor
The term Advanced HDR, as used by Technicolor, covers a group of three Technicolor HDR technologies: SL-HDR1 (Single-Layer HDR1); SL-HDR2; SL-HDR3.[24]
According to Technicolor, it is “a single-layer solution, known as Technicolor HDR (ETSI standard SL-HDR1), which ensures backwards compatibility with all non-HDR screens and non-HDR equipment. Broadcasters just need to produce a single feed, and the technology allows content to be converted into a format for both legacy screens and HDR screens.”[25][26]
