The ITU-T version of the standard that added the SCC extensions (approved in December 2016 and published in March 2017) added support for the hybrid log–gamma (HLG) transfer function and the ICtCp color matrix. This allows the fourth version of HEVC to support both of the HDR transfer functions defined in Rec. 2100. The fourth version of HEVC adds several supplemental enhancement information (SEI) messages which include: Alternative transfer characteristics information SEI message, provides information on the preferred transfer function to use. The primary use case for this would be to deliver HLG video in a way that would be backward compatible with legacy devices. Ambient viewing environment SEI message, provides information on the ambient light of the viewing environment that was used to author the video. Profiles Version 1 of the HEVC standard defines three profiles: Main, Main 10, and Main Still Picture. Version 2 of HEVC adds 21 range extensions profiles, two scalable extensions profiles, and one multi-view profile. HEVC also contains provisions for additional profiles. Extensions that were added to HEVC include increased bit depth, 4:2:2/4:4:4 chroma sampling, Multiview Video Coding (MVC), and Scalable Video Coding (SVC). The HEVC range extensions, HEVC scalable extensions, and HEVC multi-view extensions were completed in July 2014. In July 2014 a draft of the second version of HEVC was released. Screen content coding (SCC) extensions were under development for screen content video, which contains text and graphics, with an expected final draft release date of 2015. A profile is a defined set of coding tools that can be used to create a bitstream that conforms to that profile. An encoder for a profile may choose which coding tools to use as long as it generates a conforming bitstream while a decoder for a profile must support all coding tools that can be used in that profile. Version 1 profiles Main The Main profile allows for a bit depth of 8 bits per sample with 4:2:0 chroma sampling, which is the most common type of video used with consumer devices. Main 10 The Main 10 profile was added at the October 2012 HEVC meeting based on proposal JCTVC-K0109 which proposed that a 10-bit profile be added to HEVC for consumer applications. The proposal said this was to allow for improved video quality and to support the Rec. 2020 color space that has become widely used in UHDTV systems and to be able