What it is KAT MovieHDRUN is a file-naming and distribution convention used in the movie ripping/scene release community to indicate a high-dynamic-range (HDR) encode labeled "MovieHDRUN" from a release group or a labeling scheme. It usually appears as part of a release filename alongside group tags, source indicators (e.g., BluRay, WEB-DL), encoder names, resolution (2160p/1080p), codec (HEVC/x265), and container (MKV/MP4). Typical filename components (example) Group.Name.Movie.Title.Year.Source.Resolution.Codec.HDR.Type.Audio.Encoder-ReleaseGroup.mkv
