Here is the spec for HDR (high dynamic range) video. The document covers both HLG (hybrid log gamma) and PQ (perceptual quantization).

https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.2100-2-201807-I!!PDF-E.pdf

HLG is more akin to the video we know today, SDR (standard dynamic range).