The rumored Sony's new video codec XEVC which is based on HEVC version 2 claims 240Mbps peak bitrate lossless compressing 1920 x 1080, 12 bit depth, 24fps. I did a calculation and get 1:7.12 ratio.
source:
https://www.eoshd.com/2018/12/sonys-...aw-at-240mbit/