HDR Solution for OpenPHT
Based of an example of MPC-HC/MadVR settings being tweaked to the extreme to get it to display HDR video and have hardware acceleration, I thought I'd see if the same process could be done with TV Picture settings to get HDR levels to appear right in Open PHT.
Windows 10 in HDR Mode
Core i7 5820k
Radeon RX-470, Default image and video settings, 10bit 4:2:2 @60hz
Vizio Picture settings both started as the recommended bt2020 video picture settings from the AVS Forums 2016-2017 P Series owners thread.
Brad Calibrated- Color Temp Normal, Xtreme Black Engine Pro On, Game Mode On, 2.1 Gamma
Brad HDR- Color Temp Computer, Xtreme Black Engine Pro On, Game Mode On, 2.0 Gamma
I ran both stills and video from an HDR video in OpenPHT, then at the same time ran the same video in a window from the Windows Movies and TV app or MPC-HC/MadVR, both of which produce a proper HDR image. It was 'eyeball calibration' but I would go scene by scene or stills, usually from the identical frame, and get that 'Brad HDR' image from OpenPHT to look identical to the Calibrated HDR video. To my pleasant surprise, I was able to get that identical image; it even gave me the idea for some minor tweaks from the Calibrated setup to give the pic an even better look than before.
These settings should get most Vizio HDR TVs close. For others, I suggest pushing color/saturation and backlight to their limits, drop brightness by 10 and raise contrast by 10 and go from there, Tint will likely need to be adjusted. You can also try Potplayer as a possible reference player, as MPC-HC needs some extra steps and Movies and TV can't play some file types. This has been far simpler than exiting OpenPHT, going to the folder and opening a player that will just forget where to resume when you hit stop.
Addition suggested housekeeping: go into Plex Home Server, retitle your videos to 'Title- HDR' for family memebers. For files where you have 2 versions, 1 without HDR for streaming, make sure to split the files in Plex Home Server and then reititle the HDR version. I also put a different folder image on those files as an added reminder. This is now an option my wife can easily understand and use, not to mention not have to put down the Harmony remote.