OK thanks for the clarification. So in this case, nothing to do with tone mapping just the luminance portion (e.g. - a 1,000 nit HDR video source to the display’s lower max nits of say ~ 100-700 nits) while maintaining HDR PQ “gamma”?
Actually it kind of is!
If you use an HDFury product such as the Vertex2 you can spoof the EDID to the AppleTV into thinking it’s connected to a Dolby Vision display, even if it is only HDR10 capable, such as Samsung UHDTVs and HDR10 projectors.
If you set your display settings to “4K59.94 Dolby Vision” and leave “Match Dynamic Range” setting off and “Match Frame Rate” on (so you get the native frame rates like 23.975 for most movies), it will then convert your HDR10 only movies to LLDV/Dolby Vision utilizing the DV dynamic tone mapping processing and algorithms (VS10?) within the AppleTV 4K.
The Vertex2 settings I use to prove this are basically setting the HDR/AVI Custom EDID values to 10,000 nits (yes, 10,000 nits!) and then using either Automix with the DV block selected and the DV Datablock Tab set to BT2020 and Max Luminance of 1,000 nits, or you can just use Custom EDID 9 or 10 under the EDID Tab to essentially accomplish the same thing, but with less customization abilities but more plug and play for novices.
I use Infuse in this manner to play my UHD HDR Bluray rips and I never have to adjust a thing anymore on my LK990 or Samsung LSP9T projectors since its dynamically tone mapping the signal. It works on everything from super high nit movies and scenes like The Meg chapter 8, Aquaman chapter 6 to low nit titles like Blade Runner 2049, Star Wars The Last Jedi, Arrival, The Mandalorian on Disney+ streaming and everything in between!
The image is absolutely incredible and akin to buying a very high priced Lumagen Radiance Pro or MadVR Envy Video Processor but without wasting your kid’s college fund or remortgaging your home!!!