I was one of the few people that received 1809 before it got pulled back because of the loosing files situation. I noticed that after that, freesync did not work anymore in full screen games. I tried reinstalling drivers, reinstalling all VC++ etc. In the end, I even grabbed an ISO of 1809 and did a fresh install, freshly installed AMD drivers and Prismatik with that, and still, freesync did not work in full screen. However, I only discovered recently that Prismatik plays a role in this.

When I use desktop Duplication (with and without DX hooking) freesync is not engaged in full screen. when I choose WinAPI as a capture source, all works fine again: Freesync is engaged again in full screen games (with a heavy performance cost of course compared to Desktop Duplication, but that is a good trade-off vs loosing freesync for now). I can replicate the issue 100% of the time on my machine: Start game with Desktop duplication: no Freesync, choose WinAPI: Freesync engaged. Games I have tried this with:

Ghost Recon Wildlands
COD: MW 3
Kingdom Come: Deliverance
ARMA 3
Metro Last Light Redux
Squad
Total War: Rome 2
Ryse: Son of Rome
Frostpunk
DOOM
Alan Wake
3D Mark benchmarks

All applications showed the same behaviour.

I am not sure if there is a problem with desktop duplication in 1809 and it will be fixed when 1809 will be released to the public again, or that this is due to a change in how Windows handles Desktop Duplication, due to a change in AMD drivers in general, or due to the new driver model. If a change in fundamental ways Windows 10 handels Desktop Duplication is the culprit, I thought I would give you a heads up that changes are coming to systems in Windows 10 which are used by the Desktop Duplication method of Prismatik.

I included my dxdiag. I have a Fury X and this issue has been there with all the 18.9.x AMD drivers and later. 18.9.1 and 18.9.2 did not have WDDM 2.5 support yet, but I had the issue non the less on those drivers in Windows 10 1809. I am now on 18.10.2.

Feel free to ask for any more information if you need it. I would love to keep using Freesync in combination with Desktop Duplication, as Freesync is a must, and the performance impact of Desktop Duplication is so little in comparison to the WinAPI method. Glad there is a fallback method to make them both work, but it is not ideal.

DxDiag.txt

EDIT: So I was one of the few people that had VSR (virtual super resolution) support for non-standard aspect ratios (in my case, 21:9) in the latest few drivers https://www.reddit.com/r/Amd/comments/9ndqzw/amd_radeon_software_adrenalin_edition_18101/e7ls9dx . This was the case consistently: after a reinstall of drivers the option was still there. I did look at this option as the cause of my problem. I tried it enabled (with my normal resolution and refresh rate, so just the option enabled, I didnt make use of it) and disabled, it made no difference for the problem described above. I did an in-place update from 18.10.1 to 18.10.2, as this newer driver was just some added support for new games.

However, after reinstalling the latest driver (18.10.2) from scratch again today with DDU (which I always use for a clean install), I dont have the option for VSR anymore, and lo and behold: Desktop Duplication works again in games with Freesync!

Probably the VSR option was enabled by accident in some of the latest drivers for non-standard aspect ratios, as they are testing it probably for their yearly milestone driver at the end of the year (VSR for non-standard resolutions/aspect ratio is the most requested feature at the moment), but the implementation is not yet complete/final, and the code stayed with me from 18.10.1 to 18.10.2, while they removed it in 18.10.2.

As I had reinstalled multiple driver versions from scratch countless times to troubleshoot my issue, I did not think that the small driver 18.10.2 would make the difference, and did not do a fresh install for this minimally improved driver...

Once they officially roll out VSR support for non-standard aspect ratios, I will hold my breath as to whether the issue will return. I am hoping their implementation for VSR was very incomplete/in an early stage and that any resulting issues with Desktop Duplication will be solved by the time they will release it officially. It does seem to be the case that this 'experimental' feature was related to my problems.

Anyways, problem solved... for now... dramatic foreboding music

EDIT 2: For some reason, the VSR option was available to me again after a few restarts, and now indeed, the issue returns. The VSR option and the desktop duplication problem seem to be related, or at least the problem seems related to my gpu drivers.