Bug Report Drops fps inside OBS when focusing on game with blackmagic on scene

[sneaky4oe]

So, a beefy pc (1700x, gtx1070, 32gb) - not a hardware issue.
Stream isn't running, so no resource limitations or preset changes are needed.
This happens on 19.0.3 as well. Recommending to update is pointless.
Used to work fine. Now happens to every game.

I have an intensity pro 4k, and when it's capture is active (1080p50), FPS inside OBS drops to 20 or so when I focus on a game window. When I alttab somewhere else, my FPS goes back normal.
Even on an empty scene collection with n osources except BMD device, I get lowering of fps when clicking into the game.

https://gist.github.com/e91aa639d2e52f126ade599274b80cf4

If I remove blackmagic source, it goes back to 60 fps. But I use it as my camera, so would like to save.
Any tips please?

Demo recording: https://youtu.be/WfOnHDXj9n4

 

[sneaky4oe]

UPD; after some testing - I've made a clear scenes collection, and inserted game capture only. And this still happens. Seems like OS just gives all resources to the game. But game mode is off in my windows10.

 

[sneaky4oe]

Found a great solution. 10/10 will follow.
Uninstall windows 10 and get 8.1 with all updates. Works like a charm with the same set of apps, I guarantee it.