I just downloaded spacedesk and it's mostly working as intended except for being super laggy for no reason.
Regardless of what I set the compression settings like FPS Rate to, the FPS on the second monitor will be at that set value for a bit but then drop and wiggle around between 2FPS and 17FPS without any reason.
At 60FPS both my GPU and CPU (host PC) are at around 20ish% and then when the FPS decides to drop to 2FPS, both the cpu and gpu usage drop to almost nothing.
The CPU and GPU values on the PC used as a second monitor are also negligible (so is the RAM for both machines).
The app doesn't use a significant portion of my bandwidth either.
It looks like it's trying to optimise resources or something because when I move my mouse around in the 2nd screen the fps goes back up to 60, but when a youtube video is playing and my mouse is not on screen, the app keeps 'deciding' that I don't need the extra fps and it goes down to the 2-17fps range.
Is there any way to make it stick to the maximum framerate?