Canvas Framespeed drops from time to time (60 to 30 and back again)

[dfense1980]

Hi, I have a strange problem with OBS 29 (but occured on previous versions as well)
From time to time, the frame rate of the Canvas reduces from 60 to 30 frames. After a few minutes, it goes back up to 60 frames. It is very inconsistent and of course creates a diminished viewing experience. The phenomenon happens in every scene and is independent of the sources. Whether I'm just displaying an image or a webcam. In the settings, Base (Canvas) is set to 1980x1080 at 60 FPS. It also doesn't matter if I use x.264 or NVENC. The problem remains the same. I have OBS display the frames with FRAPS. At 30 FPS I already notice a significant judder.
The workload of the PC is minimal. 10-20% CPU and 5-10% GPU. The whole thing happens even when OBS idles.

Interestingly, I can immediately reset the frames to 60fps if I go to Settings - Advanced - and there, for example, briefly change the Color Format. Then the frames jump back to 60fps. This lasts for 5-10 minutes and then it drops back to 30 frames temporarily. So basically it goes up and down from time to time.

My hardware:

Intel i7-7700
32GB RAM
NVIDIA GTX 1660 Super
500GB 970 EVO
OBS 29.0.1
Elgato HD 60 Pro
OSSC 1.6

I am streaming mostly retro (like Super Nintendo, Sega, etc.) but Nintendo Switch as well. This problem occurs on both kind of games.
Is this an OBS bug? I will upload a video/picture later which shows this problem.

Best regards

Edit: I start OBS with Adminrights and the process priority is high in the settings

 

[dfense1980]

Here is a video showing the problem. The framecounter jumps around back and forth in OBS.

 

[dfense1980]

I've been doing some more research on the subject. First of all, the frame drops seem to refer ONLY to the preview. In the stream, the frame rate remains at 60. Still, this must be an unbalanced behavior between Windows, DirectX and OBS. When I set the renderer to OpenGL, the preview frame rate remains at a stable 60FPS but the average time to render frames is way too high then. So OpenGL is NOT the solution.
However, I can confirm that this phenomenon occurs on several test machines. All were Windows 10 maschines btw (Intel i7, AMD Ryzen 7 Pro etc). I would declare this as a general problem.

Maybe others can do a test and give feedback on this. You only need to install Fraps, run it while OBS is opened and view the framerate.

Best regards