Question / Help OBS and 2 GPUs (Not crossfired).

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DarkMain

New Member
I posted this over on Reddit but am re-posting here as well in hopes of getting a reply.

Hi. I have a bit of a 'unique' issue that seems to be caused by running multiple monitors at different refresh rates.

First of all, my system specs: Intel i7 4930k (Running at stock speeds) AMD R9 295x2 16GB DDR3 Memory. OS and apps on a single SSD and games on 2 SSDs in RAID0.

My main monitor is 1440p @ 144Hz and the other two are 1080p @ 60Hz.

If I'm gaming on the main monitor and have something displayed on the secondary monitors (Twitch chat, OBS, Youtube...) I run into a strange problem where my game FEELS like the FPS is dipping, even though the FPS isn't changing. If I close the programs (or even sometimes minimize them) this issues goes away.

Now its not really a problem, except if I'm streaming I'm effectively limited to a single monitor, which means I can't watch chat, or keep an eye on the stream for dropped frames. (As a side not, it only happens with running games in windowed/bordeless windowed mode. If the game is running in exclusive full screen It doesn't seem to happen, or I don't notice it (The secondary monitors might 'lag' though. However, streaming in exclusive full screen brings with it its own problems with Alt+Tabbing and such).

I was thinking about pricking up a second Graphics card (Maybe an Rx 460 or 470) and running the secondary monitors off this new card leaving my main card to only have to deal with displaying whats on the primary monitor.

However, I'm a) Not sure if this will actually fix my problem and b) how OBS will work with 2 cards (capturing from one, when (I assume) its output is being rendered by the second...

Any insight to this would be great. Cheers.
 
Sapiens

Sapiens

Forum Moderator
Enable vsync or set a reasonable frame rate limit that your GPU can handle without hitting 100% usage. If that's not enough you may also need to turn down some of the video quality options in the game. You can also try turning off the OBS preview, that's helped fix some performance issues before when running monitors at different refresh rates.
 
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DarkMain

New Member
Sapiens said:
Enable vsync or set a reasonable frame rate limit that your GPU can handle without hitting 100% usage. If that's not enough you may also need to turn down some of the video quality options in the game. You can also try turning off the OBS preview, that's helped fix some performance issues before when running monitors at different refresh rates.
Click to expand...

I already have a frame rate limit set to 143 for Freesync, I don't think it applies in windowed mode though. I'll give V-Sync a shot and see how that goes.

There is no 'performance' issue with the game. Its still rendering out over 100fps while playing. (I seem to lose around 5-10fps while capturing which, I guess, is to be expected) CPU usage is low according to task manager as well. The feeling of an FPS drop is more like input lag I guess. The game just get 'floaty'.

I would also like to point out that I don't have the same problem when using 'Mirillis Action' to stream, but that software is VERY basic when it comes to streaming (and it uses VBR which is annoying).
 
Sapiens

Sapiens

Forum Moderator
It doesn't matter if there are performance issues in the game, if the GPU is maxing out then OBS will have its own performance issues. It needs a bit of GPU power for scene compositing, maxing out the GPU causes problems with that.
 
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DarkMain

New Member
Sapiens said:
It doesn't matter if there are performance issues in the game, if the GPU is maxing out then OBS will have its own performance issues. It needs a bit of GPU power for scene compositing, maxing out the GPU causes problems with that.
Click to expand...

K, I'll make sure I have afterburner loaded up next time and Ill keep a close eye on the GPU usage.
 
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DarkMain

New Member
Sapiens said:
It doesn't matter if there are performance issues in the game, if the GPU is maxing out then OBS will have its own performance issues. It needs a bit of GPU power for scene compositing, maxing out the GPU causes problems with that.
Click to expand...

Well this is interesting (to me at least). Even if I limit the game to 30FPS My GPU usage is still hitting 100% at times.
The core clock was stupidly low though. Around 1/2 of what its capable of.
 
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DarkMain

New Member
K, so limiting the FPS seems to have fixed the issue, but I need to limit to 60 (Which doesn't feel great when you have a 144Hz monitor)...

So onto the next part of my question... Will a second graphics card or a capture card help?

If OBS is on a secondary monitor that's plugged into a second graphics card wont that second GPU be rendering the preview? Which card will be doing the scene compositing though?

And a capture card... That will just take stress off the CPU rather than the GPU right?
 
Sapiens

Sapiens

Forum Moderator
No, a second GPU wouldn't help as OBS has issues with SLI/Crossfire due to the way it works. A capture card wouldn't help unless you put it in a second PC, and would further complicate issues since they generally require 60 Hz input, not 144 Hz. The best solution would be to get a video card that's actually suitable for driving a 1440p display at 144 Hz, your current one is not.
 
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DarkMain

New Member
I'm not talking about using a second card in Crossfire... I'm talking about using it to drive the secondary monitors... (eg, plug the 1440p into the R9 295x2 and plug the other monitors into a second card).

This way the 295x2 will only be rendering the game and the other card will be rendering everything else.

Its a pity OBS doesn't like Crossfire. The 295x2 isn't technically Crossfire as its 2 GPUs on a single PCB, but its essentially works the same. Its also more than capable of driving 1440p at 144Hz.

Once again, the software I use to record video (Mirillis Action) has no problem with the multi GPUs. I'm also using the AMD VCE branch of OBS and if I select that as the encoder I don't have any problems, however the quality isn't to my liking and would rather use the CPU.
 
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DarkMain

New Member
The more threads I read concerning 144hz the more I don't think I'm explaining my problem properly.

  1. Game FPS is still high and performance is good.
  2. OBS recordings and playback is fine.
  3. If OBS is on the same monitor as the game I do not have any issues. If I move OBS to a second monitor then the issues start.
  4. GPU usage is at 100% but the clock speed is not maxed out. This happens regardless of the resolution or refresh rate used.
  5. 1440p at 60 FPS does not cause any problems at all, but 1080p at 144Hz (Or anything above 60Hz for that matter) does.
  6. The issue only seems to exist when using CPU encoding. It does not happen with VCE.

I don't know if you have ever experienced 'micro-stutter' on a crossfire setup but that's the best way I can explain what happens. The game is outputting high FPS, but it FEELS like its 30fps.

The more I think about it, the more I'm starting to think its not an OBS problem (Or at least not limited to OBS) and it might actually be an OS or AMD driver issue instead and its just 'exaggerated' or more noticeable with the use of OBS recording.

I would be willing to bet that if my secondary monitor was 144hz I would not be having this problem (Unfortunately I don't have one to test with).

Anyway, I just want to thank you for your help Sapiens. Through your explanations and suggestions alongside all the testing I have done I have managed to work out what setting will work and what ones won't, and although not ideal, its better than nothing.
 
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