Question / Help Why Can't OBS Handle NVENC at High Res? (3440x1440 Rendering Lag)

[Lurn]

I've been trying to fine tune my OBS settings for Local recording but run into encoding overload issues at my native resolution of 3440x1440 with NVENC. Upwards of 38% of lagged frames due to rendering lag which is bizarre because I can record with shadowplay at my native resolution with no issues and the footage comes out buttery smooth.

Here's a sample log file: https://gist.github.com/anonymous/63a5195c5e535b5114010c2752bbe9e1

I set the output resolution to 2580x1080 and it knocks the overload down to ~3.5% of lagged frames due to rendering lag/stalls. But I have to bring it all the way down to 2292x960 with bicubic downscale before I stop missing frames due to rendering lag.

It doesnt make much sense to me that I'd get 2-4% dropped frames recording NVENC through OBS at 2580x1080 60 and 38% when recording at 3440x1440 60. When I can record NVENC through shadowplay at my native res at 60fps with no noticeable frame drop.

What is the reason this is happening with OBS and not shadowplay? And what hardware do I need to be able to record at 3440x1440 60 without lag stalls through OBS?
I have spare GPU's but offloading NVENC to one of them seems to have very minimal benefit.

 

[Rodney]

As a result of having so many GPUs the individual link speed will be reduced which can result in bandwidth bottlenecks.
Generally it is not recommended to run more than 1 GPU, especially on a system with limited PCIe connectivity, to avoid all the issues it can cause. Offloading Nvenc has very little effect since it's not part of the main GPU or its computing load in the first place.

The reason shadowplay works is because it doesn't do any of the compositing/rendering that obs does and also has access to private high performance capture APIs that third party applications (outside of Steam) cannot access.

 

[Lurn]

Ryzen has 24 pcie lanes so even with my 6 gpu gaming/mining setup my main gpu is running x8 @ 3.0 which is not a bottleneck for a 1080 from what I've been told. Does that sound right?

Battle nonsense did a nice video (https://youtu.be/-ceoQitMogA) that showed using a second gpu on a second monitor for shadowplay encoding can recoup ~5% performance in OBS. But 5% won't makeup for my 38% rendering lag at native res so is there anything I can do to record native res through OBS? I really want triple multi track recording and I need constant frame rate that OBS records in for editing. The variable frame rate of shadowplay goes out of sync in premiere and its a huge hassle to handbrake all my shadowplay footage to a constant frame rate.

What setup would you recommend to record native res 3440 60fps in OBS does a single pc solution exist?

 

[Harold]

my main gpu is running x8 @ 3.0 which is not a bottleneck for a 1080 from what I've been told. Does that sound right?

So you're trying to shove 10 lanes of traffic over 8 lanes. That's what I'm getting from your post.

Don't try to stream on a mining rig.

 

[Rodney]

Ryzen has 24 pcie lanes so even with my 6 gpu gaming/mining setup my main gpu is running x8 @ 3.0 which is not a bottleneck for a 1080 from what I've been told. Does that sound right?

4 of those lanes go to the chipset, so you're sharing the remaining 20 between 5 GPUs, depending on your setup that might still give you x8 on the first one. But that definetly can be a bottleneck in some situations.

 

[Lurn]

So you're trying to shove 10 lanes of traffic over 8 lanes. That's what I'm getting from your post.

Don't try to stream on a mining rig.

Not streaming, doing local recordings. The main gpu has the same exact pcie bandwidth as a rig configured with 2 1080's in sli so, "Don't try to stream on a mining rig" doesn't really make sense unless there is some other limiting factor other than pcie speed. And regardless this rig runs shadowplay at those resolutions as configured just fine so there's something else going on obviously. I get people don't like mining but I'm just looking for advice.

 

[Boildown]

The reason shadowplay works is because it doesn't do any of the compositing/rendering that obs does and also has access to private high performance capture APIs that third party applications (outside of Steam) cannot access.

This is probably the right answer.

Try setting the preset to HP (high performance) instead of HQ that you're using. Also set 2-pass to false.

 

[Rodney]

You can post a log with a recording attempt and profiling information in it. To do so close OBS after doing a short test recording, reopen it, use the menu to upload the last log and post it here. That will tell us more.