Question / Help OpenCL on a second card.

[gonzotw]

First: This post is not about the spottyness of turning on OpenCL support, or its impact, or lack of impact, on performance.

I've been playing with enabling openCL in OBS, but no matter what I do, there seems to be absolutely no change.

I have a GTX 470 as my main GPU.
I'm trying to offload any OpenCL tasks to my secondary 9800GTX+

First, I just tried "opencl=true"

GPU and CPU stayed the same.

I also added "opencl-device=0" (also tried device 1 and 2) GPU and CPU usage remained the same, no using on my second GPU. For some reason, Afterburner lists my secondary card as "GPU1" and my main card as "GPU2"

It seems to matter what I've tried, I can not actually offload anything to my GPU. I'd like to give it a try just to see if I notice any improvement.

Am I missing a switch?

It it because I was only trying in preview mode? As a side note to that, I never noticed that my GPU usage would go as high as 20% even when previewing a stream of a static image.

TLDR - I'm trying to enable OpenCL help for the x264 encoder, but nothing I do seems to actually have an effect.

 

[gonzotw]

I've come to the conclusion that adding the "opencl=true" flag doesn't actually do anything. I have seen literally zero change in either CPU or GPU usage when I turn it on.

I have confirmed that OpenCL works on both cards with LuxMark.

Am I doing something horribly wrong?

 

[Sapiens]

OpenCL support in x264 has a negligible impact on encoding performance, slightly lowers quality, and is unstable, leading to more frequent encoder crashes. Don't bother with it.

 

[Videophile]

OpenCL support in x264 has a negligible impact on encoding performance, slightly lowers quality, and is unstable, leading to more frequent encoder crashes. Don't bother with it.

How does opencl decrease quality?

 

[Sapiens]

There is also typically a small quality loss seen when using the OpenCL lookahead, caused by the iterative nature of the OpenCL motion search and H.264's data dependencies.

http://forum.doom9.org/showthread.php?t=165984

It's only used for lookahead anyway, so even if using it resulted in identical quality its instability makes it a generally undesirable option.

 

[gonzotw]

From my previous reading of thread, I believe the early instability was fixed.

But, as per the first line OP, I'm not looking for the benefits, disadvantages, and pitfalls. I'm trying to get it enabled so I can test it myself.

The problem being, the only way I've seen to supposedly enable it doesn't seem to actually have any effect.