Is video capture supposed to work as good as shadowplay?

Hello.

I'm trying to capture 4K video with RTSS (installed together with MSI Afterburner 4.2.0). I selected the nvenc plugin. I thought this works the same as shadowplay. But it doesn't. I can't capture 60FPS at 3840x2160. Performance drops to 35-40FPS.

With shadowplay, I get a solid 60FPS video capture.

I'm using Windows 8.1 64-bit, and I have a GTX 980 Ti.

(I use the same bitrate in both shadowplay and RTSS.)

 

Shadowplay all the way here, love it really.

Last video:

 

Yeah, it seems RTSS, even though it uses the GPU for encoding, is much less efficient during the actual screen grabbing compared to shadowplay.

I suspect nvenc is only half the story. Grabbing the frames prior to encoding them is the other half, and RTSS doesn't do that part fast enough.