Perhaps the intrinsic computational resources needed to encode your frames into a video is responsible for the frame rate drop?

I have a not-so-able-anymore card and I get drops of about 10 fps when I try to record via FRAPS.

But what's weird is that video encoding would entail processing power instead of GPU power yet the drops are still relative to your GPU power.

If you find any better recording alternative Sir Jun, share naman diyan