Dolphin in 4k Ultra HD Video Collection Now with 6xIR!

[Kodiack]

At the very least, you should be able to record at 4xIR without any slowdown, especially if you're not encoding with your CPU or something that relies on your primary GPU. Hell, for most games, I can record at 2560x1440 with 6xIR (3840x3168) at 100%+ speed with ease. I think that perhaps you overestimate just how demanding recording at 4K is. I'd double-check your configuration first and foremost. If you're set up properly, switching your internal resolution absolutely should not affect your performance so heavily while recording.