I've been playing around with this problem for months now and just cannot solve it. I have two PC's, one running Windows 8.1 with a ultra-wide 2560 x 1080 monitor, the other running Windows 10 with a 1920 x 1080. I have the same latest version of OBS on each. I try to capture a selection of the screen on each PC using identical settings in OBS (except for the two monitor resolution differences in Settings >Video > Base and Settings >Video >output which match the monitors).
But when I capture anything, on the Windows 10 PC the output is fine and fills the frame in VLC etc on playback. But on the Windows 8.1 PC the output is very small, about 1/5th size of what I expected. As I have identical settings for both PC;'s why is one a lot smaller than the other? It's driving me nuts as I can't solve it after months of trying. Can anyone help please?