Only 48FPS out of 60 on USB camera

[vespaman]

Hi all,

Yesterday, I started a reinstall of a three year old box, that I decided to try Manjaro on, when I got it. Its sole job it to run OpenPnP for populating components on PCBs.

(The experience of Manjaro was interesting, but I soon felt the package managers where so-so)

Now, the thing is, that on the Pick and Place machine, there's a camera that is doing vision of component position and rotation from below. This needs to be quick.

The camera is a uvc camera on USB3 Superspeed, and does 60FPS according to what shows up in the selection menu.
This was also true on Manjaro, I got 60FPS.

But:- in gentoo, all programs I have tested with, arrives at about 48.6FPS. I have tried to change the settings on the camera (such as exposure time), but there's no change at all.
I also tested with running qv4l2 I ran as root, so it is not some user restriction, afaict.
I tried a few programs that does not give video output, just swallow the video and report FPS, and they also stay at ~48.6FPS.


Now I don't know where to look... Could it be kernel scheduler, or something USB?

Camera comes up like this on boot;