Sometimes you may have a webcam that shows flickering.

How to solve it?

In my case, I have a Logitech C920 HD Pro and I was having this problem.

Why it happens

Usually it is because the camera is working at 60 Hz and the monitor at 50, or vice versa.

How to solve it in Windows

For my particular camera, it was simple:

  1. download and install the Camera Settings application.
  2. Open it.
  3. Set the camera’s refresh rate to match that of the monitor.

How to solve it on Linux

On Linux it is also easy to do if you install the gtk-v4l package. If you are on Fedora 35:

# Install the package
sudo dnf -y install gtk-v4l

# Run the app (you'll find it in the menu too)

It will open a graphical interface from which you can alter that parameter (“Power Line Frequency” in the picture) and many others:

gtk-v4l UI

The difficulty lies in making this change permanent, since what you change here will be undone after your next restart.

To do this, you need to create a udev rule. In this video and this blog they explain very well how to “cook” your rule, so I will post mine here:

SUBSYSTEM=="video4linux", \
SUBSYSTEMS=="usb", \
ATTRS{product}=="HD Pro Webcam C920", \
ATTRS{idProduct}=="082d", \
ATTRS{idVendor}=="046d", \
PROGRAM="/usr/bin/v4l2-ctl --device $devnode --set-ctrl power_line_frequency=1"

I saved it in /etc/udev/rules.d/100-yajo-logitech-webcam.rules. Obviously, for this we need to have v4l2-ctl installed, so for that:

sudo dnf install -y v4l-utils
systemctl reboot

After the reboot, your webcam will work as it should.