Christopher Smart: Fixing webcam flicker in Linux with udev

I recently got a new Dell XPS 13 (9360) laptop for work and it’s running Fedora pretty much perfectly.

However, when I load up Cheese (or some other webcam program) the video from the webcam flickers. Given that I live in Australia, I had to change the powerline frequency from 60Hz to 50Hz to fix it.

sudo dnf install v4l2-ctl
v4l2-ctl --set-ctrl power_line_frequency=1

I wanted this to be permanent each time I turned my machine on, so I created a udev rule to handle that.

cat << EOF | sudo tee /etc/udev/rules.d/50-dell-webcam.rules
SUBSYSTEM=="video4linux",
SUBSYSTEMS=="usb",
ATTRS{idVendor}=="0c45",
ATTRS{idProduct}=="670c",
PROGRAM="/usr/bin/v4l2-ctl --set-ctrl
power_line_frequency=1 --device /dev/%k",
SYMLINK+="dell-webcam"
EOF

It’s easy to test. Just turn flicker back on, reload the rules and watch the flicker in Cheese automatically disappear 🙂

v4l2-ctl --set-ctrl power_line_frequency=0
sudo udevadm control --reload-rules && sudo udevadm trigger

Of course I also tested with a reboot.

It’s easy to do with any webcam, just take a look on the USB bus for the vendor and product IDs. For example, here’s a Logitech C930e (which is probably the nicest webcam I’ve ever used, and also works perfectly under Fedora).

Bus 001 Device 022: ID 046d:0843 Logitech, Inc. Webcam C930e

So you would replace the following in your udev rule:

  • ATTRS{idVendor}==“046d”
  • ATTRS{idProduct}==“0843”
  • SYMLINK+=“c930e”

Note that SYMLINK is not necessary, it just creates an extra /dev entry, such as /dev/c930e, which is useful if you have multiple webcams.


Source From: fedoraplanet.org.
Original article title: Christopher Smart: Fixing webcam flicker in Linux with udev.
This full article can be read at: Christopher Smart: Fixing webcam flicker in Linux with udev.

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