Fix the Logitech HD Pro Webcam C920

This repository contains tweaks to the autofocus of the Logitech HD Pro Webcam C920 for Linux.

The webcam is pretty good and works out of the box, but it tends to go out of focus randomly. This is not a deal breaker and usually bringing an object close to the lense (your finger) will refocus the camera.

Although it should be possible to disable the autofocus so that the camera doesn't change the focus.

This is inspired by the video How to disable autofocus on webcam in Linux | Logitech C920.

This repo provides a script and a systemd service for tweaking the camera at startup.

Installation

Clone the repo and run:

make install

Uninstallation

make uninstall

Troubleshooting

You can see the status of the service with:

make status

And you can get the logs with:

make logs

How it works

This package installs an udev rule that's used for detecting when the webcam is plugged and to run a script to alter the configuration via a systemd service.

The script will in turn change the webcam settings so that the focus works better. These changes are not permanent and need to be reapplied at each reboot or when the camera is plugged in. The udev rule is in charge of detecting when new hardware is plugged in and to apply the configuration changes.

udev rule

The udev rule is installed under /etc/udev/rules.d/99-fix-Logitech-HD-Pro-Webcam-C920.rules and contains:

# Detect a "Logitech, Inc. HD Pro Webcam C920"
ACTION=="add", \
  SUBSYSTEM=="video4linux", \
  ATTRS{idVendor}=="046d", \
  ATTRS{idProduct}=="082d", \
  ENV{ID_V4L_CAPABILITIES}==":capture:", \
  SYMLINK+="web-c920", \
  TAG+="systemd", \
  MODE="0666", \
  ENV{SYSTEMD_WANTS}="fix-Logitech-HD-Pro-Webcam-C920.service"

This rules matches the equivalent of of lsusb:

Bus 005 Device 002: ID 046d:082d Logitech, Inc. HD Pro Webcam C920

NOTE: Your Bus and Device numbers will most likely not match. What needs to match is the ID: 046d:082d.

The udev rule will create a symlink named /dev/web-c920 that will point to the webcam's main device entry (e.g. /dev/video0). It will then invoke the systemd service fix-Logitech-HD-Pro-Webcam-C920.service to apply the configuration changes.

systemd service

This service runs a simple shell script that uses v4l2-ctl for reconfiguring some parameters of the webcam.

The systemd service will then run the equivalent of:

v4l2-ctl --device /dev/web-c920 --set-ctrl=focus_auto=0