Using a Digital Camera as a Webcam on Linux
This method makes use of gphoto2 and
v4l2loopback packages. Testing was done with a Canon EOS R
mirrorless digital camera. A list of the supported cameras can be found on
the
Supported Cameras
web-page on the gphoto.org website.
Installation
Install the required packages:
sudo pacman -S gphoto2 v4l2loopback-utils ffmpeg linux-headers
The v4l2loopback package is a kernel module that allows one to
create virtual video devices (V4L2 loopback devices). Hence, it depends on
Dynamic Kernel Module Support (DKMS), and therefore, the dkms package is installed as one of its
dependencies. However, DKMS requires the headers for the target kernel (i.e.
the Linux kernel), and so, one also has to install the
linux-headers. If one is using a kernel other than the default
Linux kernel, then the associated headers for that kernel will have to be
installed instead.
Setup
Connect the camera to the computer via a compatible USB cable (e.g. the OEM cable bundled with the camera). Poor quality cables may cause issues. Power-on the camera and set it to its video mode (assuming one wants 16:9 aspect ratio content). Disable the battery-saving, automatic power-off feature if unexpected power-off events occur.
List all video devices:
ls /dev/video*
Note the devices listed (there should be none if no video devices have been configured).
Configuring the v4l2loopback Module
Load the v4l2loopback kernel module:
sudo modprobe v4l2loopback
Options for the above command can be found on the v4l2loopback GitHub repository.
If the digital camera will be used as a video device for
WebRTC-based
applications, then one might have to pass the
exclusive_caps=1 argument to the above command. For example,
applications like Zoom and browsers that allow video calling will most
likely implement WebRTC.
If one realises that the v4l2loopback options have to be
changed after the module has already been loaded, then one will have to
first unload the module:
sudo modprobe -r v4l2loopback
Then reload the module with the required options set:
sudo modprobe v4l2loopback exclusive_caps=1
Check that the module is working by listing the available devices:
v4l2-ctl --list-devices
Review the available devices and compare it to what was listed earlier. The
newly listed device (e.g. /dev/video0) will be the recently
connected digital camera. This will be the device used going forward.
Check if gphoto2 recognises the digital camera make and model
(e.g. Canon EOS R):
gphoto2 --auto-detect
Setting Up the Virtual Webcam
Get the live-view size options from gphoto2:
gphoto2 --get-config liveviewsize
There will usually be three options: 0 for large, 1 for medium and 2 for
small live-view sizes. Select one depending the required resolution and pass
it to the liveviewsize argument in the subsequent command.
To adjust the output resolution, pass it to the -s:v argument
in the subsequent command.
Capture the output from the camera using gphoto2 and then pipe
the output to ffmpeg to create a virtual webcam:
gphoto2 --stdout --set-config liveviewsize=0 --capture-movie | ffmpeg -i - -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 -s:v 1920x1080 /dev/video0
Loading the v4l2loopback Module at Boot
Let systemd load the module at boot by creating the
/etc/modules-load.d/v4l2loopback.conf file and adding the
following lines:
v4l2loopback options v4l2loopback exclusive_caps=1
At a minimum, there should be v4l2loopback on one line.
Necessary options should then follow, ensuring that only one option is
listed per line.