Using digicam as a webcam on Linux
Buying a proper webcamera can turn out pretty costly, so why not fetch your old camera from a cellar and plug it into your laptop? How hard can it be?
I recently dug out a pretty old Canon EOS 550D, and since I only have a poor built-in webcam, that was a chance to improve my video quality significantly!
Once plugged into a USB port, the camera is detected just as storage. We need two things to make it work properly:
- Stream the video feed from it
- Pipe this feed into a virtual video input device
🔗Grabbing the video feed
The first step is pretty simple — just use gphoto2
:
)
<enjoy
🔗Creating a fake video device
The second piece of the puzzle is v4l
, in particular, v4l2loopback
. If you’re using Arch like me, you can just install it:
This will also install the required DKMS package to bring in the kernel module named v4l2loopback
.
Now run
To create a virtual video device. You can check the kernel logs for the exact path; in my case, it was /dev/video2
Now we can stream the video feed from the camera to that device using ffmpeg
!
| \
NB: If this command fails with a permission error, make sure that your user is in
video
group:sudo usermod -aG video $USER
Now we need to enable this module on boot:
v4l2loopback
And finally let’s set default module options:
=1 card_label="GPhoto2 Webcam"
v4l2loopback exclusive_caps
NB: After reboot, this module will load very early, earlier that other camera drivers, so the device path will be
/dev/video0
Reboot and verify that this command still works:
| \
🔗Automation
Manually running a script every time we join a video call is not fun. Luckily, we have two ways of solving this, pick one!
🔗Full
Let’s automate staring the capture using udev
.
First, create a udev script
#!/bin/bash
# Uncomment the next line in you want the camera to focus before capturing
#gphoto2 --set-config autofocusdrive=1
| \
&
And now we can use gphoto2’s screet to generate udev rules for us:
# magic script script name
| \
The script will be called when you connect any camera, which is nice IMO.
🔗Semi-automation
Running the capture all the time consumes CPU, so maybe it’s not something you want. Worry not, we can still make a nice button to start capture in KDE.
Go to Setting → Removable Storage → Device Actions
. We’re going to add two new actions:
After relogin and reconnecting the camera, you will see these two new action in the device menu:
NB: If you choose this approach, remember to undo the “Full automation” step by either removing
/etc/udev/rules.d/90-libgphoto2.rules
or commenting out all the lines in/lib/udev/gphoto2-start-capture
🔗Mount
There is not much use for a camera that which lies on your table. We need a proper mount for it!
After some research, I found RAM Mounts. They are modular, so you can build anything you need for your desk setup. They also have two types of labels on each part: either “PATENTED” or “PATENT PENDING”. Probably this is the reason why they are so damn expensive.
Luckily, after some more research, I found Arkon Mounts, which don’t have these labels and are twice cheaper.
And now I have this amazing attachment to my monitor mount:
🔗Battery
If you’re following this guide, pretty soon you’ll find out that the camera’s battery dies very fast: in about two hours. Charging it after every video call is pretty cumbersome, and after a couple of months the capacity will be reduced significantly.
The last pice of the puzzle it a dummy battery (bought here):
I think that the intendant purpose is to power you camera from a “Power Bank”, but we can just plug it into any USB port.
🔗Did it worth it?
Overall, I’m happy with the result. I hate buying new things when I already posses something that has the required capabilities.
I had to buy two new things though: a “dummy battery” and a mount, but both of them can be used for other purposes.