Using video loopback opens up some great creative possibilities for fun with video conferencing.
There's one thing I'd love to achieve though, which seems not possible on Linux desktop (specifically kubuntu)....
I want to be able to use the loopback as the source for screen share instead of webcam; i.e. to use the loopback as the conference presentation.
Has anyone got any ideas how to achieve this? Given most conference solutions on Linux do not seem to support either 'share this window' or 'share this screen region'. It seems to be the whole desktop or nothing.
Yes. Thanks for giving me a reason to write this up.
1. Download and install OBS. OBS will be your video processor; among other things it's super easy to make it capture the whole screen or individual windows.
2. Install the v4l2 loopback kernel module[1]. This makes it possible to have a virtual webcam. On Ubuntu 19.10, this was as easy as apt install v4l2loopback-dkms and then modprobe v4l2loopback.
3. Install the OBS plugin obs-v4l2sink[5]. This exports the OBS output to the new virtual webcam device. I just installed the deb file provided by the project[2]. In OBS, under Tools, select v4l2sink and Start.
That's all I had to do. Surprisingly straightforward. At least Chrome and Firefox[3] will now pick up a "Dummy Video Device" webcam that streams the window, or whatever scene I set up in OBS.
In my case, the primary advantage was that this virtual webcam is streamed in Jitsi Meet at a higher quality/framerate than the regular desktop share feature. It's also much lower latency than both Twitch and Youtube Live streaming (Jitsi Meet/WebRTC: <1s, Twitch: 5s, Youtube: 15s[4]; YMMV).
You also get to enjoy the rich feature set OBS provides for Twitch streams; for one thing, you can include the real webcam video.
Bonus: Desktop audio "just worked" in Firefox, which offers the pulseaudio monitor (loopback) device as an input. Chrome doesn't -- probably the intended behaviour. I'm sure there's a workaround.
[1] https://github.com/umlaeute/v4l2loopback
[2] https://github.com/CatxFish/obs-v4l2sink/releases
[3] For some reason, Gnome's Cheese won't
[4] Microsoft's Mixer allegedly has super-low-latency streaming (FTL protocol), but new account are cleared manually and I haven't had the chance to try
[5] For Windows, you can use OBS Virtualcam https://obsproject.com/forum/resources/obs-virtualcam.539/