You can use OBS for things like compositing a video of your face over a video of your computer screen, and allowing output to a loopback monitor interface (i.e. virtual camera / microphone) would allow you to share that view via generic video conferencing software like Jitsi or Zoom.
This. It's currently impossible, AFAICT, to use OBS to composite/produce a stream that is fed into video chat software like Zoom, Hangouts, Bluejeans, etc.
Using a plugin for OBS (Windows at least), you can absolutely output to a virtual camera, and use all of the compositing, filters, scenes etc in OBS. You don't get audio output, but you could probably solve that with a virtual audio cable. I do the video thing with Workchat and Bluejeans without issue, and just use my headset for audio.
I currently composite a view of my local harbour, my webcam, and a chroma-keyed nyancat gif, with a second scene for full-sized webcam. Works a charm, and actually uses less CPU that Chrome does when Chrome is routing that video to the VC.
Yesterday (actually 3h before that bounty was posted), I wanted exactly that feature, but I couldn't get it soon enough (I did find obs-virtual-cam at the same time as the bounty was posted, what are the odds).
A bunch of friends and I were listening to a live quiz, on Facebook and we were in a Messenger video calls together to solve it together. The issue was that it was quite hard to watch it together while being live together, so I just pointed my phone at my computer screen, but it was far from ideal.
Essentially my goal was to screenshare on my computer and then the sound quality would have been much better. Messenger does support screenshare but it's weird and doesn,t seems to works if someone is on his phone (which we all were).
So essentially the use case is to share your screen, but also be able to add stuff to it, like your own webcam, and use that on ANY streaming software. Many does support screensharing, but not all of them, and even if they do, adding a camera on top of it is most probably not possible.
My company has a ton of video content we need to deliver, all of which has been moved from studio recordings to zoom. Recording webcam locally using obs while passing the webcam through to zoom doesn't have an easy solution, but we want one badly.