Software video routers
June 3, 2017 — September 8, 2021
I am sure there are many options to do this; here are some I have used.
1 Camtwist
Camtwist. (macOS) Camtwist applies live video effects oddities to your webcam and creates virtual cameras out of screen captures. I have used this one. It is simple and handy, like OBS but does not explode so often.
2 OBS
OBS is a maximalist open-source screen broadcasting package that does everything including running VST effects on your audio stream. Oriented to live use. Somewhat quirky. Windows/Mac/Linux. Linux support is reportedly restricted by choppy support in Wayland, the modern windowing system.
Additionally, it has OBS-virtualcam (Windows) / OBS-mac-virtualcam (Mac) / obs-v4l2sink (Linux) which turns OBS into a virtual camera input for your video conference.
3 Syphon
Syphon is an open source Mac OS X technology that allows applications to share frames — full frame rate video or stills — with one another in realtime. Now you can leverage the expressive power of a plethora of tools to mix, mash, edit, sample, texture-map, synthesize, and present your imagery using the best tool for each part of the job. Syphon gives you flexibility to break out of single-app solutions and mix creative applications to suit your needs.
4 Spout
Spout leverages your graphics card enabling you to send realtime video between Windows applications with near-zero latency or overhead. It is provided free and open source thanks to support from its users.
Disclaimer: I know the author of Spout, and he is bloody lovely.
5 Everything is virtual cameras now
A number of projects provide virtual cameras for plugging into other things, notably mmhmm from the video conferencing/editing world.