There are 3 repositories under coremediaio topic.
akvirtualcamera, virtual camera for Mac and Windows
Apple's CoreMediaIO DAL plugin example - modernized
Simple command line tool to record video and audio from any attached capture device
Simple CoreMediaIO DAL virtual camera plugin example written in Swift
OSX command line application to report if any camera is active
Stay Focused, Stay Private: WFH Camera - Your Virtual Shield for Video Calls!