#Fake Webcam
#Using your screen as a webcam input device
#install drivers and tools
sudo apt install v4l2loopback-utils

#Load Module/Driver
sudo modprobe v4l2loopback

#capture screen and pipe it to your video device
ffmpeg -f x11grab -r 15 -s 1920x1080 -i :0.0+0,0 -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 /dev/video0

#now you should be able use it with software that uses Video/Webcam input.
#Note: Cheese doesn't seem to like it.
guvcview
mpv av://v4l2:/dev/video0


##############Video file to Web Cam###############
#note here will be no sound from the video
ffmpeg -re -i input.mp4 -map 0:v -f v4l2 /dev/video0