[Unit]
Description=Set up loopback cameras

[Service]
ExecStartPre=/sbin/modprobe v4l2loopback devices=3
ExecStart=/usr/bin/ffmpeg -f video4linux2 -input_format yuv420p -video_size 1280x720 -i /dev/video0 -codec copy -f v4l2 /dev/video1 -codec copy -f v4l2 /dev/video2 -codec copy -f v4l2 /dev/video3
Restart=always
RestartSec=2

[Install]
WantedBy=default.target