[Biganon]

Are you using this with zoom, by any chance? I had no luck trying to capture my Webcam with ffmpeg, add text to it with ffmpeg, and output everything to a fake Webcam with video4linux. Actually, it works perfectly well, but this particular stream I can't open with zoom, even though zoom will accept it perfectly if instead of my Webcam, I add text to a video file.

I suppose zoom detects that my actual Webcam is in use, and therefore refuses to display... any webcam whatsoever, including the virtual one...? Makes little sense but maybe...

[madars]

I have not tried it with Zoom but Chrome refused to recognize any loopback video devices unless they were capture-only. So the following worked:

    # modprobe -r v4l2loopback
    # modprobe v4l2loopback video_nr=7 exclusive_caps=1 card_label='Screenshare'

where exclusive_caps=1 is the work-around for Chrome (both video_nr for /dev/video7 and card_label should be able to be set to ~arbitrary values). You need to first start writing stream to the loopback device and then it would switch itself into a capture-only device and Chrome will recognize it.

[gary-kim]

I use it with Zoom as well and haven't had a problem with it. I haven't tried using pure ffmpeg to output to the dummy device though.