Make duo camera available for ffmpeg via v4l2

Hi there! I’ve managed to build working image with ffmpeg and even could create a video from jpeg image in a loop. Next step is a simple ffmpeg pipeline into .mpeg file. I’m using v4l2 as input format and /dev/cvi-vi as input device as i found it in dmesg.
Pipeline: ffmpeg -f video4linux2 -input_format mjpeg -i /dev/cvi-vi out.mpeg
The problem is that v4l2 can not identify this device as tty and pipeline is not working. Maybe someone had experience with connect duo’s camera with any other applications except this script? Maybe cvi-vi is not a proper device?
Any help will be appreciated, thank you.