Ffmpeg Use a Dummy Webcam

1 min read July 22, 2023 183 words

Preface

I experienced my first proctored exam today. Being that I'm a technologist, I thought it'd be pretty fun to pre-record myself and have that recording output to a virtual webcam. Here's a not so descriptive guide on using ffmpeg with the v4l2loopback kernel module to create a virtual dummy webcam.

Installing v4l2loopback kernel module

This module allows for the creation of virtual video devices.

# Dependencies
sudo apt install -y build-essential linux-headers-$(uname -r) v4l-utils help2man

# Installation
git clone https://github.com/umlaeute/v4l2loopback.git
cd v4l2loopback
make -j $(nproc)
sudo make install
sudo cp v4l2loopback.ko /lib/modules/$(uname -r)
sudo depmod -a
sudo modprobe v4l2loopback

# Testing. You should see "Dummy video devices"
v4l2-ctl --list-device

Outputting a video/image to the dummy cam

Subsitute /dev/video3 for whatever devices your dummy webcam is using.

# For video
ffmpeg -re -stream_loop -1 -i "video.mp4" -f v4l2 /dev/video3

# For image
ffmpeg -framerate 1 -loop 1 -re -i "image.png" -f v4l2 -vcodec rawvideo -pix_fmt yuv420p /dev/video3

Outputting existing webcam to dummy cam

Useful if your virtual machine can't install the drivers for your webcam.

ffmpeg -i "/dev/video0" -f v4l2 -vcodec rawvideo  /dev/video2