Creating a Virtual Camera for Conferences

We don’t always want to include a camera during the conference, so we found a way to display video or static images instead. The means of OS or browser doesn’t provide this out of the box. I found this article and, indeed, created a virtual camera module that is recognized by browsers as an ordinary camera 😄

Below is a script with detailed comments. The only argument to it is the path to the file or image that should be transmitted in the stream.

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#!/usr/bin/env sh
set -e

# label for the new webcam as it will be seen in browser
LABEL="VirtualCam #0"

# module insertion in case if it was not inserted during this boot
if ! lsmod | grep -qE '^v4l2loopback'; then
  # camera is being created during the module loading
  sudo modprobe v4l2loopback devices=1 exclusive_caps=1 max_buffers=2 card_label="$LABEL"
  # wait for a while to finish module initialization
  sleep 1
fi

# path to media file
F="${1:?File is not passed}"
# getting path to newly created camera device
DEV="$(v4l2-ctl --list-devices 2>/dev/null | grep -A1 "$LABEL" | grep -oE '/dev/video[0-9]+')"

if [ ! -f "$F" ]; then
  # check in case if media file path does not exists
  echo "error: file $F does not exists" >&2
  exit 1
fi

# get file type and use proper streaming command
case "$(file --mime-type --brief "$F" | cut -d/ -f1)" in
  video)
    # in case if file is video
    ffmpeg -re -i "$F" -f v4l2 -vcodec rawvideo -pix_fmt yuv420p "$DEV"
    ;;
  image)
    # in case if file is picture
    ffmpeg -loop 1 -re -i "$F" -f v4l2 -vcodec rawvideo -pix_fmt yuv420p "$DEV"
    ;;
  *)
    # in case if file is something else
    echo 'error: unknown mime type' >&2
    exit 2
    ;;
esac

So, in the end, we were able to stream Rick Ashley - Never Gonna Give You Up.

One notable drawback is that FFmpeg consumes almost an entire core. Additionally, we are, of course, only transmitting the image, without any sound.