My Nix module to work with v4l2loopback

v4l2.nix

{ lib, config, pkgs, ... }:

with lib;

{
  options.v4l2 = mkEnableOption "Enable the confguration to use the reflex as a webcam";
  config = mkIf config.v4l2 {
    # 20.03: v4l2loopback 0.12.5 is required for kernel >= 5.5
    # https://github.com/umlaeute/v4l2loopback/issues/257

    # Extra kernel modules
    boot.extraModulePackages = with unstable; [
      config.boot.kernelPackages.v4l2loopback
    ];

    # Register a v4l2loopback device at boot
    boot.kernelModules = [
      "v4l2loopback"
    ];

    boot.extraModprobeConfig = ''
      options v4l2loopback exclusive_caps=1 video_nr=9 card_label=a7III
    '';
  };
}

v4l2.sh

#! /usr/bin/env nix-shell
#! nix-shell -i bash -p gphoto2 ffmpeg zoom-us

set -euo pipefail

function connect-camera() {
   gphoto2 --stdout --capture-movie 2> ~/tmp/camera.log | ffmpeg -i - -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 /dev/video9 > /dev/null 2> ~/tmp/encoding-err.log &
   PID_CAM=$!
}

function main() {
	connect-camera &&\
	read -n 1 -s -r -p "Press any key to continue" &&\
	zoom-us 2> ~/tmp/zoom-output.log &&\
	kill -KILL $PID_CAM 
}

main