obs-v4l2sink: init at unstable-20181012

[colemickens]

Motivation for this change

If I recall correctly I started this, couldn't get it built, @grahamc got it built, couldn't get it working.

I got it working. YUY2 format, exclusive_caps=1 with v4l2loopback. I flipped the video on hte OBS stage, but I think that Jitsi mirror your local video, so this is probably actually the wrong thing to do.

Here's a screenshot of my Sway desktop being captured in OBS-Studio (specifically, this build: obsproject/obs-studio#2484) and then shown in a Jit.si Meet call.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[grahamc]

I setup my system like this:

{
  boot = {
    kernelPackages = pkgs.linuxPackages_latest;
    extraModulePackages = [
      (pkgs.linuxPackages_latest.v4l2loopback.overrideAttrs ({ ... }: {
        src = pkgs.fetchFromGitHub {
          owner = "umlaeute";
          repo = "v4l2loopback";
          # master 2020-04-17
          rev = "10b1c7e6bda4255fdfaa187ce2b3be13433416d2";
          sha256 = "0xsn4yzj7lwdg0n7q3rnqpz07i9i011k2pwn06hasd45313zf8j2";
        };
      }))
    ];
    extraModprobeConfig = ''
      options v4l2loopback exclusive_caps=1 video_nr=9 card_label="obs"
    '';
  };
}

I then rebooted to be sure I got all the latest, greatest kernely goodness and ran sudo modprobe v4l2loopback exclusive_caps=1 video_nr=9 card_label="obs"

Then, I merged this PR in to master locally, built this plugin and obs-studio:

nix-build . -A obs-v4l2sink -A obs-studio

and linked the plugin in to place:

ln -s $(realpath ./result)/share/obs/obs-plugins/v4l2sink/ ~/.config/obs-studio/plugins/v4l2sink

and then ran obs:

./result-2/bin/obs

and