nixos/v4l2-relayd: init

nixos/doc/manual/release-notes/rl-2305.section.md

···
 
 - [ReGreet](https://github.com/rharish101/ReGreet), a clean and customizable greeter for greetd. Available as [programs.regreet](#opt-programs.regreet.enable).
 
+- [v4l2-relayd](https://git.launchpad.net/v4l2-relayd), a streaming relay for v4l2loopback using gstreamer. Available as [services.v4l2-relayd](#opt-services.v4l2-relayd.instances._name_.enable).
+
 ## Backward Incompatibilities {#sec-release-23.05-incompatibilities}
 
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->

nixos/modules/module-list.nix

···
   ./services/video/replay-sorcery.nix
   ./services/video/rtsp-simple-server.nix
   ./services/video/unifi-video.nix
+  ./services/video/v4l2-relayd.nix
   ./services/wayland/cage.nix
   ./services/web-apps/akkoma.nix
   ./services/web-apps/alps.nix

nixos/modules/services/video/v4l2-relayd.nix

···
+{ config, lib, pkgs, utils, ... }:
+let
+
+  inherit (lib) attrValues concatStringsSep filterAttrs length listToAttrs literalExpression
+    makeSearchPathOutput mkEnableOption mkIf mkOption nameValuePair optionals types;
+  inherit (utils) escapeSystemdPath;
+
+  cfg = config.services.v4l2-relayd;
+
+  kernelPackages = config.boot.kernelPackages;
+
+  gst = (with pkgs.gst_all_1; [
+    gst-plugins-bad
+    gst-plugins-base
+    gst-plugins-good
+    gstreamer.out
+  ]);
+
+  instanceOpts = { name, ... }: {
+    options = {
+      enable = mkEnableOption (lib.mdDoc "this v4l2-relayd instance");
+
+      name = mkOption {
+        type = types.str;
+        default = name;
+        description = lib.mdDoc ''
+          The name of the instance.
+        '';
+      };
+
+      cardLabel = mkOption {
+        type = types.str;
+        description = lib.mdDoc ''
+          The name the camera will show up as.
+        '';
+      };
+
+      extraPackages = mkOption {
+        type = with types; listOf package;
+        default = [ ];
+        description = lib.mdDoc ''
+          Extra packages to add to {env}`GST_PLUGIN_PATH` for the instance.
+        '';
+      };
+
+      input = {
+        pipeline = mkOption {
+          type = types.str;
+          description = lib.mdDoc ''
+            The gstreamer-pipeline to use for the input-stream.
+          '';
+        };
+
+        format = mkOption {
+          type = types.str;
+          default = "YUY2";
+          description = lib.mdDoc ''
+            The video-format to read from input-stream.
+          '';
+        };
+
+        width = mkOption {
+          type = types.ints.positive;
+          default = 1280;
+          description = lib.mdDoc ''
+            The width to read from input-stream.
+          '';
+        };
+
+        height = mkOption {
+          type = types.ints.positive;
+          default = 720;
+          description = lib.mdDoc ''
+            The height to read from input-stream.
+          '';
+        };
+
+        framerate = mkOption {
+          type = types.ints.positive;
+          default = 30;
+          description = lib.mdDoc ''
+            The framerate to read from input-stream.
+          '';
+        };
+      };
+
+      output = {
+        format = mkOption {
+          type = types.str;
+          default = "YUY2";
+          description = lib.mdDoc ''
+            The video-format to write to output-stream.
+          '';
+        };
+      };
+
+    };
+  };
+
+in
+{
+
+  options.services.v4l2-relayd = {
+
+    instances = mkOption {
+      type = with types; attrsOf (submodule instanceOpts);
+      default = { };
+      example = literalExpression ''
+        {
+          example = {
+            cardLabel = "Example card";
+            input.pipeline = "videotestsrc";
+          };
+        }
+      '';
+      description = lib.mdDoc ''
+        v4l2-relayd instances to be created.
+      '';
+    };
+
+  };
+
+  config =
+    let
+
+      mkInstanceService = instance: {
+        description = "Streaming relay for v4l2loopback using GStreamer";
+
+        after = [ "[e-mail]" "systemd-logind.service" ];
+        wantedBy = [ "multi-user.target" ];
+
+        serviceConfig = {
+          Type = "simple";
+          Restart = "always";
+          PrivateNetwork = true;
+          PrivateTmp = true;
+          LimitNPROC = 1;
+        };
+
+        environment = {
+          GST_PLUGIN_PATH = makeSearchPathOutput "lib" "lib/gstreamer-1.0" (gst ++ instance.extraPackages);
+          V4L2_DEVICE_FILE = "/run/v4l2-relayd-${instance.name}/device";
+        };
+
+        script =
+          let
+            appsrcOptions = concatStringsSep "," [
+              "caps=video/x-raw"
+              "format=${instance.input.format}"
+              "width=${toString instance.input.width}"
+              "height=${toString instance.input.height}"
+              "framerate=${toString instance.input.framerate}/1"
+            ];
+
+            outputPipeline = [
+              "appsrc name=appsrc ${appsrcOptions}"
+              "videoconvert"
+            ] ++ optionals (instance.input.format != instance.output.format) [
+              "video/x-raw,format=${instance.output.format}"
+              "queue"
+            ] ++ [ "v4l2sink name=v4l2sink device=$(cat $V4L2_DEVICE_FILE)" ];
+          in
+          ''
+            exec ${pkgs.v4l2-relayd}/bin/v4l2-relayd -i "${instance.input.pipeline}" -o "${concatStringsSep " ! " outputPipeline}"
+          '';
+
+        preStart = ''
+          mkdir -p $(dirname $V4L2_DEVICE_FILE)
+          ${kernelPackages.v4l2loopback.bin}/bin/v4l2loopback-ctl add -x 1 -n "${instance.cardLabel}" > $V4L2_DEVICE_FILE
+        '';
+
+        postStop = ''
+          ${kernelPackages.v4l2loopback.bin}/bin/v4l2loopback-ctl delete $(cat $V4L2_DEVICE_FILE)
+          rm -rf $(dirname $V4L2_DEVICE_FILE)
+        '';
+      };
+
+      mkInstanceServices = instances: listToAttrs (map
+        (instance:
+          nameValuePair "v4l2-relayd-${escapeSystemdPath instance.name}" (mkInstanceService instance)
+        )
+        instances);
+
+      enabledInstances = attrValues (filterAttrs (n: v: v.enable) cfg.instances);
+
+    in
+    {
+
+      boot = mkIf ((length enabledInstances) > 0) {
+        extraModulePackages = [ kernelPackages.v4l2loopback ];
+        kernelModules = [ "v4l2loopback" ];
+      };
+
+      systemd.services = mkInstanceServices enabledInstances;
+
+    };
+
+  meta.maintainers = with lib.maintainers; [ betaboon ];
+}