JACK: Difference between revisions

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-When on nixos-unstable, one may use [https://github.com/NixOS/nixpkgs-channels/blob/nixos-unstable/nixos/modules/services/audio/jack.nix JACK module]. It works both with and without PulseAudio. Enable it this way and reboot:
+One may use [https://github.com/NixOS/nixpkgs/blob/nixos-unstable/nixos/modules/services/audio/jack.nix JACK module]. It works both with and without PulseAudio. Enable it this way '''and reboot''':
 {{file|/etc/nixos/configuration.nix|nix|<nowiki>
    services.jack = {
@@ Line 9: / Line 9: @@
        enable = true;
        # buffering parameters for dmix device to work with ALSA only semi-professional sound programs
-       dmixConfig = ''
+       #dmixConfig = ''
-        period_size 2048
+      #  period_size 2048
-       '';
+       #'';
      };
    };
    users.extraUsers.YOURUSER.extraGroups = [ "jackaudio" ];
 </nowiki>}}
+Since the config above and below apparently does not work for several users, according to forum posts, here a solution that works:
+- Add musnix channel (https://github.com/musnix/musnix)
+{{file|/etc/nixos/configuration.nix|nix|<nowiki>
+  imports = [ <musnix> ];
+  environment.systemPackages = with pkgs; [ libjack2 jack2 qjackctl ];
+  environment.systemPackages = with pkgs; [ pavucontrol libjack2 jack2 qjackctl jack2Full jack_capture ];
+  security.sudo.extraConfig = ''
+    moritz  ALL=(ALL) NOPASSWD: ${pkgs.systemd}/bin/systemctl
+    '';
+  musnix = {
+    enable = true;
+    alsaSeq.enable = false;
+    # Find this value with `lspci | grep -i audio` (per the musnix readme).
+    # PITFALL: This is the id of the built-in soundcard.
+    #   When I start using the external one, change it.
+    soundcardPciId = "00:1f.3";
+    # magic to me
+    rtirq = {
+      # highList = "snd_hrtimer";
+      resetAll = 1;
+      prioLow = 0;
+      enable = true;
+      nameList = "rtc0 snd";
+    };
+  };
+</nowiki>}}
+After a reboot, you can enable JACKD using "pasuspender qjackctl" and start jackd by pressing the start button.
+You can test, if your JACK works, using the command jack_simple_client, which produces a sound if JACK is running.
+Sources:
+https://discourse.nixos.org/t/declarative-audio-config-how-to-start-and-maybe-use-jack/5458
+https://github.com/NixOS/nixpkgs/issues/71283
 {{Outdated|needs cleanup}}
@@ Line 138: / Line 176: @@
 };
 </syntaxHighlight>
-[[Category:Configuration]] [[Category:PulseAudio]] [[Category:Audio]]
+== Connecting nix JACK clients to Pipewire installed via other package managers ==
+Pipewire offers a JACK API, but applications installed via nix are not able to connect to it out of the box.
+Use the following command to make them work (using qsynth as an example):
+<syntaxHighlight lang="bash">
+LD_LIBRARY_PATH="$(nix build nixpkgs#pipewire.jack --print-out-paths)/lib" nix run nixpkgs#qsynth
+</syntaxHighlight>
+You can also wrap it in a script, for adding this to your home-manager config will allow using `nix-jack nix run nixpkgs#qsynth`
+<syntaxHighlight lang="nix">
+home.packages = with pkgs; [
+    (writeShellScriptBin "nix-jack" ''
+      exec /usr/bin/env \
+        LD_LIBRARY_PATH=${pipewire.jack}/lib''${LD_LIBRARY_PATH:+:''${LD_LIBRARY_PATH}} \
+        "''$@"
+    '')
+]
+</syntaxHighlight>
+or
+<syntaxHighlight lang="nix">
+let
+  jackWrap = drv: pkgs.symlinkJoin {
+    name = "${drv.name}-jackwrapped";
+    paths = [ drv ];
+    buildInputs = [ pkgs.makeWrapper ];
+    postBuild = ''
+      ls "$out/bin"
+      for b in "$out/bin/"*; do
+        wrapProgram "$b" \
+          --prefix LD_LIBRARY_PATH : "${pkgs.pipewire.jack}/lib"
+      done
+    '';
+  };
+in [
+  (jackWrap pkgs.qsynth)
+]
+</syntaxHighlight>
+This is necessary because of the way the pipewire jack interface works. By using a pipewire-provided dynamically linked library, the connection attempt is translated to a pipewire connection inside the client process. Other distributions such as Arch Linux implement this by just placing the .so files in /usr/lib but since nix application don't include that directory we need this approach.
+(Tested on Arch Linux in May 2023)
+If you know of a way to do this without wrapping each individual package, please add it here.
+[[Category:Audio]]
+[[Category:Applications]]