PipeWire: Difference between revisions

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    };
 };
+</syntaxHighlight>
+==Low-latency setup==
+Audio production and rhythm games require lower latency audio than general applications. PipeWire can achieve the required latency with much less CPU usage compared to PulseAudio, with the appropriate configuration.
+The minimum period size controls how small a buffer can be. The lower it is, the less latency there is. PipeWire has a value of 32 by default, which amounts to 1.33ms. It can be brought lower if needed:
+<syntaxHighlight lang="nix">
+services.pipewire = {
+  config.pipewire = {
+    "context.properties" = {
+      "default.clock.min-quantum" = 16 # going lower may cause crackles and distorted audio
+    };
+  };
+};
+</syntaxHighlight>
+===PulseAudio backend===
+Applications using the Pulse backend have a separate configuration. The default minimum value is 1024, so it needs to be tweaked if low-latency audio is desired.
+<syntaxHighlight lang="nix">
+services.pipewire = {
+  config.pipewire-pulse = {
+    "context.modules" = [
+      {
+        name = "libpipewire-module-protocol-pulse";
+        args = {
+          "pulse.min.quantum" = 16; # controls minimum playback quant
+          "pulse.min.req" = 16; # controls minimum recording quant
+          "pulse.min.frag" = 16; # controls minimum fragment size
+          "server.address" = [ "unix:native" ]; # the default address of the server
+        };
+      };
+    ];
+  };
+};
+</syntaxHighlight>
+As a general rule, the values in <code>pipewire-pulse</code> should not be lower than the ones in <code>pipewire</code>.
+===Controlling the ALSA devices===
+It is possible to configure various aspects of soundcards through <code>/etc/pipewire/media-session.d/alsa-monitor.conf</code>. Since there's no config option for it in the module, the file needs to be manually written:
+<syntaxHighlight lang="nix">
+environment.etc."pipewire/media-session.d/alsa-monitor.conf".text = ''
+  rules = [
+    {
+      matches = [ { node.name = alsa_output.* } ]
+      actions = {
+        update-props = {
+          audio.format = "S16LE"
+          audio.rate = 48000
+          api.alsa.period-size = 160 # defaults to 1024, tweak by trial-and-error
+          #api.alsa.disable-batch = true # generally, USB soundcards use the batch mode
+        }
+      }
+    }
+  ];
+'';
+</syntaxHighlight>
+The <code>matches</code> attribute applies the <code>actions</code> to the devices/properties listed there. It is usually used with soundcard names, like shown in the config above. <code><alsa_device></code> can be one of the outputs of
+<syntaxHighlight lang="bash">
+$ pw-dump | grep node.name | grep alsa
 </syntaxHighlight>