music/bitvis: Add a gain filter

roles/music/templates/pw-bitvis-mixer.conf

@@ -0,0 +1,38 @@
+# {{ ansible_managed }}
+
+context.modules = [
+    {
+        name = libpipewire-module-filter-chain
+        args = {
+            node.description = "bitvis-mixer"
+            media.name       = "bitvis-mixer"
+            filter.graph = {
+                nodes = [
+                    {
+                        name   = mix
+                        type   = builtin
+                        label  = mixer
+                        control = {
+                          "Gain 1" = 10
+                          "Gain 2" = 10
+                        }
+                    }
+                ]
+                inputs  = [ "mix:In 1" "mix:In 2" ]
+                outputs = [ "mix:Out" ]
+            }
+            capture.props = {
+                node.name         = "mix_input.bitvis"
+                audio.position    = [ FL FR ]
+                media.class       = "Audio/Sink"
+            }
+            playback.props = {
+                node.name         = "mix_output.bitvis"
+                audio.position    = [ FL ]
+                stream.dont-remix = true
+                node.passive      = true
+                node.autoconnect  = false
+            }
+        }
+    }
+]