cava: stop the capture stream from dragging the pipewire quantum down

ref #810
port 2.0

quickshell/Modules/DBar/Widgets/AudioVisualization.qml

@@ -29,7 +29,7 @@ Item {
     }
 
     Loader {
-        active: root.live
+        active: root.live && root.available
         sourceComponent: Component {
             Ref {
                 service: CavaService
@@ -39,7 +39,7 @@ Item {
 
     Connections {
         target: CavaService
-        enabled: root.live
+        enabled: root.live && root.available
         function onValuesChanged() {
             const v = CavaService.values;
             if (v.length < 6)

quickshell/Services/CavaService.qml

@@ -41,6 +41,11 @@ Singleton {
         id: cavaProcess
 
         running: root.cavaAvailable && root.refCount > 0
+        // cava asks for 512 frames, which drags the graph quantum down on spawn and back up on exit, audible on some hardware (#810)
+        environment: ({
+                "PIPEWIRE_LATENCY": "2400/48000",
+                "PULSE_LATENCY_MSEC": "50"
+            })
         command: ["sh", "-c", `cat <<'CAVACONF' > ${root._confPath}
 [general]
 framerate=25