monitor output: hear your mic through speakers

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: JacobCoffee

App/Loopbacker/Sources/Models/AudioSource.swift

@@ -41,6 +41,9 @@ struct AudioSource: Identifiable, Equatable, Codable {
     var isMuted: Bool
     /// The CoreAudio device UID for this source (used by AudioRouter)
     var deviceUID: String
+    /// Physical output device UID for monitoring (hear yourself through speakers)
+    var monitorOutputUID: String
+    var monitorOutputName: String
 
     init(
         id: UUID = UUID(),
@@ -50,7 +53,9 @@ struct AudioSource: Identifiable, Equatable, Codable {
         isEnabled: Bool = true,
         isPassThrough: Bool = false,
         isMuted: Bool = false,
-        deviceUID: String = ""
+        deviceUID: String = "",
+        monitorOutputUID: String = "",
+        monitorOutputName: String = ""
     ) {
         self.id = id
         self.name = name
@@ -60,11 +65,12 @@ struct AudioSource: Identifiable, Equatable, Codable {
         self.isPassThrough = isPassThrough
         self.isMuted = isMuted
         self.deviceUID = deviceUID
+        self.monitorOutputUID = monitorOutputUID
+        self.monitorOutputName = monitorOutputName
     }
 
-    // Backward-compatible decoding: isMuted may not exist in old configs
     enum CodingKeys: String, CodingKey {
-        case id, name, icon, channels, isEnabled, isPassThrough, isMuted, deviceUID
+        case id, name, icon, channels, isEnabled, isPassThrough, isMuted, deviceUID, monitorOutputUID, monitorOutputName
     }
 
     init(from decoder: Decoder) throws {
@@ -77,6 +83,8 @@ struct AudioSource: Identifiable, Equatable, Codable {
         isPassThrough = try container.decode(Bool.self, forKey: .isPassThrough)
         isMuted = (try? container.decode(Bool.self, forKey: .isMuted)) ?? false
         deviceUID = try container.decode(String.self, forKey: .deviceUID)
+        monitorOutputUID = (try? container.decode(String.self, forKey: .monitorOutputUID)) ?? ""
+        monitorOutputName = (try? container.decode(String.self, forKey: .monitorOutputName)) ?? ""
     }
 }
 

App/Loopbacker/Sources/Views/ContentView.swift

@@ -21,6 +21,10 @@ struct ContentView: View {
             DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
                 syncAudioRouting(sources: routingState.sources, routes: routingState.routes)
                 syncOutputRouting(destinations: routingState.outputDestinations)
+                // Start monitoring for any sources that have a saved monitor output
+                for source in routingState.sources where !source.monitorOutputUID.isEmpty && source.isEnabled && !source.isMuted {
+                    audioRouter.startMonitoring(sourceDeviceUID: source.deviceUID, outputDeviceUID: source.monitorOutputUID)
+                }
             }
         }
         .onChange(of: routingState.sources) { _, newSources in
@@ -58,6 +62,11 @@ struct ContentView: View {
                     audioRouter.stopRouting(sourceDeviceUID: source.deviceUID)
                 }
             }
+
+            // Monitor: only manage stop. Start is handled by the picker in SourceCardView.
+            if !shouldRoute && !source.monitorOutputUID.isEmpty {
+                audioRouter.stopOutputRouting(virtualDeviceUID: "monitor:\(source.deviceUID)")
+            }
         }
     }
 

App/Loopbacker/Sources/Views/SourceCardView.swift

@@ -3,6 +3,8 @@ import SwiftUI
 struct SourceCardView: View {
     @Binding var source: AudioSource
     @EnvironmentObject var routingState: RoutingState
+    @EnvironmentObject var audioDeviceManager: AudioDeviceManager
+    @EnvironmentObject var audioRouter: AudioRouter
     @State private var isHovering = false
     @State private var showOptions = false
 
@@ -155,24 +157,19 @@ struct SourceCardView: View {
             Divider()
                 .background(LoopbackerTheme.border)
 
-            // Pass-Through toggle
-            HStack {
-                Text("Pass-Thru")
-                    .font(.system(size: 11))
+            // Monitor output picker
+            HStack(spacing: 6) {
+                Image(systemName: "speaker.wave.2")
+                    .font(.system(size: 10))
                     .foregroundColor(LoopbackerTheme.textSecondary)
-                    .tooltip("Also play this source through your speakers for monitoring")
 
-                Spacer()
+                Text("Monitor:")
+                    .font(.system(size: 11))
+                    .foregroundColor(LoopbackerTheme.textSecondary)
 
-                Toggle("", isOn: $source.isPassThrough)
-                    .toggleStyle(.switch)
-                    .controlSize(.mini)
-                    .tint(LoopbackerTheme.accent)
-                    .onChange(of: source.isPassThrough) { _, _ in
-                        routingState.save()
-                    }
-                    .tooltip("Pass audio through without processing (monitor mode)")
+                monitorPicker
             }
+            .tooltip("Hear this source through a physical output (speakers/headphones)")
 
             // Mute toggle
             HStack {
@@ -245,6 +242,36 @@ struct SourceCardView: View {
         .padding(.bottom, 4)
     }
 
+    // MARK: - Monitor output picker
+
+    @ViewBuilder
+    private var monitorPicker: some View {
+        let devices = audioDeviceManager.outputDevices
+
+        Picker("", selection: Binding(
+            get: { source.monitorOutputUID },
+            set: { newUID in
+                if !source.monitorOutputUID.isEmpty {
+                    audioRouter.stopOutputRouting(virtualDeviceUID: "monitor:\(source.deviceUID)")
+                }
+                source.monitorOutputUID = newUID
+                source.monitorOutputName = devices.first(where: { $0.uid == newUID })?.name ?? ""
+                routingState.save()
+                if !newUID.isEmpty && source.isEnabled && !source.isMuted {
+                    audioRouter.startMonitoring(sourceDeviceUID: source.deviceUID, outputDeviceUID: newUID)
+                }
+            }
+        )) {
+            Text("None").tag("")
+            ForEach(devices) { device in
+                Text(device.name).tag(device.uid)
+            }
+        }
+        .pickerStyle(.menu)
+        .frame(maxWidth: .infinity, alignment: .leading)
+        .tint(LoopbackerTheme.accent)
+    }
+
     // MARK: - Options toggle button
 
     private var optionsToggle: some View {