Audio engine observer fixes (#571)

livekit · Feb 1, 2025 · 20f8c3e · 20f8c3e
1 parent 9e750d1
commit 20f8c3e
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Showing 6 changed files with 62 additions and 35 deletions.
diff --git a/Sources/LiveKit/Audio/AudioDeviceModuleDelegateAdapter.swift b/Sources/LiveKit/Audio/AudioDeviceModuleDelegateAdapter.swift
@@ -40,49 +40,49 @@ class AudioDeviceModuleDelegateAdapter: NSObject, LKRTCAudioDeviceModuleDelegate
 
     func audioDeviceModule(_: LKRTCAudioDeviceModule, didCreateEngine engine: AVAudioEngine) {
         guard let audioManager else { return }
-        let entryPoint = audioManager._state.engineObservers.buildChain()
+        let entryPoint = audioManager.buildEngineObserverChain()
         entryPoint?.engineDidCreate(engine)
     }
 
     func audioDeviceModule(_: LKRTCAudioDeviceModule, willEnableEngine engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool) {
         guard let audioManager else { return }
-        let entryPoint = audioManager._state.engineObservers.buildChain()
+        let entryPoint = audioManager.buildEngineObserverChain()
         entryPoint?.engineWillEnable(engine, isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
     }
 
     func audioDeviceModule(_: LKRTCAudioDeviceModule, willStartEngine engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool) {
         guard let audioManager else { return }
-        let entryPoint = audioManager._state.engineObservers.buildChain()
+        let entryPoint = audioManager.buildEngineObserverChain()
         entryPoint?.engineWillStart(engine, isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
     }
 
     func audioDeviceModule(_: LKRTCAudioDeviceModule, didStopEngine engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool) {
         guard let audioManager else { return }
-        let entryPoint = audioManager._state.engineObservers.buildChain()
+        let entryPoint = audioManager.buildEngineObserverChain()
         entryPoint?.engineDidStop(engine, isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
     }
 
     func audioDeviceModule(_: LKRTCAudioDeviceModule, didDisableEngine engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool) {
         guard let audioManager else { return }
-        let entryPoint = audioManager._state.engineObservers.buildChain()
+        let entryPoint = audioManager.buildEngineObserverChain()
         entryPoint?.engineDidDisable(engine, isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
     }
 
     func audioDeviceModule(_: LKRTCAudioDeviceModule, willReleaseEngine engine: AVAudioEngine) {
         guard let audioManager else { return }
-        let entryPoint = audioManager._state.engineObservers.buildChain()
+        let entryPoint = audioManager.buildEngineObserverChain()
         entryPoint?.engineWillRelease(engine)
     }
 
     func audioDeviceModule(_: LKRTCAudioDeviceModule, engine: AVAudioEngine, configureInputFromSource src: AVAudioNode?, toDestination dst: AVAudioNode, format: AVAudioFormat) -> Bool {
         guard let audioManager else { return false }
-        let entryPoint = audioManager._state.engineObservers.buildChain()
+        let entryPoint = audioManager.buildEngineObserverChain()
         return entryPoint?.engineWillConnectInput(engine, src: src, dst: dst, format: format) ?? false
     }
 
     func audioDeviceModule(_: LKRTCAudioDeviceModule, engine: AVAudioEngine, configureOutputFromSource src: AVAudioNode, toDestination dst: AVAudioNode?, format: AVAudioFormat) -> Bool {
         guard let audioManager else { return false }
-        let entryPoint = audioManager._state.engineObservers.buildChain()
+        let entryPoint = audioManager.buildEngineObserverChain()
         return entryPoint?.engineWillConnectOutput(engine, src: src, dst: dst, format: format) ?? false
     }
 }
diff --git a/Sources/LiveKit/Audio/AudioEngineObserver.swift b/Sources/LiveKit/Audio/AudioEngineObserver.swift
@@ -18,7 +18,8 @@ import AVFAudio
 
 /// Do not retain the engine object.
 public protocol AudioEngineObserver: NextInvokable, Sendable {
-    func setNext(_ handler: any AudioEngineObserver)
+    associatedtype Next = any AudioEngineObserver
+    var next: (any AudioEngineObserver)? { get set }
 
     func engineDidCreate(_ engine: AVAudioEngine)
     func engineWillEnable(_ engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool)
@@ -39,25 +40,35 @@ public protocol AudioEngineObserver: NextInvokable, Sendable {
 
 /// Default implementation to make it optional.
 public extension AudioEngineObserver {
-    func engineDidCreate(_: AVAudioEngine) {}
-    func engineWillEnable(_: AVAudioEngine, isPlayoutEnabled _: Bool, isRecordingEnabled _: Bool) {}
-    func engineWillStart(_: AVAudioEngine, isPlayoutEnabled _: Bool, isRecordingEnabled _: Bool) {}
-    func engineDidStop(_: AVAudioEngine, isPlayoutEnabled _: Bool, isRecordingEnabled _: Bool) {}
-    func engineDidDisable(_: AVAudioEngine, isPlayoutEnabled _: Bool, isRecordingEnabled _: Bool) {}
-    func engineWillRelease(_: AVAudioEngine) {}
-
-    func engineWillConnectOutput(_: AVAudioEngine, src _: AVAudioNode, dst _: AVAudioNode?, format _: AVAudioFormat) -> Bool { false }
-    func engineWillConnectInput(_: AVAudioEngine, src _: AVAudioNode?, dst _: AVAudioNode, format _: AVAudioFormat) -> Bool { false }
-}
+    func engineDidCreate(_ engine: AVAudioEngine) {
+        next?.engineDidCreate(engine)
+    }
+
+    func engineWillEnable(_ engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool) {
+        next?.engineWillEnable(engine, isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
+    }
+
+    func engineWillStart(_ engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool) {
+        next?.engineWillStart(engine, isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
+    }
 
-extension [any AudioEngineObserver] {
-    func buildChain() -> Element? {
-        guard let first else { return nil }
+    func engineDidStop(_ engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool) {
+        next?.engineDidStop(engine, isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
+    }
+
+    func engineDidDisable(_ engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool) {
+        next?.engineDidDisable(engine, isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
+    }
 
-        for i in 0 ..< count - 1 {
-            self[i].setNext(self[i + 1])
-        }
+    func engineWillRelease(_ engine: AVAudioEngine) {
+        next?.engineWillRelease(engine)
+    }
+
+    func engineWillConnectOutput(_ engine: AVAudioEngine, src: AVAudioNode, dst: AVAudioNode?, format: AVAudioFormat) -> Bool {
+        next?.engineWillConnectOutput(engine, src: src, dst: dst, format: format) ?? false
+    }
 
-        return first
+    func engineWillConnectInput(_ engine: AVAudioEngine, src: AVAudioNode?, dst: AVAudioNode, format: AVAudioFormat) -> Bool {
+        next?.engineWillConnectInput(engine, src: src, dst: dst, format: format) ?? false
     }
 }
diff --git a/Sources/LiveKit/Audio/DefaultAudioSessionObserver.swift b/Sources/LiveKit/Audio/DefaultAudioSessionObserver.swift
@@ -24,7 +24,7 @@ internal import LiveKitWebRTC
 @_implementationOnly import LiveKitWebRTC
 #endif
 
-public final class DefaultAudioSessionObserver: AudioEngineObserver, Loggable {
+public class DefaultAudioSessionObserver: AudioEngineObserver, Loggable, @unchecked Sendable {
     struct State {
         var isSessionActive = false
         var next: (any AudioEngineObserver)?
@@ -36,7 +36,12 @@ public final class DefaultAudioSessionObserver: AudioEngineObserver, Loggable {
 
     let _state = StateSync(State())
 
-    init() {
+    public var next: (any AudioEngineObserver)? {
+        get { _state.next }
+        set { _state.mutate { $0.next = newValue } }
+    }
+
+    public init() {
         // Backward compatibility with `customConfigureAudioSessionFunc`.
         _state.onDidMutate = { new_, old_ in
             if let config_func = AudioManager.shared._state.customConfigureFunc,
@@ -51,10 +56,6 @@ public final class DefaultAudioSessionObserver: AudioEngineObserver, Loggable {
         }
     }
 
-    public func setNext(_ nextHandler: any AudioEngineObserver) {
-        _state.mutate { $0.next = nextHandler }
-    }
-
     public func engineWillEnable(_ engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool) {
         if AudioManager.shared._state.customConfigureFunc == nil {
             log("Configuring audio session...")

diff --git a/Sources/LiveKit/Protocols/NextInvokable.swift b/Sources/LiveKit/Protocols/NextInvokable.swift
@@ -18,5 +18,5 @@ import Foundation
 
 public protocol NextInvokable {
     associatedtype Next
-    func setNext(_ handler: Next)
+    var next: Next? { get set }
 }
diff --git a/Sources/LiveKit/Track/AudioManager.swift b/Sources/LiveKit/Track/AudioManager.swift
@@ -341,3 +341,16 @@ public extension AudioManager {
         renderPreProcessingDelegateAdapter.remove(delegate: delegate)
     }
 }
+
+extension AudioManager {
+    func buildEngineObserverChain() -> (any AudioEngineObserver)? {
+        var objects = _state.engineObservers
+        guard !objects.isEmpty else { return nil }
+
+        for i in 0 ..< objects.count - 1 {
+            objects[i].next = objects[i + 1]
+        }
+
+        return objects.first
+    }
+}
diff --git a/Tests/LiveKitTests/AudioEngineTests.swift b/Tests/LiveKitTests/AudioEngineTests.swift
@@ -282,9 +282,10 @@ class AudioEngineTests: XCTestCase {
 }
 
 final class SineWaveNodeHook: AudioEngineObserver {
+    var next: (any LiveKit.AudioEngineObserver)?
+
     let sineWaveNode = SineWaveSourceNode()
 
-    func setNext(_: any LiveKit.AudioEngineObserver) {}
     func engineDidCreate(_ engine: AVAudioEngine) {
         engine.attach(sineWaveNode)
     }
@@ -301,6 +302,8 @@ final class SineWaveNodeHook: AudioEngineObserver {
 }
 
 final class PlayerNodeHook: AudioEngineObserver {
+    var next: (any LiveKit.AudioEngineObserver)?
+
     public let playerNode = AVAudioPlayerNode()
     public let playerMixerNode = AVAudioMixerNode()
     public let playerNodeFormat: AVAudioFormat
@@ -309,7 +312,6 @@ final class PlayerNodeHook: AudioEngineObserver {
         self.playerNodeFormat = playerNodeFormat
     }
 
-    func setNext(_: any LiveKit.AudioEngineObserver) {}
     public func engineDidCreate(_ engine: AVAudioEngine) {
         engine.attach(playerNode)
         engine.attach(playerMixerNode)