From 488bc25b28936f78045e4887e669a5ee23c7d9a5 Mon Sep 17 00:00:00 2001
From: Hiroshi Horie <548776+hiroshihorie@users.noreply.github.com>
Date: Fri, 31 Oct 2025 15:12:38 +0700
Subject: [PATCH 1/5] squash progress

---
 .../LiveKit/Audio/MixerEngineObserver.swift   | 123 +++++++++---
 Sources/LiveKit/Audio/SoundPlayer.swift       | 178 ++++++++++++++++++
 .../Support/Audio/AudioConverter.swift        |   4 +-
 .../LiveKit/Support/AudioPlayerRenderer.swift |   2 +
 4 files changed, 281 insertions(+), 26 deletions(-)
 create mode 100644 Sources/LiveKit/Audio/SoundPlayer.swift

diff --git a/Sources/LiveKit/Audio/MixerEngineObserver.swift b/Sources/LiveKit/Audio/MixerEngineObserver.swift
index df4422056..3cbbad2c7 100644
--- a/Sources/LiveKit/Audio/MixerEngineObserver.swift
+++ b/Sources/LiveKit/Audio/MixerEngineObserver.swift
@@ -37,8 +37,8 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
 
     /// Adjust the volume of captured app audio. Range is 0.0 ~ 1.0.
     public var appVolume: Float {
-        get { _state.read { $0.appMixerNode.outputVolume } }
-        set { _state.mutate { $0.appMixerNode.outputVolume = newValue } }
+        get { _state.read { $0.inputPlayerMixerNode.outputVolume } }
+        set { _state.mutate { $0.inputPlayerMixerNode.outputVolume = newValue } }
     }
 
     /// Adjust the volume of microphone audio. Range is 0.0 ~ 1.0.
@@ -50,7 +50,7 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
     // MARK: - Internal
 
     var appAudioNode: AVAudioPlayerNode {
-        _state.read { $0.appNode }
+        _state.read { $0.inputPlayerNode }
     }
 
     var micAudioNode: AVAudioPlayerNode {
@@ -60,26 +60,32 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
     struct State {
         var next: (any AudioEngineObserver)?
 
-        // AppAudio
-        let appNode = AVAudioPlayerNode()
-        let appMixerNode = AVAudioMixerNode()
+        // Input app audio
+        let inputPlayerNode = AVAudioPlayerNode()
+        let inputPlayerMixerNode = AVAudioMixerNode()
+        var inputPlayerNodeFormat: AVAudioFormat?
 
         // Not connected for device rendering mode.
         let micNode = AVAudioPlayerNode()
         let micMixerNode = AVAudioMixerNode()
 
+        //
+        let outputPlayerNode = AVAudioPlayerNode()
+        let outputPlayerMixerNode = AVAudioMixerNode()
+        var outputPlayerNodeFormat: AVAudioFormat?
+
         // Reference to mainMixerNode
         weak var mainMixerNode: AVAudioMixerNode?
+
+        // Keep track of preferred output volume before nodes attach
         var outputVolume: Float = 1.0
 
         // Internal states
         var isInputConnected: Bool = false
+        var isOutputConnected: Bool = false
 
         // Cached converters
         var converters: [AVAudioFormat: AudioConverter] = [:]
-
-        // Reference to engine format
-        var playerNodeFormat: AVAudioFormat?
     }
 
     let _state = StateSync(State())
@@ -92,15 +98,19 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
 
     public func engineDidCreate(_ engine: AVAudioEngine) -> Int {
         log("isManualRenderingMode: \(engine.isInManualRenderingMode)")
-        let (appNode, appMixerNode, micNode, micMixerNode) = _state.read {
-            ($0.appNode, $0.appMixerNode, $0.micNode, $0.micMixerNode)
+
+        let (inputPlayerNode, inputPlayerMixerNode, micNode, micMixerNode, outputPlayerNode, outputPlayerMixerNode) = _state.read {
+            ($0.inputPlayerNode, $0.inputPlayerMixerNode, $0.micNode, $0.micMixerNode, $0.outputPlayerNode, $0.outputPlayerMixerNode)
         }
 
-        engine.attach(appNode)
-        engine.attach(appMixerNode)
+        engine.attach(inputPlayerNode)
+        engine.attach(inputPlayerMixerNode)
         engine.attach(micNode)
         engine.attach(micMixerNode)
 
+        engine.attach(outputPlayerNode)
+        engine.attach(outputPlayerMixerNode)
+
         // Invoke next
         return next?.engineDidCreate(engine) ?? 0
     }
@@ -110,15 +120,18 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
         // Invoke next
         let nextResult = next?.engineWillRelease(engine)
 
-        let (appNode, appMixerNode, micNode, micMixerNode) = _state.read {
-            ($0.appNode, $0.appMixerNode, $0.micNode, $0.micMixerNode)
+        let (inputPlayerNode, inputPlayerMixerNode, micNode, micMixerNode, outputPlayerNode, outputPlayerMixerNode) = _state.read {
+            ($0.inputPlayerNode, $0.inputPlayerMixerNode, $0.micNode, $0.micMixerNode, $0.outputPlayerNode, $0.outputPlayerMixerNode)
         }
 
-        engine.detach(appNode)
-        engine.detach(appMixerNode)
+        engine.detach(inputPlayerNode)
+        engine.detach(inputPlayerMixerNode)
         engine.detach(micNode)
         engine.detach(micMixerNode)
 
+        engine.detach(outputPlayerNode)
+        engine.detach(outputPlayerMixerNode)
+
         return nextResult ?? 0
     }
 
@@ -134,7 +147,7 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
 
         // Read nodes from state lock.
         let (appNode, appMixerNode, micNode, micMixerNode) = _state.read {
-            ($0.appNode, $0.appMixerNode, $0.micNode, $0.micMixerNode)
+            ($0.inputPlayerNode, $0.inputPlayerMixerNode, $0.micNode, $0.micMixerNode)
         }
 
         // AVAudioPlayerNode doesn't support Int16 so we ensure to use Float32
@@ -162,11 +175,11 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
         engine.connect(micMixerNode, to: mainMixerNode, format: format)
 
         _state.mutate {
-            if let previousEngineFormat = $0.playerNodeFormat, previousEngineFormat != format {
+            if let previousInputEngineFormat = $0.inputPlayerNodeFormat, previousInputEngineFormat != format {
                 // Clear cached converters when engine format changes
                 $0.converters.removeAll()
             }
-            $0.playerNodeFormat = playerNodeFormat
+            $0.inputPlayerNodeFormat = playerNodeFormat
             $0.isInputConnected = true
         }
 
@@ -174,6 +187,8 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
         return next?.engineWillConnectInput(engine, src: src, dst: dst, format: format, context: context) ?? 0
     }
 
+    // let sineWaveNode = SineWaveSourceNode()
+
     public func engineWillConnectOutput(_ engine: AVAudioEngine, src: AVAudioNode, dst: AVAudioNode?, format: AVAudioFormat, context: [AnyHashable: Any]) -> Int {
         log("isManualRenderingMode: \(engine.isInManualRenderingMode)")
         // Get the main mixer
@@ -184,15 +199,51 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
 
         engine.mainMixerNode.outputVolume = outputVolume
 
+        // Read nodes from state lock.
+        let outAppPlayerNode = _state.read {
+            $0.outputPlayerNode
+        }
+
+        // AVAudioPlayerNode doesn't support Int16 so we ensure to use Float32
+        let playerNodeFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32,
+                                             sampleRate: format.sampleRate,
+                                             channels: format.channelCount,
+                                             interleaved: format.isInterleaved)!
+
+        engine.connect(outAppPlayerNode, to: engine.mainMixerNode, format: playerNodeFormat)
+
+        _state.mutate {
+            if let previousOutputEngineFormat = $0.outputPlayerNodeFormat, previousOutputEngineFormat != format {
+                // Clear cached converters when engine format changes
+                $0.converters.removeAll()
+            }
+            $0.outputPlayerNodeFormat = playerNodeFormat
+            $0.isOutputConnected = true
+        }
+
         return next?.engineWillConnectOutput(engine, src: src, dst: dst, format: format, context: context) ?? 0
     }
 }
 
 extension MixerEngineObserver {
     // Create or use cached AudioConverter.
-    func converter(for format: AVAudioFormat) -> AudioConverter? {
+    func inputConverter(for format: AVAudioFormat) -> AudioConverter? {
+        _state.mutate {
+            guard let playerNodeFormat = $0.inputPlayerNodeFormat else { return nil }
+
+            if let converter = $0.converters[format] {
+                return converter
+            }
+
+            let newConverter = AudioConverter(from: format, to: playerNodeFormat)
+            $0.converters[format] = newConverter
+            return newConverter
+        }
+    }
+
+    func outputConverter(for format: AVAudioFormat) -> AudioConverter? {
         _state.mutate {
-            guard let playerNodeFormat = $0.playerNodeFormat else { return nil }
+            guard let playerNodeFormat = $0.outputPlayerNodeFormat else { return nil }
 
             if let converter = $0.converters[format] {
                 return converter
@@ -207,7 +258,7 @@ extension MixerEngineObserver {
     // Capture appAudio and apply conversion automatically suitable for internal audio engine.
     public func capture(appAudio inputBuffer: AVAudioPCMBuffer) {
         let (isConnected, appNode) = _state.read {
-            ($0.isInputConnected, $0.appNode)
+            ($0.isInputConnected, $0.inputPlayerNode)
         }
 
         guard isConnected, let engine = appNode.engine, engine.isRunning else {
@@ -216,7 +267,7 @@ extension MixerEngineObserver {
         }
 
         // Create or update the converter if needed
-        let converter = converter(for: inputBuffer.format)
+        let converter = inputConverter(for: inputBuffer.format)
 
         guard let converter else { return }
 
@@ -227,4 +278,28 @@ extension MixerEngineObserver {
             appNode.play()
         }
     }
+
+    // Capture out-appAudio and apply conversion automatically suitable for internal audio engine.
+    public func capture(outAppAudio outputBuffer: AVAudioPCMBuffer) {
+        let (isConnected, appNode) = _state.read {
+            ($0.isOutputConnected, $0.outputPlayerNode)
+        }
+
+        guard isConnected, let engine = appNode.engine, engine.isRunning else {
+            log("Engine is not running", .warning)
+            return
+        }
+
+        // Create or update the converter if needed
+        let converter = outputConverter(for: outputBuffer.format)
+
+        guard let converter else { return }
+
+        let buffer = converter.convert(from: outputBuffer)
+        appNode.scheduleBuffer(buffer)
+
+        if !appNode.isPlaying {
+            appNode.play()
+        }
+    }
 }
diff --git a/Sources/LiveKit/Audio/SoundPlayer.swift b/Sources/LiveKit/Audio/SoundPlayer.swift
new file mode 100644
index 000000000..a59c3f8d7
--- /dev/null
+++ b/Sources/LiveKit/Audio/SoundPlayer.swift
@@ -0,0 +1,178 @@
+/*
+ * Copyright 2025 LiveKit
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+@preconcurrency import AVFAudio
+
+public class SoundPlayer: Loggable, @unchecked Sendable {
+    private let engine = AVAudioEngine()
+    private let playerNodes = AVAudioPlayerNodePool()
+    public let outputFormat: AVAudioFormat
+
+    private struct State {
+        var sounds: [String: AVAudioPCMBuffer] = [:]
+    }
+
+    private let _state = StateSync(State())
+
+    public init() {
+        outputFormat = engine.outputNode.outputFormat(forBus: 0)
+        playerNodes.attach(to: engine)
+    }
+
+    public func startEngine() async throws {
+        guard !engine.isRunning else {
+            log("Engine already running", .info)
+            return
+        }
+        log("Starting audio engine...")
+
+        playerNodes.connect(to: engine, node: engine.mainMixerNode, format: outputFormat)
+
+        try engine.start()
+        log("Audio engine started")
+    }
+
+    public func stopEngine() {
+        guard engine.isRunning else {
+            log("Engine already stopped", .info)
+            return
+        }
+        log("Stopping audio engine...")
+
+        playerNodes.stop()
+        engine.stop()
+
+        log("Audio engine stopped")
+    }
+
+    public func prepare(url: URL, withId id: String) throws {
+        // Prepare audio file
+        let audioFile = try AVAudioFile(forReading: url)
+        // Prepare buffer
+        guard let readBuffer = AVAudioPCMBuffer(pcmFormat: audioFile.processingFormat, frameCapacity: AVAudioFrameCount(audioFile.length)) else {
+            throw NSError(domain: "Audio", code: 2, userInfo: [NSLocalizedDescriptionKey: "Cannot allocate buffer"])
+        }
+        // Read all into buffer
+        try audioFile.read(into: readBuffer, frameCount: AVAudioFrameCount(audioFile.length))
+        // Compute required convert buffer capacity
+        let outputBufferCapacity = AudioConverter.frameCapacity(from: readBuffer.format, to: outputFormat, inputFrameCount: readBuffer.frameLength)
+        // Create converter
+        guard let converter = AudioConverter(from: readBuffer.format, to: outputFormat, outputBufferCapacity: outputBufferCapacity) else {
+            throw NSError(domain: "Audio", code: 2, userInfo: [NSLocalizedDescriptionKey: "Cannot create converter"])
+        }
+        // Convert to suitable format for audio engine
+        let convertedBuffer = converter.convert(from: readBuffer)
+        // Register
+        _state.mutate {
+            $0.sounds[id] = convertedBuffer
+        }
+    }
+
+    public func play(id: String) async throws {
+        guard engine.isRunning else {
+            throw NSError(domain: "Audio", code: 2, userInfo: [NSLocalizedDescriptionKey: "Engine not running"])
+        }
+        guard let audioBuffer = _state.read(\.sounds[id]) else {
+            throw NSError(domain: "Audio", code: 2, userInfo: [NSLocalizedDescriptionKey: "Sound not prepared"])
+        }
+        try playerNodes.scheduleBuffer(audioBuffer)
+    }
+}
+
+// Support scheduling buffer to play concurrently
+class AVAudioPlayerNodePool: @unchecked Sendable, Loggable {
+    let poolSize: Int
+    private let mixerNode = AVAudioMixerNode()
+
+    private struct State {
+        var playerNodes: [AVAudioPlayerNode]
+    }
+
+    private let audioCallbackQueue = DispatchQueue(label: "audio.playerNodePool.queue")
+
+    private let _state: StateSync<State>
+
+    init(poolSize: Int = 10) {
+        self.poolSize = poolSize
+        let playerNodes = (0 ..< poolSize).map { _ in AVAudioPlayerNode() }
+        _state = StateSync(State(playerNodes: playerNodes))
+    }
+
+    func attach(to engine: AVAudioEngine) {
+        let playerNodes = _state.read(\.playerNodes)
+        // Attach playerNodes
+        for playerNode in playerNodes {
+            engine.attach(playerNode)
+        }
+        // Attach mixerNode
+        engine.attach(mixerNode)
+    }
+
+    func connect(to engine: AVAudioEngine, node: AVAudioNode, format: AVAudioFormat? = nil) {
+        let playerNodes = _state.read(\.playerNodes)
+        for playerNode in playerNodes {
+            engine.connect(playerNode, to: mixerNode, format: format)
+        }
+        engine.connect(mixerNode, to: node, format: format)
+    }
+
+    func detach(from engine: AVAudioEngine) {
+        let playerNodes = _state.read(\.playerNodes)
+        // Detach playerNodes
+        for playerNode in playerNodes {
+            playerNode.stop()
+            engine.detach(playerNode)
+        }
+        // Detach mixerNode
+        engine.detach(mixerNode)
+    }
+
+    func scheduleBuffer(_ buffer: AVAudioPCMBuffer) throws {
+        guard let node = nextAvailablePlayerNode() else {
+            throw NSError(domain: "Audio", code: 2, userInfo: [NSLocalizedDescriptionKey: "No available player nodes"])
+        }
+        log("Next node: \(node)")
+
+        node.scheduleBuffer(buffer, completionCallbackType: .dataPlayedBack) { [weak self, weak node] _ in
+            guard let self else { return }
+            audioCallbackQueue.async { [weak node] in
+                guard let node else { return }
+                node.stop() // Stop the node
+            }
+        }
+        node.play()
+    }
+
+    // Stops all player nodes
+    func stop() {
+        for node in _state.read(\.playerNodes) {
+            node.stop()
+        }
+    }
+
+    private func nextAvailablePlayerNode() -> AVAudioPlayerNode? {
+        // Find first available node
+        guard let node = _state.read({ $0.playerNodes.first(where: { !$0.isPlaying }) }) else {
+            return nil
+        }
+
+        // Ensure node settings
+        node.volume = 1.0
+        node.pan = 0.0
+
+        return node
+    }
+}
diff --git a/Sources/LiveKit/Support/Audio/AudioConverter.swift b/Sources/LiveKit/Support/Audio/AudioConverter.swift
index ce497a070..2177a0ac3 100644
--- a/Sources/LiveKit/Support/Audio/AudioConverter.swift
+++ b/Sources/LiveKit/Support/Audio/AudioConverter.swift
@@ -28,10 +28,10 @@ final class AudioConverter: Sendable {
         let inputSampleRate = inputFormat.sampleRate
         let outputSampleRate = outputFormat.sampleRate
         // Compute the output frame capacity based on sample rate ratio
-        return AVAudioFrameCount(Double(inputFrameCount) * (outputSampleRate / inputSampleRate))
+        return AVAudioFrameCount(ceil(Double(inputFrameCount) * (outputSampleRate / inputSampleRate)))
     }
 
-    init?(from inputFormat: AVAudioFormat, to outputFormat: AVAudioFormat, outputBufferCapacity: AVAudioFrameCount = 9600) {
+    init?(from inputFormat: AVAudioFormat, to outputFormat: AVAudioFormat, outputBufferCapacity: AVAudioFrameCount = 1024 * 10) {
         guard let converter = AVAudioConverter(from: inputFormat, to: outputFormat),
               let buffer = AVAudioPCMBuffer(pcmFormat: outputFormat, frameCapacity: outputBufferCapacity)
         else {
diff --git a/Sources/LiveKit/Support/AudioPlayerRenderer.swift b/Sources/LiveKit/Support/AudioPlayerRenderer.swift
index 9d4567f92..c41c6e122 100644
--- a/Sources/LiveKit/Support/AudioPlayerRenderer.swift
+++ b/Sources/LiveKit/Support/AudioPlayerRenderer.swift
@@ -29,6 +29,7 @@ public class AudioPlayerRenderer: AudioRenderer, Loggable, @unchecked Sendable {
     }
 
     public func start() async throws {
+        guard !engine.isRunning else { return }
         log("Starting audio engine...")
 
         let format = engine.outputNode.outputFormat(forBus: 0)
@@ -41,6 +42,7 @@ public class AudioPlayerRenderer: AudioRenderer, Loggable, @unchecked Sendable {
     }
 
     public func stop() {
+        guard engine.isRunning else { return }
         log("Stopping audio engine...")
 
         playerNode.stop()

From b21ae42d7ac07f021116892b2c75052d71fcc41f Mon Sep 17 00:00:00 2001
From: Hiroshi Horie <548776+hiroshihorie@users.noreply.github.com>
Date: Fri, 31 Oct 2025 23:24:47 +0700
Subject: [PATCH 2/5] revert changes to mixer

---
 .../LiveKit/Audio/MixerEngineObserver.swift   | 123 ++++--------------
 1 file changed, 24 insertions(+), 99 deletions(-)

diff --git a/Sources/LiveKit/Audio/MixerEngineObserver.swift b/Sources/LiveKit/Audio/MixerEngineObserver.swift
index 3cbbad2c7..df4422056 100644
--- a/Sources/LiveKit/Audio/MixerEngineObserver.swift
+++ b/Sources/LiveKit/Audio/MixerEngineObserver.swift
@@ -37,8 +37,8 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
 
     /// Adjust the volume of captured app audio. Range is 0.0 ~ 1.0.
     public var appVolume: Float {
-        get { _state.read { $0.inputPlayerMixerNode.outputVolume } }
-        set { _state.mutate { $0.inputPlayerMixerNode.outputVolume = newValue } }
+        get { _state.read { $0.appMixerNode.outputVolume } }
+        set { _state.mutate { $0.appMixerNode.outputVolume = newValue } }
     }
 
     /// Adjust the volume of microphone audio. Range is 0.0 ~ 1.0.
@@ -50,7 +50,7 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
     // MARK: - Internal
 
     var appAudioNode: AVAudioPlayerNode {
-        _state.read { $0.inputPlayerNode }
+        _state.read { $0.appNode }
     }
 
     var micAudioNode: AVAudioPlayerNode {
@@ -60,32 +60,26 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
     struct State {
         var next: (any AudioEngineObserver)?
 
-        // Input app audio
-        let inputPlayerNode = AVAudioPlayerNode()
-        let inputPlayerMixerNode = AVAudioMixerNode()
-        var inputPlayerNodeFormat: AVAudioFormat?
+        // AppAudio
+        let appNode = AVAudioPlayerNode()
+        let appMixerNode = AVAudioMixerNode()
 
         // Not connected for device rendering mode.
         let micNode = AVAudioPlayerNode()
         let micMixerNode = AVAudioMixerNode()
 
-        //
-        let outputPlayerNode = AVAudioPlayerNode()
-        let outputPlayerMixerNode = AVAudioMixerNode()
-        var outputPlayerNodeFormat: AVAudioFormat?
-
         // Reference to mainMixerNode
         weak var mainMixerNode: AVAudioMixerNode?
-
-        // Keep track of preferred output volume before nodes attach
         var outputVolume: Float = 1.0
 
         // Internal states
         var isInputConnected: Bool = false
-        var isOutputConnected: Bool = false
 
         // Cached converters
         var converters: [AVAudioFormat: AudioConverter] = [:]
+
+        // Reference to engine format
+        var playerNodeFormat: AVAudioFormat?
     }
 
     let _state = StateSync(State())
@@ -98,19 +92,15 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
 
     public func engineDidCreate(_ engine: AVAudioEngine) -> Int {
         log("isManualRenderingMode: \(engine.isInManualRenderingMode)")
-
-        let (inputPlayerNode, inputPlayerMixerNode, micNode, micMixerNode, outputPlayerNode, outputPlayerMixerNode) = _state.read {
-            ($0.inputPlayerNode, $0.inputPlayerMixerNode, $0.micNode, $0.micMixerNode, $0.outputPlayerNode, $0.outputPlayerMixerNode)
+        let (appNode, appMixerNode, micNode, micMixerNode) = _state.read {
+            ($0.appNode, $0.appMixerNode, $0.micNode, $0.micMixerNode)
         }
 
-        engine.attach(inputPlayerNode)
-        engine.attach(inputPlayerMixerNode)
+        engine.attach(appNode)
+        engine.attach(appMixerNode)
         engine.attach(micNode)
         engine.attach(micMixerNode)
 
-        engine.attach(outputPlayerNode)
-        engine.attach(outputPlayerMixerNode)
-
         // Invoke next
         return next?.engineDidCreate(engine) ?? 0
     }
@@ -120,18 +110,15 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
         // Invoke next
         let nextResult = next?.engineWillRelease(engine)
 
-        let (inputPlayerNode, inputPlayerMixerNode, micNode, micMixerNode, outputPlayerNode, outputPlayerMixerNode) = _state.read {
-            ($0.inputPlayerNode, $0.inputPlayerMixerNode, $0.micNode, $0.micMixerNode, $0.outputPlayerNode, $0.outputPlayerMixerNode)
+        let (appNode, appMixerNode, micNode, micMixerNode) = _state.read {
+            ($0.appNode, $0.appMixerNode, $0.micNode, $0.micMixerNode)
         }
 
-        engine.detach(inputPlayerNode)
-        engine.detach(inputPlayerMixerNode)
+        engine.detach(appNode)
+        engine.detach(appMixerNode)
         engine.detach(micNode)
         engine.detach(micMixerNode)
 
-        engine.detach(outputPlayerNode)
-        engine.detach(outputPlayerMixerNode)
-
         return nextResult ?? 0
     }
 
@@ -147,7 +134,7 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
 
         // Read nodes from state lock.
         let (appNode, appMixerNode, micNode, micMixerNode) = _state.read {
-            ($0.inputPlayerNode, $0.inputPlayerMixerNode, $0.micNode, $0.micMixerNode)
+            ($0.appNode, $0.appMixerNode, $0.micNode, $0.micMixerNode)
         }
 
         // AVAudioPlayerNode doesn't support Int16 so we ensure to use Float32
@@ -175,11 +162,11 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
         engine.connect(micMixerNode, to: mainMixerNode, format: format)
 
         _state.mutate {
-            if let previousInputEngineFormat = $0.inputPlayerNodeFormat, previousInputEngineFormat != format {
+            if let previousEngineFormat = $0.playerNodeFormat, previousEngineFormat != format {
                 // Clear cached converters when engine format changes
                 $0.converters.removeAll()
             }
-            $0.inputPlayerNodeFormat = playerNodeFormat
+            $0.playerNodeFormat = playerNodeFormat
             $0.isInputConnected = true
         }
 
@@ -187,8 +174,6 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
         return next?.engineWillConnectInput(engine, src: src, dst: dst, format: format, context: context) ?? 0
     }
 
-    // let sineWaveNode = SineWaveSourceNode()
-
     public func engineWillConnectOutput(_ engine: AVAudioEngine, src: AVAudioNode, dst: AVAudioNode?, format: AVAudioFormat, context: [AnyHashable: Any]) -> Int {
         log("isManualRenderingMode: \(engine.isInManualRenderingMode)")
         // Get the main mixer
@@ -199,51 +184,15 @@ public final class MixerEngineObserver: AudioEngineObserver, Loggable {
 
         engine.mainMixerNode.outputVolume = outputVolume
 
-        // Read nodes from state lock.
-        let outAppPlayerNode = _state.read {
-            $0.outputPlayerNode
-        }
-
-        // AVAudioPlayerNode doesn't support Int16 so we ensure to use Float32
-        let playerNodeFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32,
-                                             sampleRate: format.sampleRate,
-                                             channels: format.channelCount,
-                                             interleaved: format.isInterleaved)!
-
-        engine.connect(outAppPlayerNode, to: engine.mainMixerNode, format: playerNodeFormat)
-
-        _state.mutate {
-            if let previousOutputEngineFormat = $0.outputPlayerNodeFormat, previousOutputEngineFormat != format {
-                // Clear cached converters when engine format changes
-                $0.converters.removeAll()
-            }
-            $0.outputPlayerNodeFormat = playerNodeFormat
-            $0.isOutputConnected = true
-        }
-
         return next?.engineWillConnectOutput(engine, src: src, dst: dst, format: format, context: context) ?? 0
     }
 }
 
 extension MixerEngineObserver {
     // Create or use cached AudioConverter.
-    func inputConverter(for format: AVAudioFormat) -> AudioConverter? {
-        _state.mutate {
-            guard let playerNodeFormat = $0.inputPlayerNodeFormat else { return nil }
-
-            if let converter = $0.converters[format] {
-                return converter
-            }
-
-            let newConverter = AudioConverter(from: format, to: playerNodeFormat)
-            $0.converters[format] = newConverter
-            return newConverter
-        }
-    }
-
-    func outputConverter(for format: AVAudioFormat) -> AudioConverter? {
+    func converter(for format: AVAudioFormat) -> AudioConverter? {
         _state.mutate {
-            guard let playerNodeFormat = $0.outputPlayerNodeFormat else { return nil }
+            guard let playerNodeFormat = $0.playerNodeFormat else { return nil }
 
             if let converter = $0.converters[format] {
                 return converter
@@ -258,7 +207,7 @@ extension MixerEngineObserver {
     // Capture appAudio and apply conversion automatically suitable for internal audio engine.
     public func capture(appAudio inputBuffer: AVAudioPCMBuffer) {
         let (isConnected, appNode) = _state.read {
-            ($0.isInputConnected, $0.inputPlayerNode)
+            ($0.isInputConnected, $0.appNode)
         }
 
         guard isConnected, let engine = appNode.engine, engine.isRunning else {
@@ -267,7 +216,7 @@ extension MixerEngineObserver {
         }
 
         // Create or update the converter if needed
-        let converter = inputConverter(for: inputBuffer.format)
+        let converter = converter(for: inputBuffer.format)
 
         guard let converter else { return }
 
@@ -278,28 +227,4 @@ extension MixerEngineObserver {
             appNode.play()
         }
     }
-
-    // Capture out-appAudio and apply conversion automatically suitable for internal audio engine.
-    public func capture(outAppAudio outputBuffer: AVAudioPCMBuffer) {
-        let (isConnected, appNode) = _state.read {
-            ($0.isOutputConnected, $0.outputPlayerNode)
-        }
-
-        guard isConnected, let engine = appNode.engine, engine.isRunning else {
-            log("Engine is not running", .warning)
-            return
-        }
-
-        // Create or update the converter if needed
-        let converter = outputConverter(for: outputBuffer.format)
-
-        guard let converter else { return }
-
-        let buffer = converter.convert(from: outputBuffer)
-        appNode.scheduleBuffer(buffer)
-
-        if !appNode.isPlaying {
-            appNode.play()
-        }
-    }
 }

From 1911ce02f25add1262106be1d30324c1cdb1df7d Mon Sep 17 00:00:00 2001
From: Hiroshi Horie <548776+hiroshihorie@users.noreply.github.com>
Date: Sat, 1 Nov 2025 00:08:11 +0700
Subject: [PATCH 3/5] temp: remove session setActive(false)

---
 Sources/LiveKit/Audio/AudioSessionEngineObserver.swift | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift b/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift
index a01ecab59..5a265cdd5 100644
--- a/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift
+++ b/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift
@@ -92,14 +92,7 @@ public class AudioSessionEngineObserver: AudioEngineObserver, Loggable, @uncheck
             log("AudioSession activationCount: \(session.activationCount), webRTCSessionCount: \(session.webRTCSessionCount)")
         }
 
-        if (!newState.isPlayoutEnabled && !newState.isRecordingEnabled) && (oldState.isPlayoutEnabled || oldState.isRecordingEnabled) {
-            do {
-                log("AudioSession deactivating...")
-                try session.setActive(false)
-            } catch {
-                log("AudioSession failed to deactivate with error: \(error)", .error)
-            }
-        } else if newState.isRecordingEnabled || newState.isPlayoutEnabled {
+        if newState.isRecordingEnabled || newState.isPlayoutEnabled {
             // Configure and activate the session with the appropriate category
             let playAndRecord: AudioSessionConfiguration = newState.isSpeakerOutputPreferred ? .playAndRecordSpeaker : .playAndRecordReceiver
             let config: AudioSessionConfiguration = newState.isRecordingEnabled ? playAndRecord : .playback

From 38d225c5a40bb21e73dadba857012d0181fcabee Mon Sep 17 00:00:00 2001
From: Hiroshi Horie <548776+hiroshihorie@users.noreply.github.com>
Date: Sat, 1 Nov 2025 00:25:41 +0700
Subject: [PATCH 4/5] Revert "temp: remove session setActive(false)"

This reverts commit 1911ce02f25add1262106be1d30324c1cdb1df7d.
---
 Sources/LiveKit/Audio/AudioSessionEngineObserver.swift | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift b/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift
index 5a265cdd5..a01ecab59 100644
--- a/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift
+++ b/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift
@@ -92,7 +92,14 @@ public class AudioSessionEngineObserver: AudioEngineObserver, Loggable, @uncheck
             log("AudioSession activationCount: \(session.activationCount), webRTCSessionCount: \(session.webRTCSessionCount)")
         }
 
-        if newState.isRecordingEnabled || newState.isPlayoutEnabled {
+        if (!newState.isPlayoutEnabled && !newState.isRecordingEnabled) && (oldState.isPlayoutEnabled || oldState.isRecordingEnabled) {
+            do {
+                log("AudioSession deactivating...")
+                try session.setActive(false)
+            } catch {
+                log("AudioSession failed to deactivate with error: \(error)", .error)
+            }
+        } else if newState.isRecordingEnabled || newState.isPlayoutEnabled {
             // Configure and activate the session with the appropriate category
             let playAndRecord: AudioSessionConfiguration = newState.isSpeakerOutputPreferred ? .playAndRecordSpeaker : .playAndRecordReceiver
             let config: AudioSessionConfiguration = newState.isRecordingEnabled ? playAndRecord : .playback

From d14b092b58fdc83465506e0c634283f925c88e7f Mon Sep 17 00:00:00 2001
From: Hiroshi Horie <548776+hiroshihorie@users.noreply.github.com>
Date: Sat, 1 Nov 2025 00:44:00 +0700
Subject: [PATCH 5/5] session requirement

---
 .../Audio/AudioSessionEngineObserver.swift    | 45 ++++++++++++++-----
 Sources/LiveKit/Audio/SoundPlayer.swift       | 12 +++++
 2 files changed, 47 insertions(+), 10 deletions(-)

diff --git a/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift b/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift
index a01ecab59..a3245ddfc 100644
--- a/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift
+++ b/Sources/LiveKit/Audio/AudioSessionEngineObserver.swift
@@ -48,17 +48,40 @@ public class AudioSessionEngineObserver: AudioEngineObserver, Loggable, @uncheck
         set { _state.mutate { $0.isSpeakerOutputPreferred = newValue } }
     }
 
+    public struct SessionRequirement: Sendable {
+        public static let none = Self(isPlayoutEnabled: false, isRecordingEnabled: false)
+        public static let playbackOnly = Self(isPlayoutEnabled: true, isRecordingEnabled: false)
+        public static let recordingOnly = Self(isPlayoutEnabled: false, isRecordingEnabled: true)
+        public static let playbackAndRecording = Self(isPlayoutEnabled: true, isRecordingEnabled: true)
+
+        public let isPlayoutEnabled: Bool
+        public let isRecordingEnabled: Bool
+
+        public init(isPlayoutEnabled: Bool = false, isRecordingEnabled: Bool = false) {
+            self.isPlayoutEnabled = isPlayoutEnabled
+            self.isRecordingEnabled = isRecordingEnabled
+        }
+    }
+
     struct State: Sendable {
         var next: (any AudioEngineObserver)?
 
         var isAutomaticConfigurationEnabled: Bool = true
-        var isPlayoutEnabled: Bool = false
-        var isRecordingEnabled: Bool = false
         var isSpeakerOutputPreferred: Bool = true
+
+        //
+        var sessionRequirements: [UUID: SessionRequirement] = [:]
+
+        // Computed
+        var isPlayoutEnabled: Bool { sessionRequirements.values.contains(where: \.isPlayoutEnabled) }
+        var isRecordingEnabled: Bool { sessionRequirements.values.contains(where: \.isRecordingEnabled) }
     }
 
     let _state = StateSync(State())
 
+    // Session requirement id for this object
+    private let sessionRequirementId = UUID()
+
     public var next: (any AudioEngineObserver)? {
         get { _state.next }
         set { _state.mutate { $0.next = newValue } }
@@ -83,6 +106,10 @@ public class AudioSessionEngineObserver: AudioEngineObserver, Loggable, @uncheck
         }
     }
 
+    public func set(requirement: SessionRequirement, for id: UUID) {
+        _state.mutate { $0.sessionRequirements[id] = requirement }
+    }
+
     @Sendable func configure(oldState: State, newState: State) {
         let session = LKRTCAudioSession.sharedInstance()
 
@@ -92,6 +119,8 @@ public class AudioSessionEngineObserver: AudioEngineObserver, Loggable, @uncheck
             log("AudioSession activationCount: \(session.activationCount), webRTCSessionCount: \(session.webRTCSessionCount)")
         }
 
+        log("configure isRecordingEnabled: \(newState.isRecordingEnabled), isPlayoutEnabled: \(newState.isPlayoutEnabled)")
+
         if (!newState.isPlayoutEnabled && !newState.isRecordingEnabled) && (oldState.isPlayoutEnabled || oldState.isRecordingEnabled) {
             do {
                 log("AudioSession deactivating...")
@@ -123,10 +152,8 @@ public class AudioSessionEngineObserver: AudioEngineObserver, Loggable, @uncheck
     }
 
     public func engineWillEnable(_ engine: AVAudioEngine, isPlayoutEnabled: Bool, isRecordingEnabled: Bool) -> Int {
-        _state.mutate {
-            $0.isPlayoutEnabled = isPlayoutEnabled
-            $0.isRecordingEnabled = isRecordingEnabled
-        }
+        let requirement = SessionRequirement(isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
+        set(requirement: requirement, for: sessionRequirementId)
 
         // Call next last
         return _state.next?.engineWillEnable(engine, isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled) ?? 0
@@ -136,10 +163,8 @@ public class AudioSessionEngineObserver: AudioEngineObserver, Loggable, @uncheck
         // Call next first
         let nextResult = _state.next?.engineDidDisable(engine, isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
 
-        _state.mutate {
-            $0.isPlayoutEnabled = isPlayoutEnabled
-            $0.isRecordingEnabled = isRecordingEnabled
-        }
+        let requirement = SessionRequirement(isPlayoutEnabled: isPlayoutEnabled, isRecordingEnabled: isRecordingEnabled)
+        set(requirement: requirement, for: sessionRequirementId)
 
         return nextResult ?? 0
     }
diff --git a/Sources/LiveKit/Audio/SoundPlayer.swift b/Sources/LiveKit/Audio/SoundPlayer.swift
index a59c3f8d7..56216890e 100644
--- a/Sources/LiveKit/Audio/SoundPlayer.swift
+++ b/Sources/LiveKit/Audio/SoundPlayer.swift
@@ -21,6 +21,9 @@ public class SoundPlayer: Loggable, @unchecked Sendable {
     private let playerNodes = AVAudioPlayerNodePool()
     public let outputFormat: AVAudioFormat
 
+    // Session requirement id for this object
+    private let sessionRequirementId = UUID()
+
     private struct State {
         var sounds: [String: AVAudioPCMBuffer] = [:]
     }
@@ -41,6 +44,11 @@ public class SoundPlayer: Loggable, @unchecked Sendable {
 
         playerNodes.connect(to: engine, node: engine.mainMixerNode, format: outputFormat)
 
+        // Request
+        #if os(iOS) || os(visionOS) || os(tvOS)
+        AudioManager.shared.audioSession.set(requirement: .playbackOnly, for: sessionRequirementId)
+        #endif
+
         try engine.start()
         log("Audio engine started")
     }
@@ -55,6 +63,10 @@ public class SoundPlayer: Loggable, @unchecked Sendable {
         playerNodes.stop()
         engine.stop()
 
+        #if os(iOS) || os(visionOS) || os(tvOS)
+        AudioManager.shared.audioSession.set(requirement: .none, for: sessionRequirementId)
+        #endif
+
         log("Audio engine stopped")
     }