Fix add(audioRenderer:) (#352)

Fixes issue #350

Sources/LiveKit/Support/MulticastDelegate.swift

@@ -37,6 +37,13 @@ public class MulticastDelegate<T>: NSObject, Loggable {
         _queue = DispatchQueue(label: "LiveKitSDK.Multicast.\(label)", qos: qos, attributes: [])
     }
 
+    public var allDelegates: [T] {
+        _queue.sync { [weak self] in
+            guard let self else { return [] }
+            return self._set.allObjects.compactMap { $0 as? T }
+        }
+    }
+
     /// Add a single delegate.
     public func add(delegate: T) {
         guard let delegate = delegate as AnyObject? else {

Sources/LiveKit/Track/Remote/RemoteAudioTrack.swift

@@ -14,12 +14,22 @@
  * limitations under the License.
  */
 
+import CoreMedia
 import Foundation
 
 @_implementationOnly import LiveKitWebRTC
 
 @objc
 public class RemoteAudioTrack: Track, RemoteTrack, AudioTrack {
+    // State used to manage AudioRenderers
+    private struct RendererState {
+        var didAttacheAudioRendererAdapter: Bool = false
+        let audioRenderers = MulticastDelegate<AudioRenderer>(label: "AudioRenderer")
+    }
+
+    private lazy var _audioRendererAdapter = AudioRendererAdapter(target: self)
+    private let _rendererState = StateSync(RendererState())
+
     /// Volume with range 0.0 - 1.0
     public var volume: Double {
         get {
@@ -46,12 +56,26 @@ public class RemoteAudioTrack: Track, RemoteTrack, AudioTrack {
 
     public func add(audioRenderer: AudioRenderer) {
         guard let audioTrack = mediaTrack as? LKRTCAudioTrack else { return }
-        audioTrack.add(AudioRendererAdapter(target: audioRenderer))
+
+        _rendererState.mutate {
+            $0.audioRenderers.add(delegate: audioRenderer)
+            if !$0.didAttacheAudioRendererAdapter {
+                audioTrack.add(_audioRendererAdapter)
+                $0.didAttacheAudioRendererAdapter = true
+            }
+        }
     }
 
     public func remove(audioRenderer: AudioRenderer) {
         guard let audioTrack = mediaTrack as? LKRTCAudioTrack else { return }
-        audioTrack.remove(AudioRendererAdapter(target: audioRenderer))
+
+        _rendererState.mutate {
+            $0.audioRenderers.remove(delegate: audioRenderer)
+            if $0.audioRenderers.allDelegates.isEmpty {
+                audioTrack.remove(_audioRendererAdapter)
+                $0.didAttacheAudioRendererAdapter = false
+            }
+        }
     }
 
     // MARK: - Internal
@@ -64,3 +88,11 @@ public class RemoteAudioTrack: Track, RemoteTrack, AudioTrack {
         AudioManager.shared.trackDidStop(.remote)
     }
 }
+
+extension RemoteAudioTrack: AudioRenderer {
+    public func render(sampleBuffer: CMSampleBuffer) {
+        _rendererState.audioRenderers.notify { audioRenderer in
+            audioRenderer.render(sampleBuffer: sampleBuffer)
+        }
+    }
+}

Tests/LiveKitTests/PublishTests.swift

@@ -105,4 +105,102 @@ class PublishTests: XCTestCase {
         // Reset
         await room1.localParticipant.unpublishAll()
     }
+
+    // Test if possible to receive audio buffer by adding audio renderer to RemoteAudioTrack.
+    func testAddAudioRenderer() async throws {
+        // LocalParticipant's identity should not be nil after a sucessful connection
+        guard let publisherIdentity = room1.localParticipant.identity else {
+            XCTFail("Publisher's identity is nil")
+            return
+        }
+
+        // Get publisher's participant
+        guard let remoteParticipant = room2.remoteParticipants[publisherIdentity] else {
+            XCTFail("Failed to lookup Publisher (RemoteParticipant)")
+            return
+        }
+
+        // Set up expectation...
+        let didSubscribeToRemoteAudioTrack = expectation(description: "Did subscribe to remote audio track")
+        didSubscribeToRemoteAudioTrack.assertForOverFulfill = false
+
+        var remoteAudioTrack: RemoteAudioTrack?
+
+        // Start watching RemoteParticipant for audio track...
+        let watchParticipant = remoteParticipant.objectWillChange.sink { _ in
+            if let track = remoteParticipant.firstAudioPublication?.track as? RemoteAudioTrack, remoteAudioTrack == nil {
+                remoteAudioTrack = track
+                didSubscribeToRemoteAudioTrack.fulfill()
+            }
+        }
+
+        // Publish mic
+        try await room1.localParticipant.setMicrophone(enabled: true)
+
+        // Wait for track...
+        print("Waiting for first audio track...")
+        await fulfillment(of: [didSubscribeToRemoteAudioTrack], timeout: 30)
+
+        guard let remoteAudioTrack else {
+            XCTFail("RemoteAudioTrack is nil")
+            return
+        }
+
+        // Received RemoteAudioTrack...
+        print("remoteAudioTrack: \(String(describing: remoteAudioTrack))")
+
+        // Set up expectation...
+        let didReceiveAudioFrame = expectation(description: "Did receive audio frame")
+        didReceiveAudioFrame.assertForOverFulfill = false
+
+        // Start watching for audio frame...
+        let audioFrameWatcher = AudioFrameWatcher(id: "notifier01") { _ in
+            didReceiveAudioFrame.fulfill()
+        }
+
+        // Attach audio frame watcher...
+        remoteAudioTrack.add(audioRenderer: audioFrameWatcher)
+
+        // Wait for audio frame...
+        print("Waiting for first audio frame...")
+        await fulfillment(of: [didReceiveAudioFrame], timeout: 30)
+
+        // Remove audio frame watcher...
+        remoteAudioTrack.remove(audioRenderer: audioFrameWatcher)
+
+        // Clean up
+        watchParticipant.cancel()
+        // Reset
+        await room1.localParticipant.unpublishAll()
+    }
+}
+
+actor AudioFrameWatcher: AudioRenderer {
+    public let id: String
+    private let onReceivedFirstFrame: (_ sid: String) -> Void
+    public private(set) var didReceiveFirstFrame: Bool = false
+
+    init(id: String, onReceivedFrame: @escaping (String) -> Void) {
+        self.id = id
+        onReceivedFirstFrame = onReceivedFrame
+    }
+
+    public func reset() {
+        didReceiveFirstFrame = false
+    }
+
+    private func onDidReceiveFirstFrame() {
+        if !didReceiveFirstFrame {
+            didReceiveFirstFrame = true
+            onReceivedFirstFrame(id)
+        }
+    }
+
+    nonisolated
+    func render(sampleBuffer: CMSampleBuffer) {
+        print("did receive first audio frame: \(String(describing: sampleBuffer))")
+        Task {
+            await onDidReceiveFirstFrame()
+        }
+    }
 }