Recover AudioStream when system audio output device changes

Runtime/Scripts/AudioStream.cs

@@ -15,7 +15,7 @@ public sealed class AudioStream : IDisposable
     {
         internal readonly FfiHandle Handle;
         private readonly AudioSource _audioSource;
-        private readonly AudioProbe _probe;
+        private AudioProbe _probe;
         private RingBuffer _buffer;
         private short[] _tempBuffer;
         private short[] _crossfadeScratch;
@@ -73,6 +73,11 @@ public AudioStream(RemoteAudioTrack audioTrack, AudioSource source)
 
             // Subscribe to application pause events to handle background/foreground transitions
             MonoBehaviourContext.OnApplicationPauseEvent += OnApplicationPause;
+
+            // Unity stops every AudioSource when the system audio output device changes
+            // (e.g. headphones unplugged). Without re-playing the source, OnAudioFilterRead
+            // stops firing and the stream goes silent until the AudioStream is recreated.
+            AudioSettings.OnAudioConfigurationChanged += OnAudioConfigurationChanged;
         }
 
         // Called on Unity audio thread
@@ -211,6 +216,34 @@ static float S16ToFloat(short v)
             }
         }
 
+        // Called when the system audio output device changes (e.g. plug/unplug headphones)
+        // or AudioSettings.Reset is invoked. Unity tears down its audio engine in both cases,
+        // which stops every AudioSource and detaches the AudioProbe filter from the rebuilt
+        // audio graph. Just calling Play() on the existing source isn't always enough; we
+        // additionally recreate the AudioProbe so Unity re-registers the OnAudioFilterRead
+        // node on the new graph.
+        private void OnAudioConfigurationChanged(bool deviceWasChanged)
+        {
+            if (_disposed) return;
+
+            lock (_lock)
+            {
+                _buffer?.Clear();
+                _isPrimed = false;
+            }
+
+            if (_probe != null)
+            {
+                _probe.AudioRead -= OnAudioRead;
+                UnityEngine.Object.Destroy(_probe);
+            }
+            _probe = _audioSource.gameObject.AddComponent<AudioProbe>();
+            _probe.AudioRead += OnAudioRead;
+
+            _audioSource.Stop();
+            _audioSource.Play();
+        }
+
         // Called when application goes to background or returns to foreground
         internal void OnApplicationPause(bool pause)
         {
@@ -285,6 +318,7 @@ private void Dispose(bool disposing)
             // touching partially disposed state.
             FfiClient.Instance.AudioStreamEventReceived -= OnAudioStreamEvent;
             MonoBehaviourContext.OnApplicationPauseEvent -= OnApplicationPause;
+            AudioSettings.OnAudioConfigurationChanged -= OnAudioConfigurationChanged;
 
             lock (_lock)
             {

Tests/EditMode/MediaStreamLifetimeTests.cs

@@ -122,6 +122,7 @@ public void AudioStream_Dispose_UnsubscribesAndReleasesOwnedResources()
 
             StringAssert.Contains("FfiClient.Instance.AudioStreamEventReceived -= OnAudioStreamEvent;", source);
             StringAssert.Contains("_probe.AudioRead -= OnAudioRead;", source);
+            StringAssert.Contains("AudioSettings.OnAudioConfigurationChanged -= OnAudioConfigurationChanged;", source);
             StringAssert.Contains("_buffer?.Dispose();", source);
             StringAssert.Contains("_resampler?.Dispose();", source);
             StringAssert.Contains("Handle.Dispose();", source);