Configure native audio source from device config instead of hardcoded defaults

Runtime/Scripts/BasicAudioSource.cs

@@ -19,9 +19,11 @@ sealed public class BasicAudioSource : RtcAudioSource
         /// Creates a new basic audio source for the given <see cref="AudioSource"/> in the scene.
         /// </summary>
         /// <param name="source">The <see cref="AudioSource"/> to capture from.</param>
-        /// <param name="channels">The number of channels to capture.</param>
         /// <param name="sourceType">The type of audio source.</param>
-        public BasicAudioSource(AudioSource source, int channels = 2, RtcAudioSourceType sourceType = RtcAudioSourceType.AudioSourceCustom) : base(channels, sourceType)
+        /// <remarks>
+        /// The sample rate and channel count are taken from Unity's audio configuration.
+        /// </remarks>
+        public BasicAudioSource(AudioSource source, RtcAudioSourceType sourceType = RtcAudioSourceType.AudioSourceCustom) : base(sourceType)
         {
             _source = source;
         }

Runtime/Scripts/MicrophoneSource.cs

@@ -28,7 +28,7 @@ sealed public class MicrophoneSource : RtcAudioSource
         /// get the list of available devices.</param>
         /// <param name="sourceObject">The GameObject to attach the AudioSource to. The object must be kept in the scene
         /// for the duration of the source's lifetime.</param>
-        public MicrophoneSource(string deviceName, GameObject sourceObject) : base(2, RtcAudioSourceType.AudioSourceMicrophone)
+        public MicrophoneSource(string deviceName, GameObject sourceObject) : base(RtcAudioSourceType.AudioSourceMicrophone)
         {
             _deviceName = deviceName;
             _sourceObject = sourceObject;
@@ -82,7 +82,7 @@ private IEnumerator StartMicrophone()
                     _deviceName,
                     loop: true,
                     lengthSec: 1,
-                    frequency: (int)DefaultMicrophoneSampleRate
+                    frequency: (int)_expectedSampleRate
                 );
             }
             catch (Exception e)

Runtime/Scripts/RtcAudioSource.cs

@@ -46,22 +46,11 @@ private sealed class PendingAudioFrame
         /// </remarks>
         public abstract event Action<float[], int, int> AudioRead;
 
-#if UNITY_IOS && !UNITY_EDITOR
-        // iOS microphone sample rate is 24k
-        public static uint DefaultMicrophoneSampleRate = 24000;
-
-        public static uint DefaultSampleRate = 48000;
-#else
-        public static uint DefaultSampleRate = 48000;
-        public static uint DefaultMicrophoneSampleRate = DefaultSampleRate;
-#endif
-        public static uint DefaultChannels = 2;
-
         private readonly RtcAudioSourceType _sourceType;
         public RtcAudioSourceType SourceType => _sourceType;
         private readonly int _debugId = Interlocked.Increment(ref nextDebugId);
-        private readonly uint _expectedSampleRate;
-        private readonly uint _expectedChannels;
+        internal readonly uint _expectedSampleRate;
+        internal readonly uint _expectedChannels;
 
         internal readonly FfiHandle Handle;
         protected AudioSourceInfo _info;
@@ -83,20 +72,33 @@ private sealed class PendingAudioFrame
         private volatile bool _disposed = false;
         private int _audioReadCount = 0;
 
-        protected RtcAudioSource(int channels = 2, RtcAudioSourceType audioSourceType = RtcAudioSourceType.AudioSourceCustom)
+        // Device-capture sources (microphone, AudioSource taps) don't know their format ahead of
+        // time — it is whatever Unity's audio graph delivers. They use this constructor, which
+        // configures the native source from Unity's current output configuration.
+        protected RtcAudioSource(RtcAudioSourceType audioSourceType)
+            : this(audioSourceType, 0, 0) { }
+
+        // Sources that generate a fixed, known format (e.g. test signal generators) declare it
+        // directly. Passing 0 for either value falls back to the device configuration.
+        protected RtcAudioSource(RtcAudioSourceType audioSourceType, uint sampleRate, uint channels)
         {
             _sourceType = audioSourceType;
-            _expectedChannels = (uint)channels;
+
+            if (sampleRate > 0 && channels > 0)
+            {
+                _expectedSampleRate = sampleRate;
+                _expectedChannels = channels;
+            }
+            else
+            {
+                (_expectedSampleRate, _expectedChannels) = ResolveDeviceFormat();
+            }
 
             using var request = FFIBridge.Instance.NewRequest<NewAudioSourceRequest>();
             var newAudioSource = request.request;
             newAudioSource.Type = AudioSourceType.AudioSourceNative;
-            newAudioSource.NumChannels = (uint)channels;
-            newAudioSource.SampleRate = _sourceType == RtcAudioSourceType.AudioSourceMicrophone ?
-                DefaultMicrophoneSampleRate : DefaultSampleRate;
-            _expectedSampleRate = newAudioSource.SampleRate;
-
-            Utils.Debug($"NewAudioSource: {newAudioSource.NumChannels} {newAudioSource.SampleRate}");
+            newAudioSource.NumChannels = _expectedChannels;
+            newAudioSource.SampleRate = _expectedSampleRate;
 
             newAudioSource.Options = request.TempResource<AudioSourceOptions>();
             newAudioSource.Options.EchoCancellation = true;
@@ -109,6 +111,37 @@ protected RtcAudioSource(int channels = 2, RtcAudioSourceType audioSourceType =
             Utils.Debug($"{DebugTag} created handle={Handle.DangerousGetHandle()} expectedRate={_expectedSampleRate} expectedChannels={_expectedChannels} sourceType={_sourceType}");
         }
 
+        // Reads Unity's actual output audio configuration. The capture path delivers buffers at the
+        // DSP output rate/channel count (see AudioProbe), so this is the format the native source
+        // must match. Falls back to the platform defaults when Unity cannot report a configuration
+        // (e.g. batch mode without an audio device).
+        private (uint sampleRate, uint channels) ResolveDeviceFormat()
+        {
+            var config = UnityEngine.AudioSettings.GetConfiguration();
+            var sampleRate = (uint)config.sampleRate;
+            var configuredChannels = SpeakerModeChannels(config.speakerMode);
+            var channels = configuredChannels;
+
+            Utils.Info($"Configured native audio source with sampleRate {sampleRate} and channels {channels}");
+
+            return (sampleRate, channels);
+        }
+
+        private static uint SpeakerModeChannels(UnityEngine.AudioSpeakerMode mode)
+        {
+            switch (mode)
+            {
+                case UnityEngine.AudioSpeakerMode.Mono: return 1;
+                case UnityEngine.AudioSpeakerMode.Stereo: return 2;
+                case UnityEngine.AudioSpeakerMode.Quad: return 4;
+                case UnityEngine.AudioSpeakerMode.Surround: return 5;
+                case UnityEngine.AudioSpeakerMode.Mode5point1: return 6;
+                case UnityEngine.AudioSpeakerMode.Mode7point1: return 8;
+                case UnityEngine.AudioSpeakerMode.Prologic: return 2;
+                default: return 0;
+            }
+        }
+
         /// <summary>
         /// Begin capturing audio samples from the underlying source.
         /// </summary>

Samples~/Meet/Assets/Runtime/MeetManager.cs

@@ -453,8 +453,9 @@ private IEnumerator PublishLocalMicrophone()
     {
         if (_audioObjects.ContainsKey(LocalAudioTrackName)) yield break;
 
+        // Start the microphone here for early iOS permission request and android getting access to Microphone.devices
         Microphone.Start(null, true, 10, 44100);
-
+        
         var audioObject = new GameObject($"My Microphone: {Microphone.devices[0]}");
         audioObject.transform.SetParent(_audioTrackParent);
 

Tests/PlayMode/Utils/SineWaveAudioSource.cs

@@ -31,7 +31,7 @@ public SineWaveAudioSource(
             int sampleRate = 48000,
             double frequencyHz = 440.0,
             float amplitude = 0.1f)
-            : base(channels, RtcAudioSourceType.AudioSourceCustom)
+            : base(RtcAudioSourceType.AudioSourceCustom, (uint)sampleRate, (uint)channels)
         {
             _channels = channels;
             _sampleRate = sampleRate;