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;

Runtime/Scripts/RtcAudioSource.cs

@@ -83,20 +83,33 @@ 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 +122,49 @@ 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()
+        {
+            uint sampleRate = _sourceType == RtcAudioSourceType.AudioSourceMicrophone
+                ? DefaultMicrophoneSampleRate
+                : DefaultSampleRate;
+            uint channels = DefaultChannels;
+
+            try
+            {
+                var config = UnityEngine.AudioSettings.GetConfiguration();
+                if (config.sampleRate > 0)
+                    sampleRate = (uint)config.sampleRate;
+                var configuredChannels = SpeakerModeChannels(config.speakerMode);
+                if (configuredChannels > 0)
+                    channels = configuredChannels;
+            }
+            catch (Exception e)
+            {
+                Utils.Warning($"{DebugTag} could not read Unity audio configuration, using defaults: {e.Message}");
+            }
+
+            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>
@@ -153,9 +209,16 @@ private void OnAudioRead(float[] data, int channels, int sampleRate)
                 return;
             }
 
+            // The native source rejects frames whose rate/channels differ from how it was
+            // configured (it does not resample). This should not happen now that the source is
+            // configured from the device, but if Unity reports an inconsistent format — or the
+            // output configuration changes at runtime — we drop the frame instead of sending a
+            // mismatch the native side would error on.
             if ((uint)sampleRate != _expectedSampleRate || (uint)channels != _expectedChannels)
             {
-                Utils.Warning($"{DebugTag} audio frame #{frameIndex} metadata mismatch actualRate={sampleRate} actualChannels={channels} expectedRate={_expectedSampleRate} expectedChannels={_expectedChannels} sourceType={_sourceType}");
+                if (frameIndex == 1 || frameIndex % 100 == 0)
+                    Utils.Warning($"{DebugTag} dropping audio frame #{frameIndex}: format {sampleRate}/{channels} does not match source {_expectedSampleRate}/{_expectedChannels} (sourceType={_sourceType})");
+                return;
             }
 
             var pendingBeforeSend = PendingFrameCount();

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

@@ -453,8 +453,7 @@ private IEnumerator PublishLocalMicrophone()
     {
         if (_audioObjects.ContainsKey(LocalAudioTrackName)) yield break;
 
-        Microphone.Start(null, true, 10, 44100);
-
+        // MicrophoneSource starts the device itself, so we only need the device name here.
         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;