Configure native audio source from device config instead of hardcoded defaults (#304)

* Configure native audio source from device, not hardcoded defaults

The native (Rust) audio source was created with a hardcoded sample rate
(48000) and channel count (2). Microphone frames flow through Unity's
audio graph (AudioProbe) at the actual DSP output configuration, which
often differs — e.g. with a Bluetooth headset. The Rust source does not
resample; it rejects frames whose rate/channels don't match, causing the
metadata-mismatch warning and capture failures.

Read the source's sample rate and channel count from Unity's output
configuration (AudioSettings.GetConfiguration) instead of hardcoded
defaults, falling back to the defaults only when Unity can't report one.
The base constructor now exposes a device-mode overload (type only) and an
explicit overload (type, sampleRate, channels) for sources that generate a
fixed format. MicrophoneSource and BasicAudioSource use device mode;
BasicAudioSource drops its unused channels parameter. SineWaveAudioSource
declares its exact format.

If a frame's format still doesn't match (inconsistent Unity report or a
runtime output change), drop it with a throttled warning instead of
sending a mismatch the native side would error on. Also removes the
redundant Microphone.Start in the Meet sample.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Remove logging changes

* Adds microphone start again for iOS, adds a debug log

* Trust Unity audio selection, use sample rate detected in mic start

Author: MaxHeimbrock

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;