Enable preferred audio input device selection on Android

docs/audio-recorder.md

@@ -34,7 +34,7 @@ public class AudioRecorderViewModel
 
 ## Configure the recording options
 
-When calling `CreateRecorder` it is possible to provide an optional parameter of type `AudioRecorderOptions`, this parameter makes it possible to customize the recording settings at the platform level. **Note that currently you can only customize options for iOS and macOS**.
+When calling `CreateRecorder` it is possible to provide an optional parameter of type `AudioRecorderOptions`, this parameter makes it possible to customize the recording settings at the platform level.
 
 The following example shows how to enable both recording (input) and playback (output) of audio:
 
@@ -48,6 +48,36 @@ audioManager.CreateRecorder(
     });
 ```
 
+## Recording from a specific audio device (Android)
+
+By default, the recorder uses the system's default microphone (`AudioSource.Mic`). To record from a specific device such as a Bluetooth headset or USB microphone, use the `PreferredDevice` property.
+
+```csharp
+#if ANDROID
+using Android.Content;
+using Android.Media;
+
+var audioManager = (AudioManager)Android.App.Application.Context.GetSystemService(Context.AudioService)!;
+var btDevice = audioManager.GetDevices(GetDevicesTargets.Inputs)
+    .FirstOrDefault(d => d.Type == AudioDeviceType.BluetoothSco);
+
+var recorder = audioMgr.CreateRecorder(
+    new AudioRecorderOptions
+    {
+        PreferredDevice = btDevice
+    });
+#endif
+```
+
+> [!NOTE]
+> `SetPreferredDevice` requires Android API 23+ (Marshmallow) for WAV recording and API 28+ (Pie) for AAC recording. On older API levels, the property is ignored and the system default device is used. If the preferred device is unavailable (e.g. disconnected), recording silently falls back to the default device.
+
+> [!IMPORTANT]
+> On Android 12+ (API 31+), the `BLUETOOTH_CONNECT` runtime permission may be required to discover and select Bluetooth audio devices. Add it to your `AndroidManifest.xml`:
+> ```xml
+> <uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
+> ```
+
 ## Recording from a Bluetooth microphone (iOS/macCatalyst)
 
 By default, the recorder uses the system's built-in microphone. To enable recording from Bluetooth devices such as AirPods or other headsets, you need to opt in by setting `CategoryOptions` to `AllowBluetooth`. This makes Bluetooth HFP (Hands-Free Profile) devices available as recording inputs.

samples/Plugin.Maui.Audio.Sample/Platforms/Android/AndroidManifest.xml

@@ -5,6 +5,7 @@
 	<uses-permission android:name="android.permission.INTERNET" />
 	<uses-permission android:name="android.permission.RECORD_AUDIO"/>
 	<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
+	<uses-permission android:name="android.permission.BLUETOOTH_CONNECT" />
 	<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
 	<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 </manifest>

samples/Plugin.Maui.Audio.Sample/ViewModels/AudioRecorderPageViewModel.cs

@@ -1,5 +1,8 @@
-using System.Diagnostics;
+using System.Diagnostics;
 using static Microsoft.Maui.ApplicationModel.Permissions;
+#if ANDROID
+using Android.Media;
+#endif
 #if IOS || MACCATALYST
 using AVFoundation;
 #endif
@@ -16,6 +19,9 @@ public class AudioRecorderPageViewModel : BaseViewModel
 	readonly Stopwatch recordingStopwatch = new Stopwatch();
 	bool isPlaying;
 
+#if ANDROID
+	AudioDeviceInfo[] availableInputDevices = [];
+#endif
 #if IOS || MACCATALYST
 	AVAudioSessionPortDescription[] availableInputPorts = [];
 #endif
@@ -153,6 +159,31 @@ public bool AllowBluetooth
 
 	void LoadInputDevices()
 	{
+#if ANDROID
+		if (!OperatingSystem.IsAndroidVersionAtLeast(23))
+		{
+			InputDevices = ["Default"];
+			SelectedInputDevice = "Default";
+			return;
+		}
+
+		var androidAudioManager = (Android.Media.AudioManager?)Android.App.Application.Context.GetSystemService(Android.Content.Context.AudioService);
+		if (androidAudioManager is null)
+		{
+			return;
+		}
+
+		availableInputDevices = androidAudioManager.GetDevices(GetDevicesTargets.Inputs) ?? [];
+
+		var devices = new List<string> { "Default" };
+		foreach (var device in availableInputDevices)
+		{
+			devices.Add($"{device.ProductName} ({device.Type})");
+		}
+
+		InputDevices = devices;
+		SelectedInputDevice = "Default";
+#endif
 #if IOS || MACCATALYST
 		var session = AVAudioSession.SharedInstance();
 
@@ -217,6 +248,16 @@ async void Start()
 				options.SampleRate = SelectedSampleRate;
 			}
 
+#if ANDROID
+			if (SelectedInputDevice != "Default")
+			{
+				var index = InputDevices.IndexOf(SelectedInputDevice) - 1;
+				if (index >= 0 && index < availableInputDevices.Length)
+				{
+					options.PreferredDevice = availableInputDevices[index];
+				}
+			}
+#endif
 #if IOS || MACCATALYST
 			if (AllowBluetooth)
 			{
@@ -286,4 +327,4 @@ internal void OnNavigatedFrom()
 	{
 		audioPlayer?.Dispose();
 	}
-}
+}

samples/Plugin.Maui.Audio.Sample/ViewModels/AudioStreamerPageViewModel.cs

@@ -1,5 +1,8 @@
-using System.Diagnostics;
+using System.Diagnostics;
 using Plugin.Maui.Audio.AudioListeners;
+#if ANDROID
+using Android.Media;
+#endif
 #if IOS || MACCATALYST
 using AVFoundation;
 #endif
@@ -27,6 +30,9 @@ public class AudioStreamerPageViewModel : BaseViewModel
 	string capturedAudioWavFileLeft;
 	string capturedAudioWavFileRight;
 
+#if ANDROID
+	AudioDeviceInfo[] availableInputDevices = [];
+#endif
 #if IOS || MACCATALYST
 	AVAudioSessionPortDescription[] availableInputPorts = [];
 #endif
@@ -117,6 +123,31 @@ public bool AllowBluetooth
 
 	void LoadInputDevices()
 	{
+#if ANDROID
+		if (!OperatingSystem.IsAndroidVersionAtLeast(23))
+		{
+			InputDevices = ["Default"];
+			SelectedInputDevice = "Default";
+			return;
+		}
+
+		var androidAudioManager = (Android.Media.AudioManager?)Android.App.Application.Context.GetSystemService(Android.Content.Context.AudioService);
+		if (androidAudioManager is null)
+		{
+			return;
+		}
+
+		availableInputDevices = androidAudioManager.GetDevices(GetDevicesTargets.Inputs) ?? [];
+
+		var devices = new List<string> { "Default" };
+		foreach (var device in availableInputDevices)
+		{
+			devices.Add($"{device.ProductName} ({device.Type})");
+		}
+
+		InputDevices = devices;
+		SelectedInputDevice = "Default";
+#endif
 #if IOS || MACCATALYST
 		var session = AVAudioSession.SharedInstance();
 
@@ -314,6 +345,16 @@ async void Start()
 			audioStreamer.Options.BitDepth = SelectedBitDepth;
 			audioStreamer.Options.SampleRate = SelectedSampleRate;
 
+#if ANDROID
+			if (SelectedInputDevice != "Default")
+			{
+				var index = InputDevices.IndexOf(SelectedInputDevice) - 1;
+				if (index >= 0 && index < availableInputDevices.Length)
+				{
+					audioStreamer.Options.PreferredDevice = availableInputDevices[index];
+				}
+			}
+#endif
 #if IOS || MACCATALYST
 			if (AllowBluetooth)
 			{
@@ -434,4 +475,4 @@ internal void OnNavigatedFrom()
 	{
 		audioPlayer?.Dispose();
 	}
-}
+}

src/Plugin.Maui.Audio/AudioRecorder/AudioRecorder.android.cs

@@ -22,6 +22,11 @@ partial class AudioRecorder : IAudioRecorder
 
 	static readonly AudioRecorderOptions defaultOptions = new AudioRecorderOptions();
 
+	// Bluetooth SCO state
+	bool bluetoothScoStarted;
+	Android.Media.AudioManager? androidAudioManager;
+	Android.Media.Mode previousAudioMode;
+
 	AudioRecorderOptions audioRecorderOptions;
 
 	// Recording options that are extracted/solved
@@ -62,6 +67,16 @@ public Task StartAsync(string filePath, AudioRecorderOptions? recordingOptions =
 
 		audioFilePath = filePath;
 
+		// Determine if the preferred device is Bluetooth and requires SCO
+		bool isBluetoothDevice = IsBluetoothDevice(audioRecorderOptions.PreferredDevice);
+		AudioSource audioSource = isBluetoothDevice ? AudioSource.VoiceCommunication : AudioSource.Mic;
+
+		// Start Bluetooth SCO if needed (establishes the audio route for BT input)
+		if (isBluetoothDevice)
+		{
+			StartBluetoothSco();
+		}
+
 		// solve some parameters needed for AudioRecord/MediaRecorder
 		ChannelIn channelIn =
 			SharedChannelTypesToAndroidChannelTypes(audioRecorderOptions.Channels, audioRecorderOptions.ThrowIfNotSupported);
@@ -106,7 +121,16 @@ public Task StartAsync(string filePath, AudioRecorderOptions? recordingOptions =
 				}
 			}
 
-			audioRecord = new AudioRecord(AudioSource.Mic, sampleRate, channelIn, encoding, bufferSize);
+			audioRecord = new AudioRecord(audioSource, sampleRate, channelIn, encoding, bufferSize);
+
+			if (OperatingSystem.IsAndroidVersionAtLeast(23) && audioRecorderOptions.PreferredDevice is not null)
+			{
+				if (!audioRecord.SetPreferredDevice(audioRecorderOptions.PreferredDevice))
+				{
+					Trace.WriteLine("AudioRecorder: failed to set preferred device on AudioRecord, using default");
+				}
+			}
+
 			audioRecord.StartRecording();
 			Task.Run(WriteAudioDataToFile);
 		}
@@ -129,13 +153,22 @@ public Task StartAsync(string filePath, AudioRecorderOptions? recordingOptions =
 					.ApplicationContext); //needs context, obsoleted without context https://stackoverflow.com/questions/73598179/deprecated-mediarecorder-new-mediarecorder#73598440
 
 			mediaRecorder.Reset();
-			mediaRecorder.SetAudioSource(AudioSource.Mic);
+			mediaRecorder.SetAudioSource(audioSource);
 			mediaRecorder.SetOutputFormat(outputFormat);
 			mediaRecorder.SetAudioEncoder(audioEncoder);
 			mediaRecorder.SetAudioChannels(numChannels);
 			mediaRecorder.SetAudioSamplingRate(sampleRate);
 			mediaRecorder.SetAudioEncodingBitRate(bitRate);
 			mediaRecorder.SetOutputFile(audioFilePath);
+
+			if (OperatingSystem.IsAndroidVersionAtLeast(28) && audioRecorderOptions.PreferredDevice is not null)
+			{
+				if (!mediaRecorder.SetPreferredDevice(audioRecorderOptions.PreferredDevice))
+				{
+					Trace.WriteLine("AudioRecorder: failed to set preferred device on MediaRecorder, using default");
+				}
+			}
+
 			mediaRecorder.Prepare();
 			mediaRecorder.Start();
 
@@ -166,6 +199,9 @@ public Task<IAudioSource> StopAsync()
 			mediaRecorder?.Stop();
 		}
 
+		// Clean up Bluetooth SCO if it was started
+		StopBluetoothSco();
+
 		if (audioFilePath is null)
 		{
 			throw new InvalidOperationException("'audioFilePath' is null, this really should not happen.");
@@ -349,4 +385,49 @@ static ChannelIn SharedChannelTypesToAndroidChannelTypes(ChannelType type, bool
 				: SharedChannelTypesToAndroidChannelTypes(defaultOptions.Channels, true)
 		};
 	}
+
+	static bool IsBluetoothDevice(AudioDeviceInfo? device)
+	{
+		if (device is null || !OperatingSystem.IsAndroidVersionAtLeast(23))
+		{
+			return false;
+		}
+
+		return device.Type == AudioDeviceType.BluetoothSco
+			|| (OperatingSystem.IsAndroidVersionAtLeast(31)
+				&& (device.Type == AudioDeviceType.BleHeadset
+					|| device.Type == AudioDeviceType.BleSpeaker));
+	}
+
+	void StartBluetoothSco()
+	{
+		androidAudioManager = Android.App.Application.Context.GetSystemService(Context.AudioService) as Android.Media.AudioManager;
+		if (androidAudioManager is null)
+		{
+			return;
+		}
+
+		previousAudioMode = androidAudioManager.Mode;
+		androidAudioManager.Mode = Android.Media.Mode.InCommunication;
+		androidAudioManager.StartBluetoothSco();
+		androidAudioManager.BluetoothScoOn = true;
+		bluetoothScoStarted = true;
+
+		Trace.WriteLine("AudioRecorder: Bluetooth SCO started for BT device recording");
+	}
+
+	void StopBluetoothSco()
+	{
+		if (!bluetoothScoStarted || androidAudioManager is null)
+		{
+			return;
+		}
+
+		androidAudioManager.StopBluetoothSco();
+		androidAudioManager.BluetoothScoOn = false;
+		androidAudioManager.Mode = previousAudioMode;
+		bluetoothScoStarted = false;
+
+		Trace.WriteLine("AudioRecorder: Bluetooth SCO stopped");
+	}
 }