Add Audio Compression (AAC in M4A/MP4) Support in Android/iOS/Windows (#155)

* test project added working

* Working AAC/M4A Compression

* Update AudioRecordingOptions.cs

* Update Encoding.cs

* Simplified the sample application

* Remove the unnecessary sample project

* Add obsolete encoding option back in

* Remove unused CompressionQuality

* Consolidate multiple options classes

* Tidy up more options related bits

* Fix some warnings

* A bit more tidy up and fix merge issues

* Correct text

* Update supported versions

* Default to Wav which was the original encoding

* Remove warning

* Patch up for Windows

---------

Co-authored-by: Shaun Lawrence <[email protected]>

Author: jonmdev

samples/Plugin.Maui.Audio.Sample/Pages/AudioRecorderPage.xaml

@@ -22,18 +22,15 @@
 
 			<Picker Title="Select Channels"
 					ItemsSource="{Binding ChannelTypes}"
-					SelectedItem="{Binding SelectedChannelType, Mode=TwoWay}"
-					ItemDisplayBinding="{Binding Name}" />
+					SelectedItem="{Binding SelectedChannelType, Mode=TwoWay}" />
 
 			<Picker Title="Select Bit Depth"
 					ItemsSource="{Binding BitDepths}"
-					SelectedItem="{Binding SelectedBitDepth, Mode=TwoWay}"
-					ItemDisplayBinding="{Binding Name}" />
+					SelectedItem="{Binding SelectedBitDepth, Mode=TwoWay}" />
 
 			<Picker Title="Select Encoding"
 					ItemsSource="{Binding EncodingOptions}"
-					SelectedItem="{Binding SelectedEconding, Mode=TwoWay}"
-					ItemDisplayBinding="{Binding Name}" />
+					SelectedItem="{Binding SelectedEncoding, Mode=TwoWay}" />
 
 			<Button Text="Start"
 					Command="{Binding StartCommand}" />

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

@@ -52,8 +52,8 @@ public AudioRecorderPageViewModel(
 		this.dispatcher = dispatcher;
 	}
 
-	ChannelTypesViewModel selectedChannelType;
-	public ChannelTypesViewModel SelectedChannelType
+	ChannelType selectedChannelType;
+	public ChannelType SelectedChannelType
 	{
 		get => selectedChannelType;
 		set
@@ -62,14 +62,10 @@ public ChannelTypesViewModel SelectedChannelType
 			NotifyPropertyChanged();
 		}
 	}
-	public List<ChannelTypesViewModel> ChannelTypes { get; set; } = new List<ChannelTypesViewModel>(Enum.GetValues(typeof(ChannelType)).Cast<ChannelType>().Select(x => new ChannelTypesViewModel()
-	{
-		ChannelType = x,
-		Name = x.ToString()
-	}).ToList());
+	public List<ChannelType> ChannelTypes { get; set; } = Enum.GetValues(typeof(ChannelType)).Cast<ChannelType>().ToList();
 
-	BitDepthViewModel selectedBitDepth;
-	public BitDepthViewModel SelectedBitDepth
+	BitDepth selectedBitDepth;
+	public BitDepth SelectedBitDepth
 	{
 		get => selectedBitDepth;
 		set
@@ -78,30 +74,20 @@ public BitDepthViewModel SelectedBitDepth
 			NotifyPropertyChanged();
 		}
 	}
-	public List<BitDepthViewModel> BitDepths { get; set; } = new List<BitDepthViewModel>(Enum.GetValues(typeof(BitDepth)).Cast<BitDepth>().Select(x => new BitDepthViewModel()
-	{
-		BitDepth = x,
-		Name = x.ToString()
-	}).ToList());
+	public List<BitDepth> BitDepths { get; set; } = Enum.GetValues(typeof(BitDepth)).Cast<BitDepth>().ToList();
 
-
-	EncodingViewModel selectedEconding;
-	public EncodingViewModel SelectedEconding
+	Encoding selectedEncoding;
+	public Encoding SelectedEncoding
 	{
-		get => selectedEconding;
+		get => selectedEncoding;
 		set
 		{
-			selectedEconding = value;
+			selectedEncoding = value;
 			NotifyPropertyChanged();
 		}
 	}
 
-	public List<EncodingViewModel> EncodingOptions { get; set; } = new List<EncodingViewModel>(Enum.GetValues(typeof(Encoding)).Cast<Encoding>().Select(x => new EncodingViewModel()
-	{
-		Encoding = x,
-		Name = x.ToString()
-	}).ToList());
-
+	public List<Encoding> EncodingOptions { get; set; } = Enum.GetValues(typeof(Encoding)).Cast<Encoding>().ToList();
 
 	int selectedSampleRate = -1;
 	public int SelectedSampleRate
@@ -113,6 +99,7 @@ public int SelectedSampleRate
 			NotifyPropertyChanged();
 		}
 	}
+	
 	public List<int> SampleRates { get; set; } =
 	[
 		8000,
@@ -147,15 +134,19 @@ async void Start()
 		{
 			audioRecorder = audioManager.CreateRecorder();
 
-			var options = new AudioRecordingOptions()
+			var options = new AudioRecorderOptions
 			{
-				SampleRate = SelectedSampleRate == -1 ? AudioRecordingOptions.DefaultSampleRate : SelectedSampleRate,
-				Channels = SelectedChannelType?.ChannelType ?? AudioRecordingOptions.DefaultChannels,
-				BitDepth = SelectedBitDepth?.BitDepth ?? AudioRecordingOptions.DefaultBitDepth,
-				Encoding = SelectedEconding?.Encoding ?? AudioRecordingOptions.DefaultEncoding,
+				Channels = SelectedChannelType,
+				BitDepth = SelectedBitDepth,
+				Encoding = SelectedEncoding,
 				ThrowIfNotSupported = true
 			};
 
+			if (SelectedSampleRate != -1)
+			{
+				options.SampleRate = SelectedSampleRate;
+			}
+
 			try
 			{
 				await audioRecorder.StartAsync(options);

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

@@ -8,7 +8,7 @@ namespace Plugin.Maui.Audio;
 
 partial class AudioPlayer : IAudioPlayer
 {
-	readonly MediaPlayer player;
+	readonly MediaPlayer player; // For broader format support (FLAC, etc.), consider using ExoPlayer instead in future
 	double volume = 0.5;
 	double balance = 0;
 	string cachePath = string.Empty;

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

@@ -66,19 +66,19 @@ public bool Loop
 
 	public bool CanSeek => true;
 
-	static NSData _emptySource;
+	static NSData? emptySource;
 
 	internal AudioPlayer(AudioPlayerOptions audioPlayerOptions)
 	{
-		if (_emptySource == null)
+		if (emptySource == null)
 		{
 			byte[] empty = new byte[16];
 			int sampleRate = 44100;
 			var source = new RawAudioSource(empty, sampleRate, 1);
-			_emptySource = NSData.FromArray(source.Bytes);
+			emptySource = NSData.FromArray(source.Bytes);
 		}
 
-		player = AVAudioPlayer.FromData(_emptySource)
+		player = AVAudioPlayer.FromData(emptySource)
 				 ?? throw new FailedToLoadAudioException("Unable to create AVAudioPlayer from data.");
 
 		this.audioPlayerOptions = audioPlayerOptions;

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

@@ -25,23 +25,23 @@ public interface IAudio : IDisposable
 	///</Summary>
 	double Balance { get; set; }
 
-	///<Summary>
-	/// Gets the playback speed where 1 is normal speed. <see cref="MinimumSpeed"/> and <see cref="MaximumSpeed"/> can be used to determine the minumum and maximum value for each platform.
-	/// Sets the playback speed where 1 is normal speed. <see cref="MinimumSpeed"/> and <see cref="MaximumSpeed"/> can be used to determine the minumum and maximum value for each platform.
-	/// </summary>
+	///<summary>
+	/// Gets the playback speed where 1 is normal speed. <see cref="MinimumSpeed"/> and <see cref="MaximumSpeed"/> can be used to determine the minimum and maximum value for each platform.
+	/// Sets the playback speed where 1 is normal speed. <see cref="MinimumSpeed"/> and <see cref="MaximumSpeed"/> can be used to determine the minimum and maximum value for each platform.
+	///</summary>
 	///<remarks>
-	/// The minimum and maximum speeds that can be set here are different per platform. Setting values ouside of these ranges will not throw an exception, it will clamp to the minimum or maximum value.
+	/// The minimum and maximum speeds that can be set here are different per platform. Setting values outside of these ranges will not throw an exception, it will clamp to the minimum or maximum value.
 	///<para>- Android: between 0 and 2.5. Setting the value to 0 will pause playback, playback will not be resumed when incrementing the value again.</para>
 	///<para>- iOS: between 0.5 and 2.</para>
 	///<para>- Windows: between 0 and 8. Setting the value to 0 will pause playback, playback will be resumed when incrementing the value again.</para>
 	///</remarks>
 	double Speed { get; set; }
 
 	/// <summary>
-	/// Sets the playback speed where 1 is normal speed. <see cref="MinimumSpeed"/> and <see cref="MaximumSpeed"/> can be used to determine the minumum and maximum value for each platform.
+	/// Sets the playback speed where 1 is normal speed. <see cref="MinimumSpeed"/> and <see cref="MaximumSpeed"/> can be used to determine the minimum and maximum value for each platform.
 	/// </summary>
 	///<remarks>
-	/// The minimum and maximum speeds that can be set here are different per platform. Setting values ouside of these ranges will not throw an exception, it will clamp to the minimum or maximum value.
+	/// The minimum and maximum speeds that can be set here are different per platform. Setting values outside of these ranges will not throw an exception, it will clamp to the minimum or maximum value.
 	///<para>- Android: between 0 and 2.5. Setting the value to 0 will pause playback, playback will not be resumed when incrementing the value again.</para>
 	///<para>- iOS: between 0.5 and 2.</para>
 	///<para>- Windows: between 0 and 8. Setting the value to 0 will pause playback, playback will be resumed when incrementing the value again.</para>