Stream audio

The AudioStreamer class gives you the ability to stream audio from a microphone in your .NET MAUI application through an event handler. The AudioStreamer works pretty much the same as the recorder AudioRecorder, except that it provides raw audio data instead of a file. In order to create an AudioStreamer instance you can make use of the CreateStreamer method on the AudioManager class.

public class AudioStreamerViewModel
{
    readonly IAudioManager audioManager;
    readonly IAudioStreamer audioStreamer;

    public AudioStreamerViewModel(IAudioManager audioManager)
    {
        this.audioManager = audioManager;
        this.audioStreamer = audioManager.CreateStreamer();
        this.audioStreamer.OnAudioCaptured += OnAudioStreamerCapturedData;
    }

    public async Task StartStreamingAsync()
    {
        await audioStreamer.StartAsync();
    }

    public async Task StopStreamingAsync()
    {
        await audioStreamer.StopAsync();
    }

    private void OnAudioStreamerCapturedData(object sender, AudioStreamEventArgs args)
    {
        // You can use the args.Audio to collect, analyze or manipulate
        // args.Audio is a byte array with linear PCM audio data (like a WAV file without a header)
    }
}

Configure streaming options

When using an IAudioStreamer instance it is possible to set parameters of type AudioStreamerOptions, this parameters makes it possible to customize the recording settings at the platform level.

The following example shows how to set streaming settings of audio:

audioManager.CreateStreamer();
audioStreamer.Options.Channels = ChannelType.Mono;
audioStreamer.Options.BitDepth = BitDepth.Pcm16bit;
audioStreamer.Options.SampleRate = 441000;

Configure streaming options for whole app

In the app builder your can set the streaming options for the whole app:

builder.UseMauiApp<App>()
       .AddAudio(
         streamerOptions =>
         {
#if IOS || MACCATALYST
             recordingOptions.SampleRate = 44800;             
             streamerOptions.Category = AVFoundation.AVAudioSessionCategory.Record;
             streamerOptions.Mode = AVFoundation.AVAudioSessionMode.Default;
             streamerOptions.CategoryOptions = VFoundation.AVAudioSessionCategoryOptions.MixWithOthers;
#endif
         })....

Streaming from a Bluetooth microphone (iOS/macCatalyst)

By default, the streamer uses the system's built-in microphone. To enable streaming from Bluetooth devices such as AirPods or other headsets, set CategoryOptions to AllowBluetooth. This makes Bluetooth HFP (Hands-Free Profile) devices available as streaming inputs.

audioStreamer.Options.CategoryOptions = AVFoundation.AVAudioSessionCategoryOptions.AllowBluetooth;

To stream from a specific Bluetooth device, use the PreferredInput property — see the recorder documentation for a full example of enumerating available inputs.

AudioStreamer API

Once you have created an AudioStreamer you can interact with it in the following ways:

Properties

The AudioStreamer class provides the following properties:

CanStreamAudio

Gets whether the device is capable of streaming audio.

IsStreaming

Gets whether the streamer is currently streaming audio.

Methods and Events

The AudioStreamer class provides the following methods and events:

StartAsync()

Start streaming audio.

StopAsync()

Stop streaming audio.

EventHandler<AudioStreamEventArgs> OnAudioCaptured

Provides a stream of captured linear PCM audio data (raw WAV audio)

Platform specifics

In order to record audio some platforms require some extra additional changes.

Android

The AndroidManifest.xml file will need to be modified to include the following uses-permission inside the manifest tag.

<uses-permission android:name="android.permission.RECORD_AUDIO"/>
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

For a full example of this change check out our AndroidManifest.xml file.

iOS

The Info.plist file will need to be modified to include the following 2 entries inside the dict tag.

<key>NSMicrophoneUsageDescription</key>
<string>The [app name] wants to use your microphone to record audio.</string>

Replacing [app name] with your application name.

For a full example of this change check out our Info.plist file.

MacCatalyst

This change is identical to the iOS section but for explicitness:

The Info.plist file will need to be modified to include the following 2 entries inside the dict tag.

<key>NSMicrophoneUsageDescription</key>
<string>The [app name] wants to use your microphone to record audio.</string>

Replacing [app name] with your application name.

For a full example of this change check out our Info.plist file.

Windows

The Package.appxmanifest file will need to be modified to include the following entry inside the Capabilities tag.

<DeviceCapability Name="microphone"/>

For a full example of this change check out our Package.appxmanifest file.

Listening and Manipulating audio

Raw PCM audio (Pulse-Code Modulation) that AudioStreamer provides has a sample-by-sample structure that can be used for low-level audio manipulation and analysis. The Plugin.Maui.Audio library provides some basic IPcmAudioListener that can be used to analyse this audio. More information on the Audio Listeners page.

The Plugin.Maui.Audio library also provides PCM audio utilities via the PcmAudioHelpers class. It includes features for storing PCM audio as WAV files, converting raw PCM data into usable sample arrays, and various other audio conversions.

Sample

For a concrete example of streamed audio in a .NET MAUI application check out our sample application and specifically the AudioStreamerPageViewModel class.