Using Microphones

Feature Rich User Audio

NatDevice provides access to hardware microphones on all platforms it supports. These microphones will stream audio directly to the client on a dedicated audio thread. The audio data can then be processed by the user.

When building for iOS, you must enable the Prepare iOS for Recording setting in Player Settings.

Finding a Microphone

We begin by finding a microphone with a device query:

void Start () {
    // Create a device query to find microphones
    var filter = MediaDeviceCriteria.AudioDevice;
    var query = new MediaDeviceQuery(filter);
    // Get the microphone
    var device = query.current as AudioDevice;
}

Streaming Audio

Audio devices work by streaming audio buffers to a user-provided delegate function:

void Start () {
    ...
    // Stream audio to our callback
    device.StartRunning(OnAudioBuffer);
}

The provided delegate is invoked with AudioBuffer instances as they are streamed from the audio device:

void OnAudioBuffer (AudioBuffer audioBuffer) {
    // Do stuff
    ...
}

The audio buffers always contain linear PCM samples interleaved by channel.

The provided delegate is not guaranteed to be invoked on the Unity main thread, so refrain from using Unity APIs within this method.

Specifying the Audio Format

Audio devices allow for specifying the format of the audio from the microphone. The audio format is defined by the sampleRate and channelCount:

void Start () {
    ...
    // Set the sample rate
    device.sampleRate = 44100;
    // Set the channel count to stereo
    device.channelCount = 2;
    // Stream audio to our callback
    device.StartRunning(OnAudioBuffer);
}

Stopping Streaming

When you are done with the microphone, you must stop it:

// Stop streaming audio
device.StopRunning();