Audio Input

This section provides examples of how to use Magic Leap's APIs to record audio.

caution

This features requires the RecordAudio permission to be requested at runtime and enabled in your project's Manifest Settings (Edit > Project Settings > Magic Leap > Manifest Settings).

Raw Audio Samples

This example shows how to obtain the raw audio buffer samples from the microphone as soon as they are received

using System;
using UnityEngine.XR.MagicLeap;

public class ML2BufferClip : MLAudioInput.BufferClip
{
    public ML2BufferClip(MLAudioInput.MicCaptureType captureType, int lengthSec, int frequency) : this(captureType, (uint)lengthSec, (uint)frequency, (uint)MLAudioInput.GetChannels(captureType)) { }

    public ML2BufferClip(MLAudioInput.MicCaptureType captureType, uint samplesLengthInSeconds, uint sampleRate, uint channels)
        : base(captureType, samplesLengthInSeconds, sampleRate, channels) { }

    public event Action<float[]> OnReceiveSampleCallback;

    protected override void OnReceiveSamples(float[] samples)
    {
        base.OnReceiveSamples(samples);
        if (OnReceiveSampleCallback != null)
        {
            OnReceiveSampleCallback(samples);
        }
    }
}

Simple Audio Input Example

This example demonstrates how to record audio on Magic Leap 2 and play it back instantly.

using UnityEngine;
using UnityEngine.XR.MagicLeap;
public class AudioEventExample : MonoBehaviour
{
    [SerializeField, Tooltip("The audio source that should replay the captured audio.")]
    private AudioSource _playbackAudioSource = null;

    private readonly MLPermissions.Callbacks permissionCallbacks = new MLPermissions.Callbacks();
    private MLAudioInput.StreamingClip mlAudioStreamingClip;
    private MLAudioInput.BufferClip mlAudioBufferClip;

    void Awake()
    {
        if (_playbackAudioSource == null)
        {
            Debug.LogError("PlaybackAudioSource is not set, adding component to " + gameObject.name);
            _playbackAudioSource = gameObject.AddComponent<AudioSource>();
        }
        permissionCallbacks.OnPermissionGranted += OnPermissionGranted;
        MLPermissions.RequestPermission(MLPermission.RecordAudio, permissionCallbacks);
    }

    void OnDestroy()
    {
        StopCapture();
        permissionCallbacks.OnPermissionGranted -= OnPermissionGranted;
    }

    private void StartMicrophone()
    {
        _playbackAudioSource.Stop();
        var captureType = MLAudioInput.MicCaptureType.VoiceCapture;
        mlAudioStreamingClip = new MLAudioInput.StreamingClip(MLAudioInput.MicCaptureType.VoiceCapture, 3, MLAudioInput.GetSampleRate(captureType));

        _playbackAudioSource.pitch = 1;
        _playbackAudioSource.clip = mlAudioStreamingClip.UnityAudioClip;
        _playbackAudioSource.loop = true;
        _playbackAudioSource.Play();
    }

    private void StopCapture()
    {
        mlAudioStreamingClip?.Dispose();
        mlAudioStreamingClip = null;
        mlAudioBufferClip?.Dispose();
        mlAudioBufferClip = null;
        // Stop audio playback source and reset settings.
        _playbackAudioSource.Stop();
        _playbackAudioSource.time = 0;
        _playbackAudioSource.pitch = 1;
        _playbackAudioSource.loop = false;
        _playbackAudioSource.clip = null;
    }
    
    private void OnPermissionGranted(string permission)
    {
        StartMicrophone();
        Debug.Log($"Succeeded in requesting {permission}.");
    }
}

Delayed Audio Playback

This example demonstrates how to record audio on Magic Leap 2 when a certain volume threshold is reached, and play back the recording at a lower pitch than it was captured.

using System.Collections;
using System.Linq;
using UnityEngine;
using UnityEngine.XR.MagicLeap;
public class AudioEventExample : MonoBehaviour
{
    [SerializeField, Tooltip("The audio source that should replay the captured audio.")]
    private AudioSource _playbackAudioSource = null;
    [Header("Delayed Playback")]
    [SerializeField, Range(1, 2), Tooltip("The pitch used for delayed audio playback.")]
    private float _pitch = 1.5f;

    private bool isAudioDetected = false;
    private float audioLastDetectionTime = 0;
    private float audioDetectionStart = 0;

    private const int AUDIO_CLIP_LENGTH_SECONDS = 60;
    private const float AUDIO_SENSITVITY = 0.02f;
    private const float AUDIO_CLIP_TIMEOUT_SECONDS = 2;

    private readonly MLPermissions.Callbacks permissionCallbacks = new MLPermissions.Callbacks();
    private MLAudioInput.BufferClip mlAudioBufferClip;

    void Awake()
    {
        if (_playbackAudioSource == null)
        {
            Debug.LogError("PlaybackAudioSource is not set, adding component to " + gameObject.name);
            _playbackAudioSource = gameObject.AddComponent<AudioSource>();
        }
        permissionCallbacks.OnPermissionGranted += OnPermissionGranted;
        MLPermissions.RequestPermission(MLPermission.RecordAudio, permissionCallbacks);
    }

    void OnDestroy()
    {
        StopCapture();
        permissionCallbacks.OnPermissionGranted -= OnPermissionGranted;
    }

    private void StartMicrophone()
    {
        _playbackAudioSource.Stop();
        var captureType = MLAudioInput.MicCaptureType.VoiceCapture;
        mlAudioBufferClip = new MLAudioInput.BufferClip(MLAudioInput.MicCaptureType.VoiceCapture, AUDIO_CLIP_LENGTH_SECONDS, MLAudioInput.GetSampleRate(captureType));
        mlAudioBufferClip.OnReceivedSamples += DetectAudio;
        _playbackAudioSource.pitch = _pitch;
        _playbackAudioSource.clip = null;
        _playbackAudioSource.loop = false;
        isAudioDetected = false;
        audioDetectionStart = 0;
        audioLastDetectionTime = 0;
    }

    private void StopCapture()
    {
        mlAudioBufferClip?.Dispose();
        mlAudioBufferClip = null;

        // Stop audio playback source and reset settings.
        _playbackAudioSource.Stop();
        _playbackAudioSource.time = 0;
        _playbackAudioSource.pitch = 1;
        _playbackAudioSource.loop = false;
        _playbackAudioSource.clip = null;
    }
    
    private void DetectAudio(float[] samples)
    {
        // Analyze the input spectrum data, to determine when someone is speaking.
        float maxAudioSample = 0f;

        //Audio samples can also be read directly instead of via callback using the mlAudioBufferClip.GetData()

        maxAudioSample = samples.Append(maxAudioSample).Max();
        if (maxAudioSample > AUDIO_SENSITVITY)
        {
            audioLastDetectionTime = Time.time;
            if (isAudioDetected == false)
            {
                isAudioDetected = true;
                audioDetectionStart = Time.time;
            }
        }
        else if (isAudioDetected && (Time.time > audioLastDetectionTime + AUDIO_CLIP_TIMEOUT_SECONDS))
        {
            var audioDetectionDuration = Time.time - audioDetectionStart;

            _playbackAudioSource.clip = mlAudioBufferClip.FlushToClip();
            _playbackAudioSource.time = _playbackAudioSource.clip.length - audioDetectionDuration;
            _playbackAudioSource.Play();
            // Reset and allow for new captured speech.
            isAudioDetected = false;
            audioDetectionStart = 0;
            audioLastDetectionTime = 0;
        }
    }

    private void OnPermissionGranted(string permission)
    {
        StartMicrophone();
        Debug.Log($"Succeeded in requesting {permission}.");
    }
}

Read Audio Buffer Data

You can read the audio buffer data directly using the MLAudioInput.BufferClip.GetData() function. Here is a simple script that shows how to read buffer data. It doesn't play the audio back, but you can use it as a reference on how to obtain Audio Samples using the GetData function.

using System.Linq;
using UnityEngine;
using UnityEngine.XR.MagicLeap;
public class AudioEventExample : MonoBehaviour
{
    //Magic Leap Audio Capture Settings
    private MLAudioInput.MicCaptureType captureType = MLAudioInput.MicCaptureType.VoiceCapture;
    private MLAudioInput.BufferClip mlAudioBufferClip;
    private const int AUDIO_CLIP_LENGTH_SECONDS = 60; 

    //Used to read the buffer data directly
    private int detectionAudioPosition = 0; 
    private readonly float[] detectionAudioSamples = new float[128];

    //Magic Leap permissions
    private readonly MLPermissions.Callbacks permissionCallbacks = new MLPermissions.Callbacks();

    //True if permissions were granted and the microphone is initialized
    private bool _microphoneStarted = false;

    void Awake()
    {
        permissionCallbacks.OnPermissionGranted += OnPermissionGranted;
        MLPermissions.RequestPermission(MLPermission.RecordAudio, permissionCallbacks);
    }

    void OnDestroy()
    {
        StopCapture();
        permissionCallbacks.OnPermissionGranted -= OnPermissionGranted;
    }
    private void StopCapture()
    {
        mlAudioBufferClip?.Dispose();
        mlAudioBufferClip = null;
    }
    private void OnPermissionGranted(string permission)
    {
        StartMicrophone();
        Debug.Log($"Succeeded in requesting {permission}.");
    }

    private void StartMicrophone()
    {
        mlAudioBufferClip = new MLAudioInput.BufferClip(MLAudioInput.MicCaptureType.VoiceCapture, AUDIO_CLIP_LENGTH_SECONDS, MLAudioInput.GetSampleRate(captureType));
        detectionAudioPosition = 0;
        _microphoneStarted = true;
    }

    private void Update()
    {
        if (_microphoneStarted)
        {
            DetectAudio();
        }
    }

    private void DetectAudio()
    {
        // Analyze the input spectrum data, to determine when someone is speaking. 
        float maxAudioSample = 0f;
        while (true)
        {
            int readSampleCount = mlAudioBufferClip.GetData(detectionAudioSamples, detectionAudioPosition, out int nextPosition);
            if (readSampleCount == 0)
            {
                break;
            }
            detectionAudioPosition = nextPosition;
            maxAudioSample = detectionAudioSamples.Take(readSampleCount).Append(maxAudioSample).Max();
        }
    }
}