NAudio - Change pitch of buffered microphone audio and send to Virtual Audio Cable

Question

I decided to have a go at creating a sound board for use with Discord (or similar software) using NAudio and a Virtual Audio Cable. I was able to 'inject' the audio from the microphone to the audio cable so I could play sound files and mic audio to Discord by selecting the virtual audio cable as the input device in Discord.

For fun I thought I would see if I could modify the mic audio to make it 'squeaky' or 'deep'. So I started looking into modifying the pitch of the audio. I discovered that NAudio has an SmbPitchShiftingSampleProvider and then found this question which helps to work with buffered audio, but I can't figure out how to do it. Here's what I've got so far:

    //Inject Mic Audio
    WaveIn injectMicIn = null;
    WaveOut injectMicOut = null;
    private BufferedWaveProvider bufferedWaveProvider; //Buffer for mic audio
    public int micDeviceID; //Device ID of selected microphone
    public int virtualAudioCableID; //Device ID of selected virtual audio cable
    ISampleProvider sampleP; //#### TO DO: Remove this if I don't use it.
    NAudio.Wave.SampleProviders.SmbPitchShiftingSampleProvider pitchProvider; //#### TO DO: Remove this if I don't use it

    private void InjectMicrophone()
    {
        //Mic Input
        if (injectMicIn == null)
        {
            injectMicIn = new WaveIn();
            injectMicIn.RecordingStopped += new EventHandler<StoppedEventArgs>(OnRecordingStopped);
            injectMicIn.DataAvailable += InjectMicOnDataAvailable;
            injectMicIn.WaveFormat = new WaveFormat(44100, 1);
        }

        injectMicIn.DeviceNumber = SharedVars.micInjectInputDeviceID; //Set the users selected input device

        //Mic Output
        if (injectMicOut == null)
        {
            injectMicOut = new WaveOut();
            injectMicOut.PlaybackStopped += new EventHandler<StoppedEventArgs>(OnPlaybackStopped);

        }

        bufferedWaveProvider = new BufferedWaveProvider(injectMicIn.WaveFormat); //Prepare the buffer for the microphone audio

        sampleP = bufferedWaveProvider.ToSampleProvider(); //#### TO DO: Remove this if I don't use it for pitch shifting

        injectMicOut.DeviceNumber = SharedVars.micInjectOutputDeviceID; //Set the users selected output device
        //injectMicOut.Init(bufferedWaveProvider);

        SharedVars.currentlyInjectingMic = true;
        injectMicIn.StartRecording(); //Record the mic and
        //injectMicOut.Play(); //out play it on the selected output device

    }

    bool init = false;
    private void InjectMicOnDataAvailable(object sender, WaveInEventArgs e)
    {
        bufferedWaveProvider.AddSamples(e.Buffer, 0, e.BytesRecorded); //Add the mic audio to the buffer

        //#### TO DO: REMOVE THIS TEST CODE
        var bytesPerFrame = (injectMicIn.WaveFormat.BitsPerSample / 8) * injectMicIn.WaveFormat.Channels;
        var bufferedFrames = e.BytesRecorded / bytesPerFrame;

        var frames = new float[bufferedFrames];
        sampleP.Read(frames, 0, bufferedFrames);

        pitchProvider = new NAudio.Wave.SampleProviders.SmbPitchShiftingSampleProvider(sampleP);
        pitchProvider.PitchFactor = 2.0f;

        if (!init)
        {
            injectMicOut.Init(pitchProvider);
            init = true;
        }

        injectMicOut.Play();
        //#### TO DO: REMOVE THIS TEST CODE
    }

Any help would be greatly appreciated.

EDIT: Final Code

    //Inject Mic Audio
    WaveIn injectMicIn = null;
    WaveOut injectMicOut = null;
    private BufferedWaveProvider bufferedWaveProvider; //Buffer for mic audio
    public int micDeviceID; //Device ID of selected microphone
    public int virtualAudioCableID; //Device ID of selected virtual audio cable
    SmbPitchShiftingSampleProvider pitchProvider; //Used to adjust the pitch of the mic audio if required

    private void InjectMicrophone()
    {
        //Mic Input
        if (injectMicIn == null)
        {
            injectMicIn = new WaveIn();
            injectMicIn.RecordingStopped += new EventHandler<StoppedEventArgs>(OnRecordingStopped);
            injectMicIn.DataAvailable += InjectMicOnDataAvailable;
            injectMicIn.WaveFormat = new WaveFormat(44100, 1);
        }

        injectMicIn.DeviceNumber = SharedVars.micInjectInputDeviceID; //Set the users selected input device

        //Mic Output
        if (injectMicOut == null)
        {
            injectMicOut = new WaveOut();
            injectMicOut.PlaybackStopped += new EventHandler<StoppedEventArgs>(OnMicPlaybackStopped);    
        }

        injectMicOut.DeviceNumber = SharedVars.micInjectOutputDeviceID; //Set the users selected output device

        bufferedWaveProvider = new BufferedWaveProvider(injectMicIn.WaveFormat); //Prepare the buffer for the microphone audio

        pitchProvider = new SmbPitchShiftingSampleProvider(bufferedWaveProvider.ToSampleProvider()); //Create a pitch shifting sample provider to adjust the pitch of the mic audio if required
        pitchProvider.PitchFactor = 1.0f; //#### TO DO: Retrieve value from a UI control

        injectMicOut.Init(pitchProvider);

        SharedVars.currentlyInjectingMic = true;
        injectMicIn.StartRecording(); //Record the mic and
        injectMicOut.Play(); //out play it on the selected output device

    }

    private void InjectMicOnDataAvailable(object sender, WaveInEventArgs e)
    {
        bufferedWaveProvider.AddSamples(e.Buffer, 0, e.BytesRecorded); //Add the mic audio to the buffer
    }

Mark Heath Mark Heath · Accepted Answer · 2018-01-09T17:13:24

You're pretty close

On the recording device, just put the recorded audio directly into a BufferedWaveProvider.

On the playback device, pass in an SmbPitchShiftingProvider that reads from the BufferedWaveProvider (use ToSampleProvider to turn it into an ISampleProvider)

NAudio - Change pitch of buffered microphone audio and send to Virtual Audio Cable

1 Answers