NAudio and Concentus Record -> Encode -> Decode -> Playback trivial example

NAudioConcentusTrivialExample.cs

using Concentus;
using Concentus.Enums;
using NAudio.Wave;

internal class Program {
  private static bool stopFlag = false;
  private static List<short> pcmAccumulationBuffer = new List<short>();
  private static IOpusEncoder encoder;
  private static IOpusDecoder decoder;
  private static BufferedWaveProvider waveProvider;
  private static WaveInEvent waveIn;
  private static WaveOutEvent waveOut;
  private const int FrameSize = 960; // 20ms frame for Opus at 48kHz

  private static void Main(string[] args) {
    Console.WriteLine("Recording, encoding, decoding, and playing back. Press Enter to stop.");

    Initialize();
    StartRecording();

    // Wait for user input to stop recording
    Console.ReadLine();
    StopRecording();
  }

  private static void Initialize() {
    // Initialize encoder and decoder
    encoder = OpusCodecFactory.CreateEncoder(48000, 1, OpusApplication.OPUS_APPLICATION_AUDIO);
    decoder = OpusCodecFactory.CreateDecoder(48000, 1);

    // Initialize audio devices
    waveIn = new WaveInEvent {
      DeviceNumber = 0, // Use default recording device
      WaveFormat = new WaveFormat(48000, 1) // 48kHz, Mono
    };

    waveProvider = new BufferedWaveProvider(waveIn.WaveFormat) {
      BufferDuration = TimeSpan.FromSeconds(5), // Buffer duration
      DiscardOnBufferOverflow = false
    };

    waveOut = new WaveOutEvent();
    waveOut.Init(waveProvider);
  }

  private static void StartRecording() {
    waveIn.DataAvailable += OnDataAvailable;
    waveOut.Play();

    try {
      waveIn.StartRecording();
      Console.WriteLine("Recording started...");
    } catch (Exception ex) {
      Console.WriteLine($"Error starting recording: {ex.Message}");
    }
  }

  private static void StopRecording() {
    stopFlag = true;
    waveIn.StopRecording();
    Console.WriteLine("Recording stopped.");

    // Wait until playback completes
    while (waveOut.PlaybackState == PlaybackState.Playing || waveProvider.BufferedBytes > 0) {
      Thread.Sleep(100);
    }
    Console.WriteLine("Playback finished.");

    // Cleanup
    waveIn.Dispose();
    waveOut.Dispose();
  }

  private static void OnDataAvailable(object sender, WaveInEventArgs a) {
    if (stopFlag)
      return;

    // Convert buffer to short PCM samples and accumulate
    AddPcmDataToBuffer(a.Buffer, a.BytesRecorded);
    ProcessAudioFrames();
  }

  private static void AddPcmDataToBuffer(byte[] buffer, int bytesRecorded) {
    var pcmBuffer = new short[bytesRecorded / 2];
    Buffer.BlockCopy(buffer, 0, pcmBuffer, 0, bytesRecorded);
    pcmAccumulationBuffer.AddRange(pcmBuffer);
  }

  private static void ProcessAudioFrames() {
    // Process accumulated PCM data in chunks of frameSize
    while (pcmAccumulationBuffer.Count >= FrameSize) {
      var frame = pcmAccumulationBuffer.GetRange(0, FrameSize).ToArray();
      pcmAccumulationBuffer.RemoveRange(0, FrameSize);
      EncodeDecodeAndPlay(frame);
    }
  }

  private static void EncodeDecodeAndPlay(short[] frame) {
    byte[] encoded = new byte[4000];
    try {
      int encodedLength = encoder.Encode(frame, FrameSize, encoded, encoded.Length);
      DecodeAndPlay(encoded, encodedLength);
    } catch (Exception ex) {
      Console.WriteLine($"Error during encoding: {ex.Message}");
    }
  }

  private static void DecodeAndPlay(byte[] encoded, int encodedLength) {
    short[] decodedBuffer = new short[FrameSize];
    try {
      int decodedLength = decoder.Decode(encoded.AsSpan(0, encodedLength), decodedBuffer.AsSpan(), FrameSize);

      // Add decoded audio to the wave provider
      var byteBuffer = new byte[decodedLength * sizeof(short)];
      Buffer.BlockCopy(decodedBuffer, 0, byteBuffer, 0, byteBuffer.Length);
      waveProvider.AddSamples(byteBuffer, 0, byteBuffer.Length);
    } catch (Exception ex) {
      Console.WriteLine($"Error during decoding: {ex.Message}");
    }
  }
}