ZXSpectrum48K/Desktop/BeeperDevice.cs

using NAudio.Wave;
using System;

namespace Desktop
{
    public class BeeperDevice
    {
        private WaveOutEvent _waveOut;
        private BufferedWaveProvider _buffer;
        private float _lastSample = 0.0f;
        private float _lastFiltered = 0.0f;

        public BeeperDevice()
        {
            _waveOut = new WaveOutEvent();
            _waveOut.DesiredLatency = 50; // 100ms latency to prevent buffer stutter

            // 44.1kHz, 1 channel (Mono), Float format
            _buffer = new BufferedWaveProvider(WaveFormat.CreateIeeeFloatWaveFormat(44100, 1));
            _buffer.BufferDuration = TimeSpan.FromSeconds(1);
            _buffer.DiscardOnBufferOverflow = true;

            _waveOut.Init(_buffer);
            _waveOut.Play();
        }

        public void AddSample(bool isHigh)
        {
            //Buffer overrun check and dump
            while (_buffer.BufferedDuration.TotalMilliseconds > 80)
            {
                Thread.Sleep(1);
            }

            // Convert the boolean into a physical sound wave (-0.2 or +0.2)
            float rawSample = isHigh ? 0.2f : -0.2f;
            float filteredSample = rawSample - _lastSample + 0.995f * _lastFiltered;
            _lastSample = rawSample;
            _lastFiltered = filteredSample;

            // Convert the float to bytes and drop it in the pipe
            byte[] bytes = BitConverter.GetBytes(filteredSample);
            _buffer.AddSamples(bytes, 0, 4);
        }
    }
}