LoopbackCaptureService.cs

using NAudio.CoreAudioApi;
using NAudio.Wave;

namespace MultiAudioRouter.Core;

/// <summary>
/// システム全体の出力音声を WASAPI ループバックでキャプチャする。
/// </summary>
public sealed class LoopbackCaptureService : ICaptureSource
{
    private WasapiLoopbackCapture? _capture;
    private bool _disposed;
    private MMDevice? _device;

    public WaveFormat? WaveFormat => _capture?.WaveFormat;

    public event EventHandler<WaveInEventArgs>? DataAvailable;
    public event EventHandler<StoppedEventArgs>? RecordingStopped;

    public LoopbackCaptureService() { }
    public LoopbackCaptureService(MMDevice? renderDevice) { _device = renderDevice; }

    public void Start() => Start(_device);

    public void Start(MMDevice? renderDevice)
    {
        ObjectDisposedException.ThrowIf(_disposed, this);

        if (_capture is not null)
            throw new InvalidOperationException("既にキャプチャ中です。");

        _capture = renderDevice is null
            ? new WasapiLoopbackCapture()
            : new WasapiLoopbackCapture(renderDevice);

        _capture.DataAvailable += OnDataAvailable;
        _capture.RecordingStopped += OnRecordingStopped;
        _capture.StartRecording();
    }

    public void Stop()
    {
        _capture?.StopRecording();
    }

    private void OnDataAvailable(object? sender, WaveInEventArgs e) =>
        DataAvailable?.Invoke(this, e);

    private void OnRecordingStopped(object? sender, StoppedEventArgs e) =>
        RecordingStopped?.Invoke(this, e);

    public void Dispose()
    {
        if (_disposed) return;
        _disposed = true;
        if (_capture is not null)
        {
            try { _capture.StopRecording(); } catch { /* 二重停止対策 */ }
            _capture.DataAvailable -= OnDataAvailable;
            _capture.RecordingStopped -= OnRecordingStopped;
            _capture.Dispose();
            _capture = null;
        }
    }
}