AudioOutputService.cs

using NAudio.CoreAudioApi;
using NAudio.Wave;

namespace MultiAudioRouter.Core;

/// <summary>
/// 指定された IWaveProvider を WASAPI 共有モードで再生する。
/// </summary>
public sealed class AudioOutputService : IDisposable
{
    private WasapiOut? _output;
    private MMDevice? _ownedDevice;
    private bool _disposed;

    public WaveFormat? OutputWaveFormat => _output?.OutputWaveFormat;

    public PlaybackState PlaybackState => _output?.PlaybackState ?? PlaybackState.Stopped;

    /// <summary>出力音量 (0.0-1.0)。WasapiOut.Volume を経由してデバイス側ボリュームを操作。</summary>
    public float Volume
    {
        get => _output?.Volume ?? 1f;
        set { if (_output is not null) _output.Volume = Math.Clamp(value, 0f, 1f); }
    }

    public event EventHandler<StoppedEventArgs>? PlaybackStopped;

    /// <summary>
    /// WASAPI 共有モードで再生を開始する。共有モードではオーディオエンジン側が
    /// フォーマット変換を担うので useEventSync=false の方が堅い (event sync は
    /// デバイスのミックスフォーマット完全一致を要求しがち)。
    /// </summary>
    public void Start(MMDevice device, IWaveProvider source, int latencyMs = 100, bool useEventSync = false)
    {
        ObjectDisposedException.ThrowIf(_disposed, this);

        if (_output is not null)
            throw new InvalidOperationException("既に再生中です。");

        _ownedDevice = device;
        _output = new WasapiOut(device, AudioClientShareMode.Shared, useEventSync, latencyMs);
        _output.PlaybackStopped += OnPlaybackStopped;
        _output.Init(source);
        _output.Play();
    }

    public void Stop() => _output?.Stop();

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

    public void Dispose()
    {
        if (_disposed) return;
        _disposed = true;
        if (_output is not null)
        {
            try { _output.Stop(); } catch { /* ignore */ }
            _output.PlaybackStopped -= OnPlaybackStopped;
            _output.Dispose();
            _output = null;
        }
        _ownedDevice?.Dispose();
        _ownedDevice = null;
    }
}