用 C# 編寫網路電話 (3)：SoundPlayer 串流播放核心類別完整建構

私有欄位

#region 私有成員
private const int MaxLatencyMs = 300;
private const int NumberRecordNotifications = 4;
private readonly CircularBuffer circularBuffer;
private readonly int m_BufferBytes;
private readonly bool m_OwnsDevice;
private readonly int notifySize;
private readonly BufferPositionNotify[] positionNotify;
private bool isRunning;
private SecondaryBuffer m_Buffer;
private Device m_Device;
private int nextWriteOffset;
private AutoResetEvent notificationEvent;
private Notify notify;
private Thread notifyThread;
#endregion

多重建構子

#region 建構函數
public SoundPlayer(Control owner, WaveFormat format) : this(owner, null, format) { }

public SoundPlayer(Control owner, Device device, WaveFormat format)
{
    positionNotify = new BufferPositionNotify[5];
    notificationEvent = null; notify = null; notifyThread = null; notifySize = 0;
    m_Device = device;
    if (m_Device == null) { m_Device = new Device(); m_Device.SetCooperativeLevel(owner, CooperativeLevel.Normal); m_OwnsDevice = true; }

    // 通知大小 = 每秒位元組數 / 8 (經驗值)，下限 1024，對齊 BlockAlign
    notifySize = (1024 > (format.AverageBytesPerSecond / 8)) ? 1024 : (format.AverageBytesPerSecond / 8);
    notifySize -= notifySize % format.BlockAlign;
    m_BufferBytes = notifySize * 4; // 總緩衝區 = 4 通知區塊

    BufferDescription desc = new BufferDescription(format)
    {
        ControlVolume = true,
        ControlPositionNotify = true,
        CanGetCurrentPosition = true,
        Control3D = false,
        ControlEffects = false,
        ControlFrequency = true,
        ControlPan = true,
        GlobalFocus = true,
        BufferBytes = m_BufferBytes
    };
    m_Buffer = new SecondaryBuffer(desc, m_Device);
    circularBuffer = new CircularBuffer(m_BufferBytes * 10); // 10 倍緩衝
    InitNotifications();
    m_Buffer.Play(0, BufferPlayFlags.Looping);
}

public SoundPlayer(Control owner, int sr, short bps, short ch) : this(owner, null, DirectSoundManager.CreateWaveFormat(sr, bps, ch)) { }
public SoundPlayer(Control owner, Device device, int sr, short bps, short ch) : this(owner, device, DirectSoundManager.CreateWaveFormat(sr, bps, ch)) { }
#endregion

關鍵參數說明

• notifySize：每次通知處理的資料量，影響延遲與 CPU 平衡。
• m_BufferBytes：DirectSound 緩衝區總大小 (4 通知區塊)。
• circularBuffer：容量為 DirectSound 緩衝區 10 倍，吸收網路抖動。
• BufferPlayFlags.Looping：啟用循環播放，寫入指標自動回繞。