如何知道 SoundPlayer 何时完成播放声音

本文关键字:播放声音 何时完 SoundPlayer 何知道 | 更新日期: 2023-09-27 18:33:50

我使用以下代码在内存中动态创建频率音并异步播放音调:

public static void PlayTone(UInt16 frequency, int msDuration, UInt16 volume = 16383)
{
    using (var mStrm = new MemoryStream())
    {
        using (var writer = new BinaryWriter(mStrm))
        {
            const double tau = 2*Math.PI;
            const int formatChunkSize = 16;
            const int headerSize = 8;
            const short formatType = 1;
            const short tracks = 1;
            const int samplesPerSecond = 44100;
            const short bitsPerSample = 16;
            const short frameSize = (short) (tracks*((bitsPerSample + 7)/8));
            const int bytesPerSecond = samplesPerSecond*frameSize;
            const int waveSize = 4;
            var samples = (int) ((decimal) samplesPerSecond*msDuration/1000);
            int dataChunkSize = samples*frameSize;
            int fileSize = waveSize + headerSize + formatChunkSize + headerSize + dataChunkSize;
            writer.Write(0x46464952);
            writer.Write(fileSize);
            writer.Write(0x45564157);
            writer.Write(0x20746D66);
            writer.Write(formatChunkSize);
            writer.Write(formatType);
            writer.Write(tracks);
            writer.Write(samplesPerSecond);
            writer.Write(bytesPerSecond);
            writer.Write(frameSize);
            writer.Write(bitsPerSample);
            writer.Write(0x61746164);
            writer.Write(dataChunkSize);
            double theta = frequency*tau/samplesPerSecond;
            double amp = volume >> 2;
            for (int step = 0; step < samples; step++)
            {
                writer.Write((short) (amp*Math.Sin(theta*step)));
            }
            mStrm.Seek(0, SeekOrigin.Begin);
            using (var player = new System.Media.SoundPlayer(mStrm))
            {
                player.Play();
            }
        }
    }
}

代码工作正常。唯一的问题是,我怎么知道音调何时停止播放?在 SoundPlayer 类上似乎没有我可以订阅的 Done 事件。

如何知道 SoundPlayer 何时完成播放声音

你知道,如果你只想播放一个音调,那么有Console.Beep。当然,它不会在后台执行此操作,但是我在下面描述的技术可以很好地Console.Beep,并且它使您不必创建内存流才能播放音调。

无论如何,SoundPlayer都没有您想要的功能,但您可以模拟它。

首先,创建事件处理程序:

void SoundPlayed(object sender, EventArgs e)
{
    // do whatever here
}

更改 PlayTone 方法,使其采用回调函数参数:

public static void PlayTone(UInt16 frequency, int msDuration, UInt16 volume = 16383, EventHandler doneCallback = null)

然后,更改方法的结尾,使其调用PlaySync而不是Play,并在完成后调用doneCallback

using (var player = new System.Media.SoundPlayer(mStrm))
{
    player.PlaySync();
}    
if (doneCallback != null)
{
    // the callback is executed on the thread.
    doneCallback(this, new EventArgs());
}

然后,在线程或任务中执行它。例如:

var t = Task.Factory.StartNew(() => {PlayTone(100, 1000, 16383, SoundPlayed));

这样做的主要问题是事件通知发生在后台线程上。如果需要影响 UI,最好的办法可能是让事件处理程序与 UI 线程同步。因此,在 SoundPlayed 方法中,您将调用 Form.Invoke(对于 WinForms(或Dispatcher.Invoke (WPF( 来执行任何 UI 操作。