Question

我想开发一个与您的耳鸣频率相匹配的应用：播放频率，用户通过按加号或减号按钮来降低或增加频率。（参见代码的一部分，基于stackoverflow thx的一些编码： - ））

   public static short[] BufferSamples = new short[44100 * 1 * 2];  

    private SourceVoice sourceVoice;
    private AudioBuffer buffer;
    private int Tfreq;

    public MatchTinn()
    {
        InitializeComponent();
        Loaded += MatchTinn_Loaded;
        TFreq = 5000;
    }

    private void MatchTinn_Loaded(object sender, RoutedEventArgs e)
    {
        var dataStream = DataStream.Create(BufferSamples, true, true);

        buffer = new AudioBuffer
        {
            LoopCount = AudioBuffer.LoopInfinite,
            Stream = dataStream,
            AudioBytes = (int)dataStream.Length,
            Flags = BufferFlags.EndOfStream
        };

        FillBuffer(BufferSamples, 44100, Tfreq);

        var waveFormat = new WaveFormat();

        XAudio2 xaudio = new XAudio2();
        MasteringVoice masteringVoice = new MasteringVoice(xaudio);

        sourceVoice = new SourceVoice(xaudio, waveFormat, true);

        // Submit the buffer
        sourceVoice.SubmitSourceBuffer(buffer, null);
    }

    private void FillBuffer(short[] buffer, int sampleRate, int frequency)
    {
        if (sourceVoice != null)
        {
            sourceVoice.FlushSourceBuffers();
        }

        double totalTime = 0;

        for (int i = 0; i < buffer.Length - 1; i += 2)
        {
            double time = (double)totalTime / (double)sampleRate;

            short currentSample = (short)(Math.Sin(2 * Math.PI * frequency * time) * (double)short.MaxValue);

            buffer[i] = currentSample;
            buffer[i + 1] = currentSample;

            totalTime++;
        }


    private void m1_OnTap(object sender, GestureEventArgs e)
    {
        Tfreq = Tfreq - 1;

        if (Tfreq < 0)
        {
            Tfreq = 0;
        }

        FillBuffer(BufferSamples, 44100, Tfreq);

    }

    private void p1_OnTap(object sender, GestureEventArgs e)
    {
        Tfreq = Tfreq + 1;

        if (Tfreq > 16000)
        {
            Tfreq = 16000;
        }

        FillBuffer(BufferSamples, 44100, Tfreq);
    }

播放频率很好，但是当用户按下按钮时，您可以在频率更新时点击声音。你知道是什么让声音和我如何摆脱它吗？谢谢。

Answer 1

当您更改频率时，您会导致波形中出现点击不连续。您应该跟踪正弦计算的相位（例如，从0到2 * pi的值），而不是根据绝对时间进行信号计算，并计算出需要向相位添加多少（减去2 * pi）每次超过2 * pi时播放特定频率的下一个样本。这样，当您更改频率时，您作为Math.Sin参数提供的阶段不会突然发生变化而导致点击。

Answer 2

扩展@spender给出的答案（我需要50个代表来为他的答案添加评论），我在naudio遇到了类似的问题。我能够通过添加两个bool值来解决问题，这两个值监视正弦值的当前符号和前一个正弦值的符号。如果前一个正弦为负且当前正弦为正，我们知道我们可以安全地调整正弦波的频率。

            double sine = amplitude * Math.Sin(Math.PI * 2 * frequency * time);
            isPreviousSineWaveValPositive = isSineWaveValPositive;
            if (sine < 0)
            {
                isSineWaveValPositive = false;
            }
            else
            {
                isSineWaveValPositive = true;
            }

            // When the time is right, change the frequency
            if ( false == isPreviousSineWaveValPositive && true == isSineWaveValPositive )
            {
                time = 0.0;
                frequency = newFrequency;
            }

Answer 3

以下是一个如何摆脱点击的示例。您应该跟踪当前相位并计算相位在所需频率上的变化程度，而不是使用时间。此_currentPhase也必须是持久的，因此它将具有先前的值。（在方法中声明它会导致点击（在大多数频率上）

private double _currentPhase = 0;

private void FillBuffer(short[] buffer, int sampleRate, int frequency)
{
    if (sourceVoice != null)
    {
        sourceVoice.FlushSourceBuffers();
    }

    var phaseStep = ((Math.PI * 2) / (double)sampleRate) * frequency;

    for (int i = 0; i < buffer.Length - 1; i += 2)
    {
        _currentPhase += phaseStep;

        short currentSample = (short)(Math.Sin(_currentPhase) * (double)short.MaxValue);

        buffer[i] = currentSample;
        buffer[i + 1] = currentSample;
    }
}

XAudio2 - 更改频率点击声时播放生成的正弦值

3 个答案: