c# - 如何使用NAudio的BiQuadFilter？

Question

我使用 NAudio 录制麦克风的声音并将其保存在文件中。我用这个:

    public WaveFileWriter m_WaveFile = null;

    m_WaveFile = new WaveFileWriter(strFile, m_WaveSource.WaveFormat);  


    void DataAvailable(object sender, WaveInEventArgs e)
    {
        if (m_WaveFile != null)
        {
            m_WaveFile.Write(e.Buffer, 0, e.BytesRecorded);
        }
    }

现在我想对录制的声音应用高通滤波器和低通滤波器。到目前为止，我发现 BiQuadFilters 可以为我做到这一点，但到目前为止我不明白如何使用它。

我找到的例子都是这样的:

    var r = BiQuadFilter.LowPassFilter(44100, 1500, 1);
    var reader = new WaveFileReader(File.OpenRead(strFile));
    var filter = new MyWaveProvider(reader, r); // reader is the source for filter
    var waveOut = new WaveOut();
    waveOut.Init(filter); // filter is the source for waveOut
    waveOut.Play();

如果我理解正确，那么过滤器将应用于正在播放声音的类。但我不想播放声音，我希望将高通滤波器和对数通滤波器应用于文件并将结果保存在文件中。我怎样才能做到这一点？

编辑: 这是 MyWaveProvider 类:

class MyWaveProvider : ISampleProvider
{
    private ISampleProvider sourceProvider;
    private float cutOffFreq;
    private int channels;
    private BiQuadFilter[] filters;

    public MyWaveProvider (ISampleProvider sourceProvider, int cutOffFreq)
    {
        this.sourceProvider = sourceProvider;
        this.cutOffFreq = cutOffFreq;

        channels = sourceProvider.WaveFormat.Channels;
        filters = new BiQuadFilter[channels];
        CreateFilters();
    }

    private void CreateFilters()
    {
        for (int n = 0; n < channels; n++)
            if (filters[n] == null)
                filters[n] = BiQuadFilter.LowPassFilter(44100, cutOffFreq, 1);
            else
                filters[n].SetLowPassFilter(44100, cutOffFreq, 1);
    }

    public WaveFormat WaveFormat { get { return sourceProvider.WaveFormat; } }

    public int Read(float[] buffer, int offset, int count)
    {
        int samplesRead = sourceProvider.Read(buffer, offset, count);

        for (int i = 0; i < samplesRead; i++)
            buffer[offset + i] = filters[(i % channels)].Transform(buffer[offset + i]);

        return samplesRead;
    }
}

Answer 1

以下代码应该满足您想要执行的操作:

using (var reader = new WaveFileReader(File.OpenRead(strFile)))
{
    var r = BiQuadFilter.LowPassFilter(44100, 1500, 1);

    // reader is the source for filter
    using (var filter =  new MyWaveProvider(reader, r))
    {
        WaveFileWriter.CreateWaveFile("filteroutput.wav", filter);
    } 
}