SampleAggregator.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using NAudio.Dsp; // The Complex and FFT are here!
using System.Diagnostics;

namespace Visualizer
{
    class SampleAggregator
    {
        // FFT
        public event EventHandler<FftEventArgs> FftCalculated;
        public bool PerformFFT { get; set; }

        // This Complex is NAudio's own! 
        private Complex[] fftBuffer;
        private FftEventArgs fftArgs;
        private int fftPos;
        private int fftLength;
        private int m;

        public SampleAggregator(int fftLength)
        {
            if (!IsPowerOfTwo(fftLength))
            {
                throw new ArgumentException("FFT Length must be a power of two");
            }
            this.m = (int)Math.Log(fftLength, 2.0);
            this.fftLength = fftLength;
            this.fftBuffer = new Complex[fftLength];
            this.fftArgs = new FftEventArgs(fftBuffer);
        }

        bool IsPowerOfTwo(int x)
        {
            return (x & (x - 1)) == 0;
        }

        public void Add(float value)
        {
            if (PerformFFT && FftCalculated != null)
            {
                // Remember the window function! There are many others as well.
                fftBuffer[fftPos].X = (float)(value * FastFourierTransform.HammingWindow(fftPos, fftLength));
                fftBuffer[fftPos].Y = 0; // This is always zero with audio.
                fftPos++;
                if (fftPos >= fftLength)
                {
                    fftPos = 0;
                    FastFourierTransform.FFT(true, m, fftBuffer);
                    FftCalculated(this, fftArgs);
                }
            }
        }
    }

    public class FftEventArgs : EventArgs
    {
        [DebuggerStepThrough]
        public FftEventArgs(Complex[] result)
        {
            this.Result = result;
        }
        public Complex[] Result { get; private set; }
    }
}