Initial commit

AudioProcessing/SampleAggregator.cs

@@ -0,0 +1,61 @@
+using NAudio.Dsp;
+
+using System;
+
+namespace BeatDetector.AudioProcessing;
+
+internal class SampleAggregator
+{
+    // FFT
+    public event EventHandler<FftEventArgs>? FftCalculated;
+
+    public bool PerformFFT { get; set; }
+    private readonly Complex[] fftBuffer;
+    private readonly FftEventArgs fftArgs;
+    private int fftPos;
+    private readonly int fftLength;
+    private readonly int m;
+
+    public SampleAggregator(int fftLength)
+    {
+        if (!IsPowerOfTwo(fftLength))
+        {
+            throw new ArgumentException("FFT Length must be a power of two");
+        }
+        m = (int)Math.Log(fftLength, 2.0);
+        this.fftLength = fftLength;
+        fftBuffer = new Complex[fftLength];
+        fftArgs = new FftEventArgs(fftBuffer);
+    }
+
+    private bool IsPowerOfTwo(int x)
+    {
+        return (x & (x - 1)) == 0;
+    }
+
+    public void Add(float value)
+    {
+        if (PerformFFT && FftCalculated is not null)
+        {
+            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
+{
+    public FftEventArgs(Complex[] result)
+    {
+        Result = result;
+    }
+
+    public Complex[] Result { get; private set; }
+}