create tools module

Author: swharden

src/Spectrogram/Tools.cs

@@ -0,0 +1,91 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Spectrogram
+{
+ public static class Tools
+ {
+ /// <summary>
+ /// Collapse the 2D spectrogram into a 1D array (mean power of each frequency)
+ /// </summary>
+ public static double[] SffMeanFFT(SFF sff, bool dB = false)
+ {
+ double[] mean = new double[sff.Ffts[0].Length];
+
+ foreach (var fft in sff.Ffts)
+ for (int y = 0; y < fft.Length; y++)
+ mean[y] += fft[y];
+
+ for (int i = 0; i < mean.Length; i++)
+ mean[i] /= sff.Ffts.Count();
+
+ if (dB)
+ for (int i = 0; i < mean.Length; i++)
+ mean[i] = 20 * Math.Log10(mean[i]);
+
+ if (mean[mean.Length - 1] <= 0)
+ mean[mean.Length - 1] = mean[mean.Length - 2];
+
+ return mean;
+ }
+
+ /// <summary>
+ /// Collapse the 2D spectrogram into a 1D array (mean power of each time point)
+ /// </summary>
+ public static double[] SffMeanPower(SFF sff, bool dB = false)
+ {
+ double[] power = new double[sff.Ffts.Count];
+
+ for (int i = 0; i < sff.Ffts.Count; i++)
+ power[i] = (double)sff.Ffts[i].Sum() / sff.Ffts[i].Length;
+
+ if (dB)
+ for (int i = 0; i < power.Length; i++)
+ power[i] = 20 * Math.Log10(power[i]);
+
+ return power;
+ }
+
+ public static double GetPeakFrequency(SFF sff, bool firstFftOnly = false)
+ {
+ double[] freqs = firstFftOnly ? sff.Ffts[0] : SffMeanFFT(sff, false);
+
+ int peakIndex = 0;
+ double peakPower = 0;
+ for (int i = 0; i < freqs.Length; i++)
+ {
+ if (freqs[i] > peakPower)
+ {
+ peakPower = freqs[i];
+ peakIndex = i;
+ }
+ }
+
+ double maxFreq = sff.SampleRate / 2;
+ double frac = peakIndex / (double)sff.FftHeight;
+
+ if (sff.MelBinCount > 0)
+ {
+ double maxMel = FftSharp.Transform.MelFromFreq(maxFreq);
+ return FftSharp.Transform.MelToFreq(frac * maxMel);
+ }
+ else
+ {
+ return frac * maxFreq;
+ }
+ }
+
+ public static int GetPianoKey(double frequencyHz)
+ {
+ double pianoKey = (39.86 * Math.Log10(frequencyHz / 440)) + 49;
+ return (int)Math.Round(pianoKey);
+ }
+
+ public static int GetMidiNote(int frequencyHz)
+ {
+ return GetPianoKey(frequencyHz) + 20;
+ }
+ }
+}