/// <summary>
/// Returns an [N, 2] matrix with bin ID in column 1 and lower Herz bound in column 2 but on Mel scale
/// </summary>
public int[,] GetMelBinBounds()
{
double maxMel = (int)MFCCStuff.Mel(this.Nyquist);
int melBinCount = this.FinalBinCount;
double melPerBin = maxMel / melBinCount;
var binBounds = new int[this.FinalBinCount, 2];
for (int i = 0; i < melBinCount; i++)
{
binBounds[i, 0] = i;
double mel = i * melPerBin;
binBounds[i, 1] = (int)MFCCStuff.InverseMel(mel);
}
return(binBounds);
}
/// <summary>
/// THIS METHOD NEEDS TO BE DEBUGGED. HAS NOT BEEN USED IN YEARS!
/// Use this method to generate grid lines for mel scale image
/// Currently this method is only called from BaseSonogram.GetImage() when bool doMelScale = true;
/// Frequencyscale.Draw1kHzLines(Image<Rgb24> bmp, bool doMelScale, int nyquist, double freqBinWidth)
/// </summary>
public static int[,] GetMelGridLineLocations(int gridIntervalInHertz, int nyquistFreq, int melBinCount)
{
double maxMel = (int)MFCCStuff.Mel(nyquistFreq);
double melPerBin = maxMel / melBinCount;
int gridCount = nyquistFreq / gridIntervalInHertz;
var gridLines = new int[gridCount, 2];
for (int f = 1; f <= gridCount; f++)
{
int herz = f * 1000;
int melValue = (int)MFCCStuff.Mel(herz);
int melBinId = (int)(melValue / melPerBin);
if (melBinId < melBinCount)
{
gridLines[f - 1, 0] = melBinId;
gridLines[f - 1, 1] = herz;
}
}
return(gridLines);
}
