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.ImageHeight;
if (sff.MelBinCount > 0)
{
double maxMel = FftSharp.Transform.MelFromFreq(maxFreq);
return(FftSharp.Transform.MelToFreq(frac * maxMel));
}
else
{
return(frac * maxFreq);
}
}
/// <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);
}