/// <summary>
/// Standard deviation in dB of all samples in buffer
/// </summary>
/// <returns></returns>
public ISample StdDevDb()
{
if (_stddevdB != null)
{
return(_stddevdB);
}
ISample meandb = MeanDb();
ushort nc = _input.NumChannels;
_stddevdB = new Sample(nc);
for (int n = 0; n < _length; n++)
{
if (_data[n] != null)
{
for (ushort c = 0; c < nc; c++)
{
double devdb = (MathUtil.dB(_data[n][c]) - meandb[c]);
_stddevdB[c] += (devdb * devdb);
}
}
}
for (ushort c = 0; c < nc; c++)
{
_stddevdB[c] = Math.Sqrt(_stddevdB[c] / _length);
}
return(_stddevdB);
}
/// <summary>
/// "Average" - arithmetical mean of dB value of all samples in buffer
/// </summary>
/// <returns></returns>
public ISample MeanDb()
{
if (_meandB != null)
{
return(_meandB);
}
ushort nc = _input.NumChannels;
_meandB = new Sample(nc);
for (int n = 0; n < _length; n++)
{
if (_data[n] != null)
{
for (ushort c = 0; c < nc; c++)
{
_meandB[c] += MathUtil.dB(_data[n][c]);
}
}
}
for (ushort c = 0; c < nc; c++)
{
_meandB[c] /= _length;
}
return(_meandB);
}
/// <summary>
/// Return a list of freq/gain, only including inflection points (where the curve is flat).
/// </summary>
/// <param name="data"></param>
/// <param name="sr"></param>
/// <returns></returns>
public static FilterProfile inflections(double[] data, uint sr)
{
// Differentiate
double bins = data.Length + 1;
double[] diff = new double[data.Length];
double n = data[0];
for (int j = 0; j < data.Length; j++)
{
double d = data[j];
diff[j] = d - n;
n = d;
}
// Look for zero-crossings of the first derivative of data[]
// (always include [0] and [end])
FilterProfile pts = new FilterProfile();
int bin;
double pt = 0.1;
int last = -1;
double freq;
double lastfreq = -1;
// Always start with points for zero and 10 Hz
pts.Add(new FreqGain(0, MathUtil.dB(data[0])));
freq = 10;
bin = (int)f2bin(freq, sr, bins);
pts.Add(new FreqGain(freq, MathUtil.dB(data[bin])));
pt = diff[bin];
for (int j = bin + 1; j < data.Length; j++)
{
if ((pt > 0 && diff[j] <= 0) || (pt < 0 && diff[j] >= 0))
{
freq = bin2f(j, sr, bins);
pts.Add(new FreqGain(freq, MathUtil.dB(data[j])));
last = j;
lastfreq = freq;
}
pt = diff[j];
}
// Fill in the last few target samples
if (lastfreq < (sr / 2) - 2050)
{
freq = (sr / 2) - 2050;
bin = (int)f2bin(freq, sr, bins);
pts.Add(new FreqGain(freq, MathUtil.dB(data[bin])));
}
if (lastfreq < (sr / 2) - 1550)
{
freq = (sr / 2) - 1550;
bin = (int)f2bin(freq, sr, bins);
pts.Add(new FreqGain(freq, MathUtil.dB(data[bin])));
}
if (lastfreq < sr / 2)
{
freq = sr / 2;
pts.Add(new FreqGain(freq, MathUtil.dB(data[data.Length - 1])));
}
return(pts);
}