public static Matrix ShortTimeFourierTransform(Complex[] waveFragment, int hashSize, string fmt = "MIDI")
{
Console.Write($"\r\nBuilding a new MIDI model...\r\n");
var Model = new Matrix(hashSize);
double Xmin = double.MaxValue,
Xmax = double.MinValue,
cc = 0;
foreach (var fft in Complex.ShortTimeFourierTransform(waveFragment))
{
int t = Model.Count;
if (t >= Model.Length)
{
throw new OutOfMemoryException();
}
var vec = Model[t] = CreateMidiVector(fft);
for (var j = 0; j < vec.Axis.Length; j++)
{
Xmin = Math.Min(Xmin, vec.Axis[j].Re);
Xmax = Math.Max(Xmax, vec.Axis[j].Re);
}
cc++;
}
for (int t = 0; t < Model.Length; t++)
{
if (Model[t] == null)
{
continue;
}
var vec = Model[t];
for (var j = 0; j < vec.Axis.Length; j++)
{
vec.Axis[j].Re = (vec.Axis[j].Re - Xmin) /
(Xmax - Xmin);
if (vec.Axis[j].Re <= 0.007)
{
vec.Axis[j].Re = 0;
}
RunSpeachFrequencyFilters(
vec,
j);
}
}
var dBmax = int.MinValue;
for (int t = 0; t < Model.Length; t++)
{
if (Model[t] == null)
{
continue;
}
var vec = Model[t];
for (var j = 0; j < vec.Axis.Length; j++)
{
vec.Axis[j].Re = Math.Round(
(vec.Axis[j].Re - Xmin) / (Xmax - Xmin), 4);
if (vec.Axis[j].Re > 0 && vec.Axis[j].Re < 1E-4)
{
vec.Axis[j].Re = 0;
}
RunSpeachFrequencyFilters(
vec,
j);
if (vec.Axis[j].Re > 0)
{
var dB = Envelopes.AmplitudeTodB(vec.Axis[j].Re);
if (dB > dBmax)
{
dBmax = dB;
}
}
}
}
if (dBmax == int.MinValue)
{
dBmax = 0;
}
for (int t = 0; t < Model.Length; t++)
{
if (Model[t] == null)
{
continue;
}
var vec = Model[t];
for (var j = 0; j < vec.Axis.Length; j++)
{
if (vec.Axis[j].Re > 0)
{
var dB = Envelopes.AmplitudeTodB(vec.Axis[j].Re);
vec.Axis[j].Re =
Envelopes.dBToAmplitude(dB);
}
}
}
return(Model);
}
