private static Bin[] PitchShiftBins(float pitchShift, Bin[] bins)
{
return bins.Select(x => new Bin(x.Frequency*pitchShift, x.Magnitude)).ToArray();
//var shiftedBins = new Bin[bins.Length];
//for (var i = 0; i < shiftedBins.Length; i++)
//{
// shiftedBins[i] = new Bin(0f, 0f);
//}
//for (var i = 0; i < bins.Length; i++)
//{
// var index = (int)(i * pitchShift);
// if (index < bins.Length)
// {
// shiftedBins[i].Magnitude = bins[i].Magnitude;
// shiftedBins[i].Frequency = bins[i].Frequency * pitchShift;
// }
//}
//return shiftedBins;
}
private static Complex[] SynthesizeFft(float sampleRate, Bin[] bins)
{
const float expectedPhaseDifference = (float) (2*Math.PI);
var fftBuffer = new Complex[bins.Length * 2];
var frequencyPerBin = (sampleRate / (float)fftBuffer.Length);
var phase = 0f;
for (var i = 0; i < bins.Length; i++)
{
var tmp = bins[i].Frequency;
tmp -= i*frequencyPerBin;
tmp /= frequencyPerBin;
tmp *= (float) (2*Math.PI);
tmp += i*expectedPhaseDifference;
phase += tmp;
var real = (float)(bins[i].Magnitude * Math.Cos(phase));
var imaginary = (float)(bins[i].Magnitude * Math.Sin(phase));
fftBuffer[i] = new Complex(real, imaginary);
}
for (var i = bins.Length; i < fftBuffer.Length; i++)
{
fftBuffer[i] = new Complex(0f, 0f);
}
return fftBuffer;
}
private static Bin[] CalculateBins(int sampleRate, IList<Complex> fftBuffer)
{
const float expectedPhaseDifference = (float) (2*Math.PI);
var frequencyPerBin = sampleRate / (float) fftBuffer.Count;
var lastPhase = 0f;
var bins = new Bin[fftBuffer.Count / 2];
for (var i = 0; i < bins.Length; i++)
{
var magnitude = CalculateMagnitude(fftBuffer[i]);
var phase = CalculatePhase(fftBuffer[i]);
var tmp = phase - lastPhase;
lastPhase = phase;
tmp -= i*expectedPhaseDifference;
var qpd = (long) (tmp/Math.PI);
if (qpd >= 0) qpd += qpd & 1;
else qpd -= qpd & 1;
tmp -= (float) (Math.PI*qpd);
tmp /= expectedPhaseDifference;
tmp = i*frequencyPerBin + tmp*frequencyPerBin;
bins[i] = new Bin(tmp, magnitude);
}
return bins;
}
