/// <summary>
/// Constructor with necessary parameters
/// </summary>
/// <param name="windowSize">Size of window</param>
/// <param name="hopSize">Hop (overlap) size</param>
/// <param name="window">Type of the window function to apply</param>
/// <param name="fftSize">Size of FFT</param>
public Stft(int windowSize = 1024, int hopSize = 256, WindowTypes window = WindowTypes.Hann, int fftSize = 0)
{
_fftSize = fftSize >= windowSize ? fftSize : MathUtils.NextPowerOfTwo(windowSize);
_fft = new RealFft(_fftSize);
_hopSize = hopSize;
_windowSize = windowSize;
_window = window;
_windowSamples = Window.OfType(_window, _windowSize);
}
/// <summary>
/// Constructs Mellin transformer.
/// Parameter <paramref name="size"/> must be a power of 2.
/// </summary>
/// <param name="inputSize">Expected size of input data</param>
/// <param name="size">Size of output data</param>
/// <param name="beta">Beta coefficient (0.5 by default, which corresponds to Scale transform)</param>
public MellinTransform(int inputSize, int size, double beta = 0.5)
{
Guard.AgainstNotPowerOfTwo(size, "Output size of Mellin Transform");
InputSize = inputSize;
Size = size;
_beta = beta;
_fft = new RealFft(size);
_linScale = Enumerable.Range(0, inputSize)
.Select(i => (float)i / inputSize)
.ToArray();
_expScale = new float[size];
var cur = -(float)Math.Log(size);
var step = -cur / size;
for (var i = 0; i < _expScale.Length; i++, cur += step)
{
_expScale[i] = (float)Math.Exp(cur);
}
}