mirror of
https://github.com/f4exb/sdrangel.git
synced 2024-11-18 14:21:49 -05:00
126 lines
4.1 KiB
C++
126 lines
4.1 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
|
|
// Copyright (C) 2012 maintech GmbH, Otto-Hahn-Str. 15, 97204 Hoechberg, Germany //
|
|
// written by Christian Daniel //
|
|
// //
|
|
// This program is free software; you can redistribute it and/or modify //
|
|
// it under the terms of the GNU General Public License as published by //
|
|
// the Free Software Foundation as version 3 of the License, or //
|
|
// (at your option) any later version. //
|
|
// //
|
|
// This program is distributed in the hope that it will be useful, //
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of //
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
|
|
// GNU General Public License V3 for more details. //
|
|
// //
|
|
// You should have received a copy of the GNU General Public License //
|
|
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
|
|
///////////////////////////////////////////////////////////////////////////////////
|
|
|
|
#ifndef INCLUDE_FFTWINDOW_H
|
|
#define INCLUDE_FFTWINDOW_H
|
|
|
|
#include <vector>
|
|
#define _USE_MATH_DEFINES
|
|
#include <math.h>
|
|
#include "dsp/dsptypes.h"
|
|
#include "export.h"
|
|
|
|
#undef M_PI
|
|
#define M_PI 3.14159265358979323846
|
|
|
|
class SDRBASE_API FFTWindow {
|
|
public:
|
|
enum Function {
|
|
Bartlett,
|
|
BlackmanHarris,
|
|
Flattop,
|
|
Hamming,
|
|
Hanning,
|
|
Rectangle,
|
|
Kaiser
|
|
};
|
|
|
|
FFTWindow();
|
|
|
|
void create(Function function, int n);
|
|
void apply(const std::vector<Real>& in, std::vector<Real>* out);
|
|
void apply(const std::vector<Complex>& in, std::vector<Complex>* out);
|
|
void apply(std::vector<Complex>& in);
|
|
void apply(const Complex* in, Complex* out);
|
|
void apply(Complex* in);
|
|
void setKaiserAlpha(Real alpha); //!< set the Kaiser window alpha factor (default 2.15)
|
|
void setKaiserBeta(Real beta); //!< set the Kaiser window beta factor = pi * alpha
|
|
|
|
private:
|
|
std::vector<float> m_window;
|
|
Real m_kaiserAlpha; //!< alpha factor for Kaiser window
|
|
Real m_kaiserI0Alpha; //!< zeroethOrderBessel of alpha above
|
|
|
|
static inline Real flatTop(Real n, Real i)
|
|
{
|
|
// correction ?
|
|
return 1.0 - 1.93 * cos((2.0 * M_PI * i) / n) + 1.29 * cos((4.0 * M_PI * i) / n) - 0.388 * cos((6.0 * M_PI * i) / n) + 0.03222 * cos((8.0 * M_PI * i) / n);
|
|
}
|
|
|
|
static inline Real bartlett(Real n, Real i)
|
|
{
|
|
// amplitude correction = 2.0
|
|
return (2.0 / (n - 1.0)) * ( (n - 1.0) / 2.0 - fabs(i - (n - 1.0) / 2.0)) * 2.0;
|
|
}
|
|
|
|
static inline Real blackmanHarris(Real n, Real i)
|
|
{
|
|
// amplitude correction = 2.79
|
|
return (0.35875 - 0.48829 * cos((2.0 * M_PI * i) / n) + 0.14128 * cos((4.0 * M_PI * i) / n) - 0.01168 * cos((6.0 * M_PI * i) / n)) * 2.79;
|
|
}
|
|
|
|
static inline Real hamming(Real n, Real i)
|
|
{
|
|
// amplitude correction = 1.855, energy correction = 1.586
|
|
return (0.54 - 0.46 * cos((2.0 * M_PI * i) / n)) * 1.855;
|
|
}
|
|
|
|
static inline Real hanning(Real n, Real i)
|
|
{
|
|
// amplitude correction = 2.0, energy correction = 1.633
|
|
return (0.5 - 0.5 * cos((2.0 * M_PI * i) / n)) * 2.0;
|
|
}
|
|
|
|
static inline Real rectangle(Real, Real)
|
|
{
|
|
return 1.0;
|
|
}
|
|
|
|
// https://raw.githubusercontent.com/johnglover/simpl/master/src/loris/KaiserWindow.C
|
|
inline Real kaiser(Real n, Real i)
|
|
{
|
|
Real K = ((2.0*i) / n) - 1.0;
|
|
Real arg = sqrt(1.0 - (K*K));
|
|
return zeroethOrderBessel(m_kaiserAlpha*arg) / m_kaiserI0Alpha;
|
|
}
|
|
|
|
static inline Real zeroethOrderBessel( Real x )
|
|
{
|
|
const Real eps = 0.000001;
|
|
|
|
// initialize the series term for m=0 and the result
|
|
Real besselValue = 0;
|
|
Real term = 1;
|
|
Real m = 0;
|
|
|
|
// accumulate terms as long as they are significant
|
|
while(term > eps * besselValue)
|
|
{
|
|
besselValue += term;
|
|
|
|
// update the term
|
|
++m;
|
|
term *= (x*x) / (4*m*m);
|
|
}
|
|
|
|
return besselValue;
|
|
}
|
|
};
|
|
|
|
#endif // INCLUDE_FFTWINDOWS_H
|