sdrangel/sdrbase/dsp/fftwindow.h

147 wiersze
4.9 KiB
C++

///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2012 maintech GmbH, Otto-Hahn-Str. 15, 97204 Hoechberg, Germany //
// written by Christian Daniel //
// Copyright (C) 2015-2020, 2022 Edouard Griffiths, F4EXB <f4exb06@gmail.com> //
// Copyright (C) 2020 Kacper Michajłow <kasper93@gmail.com> //
// //
// 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>
#include <cmath>
#include "dsp/dsptypes.h"
#include "export.h"
class SDRBASE_API FFTWindow {
public:
enum Function {
Bartlett,
BlackmanHarris,
Flattop,
Hamming,
Hanning,
Rectangle,
Kaiser,
Blackman,
BlackmanHarris7
};
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) // 4 term Blackman-Harris
{
// 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 blackmanHarris7(Real n, Real i) // 7 term Blackman-Harris
{
return (0.27105
- 0.43330 * cos((2.0 * M_PI * i) / n)
+ 0.21812 * cos((4.0 * M_PI * i) / n)
- 0.065925 * cos((6.0 * M_PI * i) / n)
+ 0.010812 * cos((8.0 * M_PI * i) / n)
- 0.00077658 * cos((10.0 * M_PI * i) / n)
+ 0.000013887 * cos((12.0 * M_PI * i) / n)) * 3.72;
}
static inline Real blackman(Real n, Real i) // 3 term Blackman
{
return (0.42438
- 0.49734 * cos(2.0 * M_PI * i / n)
+ 0.078279 * cos(4.0 * M_PI * i / n)) * 2.37;
}
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