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sdrangel/include-gpl/dsp/fftwindow.h

83 lines
2.9 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 //
// //
// 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 "util/export.h"
class SDRANGELOVE_API FFTWindow {
public:
enum Function {
Bartlett,
BlackmanHarris,
Flattop,
Hamming,
Hanning,
Rectangle
};
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(const Complex* in, Complex* out);
private:
std::vector<float> m_window;
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;
}
};
#endif // INCLUDE_FFTWINDOWS_H