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https://git.rwth-aachen.de/acs/public/villas/node/
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97 lines
2.5 KiB
C++
97 lines
2.5 KiB
C++
/** A sliding/moving window.
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*
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* @file
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* @author Steffen Vogel <svogel2@eonerc.rwth-aachen.de>
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* @copyright 2014-2022, Institute for Automation of Complex Power Systems, EONERC
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* @license GNU General Public License (version 3)
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*
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* VILLAScommon
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*********************************************************************************/
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#pragma once
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#include <cmath>
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#include <vector>
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#include <villas/dsp/window.hpp>
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namespace villas {
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namespace dsp {
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template<typename T, double a0 = 1.0, double a1 = 0.0, double a2 = 0.0, double a3 = 0.0, double a4 = 0.0>
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class CosineWindow : public Window<T> {
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public:
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using size_type = typename Window<T>::size_type;
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protected:
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std::vector<T> coefficients;
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T correctionFactor;
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virtual
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T filter(T in, size_type i) const
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{
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return in * coefficients[i];
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}
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public:
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CosineWindow(size_type len, T i = 0) :
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Window<T>(len, i),
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coefficients(len),
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correctionFactor(0)
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{
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for (unsigned i = 0; i < len; i++) {
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coefficients[i] = a0
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- a1 * cos(2 * M_PI * i / len)
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+ a2 * cos(4 * M_PI * i / len)
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- a3 * cos(6 * M_PI * i / len)
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+ a4 * cos(8 * M_PI * i / len);
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correctionFactor += coefficients[i];
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}
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correctionFactor /= len;
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}
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virtual
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T getCorrectionFactor() const
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{
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return correctionFactor;
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}
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};
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// From: https://en.wikipedia.org/wiki/Window_function#Cosine-sum_windows
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template<typename T>
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using HannWindow = CosineWindow<T, 0.5, 0.5>;
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template<typename T>
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using HammingWindow = CosineWindow<T, 25./46, 1 - 25./46>;
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template<typename T>
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using FlattopWindow = CosineWindow<T, 0.21557895, 0.41663158, 0.277263158, 0.083578947, 0.006947368>; // based on MATLAB coeffs
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template<typename T>
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using NuttallWindow = CosineWindow<T, 0.355768, 0.487396, 0.144232, 0.012604>;
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template<typename T>
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using BlackmanWindow = CosineWindow<T, 0.3635819, 0.4891775, 0.1365995, 0.0106411>;
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} /* namespace dsp */
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} /* namespace villas */
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