2023-11-05 10:33:27 +01:00
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///////////////////////////////////////////////////////////////////////////////////
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2023-11-19 06:43:20 +01:00
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// Copyright (C) 2023 Edouard Griffiths, F4EXB <f4exb06@gmail.com> //
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2023-11-05 10:33:27 +01:00
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// //
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// Helper class for noise reduction //
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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 as version 3 of the License, or //
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// (at your option) 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 V3 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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#ifndef _FFTNR_H
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#define _FFTNR_H
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#include <complex>
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#include "export.h"
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class SDRBASE_API FFTNoiseReduction {
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public:
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typedef std::complex<float> cmplx;
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enum Scheme {
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SchemeAverage,
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SchemeAvgStdDev,
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SchemePeaks
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};
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FFTNoiseReduction(int len);
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~FFTNoiseReduction();
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void init(); //!< call befor start of initial FFT scan
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void push(cmplx data, int index); //!< Push FFT bin during initial FFT scan
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void calc(); //!< calculate after initial FFT scan
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bool cut(int index); //!< true if bin is to be zeroed else false (during second FFT scan)
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void setAlpha(float alpha) { m_expFilter.setAlpha(alpha); }
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void setScheme(Scheme scheme);
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float m_aboveAvgFactor; //!< above average factor
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float m_sigmaFactor; //!< sigma multiplicator for average + std deviation
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int m_nbPeaks; //!< number of peaks (peaks scheme)
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private:
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class ExponentialFilter {
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public:
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ExponentialFilter();
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float push(float newValue);
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void reset();
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void setAlpha(float alpha);
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private:
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bool m_init;
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float m_alpha;
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float m_prev;
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};
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Scheme m_scheme;
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int m_flen; //!< FFT length
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float *m_mags; //!< magnitudes (PSD)
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float *m_tmp; //!< temporary buffer
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float m_magAvg; //!< average of magnitudes
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float m_magThr; //!< magnitude threshold (peaks scheme)
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ExponentialFilter m_expFilter; //!< exponential filter for parameter smoothing
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};
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#endif
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