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127 lines
4.0 KiB
C++
127 lines
4.0 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2020 kasper93 //
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// written by Kacper Michajłow and Edouard Griffiths //
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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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#pragma once
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#include <cmath>
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#include "dsp/dsptypes.h"
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#include "dsp/misc.h"
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#include "export.h"
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namespace FirFilterGenerators
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{
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SDRBASE_API void generateLowPassFilter(int nTaps, double sampleRate, double cutoff, std::vector<Real> &taps);
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};
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template <class Type>
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class FirFilter
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{
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public:
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Type filter(Type sample)
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{
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Type acc = 0;
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unsigned int n_samples = m_samples.size();
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unsigned int n_taps = m_taps.size() - 1;
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unsigned int a = m_ptr;
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unsigned int b = a == n_samples - 1 ? 0 : a + 1;
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m_samples[m_ptr] = sample;
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for (unsigned int i = 0; i < n_taps; ++i)
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{
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acc += (m_samples[a] + m_samples[b]) * m_taps[i];
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a = (a == 0) ? n_samples - 1 : a - 1;
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b = (b == n_samples - 1) ? 0 : b + 1;
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}
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acc += m_samples[a] * m_taps[n_taps];
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m_ptr = (m_ptr == n_samples - 1) ? 0 : m_ptr + 1;
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return acc;
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}
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protected:
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void init(int nTaps)
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{
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m_ptr = 0;
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m_samples.resize(nTaps);
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for (int i = 0; i < nTaps; i++) {
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m_samples[i] = 0;
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}
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}
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protected:
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std::vector<Real> m_taps;
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std::vector<Type> m_samples;
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size_t m_ptr;
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};
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template <class T>
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struct Lowpass : public FirFilter<T>
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{
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public:
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void create(int nTaps, double sampleRate, double cutoff)
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{
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this->init(nTaps);
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FirFilterGenerators::generateLowPassFilter(nTaps, sampleRate, cutoff, this->m_taps);
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}
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};
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template <class T>
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struct Bandpass : public FirFilter<T>
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{
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void create(int nTaps, double sampleRate, double lowCutoff, double highCutoff)
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{
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this->init(nTaps);
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FirFilterGenerators::generateLowPassFilter(nTaps, sampleRate, highCutoff, this->m_taps);
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std::vector<Real> highPass;
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FirFilterGenerators::generateLowPassFilter(nTaps, sampleRate, lowCutoff, highPass);
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for (size_t i = 0; i < highPass.size(); ++i) {
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highPass[i] = -highPass[i];
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}
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highPass[highPass.size() - 1] += 1;
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for (size_t i = 0; i < this->m_taps.size(); ++i) {
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this->m_taps[i] = -(this->m_taps[i] + highPass[i]);
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}
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this->m_taps[this->m_taps.size() - 1] += 1;
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}
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};
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template <class T>
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struct Highpass : public FirFilter<T>
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{
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void create(int nTaps, double sampleRate, double cutoff)
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{
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this->init(nTaps);
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FirFilterGenerators::generateLowPassFilter(nTaps, sampleRate, cutoff, this->m_taps);
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for (size_t i = 0; i < this->m_taps.size(); ++i) {
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this->m_taps[i] = -this->m_taps[i];
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}
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this->m_taps[this->m_taps.size() - 1] += 1;
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}
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};
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