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sdrangel/sdrbase/dsp/firfilter.h
Kacper Michajłow 786640ee1f NFMDemod: Add RF filter for freq deviation
- Run CTCSS filter with reduced rate to much detection
- Convert tabs to spaces to be consistent in the file
- Fix AF squelch threshold setting after changing SR
2020-11-07 06:59:04 +01:00

127 lines
4.0 KiB
C++

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