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window: add support for cosine moving windows

This commit is contained in:
Manuel Pitz 2022-05-02 14:57:53 +02:00 committed by Steffen Vogel
parent 765b195e5f
commit b47e1294f3
2 changed files with 152 additions and 27 deletions

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@ -23,57 +23,85 @@
#pragma once
#include <villas/utils.hpp>
#include <ranges>
#include <deque>
namespace villas {
namespace dsp {
template<typename T>
class Window {
template<typename T, typename Container = std::deque<T>>
class Window : protected Container {
public:
typedef typename std::vector<T>::size_type size_type;
using iterator = typename Container::iterator;
using size_type = typename Container::size_type;
protected:
std::vector<T> data;
T init;
virtual
T filter(T in, size_type i) const
{
return in;
}
size_type steps;
size_type mask;
size_type pos;
class transform_iterator : public Container::const_iterator {
protected:
const Window *window;
using base_iterator = typename Container::const_iterator;
public:
transform_iterator(const Window<T> *w) :
base_iterator(w->Container::begin()),
window(w)
{ }
T operator*()
{
auto i = (*this) - window->begin();
const auto &v = base_iterator::operator*();
return window->filter(v, i);
}
};
public:
Window(size_type s = 0, T i = 0) :
init(i),
steps(s)
{
size_type len = LOG2_CEIL(s);
/* Allocate memory for circular history buffer */
data = std::vector<T>(len, i);
pos = len;
mask = len - 1;
}
Window(size_type l = 0, T i = 0) :
std::deque<T>(l, i)
{ }
T update(T in)
{
T out = data[(pos - steps) & mask];
Container::push_back(in);
data[pos++ & mask] = in;
auto out = (*this)[0];
Container::pop_front();
return out;
}
size_type getLength() const
// Expose a limited number of functions from deque
using Container::size;
using Container::end;
transform_iterator begin() const noexcept
{
return steps;
return transform_iterator(this);
}
T operator[](int i) const
T operator[](size_type i) const noexcept
{
return data[(pos + i) & mask];
auto v = Container::operator[](i);
return filter(v, i);
}
virtual
T getCorrectionFactor() const
{
return 1.0;
}
};

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@ -0,0 +1,97 @@
/** A sliding/moving window.
*
* @file
* @author Steffen Vogel <svogel2@eonerc.rwth-aachen.de>
* @copyright 2014-2022, Institute for Automation of Complex Power Systems, EONERC
* @license GNU General Public License (version 3)
*
* VILLAScommon
*
* 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, either version 3 of the License, or
* 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 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 <vector>
#include <villas/dsp/window.hpp>
namespace villas {
namespace dsp {
template<typename T, double a0 = 1.0, double a1 = 0.0, double a2 = 0.0, double a3 = 0.0, double a4 = 0.0>
class CosineWindow : public Window<T> {
public:
using size_type = typename Window<T>::size_type;
protected:
std::vector<T> coefficients;
T correctionFactor;
virtual
T filter(T in, size_type i) const
{
return in * coefficients[i];
}
public:
CosineWindow(size_type len, T i = 0) :
Window<T>(len, i),
coefficients(len),
correctionFactor(0)
{
for (unsigned i = 0; i < len; i++) {
coefficients[i] = a0
- a1 * cos(2 * M_PI * i / len)
+ a2 * cos(4 * M_PI * i / len)
- a3 * cos(6 * M_PI * i / len)
+ a4 * cos(8 * M_PI * i / len);
correctionFactor += coefficients[i];
}
correctionFactor /= len;
}
virtual
T getCorrectionFactor() const
{
return correctionFactor;
}
};
// From: https://en.wikipedia.org/wiki/Window_function#Cosine-sum_windows
template<typename T>
using HannWindow = CosineWindow<T, 0.5, 0.5>;
template<typename T>
using HammingWindow = CosineWindow<T, 25./46, 1 - 25./46>;
template<typename T>
using FlattopWindow = CosineWindow<T, 0.21557895, 0.41663158, 0.277263158, 0.083578947, 0.006947368>; // based on MATLAB coeffs
template<typename T>
using NuttallWindow = CosineWindow<T, 0.355768, 0.487396, 0.144232, 0.012604>;
template<typename T>
using BlackmanWindow = CosineWindow<T, 0.3635819, 0.4891775, 0.1365995, 0.0106411>;
} /* namespace dsp */
} /* namespace villas */