MovingFilter.h

/*
 * MovingFilter.h
 *
 * (c) 2022 Sofian Audry        :: info(@)sofianaudry(.)com
 *
 * 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
 * (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 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/>.
 */
 
#ifndef MOVING_FILTER_H_
#define MOVING_FILTER_H_
 
#include "PqCore.h"
#include "TimeWindowable.h"
#include "pq_moving_average.h"
 
namespace pq {
 
// Max value of _nValuesStep.
#define MOVING_FILTER_N_VALUES_STEP_MAX 63
constexpr float MOVING_FILTER_N_VALUES_STEP_MAX_MINUS_ONE = MOVING_FILTER_N_VALUES_STEP_MAX - 1;
 
// Precomputed proportion to add one value to _nValuesStep when it has reached MOVING_FILTER_N_VALUES_STEP_MAX.
constexpr float MOVING_FILTER_VALUES_STEP_ADD_ONE_PROPORTION = MOVING_FILTER_N_VALUES_STEP_MAX / (MOVING_FILTER_N_VALUES_STEP_MAX + 1.0f);
 
// N. standard deviations considered in full range.
#define MOVING_FILTER_N_STDDEV_RANGE 5.0f
 
class MovingFilter : public AnalogSource, public TimeWindowable {
protected:
  MovingFilter(Engine& engine = Engine::primary());
 
  MovingFilter(float timeWindow, Engine& engine = Engine::primary());
 
  virtual ~MovingFilter() {}
 
public:
  virtual void reset();
 
  virtual void reset(float estimatedMeanValue);
 
  virtual void reset(float estimatedMinValue, float estimatedMaxValue);
 
  virtual void resumeCalibrating();
 
  virtual void pauseCalibrating();
 
  virtual void toggleCalibrating();
 
  virtual bool isCalibrating() const;
 
  unsigned int nSamples() const { return _nSamples; }
 
  virtual bool isPreInitialized() const { return _isPreInitialized; }
 
  virtual float filter(float value) = 0;
 
protected:
  virtual void begin();
 
  // Returns the instantaneous moving average alpha for this filter.
  virtual float alpha() const {
    return movingAverageAlpha(sampleRate(), timeWindow(), nSamples(), isPreInitialized());
  }
 
  // Start/stop calibration flag.
  bool    _isCalibrating    : 1;
  bool    _isPreInitialized : 1;
  uint8_t _nValuesStep      : 6;
 
  // Number of samples that have been processed thus far.
  unsigned int _nSamples;
};
 
}
 
#endif