libpasada/pasada-lib/include/step_detector.h

//
// Created by david on 15.03.2026.
//

#ifndef PASADASUPERPROJECT_STEP_DETECTOR_H
#define PASADASUPERPROJECT_STEP_DETECTOR_H

#include "iir_filter.h"
#include "ssf_filter.h"
#include "pd_resamp.h"
#include <vector>

class StepListener {
public:
    virtual ~StepListener() {}
    virtual void playBeat() = 0;
};

/** mean-filter the gravity vector, then take acceleration downwards */
class GravityFilter {
    size_t N;
    std::vector<double> gauss_taps;
    Filt gx;
    Filt gy;
    Filt gz;
public:
    // 5 secs buffer, prime y with direction of gravity (for tests & faster init)
    GravityFilter(double fps);
    double filter(std::vector<double> values);
};

/**
 * Step detector from accelerometer signal.
 *
 * Settling time is 3.0 sec (defined in SsfStepDetector.LEN_INIT),
 * no steps are detected before.
 */
class StepDetector {
protected:
    StepListener *listener;
    GravityFilter f_grav;
    SsfFilter f_ssf;
    SsfStepDetector f_ssd;
    RunningQualityFilter f_sqi;

    bool debug;
    std::vector<double> buf_ssd;
    std::vector<double> buf_sqi;
    std::vector<double> buf_out;

    Resampler res_x;
    Resampler res_y;
    Resampler res_z;

public:
    StepDetector(double fps, StepListener *listener, bool debug = false);
    void filter(double ts, std::vector<float> values);
    void filter_a(double s1);
    std::vector<double> getBufSsd();
    std::vector<double> getBufSqi();
    std::vector<double> getBufOut();

    /**
     * Prime the filters using the given input signal.
     * Used for debugging (non-realtime processing) to align the signal.
     */
    double primeFilters(double fps, std::vector<double> sig);
};

#endif //PASADASUPERPROJECT_STEP_DETECTOR_H