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fix: remove high-pass prefilter (ssf is already a high-pass)

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This commit is contained in:
David Madl
2026-05-19 22:40:39 +02:00
parent 58ed5df87c
commit 29019f61e5
2 changed files with 1 additions and 19 deletions
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1
pasada-lib/include/step_detector.h
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@@ -24,7 +24,6 @@ public:
class StepDetector { class StepDetector {
protected: protected:
StepListener *listener; StepListener *listener;
IirFilter f_highpass;
Filt f_neg; Filt f_neg;
SsfFilter f_ssf; SsfFilter f_ssf;
SsfStepDetector f_ssd; SsfStepDetector f_ssd;

19
pasada-lib/step_detector.cpp
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@@ -4,24 +4,8 @@
#include "step_detector.h" #include "step_detector.h"
// TODO: we are hardcoding filter coefficients for 60 Hz
// TODO: this is tolerable for 50 Hz
// TODO: check if we can do with floats instead of doubles
// (check how much the [already bad] accuracy of filtering suffers)
// TODO: in Java, check if delta timestamps effectively match FPS
// TODO: FPS constant should be passed as argument to C++ (but we keep an FPS define to validate the coefficients)
// Butterworth filter: order=5, fc=0.5, fs=60, btype='highpass'
static std::vector<double> hpf_taps_b {0.91875845, -4.59379227, 9.18758454, -9.18758454, 4.59379227, -0.91875845};
static std::vector<double> hpf_taps_a {1. , -4.83056552, 9.33652742, -9.02545247, 4.36360803, -0.8441171};
static size_t upslope_width = 4;
const size_t len_refr = (size_t) (FPS / (MAX_BPM / 60));
StepDetector::StepDetector(double fps, StepListener *listener, bool debug) : StepDetector::StepDetector(double fps, StepListener *listener, bool debug) :
listener(listener), listener(listener),
f_highpass(hpf_taps_b, hpf_taps_a),
f_neg(1, 0, 0, std::vector<double> {-1.0}), f_neg(1, 0, 0, std::vector<double> {-1.0}),
f_ssf(fps), f_ssf(fps),
f_ssd(fps), f_ssd(fps),
@@ -35,8 +19,7 @@ StepDetector::StepDetector(double fps, StepListener *listener, bool debug) :
void StepDetector::filter(std::vector<float> values) { void StepDetector::filter(std::vector<float> values) {
// TODO: later on, we should use a vector projection towards gravity // TODO: later on, we should use a vector projection towards gravity
auto s0 = (double) values[1]; // take y-axis value for now auto s1 = (double) values[1]; // take y-axis value for now
auto s1 = f_highpass.filter(s0);
auto s2 = f_neg.filter(s1); auto s2 = f_neg.filter(s1);
auto s3 = f_ssf.filter(s2); auto s3 = f_ssf.filter(s2);
auto s4 = f_ssd.filter(s3); auto s4 = f_ssd.filter(s3);