feat: StepDetector

move StepDetector from lockstep android to libpasada

google-tests/test4.cpp

@@ -0,0 +1,38 @@
+//
+// Created by david on 15.03.2026.
+//
+
+#include <gtest/gtest.h>
+
+#include "step_detector.h"
+#include "npy.hpp"
+#include "test_helpers.h"
+
+TEST(StepDetector, t1_sub_sample_resolution) {
+    npy::npy_data s = npy::read_npy<double>("test4/step_150a.npy");
+
+    std::vector<double> signal = fetch_y_axis(s);
+    const size_t N = signal.size();
+    const size_t N_INIT = SsfStepDetector::initial_samples();
+
+    StepDetector det(nullptr, true);
+
+    // initialize: feed for priming the filters
+    det.primeFilters(signal);
+
+    // feed for actual test
+    for (size_t i = 0; i < N; i++) {
+        const auto a_i = static_cast<float>(signal[i]);
+        det.filter(std::vector<float> {0.0f, a_i, 0.0f});
+    }
+
+    std::vector<double> ssd = det.getBufSsd(); // raw SsfStepDetector
+    std::vector<double> sqi = det.getBufSqi(); // SQI - RunningQuality beat correlations
+    std::vector<double> out = det.getBufOut(); // steps where SQI is OK
+
+    npy_save("test4/t1_ssd.npy", ssd);
+    npy_save("test4/t1_sqi.npy", sqi);
+    npy_save("test4/t1_out.npy", out);
+
+    // http://localhost:8888/notebooks/2026-03-10%20step%20interpolate%2F2026-03-15%20synth.ipynb
+}