feat: StepDetector update FPS, more FPS fixes

google-tests/test4.cpp

@@ -25,7 +25,7 @@ TEST(StepDetector, t1_sub_sample_resolution) {
     // feed for actual test
     for (size_t i = 0; i < N; i++) {
         const auto a_i = static_cast<float>(signal[i]);
-        det.filter(ts, std::vector<float> {0.0f, a_i, 0.0f});
+        det.filter(ts * 1e9, std::vector<float> {0.0f, a_i, 0.0f});
         ts += 1.0 / fps;
     }