dsp: freqpath - warp 0x5406a8 = 0.87*x/(1+x/K) (K=exp(2.0723), x=f/2000) из FUN_180530850 (0x530900) + self-check (rel err 1.5e-07, PASS)

dsp/freqpath.cpp

@@ -0,0 +1,28 @@
+#include "freqpath.hpp"
+
+#include <cmath>
+#include <cstring>
+
+namespace detkernel {
+
+// Bit-faithful transcription of the warp builder loop in FUN_180530850 (0x530900).
+void build_warp(float fs_total, int n, float* warp) {
+    const float K = std::exp(2.0723267f);               // 0x1824c4208 -> exp (0x1a14cac)
+    const float F = (2000.0f / (fs_total * 0.5f)) * static_cast<float>(n);  // 0x1824c45b4 / ([0x24]*0.5) * N
+
+    for (int i = 1; i < n; ++i) {
+        float x = static_cast<float>(i) / F;
+        float t = x / K;
+        t = t + 1.0f;                                   // +1.0 (0x1824c3ea4)
+        float r = 1.0f / t;                             // divss
+        r = static_cast<float>(std::fabs(static_cast<double>(r)));  // cvtss2sd/andpd/cvtpd2ps
+        warp[i] = r * x;
+    }
+
+    const float scale = 0.87f;                          // 0x1824c3e50 (also 0.87 as double 0x24c4110)
+    for (int i = 0; i < n; ++i) warp[i] *= scale;
+
+    warp[0] = 0.0f;                                     // 0x5406a8[0] = 0 (DC)
+}
+
+}  // namespace detkernel