22w: faithful mask-shaping chain v1 behind RT_FAITHFUL (fnfaith.cpp) — exact 180533340 freq-warped bidir-IIR coefficients (fc_bin=85@48k/4096, constants from dump); corpus TOTAL 5.315 but comb 2.57 best-ever; decisive: mask shape cannot balance dual tones -> level contrast is created by the DETECTOR (time-domain twin bank hypothesis priority #1)

dsp/fnfaith.hpp

@@ -0,0 +1,45 @@
+#pragma once
+// FAITHFUL mask-shaping chain (22w) — transcription of FUN_180529fe0 per
+// handoff/BLOCKMAP_529fe0.md (raw asm). Replaces process_band_structural
+// when RT_FAITHFUL=1.
+//
+//   band = lvl * s                      (s = RT_FAITH_SCALE, decomp: /0x1a0*0x870*0x88c)
+//   mask = exp2(-band)                  (bigkernel exp2 family)
+//   bidir(mask, A);  bidir(mask, A)     // states reset each pass (52d650 + inline)
+//   bidir(mask, B)                      // pass #3
+//   bidir(mask, C);  bidir(mask, C)     // pass #4 x2
+//   mirror upper half; dry/wet identity.
+//
+// Bidirectional one-pole per FUN_18052d650: acc = up[i]*acc + down[i]*x[i],
+// forward over all bins, backward n-2..1 with persistent acc, reset per call.
+// Coefficients per FUN_180533340 (freq-warped): fc_bin = C/(sr/2)*nbin;
+// g = fc/i below crossover, powf(fc/i, p) above; c = 1/(g*tau/mult+1);
+// up[i] = exp(-2*pi*kappa*c*g*tau), down[i] = 1-up[i].
+//
+// Decoded defaults (FUN_180530b60 log-interp @ live 0x540878/87c = 0.5):
+//   setA/B tau=19.03 mult=360 ; set3/set4 tau=10.68 mult=2400 ; p=0.822 ;
+//   C=1000 Hz ; kappa = 1/T8 ~ 0.0094 (T8 unknown -> env).
+
+#include <cstddef>
+#include <vector>
+
+namespace fnfaith {
+
+struct Params {
+    double scale;   // RT_FAITH_SCALE
+    double kappa;   // RT_FAITH_KAPPA
+    double p;       // RT_FAITH_P
+    double tau1, mult1;   // state A (#1,#2)
+    double tau3, mult3;   // state B (#3)
+    double tau4, mult4;   // state C (#4 x2)
+    double C_hz;    // crossover (1000)
+};
+
+Params params_from_env();
+
+// Compute lower-half mask [0, nbin) for one band from lvl_raw = am/res*scale_factor.
+void band_mask_faithful(const float* am, const float* res, size_t nbin,
+                        float sample_rate, float scale_factor, const Params& pr,
+                        float* mask_out /* nbin */);
+
+}  // namespace fnfaith