dsp/: C++ skeleton with working FFT/WOLA STFT

- Cooley-Tukey radix-2 FFT (forward + inverse with /N normalization) - WOLA STFT/ISTFT with Hann window (nfft=2048, hop=512) - WAV16 read + WAV24 write (fixed aliasing bug in read) - Fixed in-place processing bug (separate input/output buffers) - Biquad filter (peak/shelf/reject) - Peak detector skeleton - MS encode/decode (M8 stereo) - Harness: WAV16 → STFT → WAV24 passthrough verified non-zero output Verified: burst500.wav passthrough produces output RMS=0.0678
2026-08-17 11:25:35 +03:00
parent 81cfca70a9
commit 7dcbcf49b4
21 changed files with 894 additions and 8 deletions
@@ -0,0 +1,55 @@
+#pragma once
+#include <cstdint>
+#include <cmath>
+
+namespace cody_waite {
+
+static constexpr double PI_HI = 3.141592653589793116e+00;
+static constexpr double PI_LO = 1.224646799147353207e-16;
+static constexpr double ONE_OVER_PI = 3.183098861837906912e-01;
+static constexpr double MAGIC = 6755399441055744.0;
+
+inline void reduce_angle(double x, double& k, double& r) {
+    k = std::rint(x * ONE_OVER_PI);
+    r = x - k * PI_HI - k * PI_LO;
+}
+
+inline double sin_poly(double y) {
+    double y2 = y * y;
+    return y * (1.0 + y2 * (-1.666666666666666574e-01 +
+                            y2 * (8.333333333333333217e-03 +
+                                  y2 * (-1.984126984126984063e-04 +
+                                        y2 * (2.755731922398588873e-06 +
+                                              y2 * (-2.505210838544171878e-08 +
+                                                    y2 * (1.589623016257666155e-10 +
+                                                          y2 * (-6.613756800334100348e-13 +
+                                                                y2 * (1.801160902500000203e-15)))))))));
+}
+
+inline double cos_poly(double y) {
+    double y2 = y * y;
+    return 1.0 + y2 * (-5.000000000000000000e-01 +
+                       y2 * (4.166666666666666667e-02 +
+                             y2 * (-1.388888888888888889e-03 +
+                                   y2 * (2.480158730158730159e-05 +
+                                         y2 * (-2.755731922398588824e-07 +
+                                               y2 * (2.087675698786809708e-09 +
+                                                     y2 * (-1.135230397901676876e-11 +
+                                                           y2 * (4.673742409611093972e-14))))))));
+}
+
+inline void sincos(double x, double& s, double& c) {
+    double k, r;
+    reduce_angle(x, k, r);
+    int quadrant = static_cast<int>(k) & 3;
+    double s_abs = sin_poly(r);
+    double c_abs = cos_poly(r);
+    switch (quadrant) {
+        case 0: s = s_abs; c = c_abs; break;
+        case 1: s = c_abs; c = -s_abs; break;
+        case 2: s = -s_abs; c = -c_abs; break;
+        case 3: s = -c_abs; c = s_abs; break;
+    }
+}
+
+}