vibe code the initial impl

main/feature_params.h

@@ -0,0 +1,24 @@
+// feature_params.h -- SINGLE SOURCE OF TRUTH for the audio feature pipeline.
+//
+// This file contains ONLY #define lines (plus comments and an include guard).
+// tools/make_template.py parses it with a regex, so firmware and Python can
+// never silently disagree.  Keep every value a plain numeric literal.
+//
+// Band edges (implemented identically in fingerprint.c and make_template.py):
+//   f_b    = F_MIN_HZ * (F_MAX_HZ / F_MIN_HZ) ^ (b / NUM_BANDS),  b = 0..NUM_BANDS
+//   bin_b  = floor(f_b * FRAME_LEN / FS_HZ + 0.5)      (round half up, double math)
+//   if bin_b < bin_(b-1) + 1  then  bin_b = bin_(b-1) + 1   (>= 1 bin per band)
+//   band b covers FFT bins [bin_b, bin_(b+1)).  bin_NUM_BANDS must be <= FRAME_LEN/2.
+#ifndef FEATURE_PARAMS_H
+#define FEATURE_PARAMS_H
+
+#define FS_HZ        16000     // sample rate of the whole pipeline
+#define FRAME_LEN    1024      // samples per analysis frame (power of two)
+#define HOP_LEN      512       // hop = 32 ms at 16 kHz
+#define NUM_BANDS    32        // log-spaced bands in the fingerprint
+#define F_MIN_HZ     100       // lower edge of band 0
+#define F_MAX_HZ     7500      // nominal upper edge of the last band
+#define LOG_EPS      1e-10f    // added to band power before log (power is of samples scaled to +-1.0)
+#define FP_DETREND   1         // 1: remove linear tilt across band index, 0: off
+
+#endif