Improved 96000 coefficients

2018-10-02 00:13:22 +01:00
parent 4635b5af0f
commit 05408915b1
4 changed files with 660 additions and 519 deletions
@@ -0,0 +1,133 @@
+/*
+ *   Copyright (C) 2002-2006  Felipe Rivera <liebremx at users.sourceforge.net>
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ *
+ *   Coefficient stuff
+ *
+ *   $Id: iir_cfs.c,v 1.2 2006/01/15 00:17:46 liebremx Exp $
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+static const double band_f031[] =
+{ 20,25,31.5,40,50,63,80,100,125,160,200,250,315,400,500,630,800,
+  1000,1250,1600,2000,2500,3150,4000,5000,6300,8000,10000,12500,16000,20000
+};
+
+#define GAIN_F0 1.0
+#define GAIN_F1 GAIN_F0 / M_SQRT2
+
+#define SAMPLING_FREQ 44100.0
+#define TETA(f) (2*M_PI*(double)f/sample_frequency)
+#define TWOPOWER(value) (value * value)
+
+#define BETA2(tf0, tf) \
+(TWOPOWER(GAIN_F1)*TWOPOWER(cos(tf0)) \
+ - 2.0 * TWOPOWER(GAIN_F1) * cos(tf) * cos(tf0) \
+ + TWOPOWER(GAIN_F1) \
+ - TWOPOWER(GAIN_F0) * TWOPOWER(sin(tf)))
+#define BETA1(tf0, tf) \
+    (2.0 * TWOPOWER(GAIN_F1) * TWOPOWER(cos(tf)) \
+     + TWOPOWER(GAIN_F1) * TWOPOWER(cos(tf0)) \
+     - 2.0 * TWOPOWER(GAIN_F1) * cos(tf) * cos(tf0) \
+     - TWOPOWER(GAIN_F1) + TWOPOWER(GAIN_F0) * TWOPOWER(sin(tf)))
+#define BETA0(tf0, tf) \
+    (0.25 * TWOPOWER(GAIN_F1) * TWOPOWER(cos(tf0)) \
+     - 0.5 * TWOPOWER(GAIN_F1) * cos(tf) * cos(tf0) \
+     + 0.25 * TWOPOWER(GAIN_F1) \
+     - 0.25 * TWOPOWER(GAIN_F0) * TWOPOWER(sin(tf)))
+
+#define GAMMA(beta, tf0) ((0.5 + beta) * cos(tf0))
+#define ALPHA(beta) ((0.5 - beta)/2.0)
+
+/*************
+ * Functions *
+ *************/
+
+/* Get the band_f031 at both sides of F0. These will be cut at -3dB */
+static void find_f1_and_f2(double f0, double octave_percent, double *f1, double *f2)
+{
+    double octave_factor = pow(2.0, octave_percent/2.0);
+    *f1 = f0/octave_factor;
+    *f2 = f0*octave_factor;
+}
+
+/* Find the quadratic root
+ * Always return the smallest root */
+static int find_root(double a, double b, double c, double *x0) {
+  double k = c-((b*b)/(4.*a));
+  double h = -(b/(2.*a));
+  double x1 = 0.;
+  if (-(k/a) < 0.)
+    return -1;
+  *x0 = h - sqrt(-(k/a));
+  x1 = h + sqrt(-(k/a));
+  if (x1 < *x0)
+    *x0 = x1;
+  return 0;
+}
+
+void calc_coeffs(double sample_frequency)
+{
+  int i, n;
+  double f1, f2;
+  double x0;
+
+    printf("    public final static IIRCoefficients iir_cf31_%d[] = {\n", (int)sample_frequency);
+    for (i = 0; i < 31; i++) {
+
+      /* Find -3dB frequencies for the center freq */
+      find_f1_and_f2(band_f031[i], 1.0/3.0, &f1, &f2);
+      /* Find Beta */
+      if ( find_root(
+            BETA2(TETA(band_f031[i]), TETA(f1)),
+            BETA1(TETA(band_f031[i]), TETA(f1)),
+            BETA0(TETA(band_f031[i]), TETA(f1)),
+            &x0) == 0)
+      {
+        /* Got a solution, now calculate the rest of the factors */
+        /* Take the smallest root always (find_root returns the smallest one)
+         *
+         * NOTE: The IIR equation is
+         *  y[n] = 2 * (alpha*(x[n]-x[n-2]) + gamma*y[n-1] - beta*y[n-2])
+         *  Now the 2 factor has been distributed in the coefficients
+         */
+        /* Now store the coefficients */
+        printf("        /* %.1f Hz */\n", band_f031[i]);
+        printf("        new IIRCoefficients(%.10e, %010e, %.10e),\n",
+            (double)(2.0 * x0),
+            (double)(2.0 * ALPHA(x0)),
+            (double)(2.0 * GAMMA(x0, TETA(band_f031[i])))
+        );
+      } else {
+        printf("  **** Where are the roots?\n");
+      }
+    }// for i
+    printf("    };\n");
+}
+
+int main(int argc, char **argv) {
+    if (argc != 2) {
+        printf("Usage: iircoeff <sample frequency>\n");
+        return -1;
+    }
+
+    double f = strtod(argv[1], NULL);
+    calc_coeffs(f);
+}