mp3lib/equalizer.c

   1 #include "mpg123.h"
   2
   3 void init_spline(float *x, float *y, int n, float *y2)
   4 {
   5
   6         int i, k;
   7         float p, qn, sig, un, *u;
   8         u = malloc(n * sizeof (float));
   9
  10         y2[0] = u[0] = 0.0;
  11
  12         for (i = 1; i < n - 1; i++)
  13         {
  14                 sig = ((float) x[i] - x[i - 1]) / ((float) x[i + 1] - x[i - 1]);
  15                 p = sig * y2[i - 1] + 2.0;
  16                 y2[i] = (sig - 1.0) / p;
  17                 u[i] = (((float) y[i + 1] - y[i]) / (x[i + 1] - x[i])) -
  18                         (((float) y[i] - y[i - 1]) / (x[i] - x[i - 1]));
  19                 u[i] = (6.0 * u[i] / (x[i + 1] - x[i - 1]) - sig * u[i - 1]) / p;
  20         }
  21         qn = un = 0.0;
  22
  23         y2[n - 1] = (un - qn * u[n - 2]) / (qn * y2[n - 2] + 1.0);
  24         for (k = n - 2; k >= 0; k--)
  25                 y2[k] = y2[k] * y2[k + 1] + u[k];
  26         free(u);
  27 }
  28
  29 float eval_spline(float xa[], float ya[], float y2a[], int n, float x)
  30 {
  31         int klo, khi, k;
  32         float h, b, a;
  33
  34         klo = 0;
  35         khi = n - 1;
  36         while (khi - klo > 1)
  37         {
  38                 k = (khi + klo) >> 1;
  39                 if (xa[k] > x)
  40                         khi = k;
  41                 else
  42                         klo = k;
  43         }
  44         h = xa[khi] - xa[klo];
  45         a = (xa[khi] - x) / h;
  46         b = (x - xa[klo]) / h;
  47         return (a * ya[klo] + b * ya[khi] + ((a * a * a - a) * y2a[klo] + (b * b * b - b) * y2a[khi])
  48                 * (h * h) / 6.0);
  49 }
  50
  51 void mpg123_set_eq(int on, float preamp, float *b)
  52 {
  53         float x[] =
  54         {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}, yf[10], val, band[10];
  55         int bands[] =
  56         {0, 4, 8, 16, 26, 78, 157, 313, 366, 418};
  57         int i, j;
  58
  59         mpg123_info->eq_active = on;
  60         if (mpg123_info->eq_active)
  61         {
  62                 for (i = 0; i < 10; i++)
  63                 {
  64                         band[i] = b[i] + preamp;
  65                 }
  66
  67                 init_spline(x, band, 10, yf);
  68                 for (i = 0; i < 9; i++)
  69                 {
  70                         for (j = bands[i]; j < bands[i + 1]; j++)
  71                         {
  72                                 val = eval_spline(x, band, yf, 10, i + ((float) (j - bands[i]) * (1.0 / (bands[i + 1] - bands[i]))));
  73                                 mpg123_info->eq_mul[j] = pow(2, val / 10.0);
  74                         }
  75                 }
  76                 for (i = bands[9]; i < 576; i++)
  77                         mpg123_info->eq_mul[i] = mpg123_info->eq_mul[bands[9] - 1];
  78         }
  79 }