mp3lib/equalizer.c

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