apps/plugins/pdbox/PDa/extra/highpass.c

   1 /* (C) Guenter Geiger <geiger@epy.co.at> */
   2
   3
   4 /*
   5
   6  These filter coefficients computations are taken from
   7  http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt
   8
   9  written by Robert Bristow-Johnson
  10
  11 */
  12
  13
  14 #ifdef ROCKBOX
  15 #include "plugin.h"
  16 #include "../../pdbox.h"
  17 #include "../src/m_pd.h"
  18 #include "math.h"
  19 #include "filters.h"
  20 #else /* ROCKBOX */
  21 #include "../src/m_pd.h"
  22 #ifdef NT
  23 #pragma warning( disable : 4244 )
  24 #pragma warning( disable : 4305 )
  25 #endif
  26 #include <math.h>
  27 #include "filters.h"
  28 #endif /* ROCKBOX */
  29
  30
  31 /* ------------------- highpass ----------------------------*/
  32
  33 static t_class *highpass_class;
  34
  35 void highpass_bang(t_rbjfilter *x)
  36 {
  37      t_atom at[5];
  38      t_float omega = e_omega(x->x_freq,x->x_rate);
  39      t_float alpha = e_alpha(x->x_bw* 0.01,omega);
  40      t_float b1 = -(1 + cos(omega));
  41      t_float b0 = -b1/2.;
  42      t_float b2 = b0;
  43      t_float a0 = 1 + alpha;
  44      t_float a1 = -2.*cos(omega);
  45      t_float a2 = 1 - alpha;
  46
  47 /*     post("bang %f %f %f",x->x_freq, x->x_gain, x->x_bw); */
  48
  49      if (!check_stability(-a1/a0,-a2/a0,b0/a0,b1/a0,b2/a0)) {
  50        post("highpass: filter unstable -> resetting");
  51        a0=1.;a1=0.;a2=0.;
  52        b0=1.;b1=0.;b2=0.;
  53      }
  54
  55      SETFLOAT(at,-a1/a0);
  56      SETFLOAT(at+1,-a2/a0);
  57      SETFLOAT(at+2,b0/a0);
  58      SETFLOAT(at+3,b1/a0);
  59      SETFLOAT(at+4,b2/a0);
  60
  61      outlet_list(x->x_obj.ob_outlet,&s_list,5,at);
  62 }
  63
  64
  65 void highpass_float(t_rbjfilter *x,t_floatarg f)
  66 {
  67      x->x_freq = f;
  68      highpass_bang(x);
  69 }
  70
  71
  72 static void *highpass_new(t_floatarg f,t_floatarg bw)
  73 {
  74     t_rbjfilter *x = (t_rbjfilter *)pd_new(highpass_class);
  75
  76     x->x_rate = 44100.0;
  77     outlet_new(&x->x_obj,&s_float);
  78 /*    floatinlet_new(&x->x_obj, &x->x_gain);    */
  79     floatinlet_new(&x->x_obj, &x->x_bw);
  80     if (f > 0.) x->x_freq = f;
  81     if (bw > 0.) x->x_bw = bw;
  82     return (x);
  83 }
  84
  85
  86 void highpass_setup(void)
  87 {
  88     highpass_class = class_new(gensym("highpass"), (t_newmethod)highpass_new, 0,
  89                                 sizeof(t_rbjfilter), 0,A_DEFFLOAT,A_DEFFLOAT,0);
  90     class_addbang(highpass_class,highpass_bang);
  91     class_addfloat(highpass_class,highpass_float);
  92 }
  93
  94