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

   1
   2 /* (C) Guenter Geiger <geiger@epy.co.at> */
   3
   4
   5 /*
   6
   7  These filter coefficients computations are taken from
   8  http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt
   9
  10  written by Robert Bristow-Johnson
  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 /* ------------------- bandpass ----------------------------*/
  31
  32 static t_class *bandpass_class;
  33
  34 void bandpass_bang(t_rbjfilter *x)
  35 {
  36      t_atom at[5];
  37      t_float omega = e_omega(x->x_freq,x->x_rate);
  38      t_float alpha = e_alpha(x->x_bw* 0.01,omega);
  39      t_float b1 = 0.;
  40      t_float b0 = alpha;
  41      t_float b2 = -alpha;
  42      t_float a0 = 1 + alpha;
  43      t_float a1 = -2.*cos(omega);
  44      t_float a2 = 1 - alpha;
  45
  46 /*     post("bang %f %f %f",x->x_freq, x->x_gain, x->x_bw); */
  47
  48      if (!check_stability(-a1/a0,-a2/a0,b0/a0,b1/a0,b2/a0)) {
  49        post("bandpass: filter unstable -> resetting");
  50        a0=1.;a1=0.;a2=0.;
  51        b0=1.;b1=0.;b2=0.;
  52      }
  53
  54      SETFLOAT(at,-a1/a0);
  55      SETFLOAT(at+1,-a2/a0);
  56      SETFLOAT(at+2,b0/a0);
  57      SETFLOAT(at+3,b1/a0);
  58      SETFLOAT(at+4,b2/a0);
  59
  60      outlet_list(x->x_obj.ob_outlet,&s_list,5,at);
  61 }
  62
  63
  64 void bandpass_float(t_rbjfilter *x,t_floatarg f)
  65 {
  66      x->x_freq = f;
  67      bandpass_bang(x);
  68 }
  69
  70
  71 static void *bandpass_new(t_floatarg f,t_floatarg bw)
  72 {
  73     t_rbjfilter *x = (t_rbjfilter *)pd_new(bandpass_class);
  74
  75     x->x_rate = 44100.0;
  76     outlet_new(&x->x_obj,&s_float);
  77 /*    floatinlet_new(&x->x_obj, &x->x_gain);    */
  78     floatinlet_new(&x->x_obj, &x->x_bw);
  79     if (f > 0.) x->x_freq = f;
  80     if (bw > 0.) x->x_bw = bw;
  81     return (x);
  82 }
  83
  84
  85 void bandpass_setup(void)
  86 {
  87     bandpass_class = class_new(gensym("bandpass"), (t_newmethod)bandpass_new, 0,
  88                                 sizeof(t_rbjfilter), 0,A_DEFFLOAT,A_DEFFLOAT,0);
  89     class_addbang(bandpass_class,bandpass_bang);
  90     class_addfloat(bandpass_class,bandpass_float);
  91 }
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  95