apps/plugins/pdbox/PDa/extra/lowshelf.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 #include "m_pd.h"
  14 #ifdef NT
  15 #pragma warning( disable : 4244 )
  16 #pragma warning( disable : 4305 )
  17 #endif
  18 #include <math.h>
  19 #include "filters.h"
  20
  21
  22
  23 /* ------------------- lowshelf ----------------------------*/
  24
  25 static t_class *lowshelf_class;
  26
  27 void lowshelf_bang(t_rbjfilter *x)
  28 {
  29      t_atom at[5];
  30      t_float omega = e_omega(x->x_freq,x->x_rate);
  31      t_float A = e_A(x->x_gain);
  32      t_float cs = cos(omega);
  33      t_float sn = sin(omega);
  34      t_float beta = e_beta(A,x->x_bw*0.01);
  35
  36      t_float b0 =    A*((A+1) - (A-1)*cs + beta*sn);
  37      t_float b1 = 2.*A*((A-1) - (A+1)*cs);
  38      t_float b2 =    A*((A+1) - (A-1)*cs - beta*sn);
  39      t_float a0 =      ((A+1) + (A-1)*cs + beta*sn);
  40      t_float a1 =  -2.*((A-1) + (A+1)*cs);
  41      t_float a2 =      ((A+1) + (A-1)*cs - beta*sn);
  42
  43 /*     post("bang %f %f %f",x->x_freq, x->x_gain, x->x_bw); */
  44
  45      if (!check_stability(-a1/a0,-a2/a0,b0/a0,b1/a0,b2/a0)) {
  46        post("lowshelf: filter unstable -> resetting");
  47        a0=1.;a1=0.;a2=0.;
  48        b0=1.;b1=0.;b2=0.;
  49      }
  50
  51      SETFLOAT(at,-a1/a0);
  52      SETFLOAT(at+1,-a2/a0);
  53      SETFLOAT(at+2,b0/a0);
  54      SETFLOAT(at+3,b1/a0);
  55      SETFLOAT(at+4,b2/a0);
  56
  57      outlet_list(x->x_obj.ob_outlet,&s_list,5,at);
  58 }
  59
  60
  61 void lowshelf_float(t_rbjfilter *x,t_floatarg f)
  62 {
  63      x->x_freq = f;
  64      lowshelf_bang(x);
  65 }
  66
  67
  68 static void *lowshelf_new(t_floatarg f,t_floatarg g,t_floatarg bw)
  69 {
  70     t_rbjfilter *x = (t_rbjfilter *)pd_new(lowshelf_class);
  71
  72     x->x_rate = 44100.0;
  73     outlet_new(&x->x_obj,&s_float);
  74     floatinlet_new(&x->x_obj, &x->x_gain);
  75     floatinlet_new(&x->x_obj, &x->x_bw);
  76     if (f > 0.) x->x_freq = f;
  77     if (bw > 0.) x->x_bw = bw;
  78     if (g != 0.) x->x_gain = g;
  79     return (x);
  80 }
  81
  82
  83 void lowshelf_setup(void)
  84 {
  85     lowshelf_class = class_new(gensym("lowshelf"), (t_newmethod)lowshelf_new, 0,
  86                                 sizeof(t_rbjfilter), 0,A_DEFFLOAT,A_DEFFLOAT,A_DEFFLOAT,0);
  87     class_addbang(lowshelf_class,lowshelf_bang);
  88     class_addfloat(lowshelf_class,lowshelf_float);
  89 }
  90
  91
  92 /* (C) Guenter Geiger <geiger@epy.co.at> */
  93
  94
  95 /*
  96
  97  These filter coefficients computations are taken from
  98  http://www.harmony-central.com/Computer/Programming/Audio-EQ-Cookbook.txt
  99
 100  written by Robert Bristow-Johnson
 101
 102 */
 103
 104 #include "m_pd.h"
 105 #ifdef NT
 106 #pragma warning( disable : 4244 )
 107 #pragma warning( disable : 4305 )
 108 #endif
 109 #include <math.h>
 110 #include "filters.h"
 111
 112
 113
 114 /* ------------------- lowshelf ----------------------------*/
 115
 116 static t_class *lowshelf_class;
 117
 118 void lowshelf_bang(t_rbjfilter *x)
 119 {
 120      t_atom at[5];
 121      t_float omega = e_omega(x->x_freq,x->x_rate);
 122      t_float A = e_A(x->x_gain);
 123      t_float cs = cos(omega);
 124      t_float sn = sin(omega);
 125      t_float beta = e_beta(A,x->x_bw*0.01);
 126
 127      t_float b0 =    A*((A+1) - (A-1)*cs + beta*sn);
 128      t_float b1 = 2.*A*((A-1) - (A+1)*cs);
 129      t_float b2 =    A*((A+1) - (A-1)*cs - beta*sn);
 130      t_float a0 =      ((A+1) + (A-1)*cs + beta*sn);
 131      t_float a1 =  -2.*((A-1) + (A+1)*cs);
 132      t_float a2 =      ((A+1) + (A-1)*cs - beta*sn);
 133
 134 /*     post("bang %f %f %f",x->x_freq, x->x_gain, x->x_bw); */
 135
 136      if (!check_stability(-a1/a0,-a2/a0,b0/a0,b1/a0,b2/a0)) {
 137        post("lowshelf: filter unstable -> resetting");
 138        a0=1.;a1=0.;a2=0.;
 139        b0=1.;b1=0.;b2=0.;
 140      }
 141
 142      SETFLOAT(at,-a1/a0);
 143      SETFLOAT(at+1,-a2/a0);
 144      SETFLOAT(at+2,b0/a0);
 145      SETFLOAT(at+3,b1/a0);
 146      SETFLOAT(at+4,b2/a0);
 147
 148      outlet_list(x->x_obj.ob_outlet,&s_list,5,at);
 149 }
 150
 151
 152 void lowshelf_float(t_rbjfilter *x,t_floatarg f)
 153 {
 154      x->x_freq = f;
 155      lowshelf_bang(x);
 156 }
 157
 158
 159 static void *lowshelf_new(t_floatarg f,t_floatarg g,t_floatarg bw)
 160 {
 161     t_rbjfilter *x = (t_rbjfilter *)pd_new(lowshelf_class);
 162
 163     x->x_rate = 44100.0;
 164     outlet_new(&x->x_obj,&s_float);
 165     floatinlet_new(&x->x_obj, &x->x_gain);
 166     floatinlet_new(&x->x_obj, &x->x_bw);
 167     if (f > 0.) x->x_freq = f;
 168     if (bw > 0.) x->x_bw = bw;
 169     if (g != 0.) x->x_gain = g;
 170     return (x);
 171 }
 172
 173
 174 void lowshelf_setup(void)
 175 {
 176     lowshelf_class = class_new(gensym("lowshelf"), (t_newmethod)lowshelf_new, 0,
 177                                 sizeof(t_rbjfilter), 0,A_DEFFLOAT,A_DEFFLOAT,A_DEFFLOAT,0);
 178     class_addbang(lowshelf_class,lowshelf_bang);
 179     class_addfloat(lowshelf_class,lowshelf_float);
 180 }
 181
 182