interpretor/faust-0.9.47mr3/examples/lowcut.dsp

   1 declare name            "lowcut";
   2 declare version         "1.0";
   3 declare author          "Grame";
   4 declare license         "BSD";
   5 declare copyright       "(c)GRAME 2006";
   6
   7 //------------------------------------------------------------------
   8 //      DAFX, Digital Audio Effects (Wiley ed.)
   9 //      chapter 2       : filters
  10 //      section 2.3 : Equalizers
  11 //      page 53         : second order shelving filter design
  12 //------------------------------------------------------------------
  13
  14 import("music.lib");
  15
  16
  17
  18 //------------------- low-frequency shelving cut (table 2.3) --------------------
  19
  20 V0(g)                   = pow(10,g/-20.0);
  21 K(fc)                   = tan(PI*fc/SR);
  22 square(x)               = x*x;
  23 denom(fc,g)             = 1 + sqrt(2*V0(g))*K(fc) + V0(g)*square(K(fc));
  24
  25 lfcut(fc, g)    = TF2(  (1 + sqrt(2)*K(fc) + square(K(fc))) / denom(fc,g),
  26                                                  2 * (square(K(fc)) - 1) / denom(fc,g),
  27                                                 (1 - sqrt(2)*K(fc) + square(K(fc))) / denom(fc,g),
  28                                                  2 * (V0(g)*square(K(fc)) - 1) / denom(fc,g),
  29                                                 (1 - sqrt(2*V0(g))*K(fc) + V0(g)*square(K(fc))) / denom(fc,g)
  30                                          );
  31
  32
  33 //------------------------------ User Interface -----------------------------------
  34
  35 freq                    = hslider("freq [unit:Hz][style:knob]", 100, 20, 5000, 1);
  36 att                             = hslider("attenuation [unit:dB][style:knob]", 0, -96, 10, 0.1);
  37
  38
  39 //----------------------------------- Process -------------------------------------
  40
  41 process                 = vgroup("low-freq shelving cut", lfcut(freq,att));
  42