// Copyright 2006, Thomas Scott Stillwell
// All rights reserved.
//
//Redistribution and use in source and binary forms, with or without modification, are permitted 
//provided that the following conditions are met:
//
//Redistributions of source code must retain the above copyright notice, this list of conditions 
//and the following disclaimer. 
//
//Redistributions in binary form must reproduce the above copyright notice, this list of conditions 
//and the following disclaimer in the documentation and/or other materials provided with the distribution. 
//
//The name of Thomas Scott Stillwell may not be used to endorse or 
//promote products derived from this software without specific prior written permission. 
//
//THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR 
//IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 
//FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS 
//BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
//(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
//PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 
//STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 
//THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

desc:RBJ 4-Band Semi-Parametric EQ
desc:RBJ 4-Band Semi-Parametric EQ [Stillwell]
//tags: equalizer
//author: Stillwell


slider1:3<1,5,1{40,80,160,315,500}>Frequency 1 (Hz)
slider2:0<-15,15,0.1>Boost/Cut (dB)
slider3:3<1,5,1{125,250,500,1k,2k}>Frequency 2 (Hz)
slider4:0<-15,15,0.1>Boost/Cut (dB)
slider5:3<1,5,1{315,630,1.2k,2.5k,5k}>Frequency 3 (Hz)
slider6:0<-15,15,0.1>Boost/Cut (dB)
slider7:3<1,5,1{1.6k,3.2k,6.4k,9k,12k}>Frequency 4 (Hz)
slider8:0<-15,15,0.1>Boost/Cut (dB)

in_pin:left input
in_pin:right input
out_pin:left output
out_pin:right output

@init
  gain1 = 0;
  freq1 = 160;
  a1 = (10^(gain1/40));
  q1 = 0.8;
  w01 = 2 * $pi * freq1/srate;
  cosw01 = cos(w01);
  sinw01 = sin(w01);
  alpha1 = sinw01 / (2 * q1);

  b01 = 1 + alpha1 * a1;
  b11 = -2 * cosw01;
  b21 = 1 - alpha1 * a1;
  a01 = 1 + alpha1 / a1;
  a11 = -2 * cosw01;
  a21 = 1 - alpha1 / a1;
  b01 /= a01;
  b11 /= a01;
  b21 /= a01;
  a11 /= a01;
  a21 /= a01;

  gain3 = 0;
  freq3 = 500;
  a3 = (10^(gain3/40));
  q3 = 0.8;
  w03 = 2 * $pi * freq3/srate;
  cosw03 = cos(w03);
  sinw03 = sin(w03);
  alpha3 = sinw03 / (2 * q3);

  b03 = 1 + alpha3 * a3;
  b13 = -2 * cosw03;
  b23 = 1 - alpha3 * a3;
  a03 = 1 + alpha3 / a3;
  a13 = -2 * cosw03;
  a23 = 1 - alpha3 / a3;
  b03 /= a03;
  b13 /= a03;
  b23 /= a03;
  a13 /= a03;
  a23 /= a03;

  gain5 = 0;
  freq5 = 1200;
  a5 = (10^(gain5/40));
  q5 = 0.8;
  w05 = 2 * $pi * freq5/srate;
  cosw05 = cos(w05);
  sinw05 = sin(w05);
  alpha5 = sinw05 / (2 * q5);

  b05 = 1 + alpha5 * a5;
  b15 = -2 * cosw05;
  b25 = 1 - alpha5 * a5;
  a05 = 1 + alpha5 / a5;
  a15 = -2 * cosw05;
  a25 = 1 - alpha5 / a5;
  b05 /= a05;
  b15 /= a05;
  b25 /= a05;
  a15 /= a05;
  a25 /= a05;

  gain7 = 0;
  freq7 = 6400;
  a7 = (10^(gain7/40));
  q7 = 0.8;
  w07 = 2 * $pi * freq7/srate;
  cosw07 = cos(w07);
  sinw07 = sin(w07);
  alpha7 = sinw07 / (2 * q7);

  b07 = 1 + alpha7 * a7;
  b17 = -2 * cosw07;
  b27 = 1 - alpha7 * a7;
  a07 = 1 + alpha7 / a7;
  a17 = -2 * cosw07;
  a27 = 1 - alpha7 / a7;
  b07 /= a07;
  b17 /= a07;
  b27 /= a07;
  a17 /= a07;
  a27 /= a07;
 
@slider
  freq1 = (slider1 == 0 ? 40 : (slider1 == 1 ? 80 : (slider1 == 2 ? 160 : (slider1 == 3 ? 315 : 500))));
  gain1 = slider2;
  freq3 = (slider3 == 0 ? 125 : (slider3 == 1 ? 250 : (slider3 == 2 ? 500 : (slider3 == 3 ? 1000 : 2000))));
  gain3 = slider4;
  freq5 = (slider5 == 0 ? 315 : (slider5 == 1 ? 630 : (slider5 == 2 ? 1200 : (slider5 == 3 ? 2500 : 5000))));
  gain5 = slider6;
  freq7 = (slider7 == 0 ? 1600 : (slider7 == 1 ? 3200 : (slider7 == 2 ? 6400 : (slider7 == 3 ? 9000 : 12000))));
  gain7 = slider8;

  a1 = (10^(gain1/40));
  q1 = 0.8;
  w01 = 2 * $pi * freq1/srate;
  cosw01 = cos(w01);
  sinw01 = sin(w01);
  alpha1 = sinw01 / (2 * q1);

  b01 = 1 + alpha1 * a1;
  b11 = -2 * cosw01;
  b21 = 1 - alpha1 * a1;
  a01 = 1 + alpha1 / a1;
  a11 = -2 * cosw01;
  a21 = 1 - alpha1 / a1;
  b01 /= a01;
  b11 /= a01;
  b21 /= a01;
  a11 /= a01;
  a21 /= a01;

  a3 = (10^(gain3/40));
  q3 = 0.8;
  w03 = 2 * $pi * freq3/srate;
  cosw03 = cos(w03);
  sinw03 = sin(w03);
  alpha3 = sinw03 / (2 * q3);

  b03 = 1 + alpha3 * a3;
  b13 = -2 * cosw03;
  b23 = 1 - alpha3 * a3;
  a03 = 1 + alpha3 / a3;
  a13 = -2 * cosw03;
  a23 = 1 - alpha3 / a3;
  b03 /= a03;
  b13 /= a03;
  b23 /= a03;
  a13 /= a03;
  a23 /= a03;

  a5 = (10^(gain5/40));
  q5 = 0.8;
  w05 = 2 * $pi * freq5/srate;
  cosw05 = cos(w05);
  sinw05 = sin(w05);
  alpha5 = sinw05 / (2 * q5);

  b05 = 1 + alpha5 * a5;
  b15 = -2 * cosw05;
  b25 = 1 - alpha5 * a5;
  a05 = 1 + alpha5 / a5;
  a15 = -2 * cosw05;
  a25 = 1 - alpha5 / a5;
  b05 /= a05;
  b15 /= a05;
  b25 /= a05;
  a15 /= a05;
  a25 /= a05;

  a7 = (10^(gain7/40));
  q7 = 0.8;
  w07 = 2 * $pi * freq7/srate;
  cosw07 = cos(w07);
  sinw07 = sin(w07);
  alpha7 = sinw07 / (2 * q7);

  b07 = 1 + alpha7 * a7;
  b17 = -2 * cosw07;
  b27 = 1 - alpha7 * a7;
  a07 = 1 + alpha7 / a7;
  a17 = -2 * cosw07;
  a27 = 1 - alpha7 / a7;
  b07 /= a07;
  b17 /= a07;
  b27 /= a07;
  a17 /= a07;
  a27 /= a07;

@sample
  gain1 != 0 ? (
  ospl0 = spl0;
  spl0 = b01 * spl0 + b11 * xl11 + b21 * xl21 - a11 * yl11 - a21 * yl21;
  xl21 = xl11;
  xl11 = ospl0;
  yl21 = yl11;
  yl11 = spl0;

  ospl1 = spl1;
  spl1 = b01 * spl1 + b11 * xr11 + b21 * xr21 - a11 * yr11 - a21 * yr21;
  xr21 = xr11;
  xr11 = ospl1;
  yr21 = yr11;
  yr11 = spl1;
  );

  gain3 != 0 ? (
  ospl0 = spl0;
  spl0 = b03 * spl0 + b13 * xl13 + b23 * xl23 - a13 * yl13 - a23 * yl23;
  xl23 = xl13;
  xl13 = ospl0;
  yl23 = yl13;
  yl13 = spl0;

  ospl1 = spl1;
  spl1 = b03 * spl1 + b13 * xr13 + b23 * xr23 - a13 * yr13 - a23 * yr23;
  xr23 = xr13;
  xr13 = ospl1;
  yr23 = yr13;
  yr13 = spl1;
  );

  gain5 != 0 ? (
  ospl0 = spl0;
  spl0 = b05 * spl0 + b15 * xl15 + b25 * xl25 - a15 * yl15 - a25 * yl25;
  xl25 = xl15;
  xl15 = ospl0;
  yl25 = yl15;
  yl15 = spl0;

  ospl1 = spl1;
  spl1 = b05 * spl1 + b15 * xr15 + b25 * xr25 - a15 * yr15 - a25 * yr25;
  xr25 = xr15;
  xr15 = ospl1;
  yr25 = yr15;
  yr15 = spl1;
  );

  gain7 != 0 ? (
  ospl0 = spl0;
  spl0 = b07 * spl0 + b17 * xl17 + b27 * xl27 - a17 * yl17 - a27 * yl27;
  xl27 = xl17;
  xl17 = ospl0;
  yl27 = yl17;
  yl17 = spl0;

  ospl1 = spl1;
  spl1 = b07 * spl1 + b17 * xr17 + b27 * xr27 - a17 * yr17 - a27 * yr27;
  xr27 = xr17;
  xr17 = ospl1;
  yr27 = yr17;
  yr17 = spl1;
  );
