// Copyright 2007, 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:Exciter (Treble Enhancer)
desc:Exciter (Treble Enhancer) [Stillwell]
//tags: processing exciter distortion
//author: Stillwell

slider1:0<0,100,0.1>Mix (%)
slider2:0<0,100,0.1>Drive (%)
slider3:5000<2000,10000,100>Frequency (Hz)


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

@init

  gain1 = 0;
  freq1 = freq;
  a1 = 1;
  s1 = 1;
  q1 = 1 / (sqrt((a1 + 1/a1)*(1/s1 - 1) + 2));
  w01 = 2 * $pi * freq1/srate;
  cosw01 = cos(w01);
  sinw01 = sin(w01);
  alpha1 = sinw01 / (2 * q1);

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

  gain3 = 0;
  freq3 = freq * 2;
  a3 = 10^(gain3/40);
  s3 = 1;
  q3 = 1 / (sqrt((a3 + 1/a3)*(1/s3 - 1) + 2));
  w03 = 2 * $pi * freq3/srate;
  cosw03 = cos(w03);
  sinw03 = sin(w03);
  alpha3 = sinw03 / (2 * q3);

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

@slider

  mix=(10 * slider1) / 100;
  drive=slider2 / 100;
  mix1 = 1 - mix;
  drive1 = 1 / (1 - (drive / 2));
  drive2 = drive / 2;
  freq = slider3;

  gain1 = 0;
  freq1 = freq;
  a1 = 1;
  s1 = 1;
  q1 = 1 / (sqrt((a1 + 1/a1)*(1/s1 - 1) + 2));
  w01 = 2 * $pi * freq1/srate;
  cosw01 = cos(w01);
  sinw01 = sin(w01);
  alpha1 = sinw01 / (2 * q1);

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

  gain3 = 0;
  freq3 = freq * 2;
  a3 = 10^(gain3/40);
  s3 = 1;
  q3 = 1 / (sqrt((a3 + 1/a3)*(1/s3 - 1) + 2));
  w03 = 2 * $pi * freq3/srate;
  cosw03 = cos(w03);
  sinw03 = sin(w03);
  alpha3 = sinw03 / (2 * q3);

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


@sample

  dry0 = spl0;
  dry1 = spl1;

  //hpf to extract HF signal
  ospl0 = dry0;
  dry0 = b01 * dry0 + b11 * xl11 + b21 * xl21 - a11 * yl11 - a21 * yl21;
  xl21 = xl11;
  xl11 = ospl0;
  yl21 = yl11;
  yl11 = dry0;

  ospl1 = dry1;
  dry1 = b01 * dry1 + b11 * xr11 + b21 * xr21 - a11 * yr11 - a21 * yr21;
  xr21 = xr11;
  xr11 = ospl1;
  yr21 = yr11;
  yr11 = dry1;

  //enhance HF signal
  wet0 = drive1 * (1.5 * dry0) * (1 - abs((1.5 * dry0) * drive2));
  wet1 = drive1 * (1.5 * dry1) * (1 - abs((1.5 * dry1) * drive2)); 
  wet0 /= 1.5;
  wet1 /= 1.5;

  //hpf to isolate enhance signal
  ospl0 = wet0;
  wet0 = b03 * wet0 + b13 * xl13 + b23 * xl23 - a13 * yl13 - a23 * yl23;
  xl23 = xl13;
  xl13 = ospl0;
  yl23 = yl13;
  yl13 = wet0;

  ospl1 = wet1;
  wet1 = b03 * wet1 + b13 * xr13 + b23 * xr23 - a13 * yr13 - a23 * yr23;
  xr23 = xr13;
  xr13 = ospl1;
  yr23 = yr13;
  yr13 = wet1;


  spl0 = spl0 + (mix) * wet0;
  spl1 = spl1 + (mix) * wet1;
