dexed/Source/PluginFx.cpp

/**
 *
 * Copyright (c) 2013-2014 Pascal Gauthier.
 * Copyright (c) 2013-2014 Filatov Vadim.
 * 
 * Filter taken from the Obxd project :
 *   https://github.com/2DaT/Obxd
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301 USA.
 */

#define _USE_MATH_DEFINES
#include <math.h>
#include "PluginFx.h"
#include "PluginProcessor.h"

const float dc = 1e-18;

inline static float tptpc(float& state,float inp,float cutoff) {
	double v = (inp - state) * cutoff / (1 + cutoff);
	double res = v + state;
	state = res + v;
	return res;
}

inline static float tptlpupw(float & state , float inp , float cutoff , float srInv) {
	cutoff = (cutoff * srInv)*juce::float_Pi;
	double v = (inp - state) * cutoff / (1 + cutoff);
	double res = v + state;
	state = res + v;
	return res;
}

static float linsc(float param,const float min,const float max) {
    return (param) * (max - min) + min;
}

static float logsc(float param, const float min,const float max,const float rolloff = 19.0f) {
	return ((expf(param * logf(rolloff+1)) - 1.0f) / (rolloff)) * (max-min) + min;
}

void PluginFx::init(int sr) {
    mm=0;
    s1=s2=s3=s4=c=d=0;
    R24=0;
    
    mmch = (int)(mm * 3);
    mmt = mm*3-mmch;

    sampleRate = sr;
    sampleRateInv = 1/sampleRate;
    float rcrate =sqrt((44000/sampleRate));
    rcor24 = (970.0 / 44000)*rcrate;
    rcor24Inv = 1 / rcor24;
    
    bright = tan((sampleRate*0.5f-10) * juce::float_Pi * sampleRateInv);
    
    R = 1;
	rcor = (480.0 / 44000)*rcrate;
    rcorInv = 1 / rcor;
    bandPassSw = false;
    
    uiCutoff = 1;
    uiReso = 0;
    
    pCutoff = -1;
    pReso = -1;
}

inline float PluginFx::NR24(float sample,float g,float lpc) {
    float ml = 1 / (1+g);
    float S = (lpc*(lpc*(lpc*s1 + s2) + s3) +s4)*ml;
    float G = lpc*lpc*lpc*lpc;
    float y = (sample - R24 * S) / (1 + R24*G);
    return y + 1e-8;
};

inline float PluginFx::NR(float sample, float g) {
    float y = ((sample- R * s1*2 - g*s1  - s2)/(1+ g*(2*R + g))) + dc;
    return y;
}

void PluginFx::process(float *work, int sampleSize) {
    // don't apply the LPF if the cutoff is to maximum
    if ( uiCutoff == 1 )
        return;
    
    if ( uiCutoff != pCutoff || uiReso != pReso ) {
        rReso = (0.991-logsc(1-uiReso,0,0.991,40));
        R24 = 3.5 * rReso;
        
        float cutoffNorm = logsc(uiCutoff,60,19000,30);
        rCutoff = (float)tan(cutoffNorm * sampleRateInv * juce::float_Pi);
        
        pCutoff = uiCutoff;
        pReso = uiReso;

        R = 1 - rReso;
    }
    
    // THIS IS MY FAVORITE 4POLE OBXd filter
    
    // maybe smooth this value
    float g = rCutoff;
    float lpc = g / (1 + g);

    for(int i=0; i < sampleSize; i++ ) {
        float s = work[i];
		s = s - 0.45*tptlpupw(c,s,15,sampleRateInv);
        s = tptpc(d,s,bright);
        
        float y0 = NR24(s,g,lpc);
        
        //first low pass in cascade
        double v = (y0 - s1) * lpc;
        double res = v + s1;
        s1 = res + v;
        
        //damping
        s1 =atan(s1*rcor24)*rcor24Inv;
        float y1= res;
        float y2 = tptpc(s2,y1,g);
        float y3 = tptpc(s3,y2,g);
        float y4 = tptpc(s4,y3,g);
        float mc;
        
        switch(mmch) {
			case 0:
				mc = ((1 - mmt) * y4 + (mmt) * y3);
				break;
			case 1:
				mc = ((1 - mmt) * y3 + (mmt) * y2);
				break;
			case 2:
				mc = ((1 - mmt) * y2 + (mmt) * y1);
				break;
			case 3:
				mc = y1;
				break;
        }
        
        //half volume comp
        work[i] = mc * (1 + R24 * 0.45);
    }
}

/*
 
 // THIS IS THE 2POLE FILTER
 
 for(int i=0; i < sampleSize; i++ ) {
 float s = work[i];
 s = s - 0.45*tptlpupw(c,s,15,sampleRateInv);
 s = tptpc(d,s,bright);
 
 //float v = ((sample- R * s1*2 - g2*s1 - s2)/(1+ R*g1*2 + g1*g2));
 float v = NR(s,g);
 float y1 = v*g + s1;
 //damping
 s1 = atan(s1 * rcor) * rcorInv;
 
 float y2 = y1*g + s2;
 s2 = y2 + y1*g;
 
 double mc;
 if(!bandPassSw)
 mc = (1-mm)*y2 + (mm)*v;
 else
 {
 
 mc =2 * ( mm < 0.5 ?
 ((0.5 - mm) * y2 + (mm) * y1):
 ((1-mm) * y1 + (mm-0.5) * v)
 );
 }
 
 work[i] = mc;
 }
 
*/