Filter.h

/*
 * This file is part of libsidplayfp, a SID player engine.
 *
 * Copyright 2011-2025 Leandro Nini <drfiemost@users.sourceforge.net>
 * Copyright 2007-2010 Antti Lankila
 * Copyright 2004 Dag Lem <resid@nimrod.no>
 *
 * 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.
 */
 
#ifndef FILTER_H
#define FILTER_H
 
#include "FilterModelConfig.h"
#include "Voice.h"
 
#include "siddefs-fp.h"
 
namespace reSIDfp
{
 
class Filter
{
private:
    unsigned short* mixer;
    unsigned short* summer;
    unsigned short* resonance;
    unsigned short* volume;
 
    FilterModelConfig& fmc;
 
    unsigned short* currentMixer = nullptr;
 
    unsigned short* currentSummer = nullptr;
 
    unsigned short* currentResonance = nullptr;
 
    unsigned short* currentVolume = nullptr;
 
protected:
    int Vhp = 0;
 
    int Vbp = 0;
 
    int Vlp = 0;
 
private:
    int Ve = 0;
 
    unsigned int fc = 0;
 
 
    bool filt1 = false;
    bool filt2 = false;
    bool filt3 = false;
    bool filtE = false;
 
    bool voice3off = false;
 
protected:
 
    bool hp = false;
    bool bp = false;
    bool lp = false;
 
private:
    unsigned char vol = 0;
 
    bool enabled = true;
 
    unsigned char filt = 0;
 
private:
    inline int getNormalizedVoice(Voice& v) const
    {
        return fmc.getNormalizedVoice(v.output(), v.envelope()->output());
    }
 
    // If voice 3 is off we still need to clock the waveform generator
    inline int getSilentVoice(Voice& v) const
    {
        v.wave()->output();
        return 0;
    }
 
protected:
    virtual void updateCenterFrequency() = 0;
 
    void updateResonance(unsigned char res) { currentResonance = resonance + (res * (1<<16)); }
 
    void updateMixing();
 
    inline unsigned int getFC() const { return fc; }
 
    virtual int solveIntegrators() = 0;
 
public:
    Filter(FilterModelConfig& fmc);
 
    virtual ~Filter() = default;
 
    unsigned short clock(Voice& v1, Voice& v2, Voice& v3);
 
    void enable(bool enable);
 
    void reset();
 
    void writeFC_LO(unsigned char fc_lo);
 
    void writeFC_HI(unsigned char fc_hi);
 
    void writeRES_FILT(unsigned char res_filt);
 
    void writeMODE_VOL(unsigned char mode_vol);
 
    void input(short input) { Ve = fmc.getNormalizedVoice(input/32768.f, 0); }
};
 
} // namespace reSIDfp
 
#if RESIDFP_INLINING || defined(FILTER_CPP)
 
namespace reSIDfp
{
 
RESIDFP_INLINE
unsigned short Filter::clock(Voice& voice1, Voice& voice2, Voice& voice3)
{
    const int V1 = getNormalizedVoice(voice1);
    const int V2 = getNormalizedVoice(voice2);
    // Voice 3 is silenced by voice3off if it is not routed through the filter.
    const int V3 = (filt3 || !voice3off) ? getNormalizedVoice(voice3) : getSilentVoice(voice3);
 
    int Vsum = 0;
    int Vmix = 0;
 
    (filt1 ? Vsum : Vmix) += V1;
    (filt2 ? Vsum : Vmix) += V2;
    (filt3 ? Vsum : Vmix) += V3;
    (filtE ? Vsum : Vmix) += Ve;
 
    Vhp = currentSummer[currentResonance[Vbp] + Vlp + Vsum];
 
    Vmix += solveIntegrators();
 
    return currentVolume[currentMixer[Vmix]];
}
 
} // namespace reSIDfp
 
#endif
 
#endif