Filter8580.h

/*
 * This file is part of libsidplayfp, a SID player engine.
 *
 * Copyright 2011-2014 Leandro Nini <drfiemost@users.sourceforge.net>
 * Copyright 2007-2010 Antti Lankila
 * Copyright 2004,2010 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 FILTER8580_H
#define FILTER8580_H
 
#include <cmath>
#include <cstring>
 
#include <stdint.h>
 
#include "siddefs-fp.h"
 
#include "Filter.h"
 
namespace reSIDfp
{
 
class antiDenormalNoise
{
private:
    uint32_t rand_state;
 
private:
    static inline float reduce(uint32_t val)
    {
        // FIXME may not be fully portable
        // This code assumes IEEE-754 floating point representation
        // and same endianness for integers and floats
        const uint32_t mantissa = val & 0x807F0000; // Keep only most significant bits
        const uint32_t flt_rnd = mantissa | 0x1E000000; // Set exponent
        float temp;
        memcpy(&temp, &flt_rnd, sizeof(float));
        return temp;
    }
 
public:
    antiDenormalNoise() :
        rand_state(1) {}
 
    inline float get()
    {
        // LCG from Numerical Recipes
        rand_state = rand_state * 1664525 + 1013904223;
 
        return reduce(rand_state);
    }
};
 
class Filter8580 : public Filter
{
private:
    double highFreq;
 
    float Vlp;
 
    float Vbp;
 
    float Vhp;
 
    float w0;
 
    float _1_div_Q;
 
    int ve;
 
    antiDenormalNoise noise;
 
public:
    Filter8580() :
        highFreq(12500.),
        Vlp(0.f),
        Vbp(0.f),
        Vhp(0.f),
        w0(0.f),
        _1_div_Q(0.f),
        ve(0) {}
 
    int clock(int voice1, int voice2, int voice3);
 
    void updatedCenterFrequency() { w0 = static_cast<float>(2. * M_PI * highFreq * fc / 2047. / 1e6); }
 
    void updatedResonance() { _1_div_Q = static_cast<float>(pow(2., (4 - res) / 8.)); }
 
    void input(int input) { ve = input << 4; }
 
    void updatedMixing() {}
 
    void setFilterCurve(double curvePosition) { highFreq = curvePosition; }
};
 
} // namespace reSIDfp
 
#if RESID_INLINING || defined(FILTER8580_CPP)
 
#include <cassert>
 
namespace reSIDfp
{
 
RESID_INLINE
int Filter8580::clock(int voice1, int voice2, int voice3)
{
    voice1 >>= 7;
    voice2 >>= 7;
    voice3 >>= 7;
 
    int Vi = 0;
    int Vo = 0;
 
    (filt1 ? Vi : Vo) += voice1;
 
    (filt2 ? Vi : Vo) += voice2;
 
    // NB! Voice 3 is not silenced by voice3off if it is routed
    // through the filter.
    if (filt3) Vi += voice3;
    else if (!voice3off) Vo += voice3;
 
    (filtE ? Vi : Vo) += ve;
 
    Vlp -= w0 * Vbp;
    Vbp -= w0 * Vhp;
    Vhp = (Vbp * _1_div_Q) - Vlp - Vi + noise.get();
 
    assert(std::fpclassify(Vlp) != FP_SUBNORMAL);
    assert(std::fpclassify(Vbp) != FP_SUBNORMAL);
    assert(std::fpclassify(Vhp) != FP_SUBNORMAL);
 
    float Vof = static_cast<float>(Vo);
 
    if (lp)
    {
        Vof += Vlp;
    }
 
    if (bp)
    {
        Vof += Vbp;
    }
 
    if (hp)
    {
        Vof += Vhp;
    }
 
    return static_cast<int>(Vof) * vol >> 4;
}
 
} // namespace reSIDfp
 
#endif
 
#endif