ZeroOrderResampler.h

/*
 * This file is part of libsidplayfp, a SID player engine.
 *
 * Copyright 2011-2013 Leandro Nini <drfiemost@users.sourceforge.net>
 * Copyright 2007-2010 Antti Lankila
 *
 * 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 ZEROORDER_RESAMPLER_H
#define ZEROORDER_RESAMPLER_H
 
#include "Resampler.h"
 
#include "siddefs-fp.h"
 
namespace reSIDfp
{

class ZeroOrderResampler final : public Resampler
{
    friend class State;
 
private:
    int32_t cachedSample = 0;

    const int cyclesPerSample;
 
    int sampleOffset = 0;

    int32_t outputValue = 0;
 
public:
    ZeroOrderResampler(double clockFrequency, double samplingFrequency) :
        cyclesPerSample(static_cast<int>(clockFrequency / samplingFrequency * 1024.))
    {}
 
    bool input(int sample) override
    {
        bool ready = false;
 
        if (unlikely(sampleOffset < 1024))
        {
            outputValue = cachedSample + (sampleOffset * (sample - cachedSample) >> 10);
            ready = true;
            sampleOffset += cyclesPerSample;
        }
 
        sampleOffset -= 1024;
 
        cachedSample = sample;
 
        return ready;
    }
 
    int32_t output() const override { return outputValue; }
 
    void reset() override
    {
        sampleOffset = 0;
        cachedSample = 0;
        outputValue = 0;
    }
};
 
} // namespace reSIDfp
 
#endif