87 lines
2.2 KiB
C
87 lines
2.2 KiB
C
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/*
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* This file is part of libsidplayfp, a SID player engine.
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*
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* Copyright 2011-2020 Leandro Nini <drfiemost@users.sourceforge.net>
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* Copyright 2007-2010 Antti Lankila
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifndef RESAMPLER_H
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#define RESAMPLER_H
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#include <cmath>
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#include "../sidcxx11.h"
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#include "../siddefs-fp.h"
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namespace reSIDfp
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{
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/**
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* Abstraction of a resampling process. Given enough input, produces output.
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* Constructors take additional arguments that configure these objects.
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*/
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class Resampler
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{
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protected:
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inline short softClip(int x) const
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{
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constexpr int threshold = 28000;
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if (likely(x < threshold))
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return x;
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constexpr double t = threshold / 32768.;
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constexpr double a = 1. - t;
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constexpr double b = 1. / a;
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double value = static_cast<double>(x - threshold) / 32768.;
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value = t + a * tanh(b * value);
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return static_cast<short>(value * 32768.);
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}
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virtual int output() const = 0;
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Resampler() {}
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public:
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virtual ~Resampler() {}
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/**
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* Input a sample into resampler. Output "true" when resampler is ready with new sample.
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*
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* @param sample input sample
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* @return true when a sample is ready
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*/
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virtual bool input(int sample) = 0;
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/**
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* Output a sample from resampler.
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*
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* @return resampled sample
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*/
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short getOutput() const
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{
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return softClip(output());
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}
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virtual void reset() = 0;
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};
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} // namespace reSIDfp
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#endif
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