forked from bartvdbraak/blender
62 lines
1.7 KiB
C++
62 lines
1.7 KiB
C++
/*
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* ***** BEGIN GPL LICENSE BLOCK *****
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*
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* Copyright 2009-2011 Jörg Hermann Müller
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*
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* This file is part of AudaSpace.
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*
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* Audaspace 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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* AudaSpace 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 Audaspace; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*
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* ***** END GPL LICENSE BLOCK *****
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*/
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/** \file audaspace/FX/AUD_LowpassFactory.cpp
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* \ingroup audfx
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*/
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#include "AUD_LowpassFactory.h"
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#include "AUD_IIRFilterReader.h"
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#include <cmath>
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#ifndef M_PI
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#define M_PI 3.14159265358979323846
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#endif
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AUD_LowpassFactory::AUD_LowpassFactory(AUD_Reference<AUD_IFactory> factory, float frequency,
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float Q) :
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AUD_DynamicIIRFilterFactory(factory),
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m_frequency(frequency),
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m_Q(Q)
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{
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}
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void AUD_LowpassFactory::recalculateCoefficients(AUD_SampleRate rate,
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std::vector<float> &b,
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std::vector<float> &a)
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{
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float w0 = 2 * M_PI * m_frequency / rate;
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float alpha = sin(w0) / (2 * m_Q);
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float norm = 1 + alpha;
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float c = cos(w0);
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a.push_back(1);
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a.push_back(-2 * c / norm);
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a.push_back((1 - alpha) / norm);
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b.push_back((1 - c) / (2 * norm));
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b.push_back((1 - c) / norm);
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b.push_back(b[0]);
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}
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