forked from bartvdbraak/blender
52ef66da4d
* Created awesome filter classes :) * Made all filter effects use the filter classes instead of having the same implementation everywhere. * Added a Python API for LTI IIR filters. * Fixed a warning in creator.c that was introduced when adding game autoplay.
73 lines
2.0 KiB
C++
73 lines
2.0 KiB
C++
/*
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* $Id$
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*
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* ***** BEGIN LGPL LICENSE BLOCK *****
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*
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* Copyright 2009 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 Lesser General Public License as published by
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* the Free Software Foundation, either version 3 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 Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with AudaSpace. If not, see <http://www.gnu.org/licenses/>.
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*
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* ***** END LGPL LICENSE BLOCK *****
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*/
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#include "AUD_ButterworthFactory.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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#define BWPB41 0.76536686473
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#define BWPB42 1.84775906502
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AUD_ButterworthFactory::AUD_ButterworthFactory(AUD_IFactory* factory,
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float frequency) :
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AUD_EffectFactory(factory),
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m_frequency(frequency)
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{
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}
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AUD_IReader* AUD_ButterworthFactory::createReader() const
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{
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AUD_IReader* reader = getReader();
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// calculate coefficients
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float omega = 2 * tan(m_frequency * M_PI / reader->getSpecs().rate);
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float o2 = omega * omega;
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float o4 = o2 * o2;
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float x1 = o2 + 2 * BWPB41 * omega + 4;
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float x2 = o2 + 2 * BWPB42 * omega + 4;
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float y1 = o2 - 2 * BWPB41 * omega + 4;
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float y2 = o2 - 2 * BWPB42 * omega + 4;
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float o228 = 2 * o2 - 8;
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float norm = x1 * x2;
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std::vector<float> a, b;
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a.push_back(1);
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a.push_back((x1 + x2) * o228 / norm);
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a.push_back((x1 * y2 + x2 * y1 + o228 * o228) / norm);
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a.push_back((y1 + y2) * o228 / norm);
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a.push_back(y1 * y2 / norm);
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b.push_back(o4 / norm);
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b.push_back(4 * o4 / norm);
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b.push_back(6 * o4 / norm);
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b.push_back(b[1]);
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b.push_back(b[0]);
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return new AUD_IIRFilterReader(reader, b, a);
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}
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