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Blender
V2.59
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00001 /* 00002 * $Id: AUD_ButterworthFactory.cpp 35141 2011-02-25 10:21:56Z jesterking $ 00003 * 00004 * ***** BEGIN GPL LICENSE BLOCK ***** 00005 * 00006 * Copyright 2009-2011 Jörg Hermann Müller 00007 * 00008 * This file is part of AudaSpace. 00009 * 00010 * Audaspace is free software; you can redistribute it and/or modify 00011 * it under the terms of the GNU General Public License as published by 00012 * the Free Software Foundation; either version 2 of the License, or 00013 * (at your option) any later version. 00014 * 00015 * AudaSpace is distributed in the hope that it will be useful, 00016 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00017 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00018 * GNU General Public License for more details. 00019 * 00020 * You should have received a copy of the GNU General Public License 00021 * along with Audaspace; if not, write to the Free Software Foundation, 00022 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. 00023 * 00024 * ***** END GPL LICENSE BLOCK ***** 00025 */ 00026 00032 #include "AUD_ButterworthFactory.h" 00033 #include "AUD_IIRFilterReader.h" 00034 00035 #include <cmath> 00036 00037 #ifndef M_PI 00038 #define M_PI 3.14159265358979323846 00039 #endif 00040 00041 #define BWPB41 0.76536686473 00042 #define BWPB42 1.84775906502 00043 00044 AUD_ButterworthFactory::AUD_ButterworthFactory(AUD_IFactory* factory, 00045 float frequency) : 00046 AUD_EffectFactory(factory), 00047 m_frequency(frequency) 00048 { 00049 } 00050 00051 AUD_IReader* AUD_ButterworthFactory::createReader() const 00052 { 00053 AUD_IReader* reader = getReader(); 00054 00055 // calculate coefficients 00056 float omega = 2 * tan(m_frequency * M_PI / reader->getSpecs().rate); 00057 float o2 = omega * omega; 00058 float o4 = o2 * o2; 00059 float x1 = o2 + 2 * BWPB41 * omega + 4; 00060 float x2 = o2 + 2 * BWPB42 * omega + 4; 00061 float y1 = o2 - 2 * BWPB41 * omega + 4; 00062 float y2 = o2 - 2 * BWPB42 * omega + 4; 00063 float o228 = 2 * o2 - 8; 00064 float norm = x1 * x2; 00065 std::vector<float> a, b; 00066 a.push_back(1); 00067 a.push_back((x1 + x2) * o228 / norm); 00068 a.push_back((x1 * y2 + x2 * y1 + o228 * o228) / norm); 00069 a.push_back((y1 + y2) * o228 / norm); 00070 a.push_back(y1 * y2 / norm); 00071 b.push_back(o4 / norm); 00072 b.push_back(4 * o4 / norm); 00073 b.push_back(6 * o4 / norm); 00074 b.push_back(b[1]); 00075 b.push_back(b[0]); 00076 00077 return new AUD_IIRFilterReader(reader, b, a); 00078 }