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