MMDVMHost-Private/IIRDirectForm1Filter.cpp

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2020-05-08 18:41:57 +00:00
/*
* Copyright (C) 2015-2020 by Jonathan Naylor G4KLX
* Copyright (C) 2020 by Geoffrey Merck - F4FXL KC3FRA
*
* This program 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.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include "IIRDirectForm1Filter.h"
#include "math.h"
CIIRDirectForm1Filter::CIIRDirectForm1Filter(float b0, float b1, float b2, float , float a1, float a2, float addtionalGaindB) :
m_b0(b0),
m_b1(b1),
m_b2(b2),
m_a1(a1),
m_a2(a2),
m_additionalGainLin(::powf(10.0F, addtionalGaindB / 20.0F))
{
}
float CIIRDirectForm1Filter::filter(float sample)
{
float output = m_b0 * sample
+ m_b1 * m_x1
+ m_b2 * m_x2
- m_a1 * m_y1
- m_a2 * m_y2;
m_x2 = m_x1;
m_y2 = m_y1;
m_x1 = sample;
m_y1 = output;
return output * m_additionalGainLin;
}
void CIIRDirectForm1Filter::reset()
{
m_x1 = 0.0f;
m_x2 = 0.0f;
m_y1 = 0.0f;
m_y2 = 0.0f;
}