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/*
dsp/OnePole.h
Copyright 2003-14 Tim Goetze <tim@quitte.de>
http://quitte.de/dsp/
first-order IIR hi- and lo-pass filters.
*/
/*
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 3
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., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA or point your web browser to http://www.gnu.org.
*/
#ifndef IIR1_H
#define IIR1_H
namespace DSP {
template <class T>
class LP1
{
public:
T a0, b1, y1;
LP1 (T d = 1.)
{
set (d);
y1 = 0.;
}
sample_t last() {return y1;}
inline void reset() { y1 = 0.; }
inline void decay (T d)
{
a0 *= d;
b1 = 1. - a0;
}
inline void set_f (T fc)
{
set (1 - exp(-2*M_PI*fc));
}
inline void set (T d)
{
a0 = d;
b1 = 1 - d;
}
inline T process (T x) { return y1 = a0*x + b1*y1; }
};
template <class T>
class HP1
{
public:
T a0, a1, b1, x1, y1;
HP1 (T d = 1.)
{
set (d);
reset();
}
sample_t last() {return y1;}
void set_f (T f)
{
set (exp (-2*M_PI*f));
}
inline void set (T d)
{
a0 = .5*(1. + d);
a1 = -.5*(1. + d);
b1 = d;
}
inline T process (T x)
{
y1 = a0*x + a1*x1 + b1*y1;
x1 = x;
return y1;
}
void identity()
{
a0=1;
a1=b1=0;
}
void reset()
{
x1 = y1 = 0;
}
};
} /* namespace DSP */
#endif /* IIR1 */
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