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/*
Copyright (C) 2003-2015 Paul Brossier <piem@aubio.org>
This file is part of aubio.
aubio 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.
aubio 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 aubio. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef AUBIO_FILTER_BIQUAD_H
#define AUBIO_FILTER_BIQUAD_H
/** \file
Second order Infinite Impulse Response filter
This file implements a normalised biquad filter (second order IIR):
\f$ y[n] = b_0 x[n] + b_1 x[n-1] + b_2 x[n-2] - a_1 y[n-1] - a_2 y[n-2] \f$
The filtfilt version runs the filter twice, forward and backward, to
compensate the phase shifting of the forward operation.
See also <a href="http://en.wikipedia.org/wiki/Digital_biquad_filter">Digital
biquad filter</a> on wikipedia.
\example temporal/test-biquad.c
*/
#ifdef __cplusplus
extern "C" {
#endif
/** set coefficients of a biquad filter
\param f filter object as returned by new_aubio_filter()
\param b0 forward filter coefficient
\param b1 forward filter coefficient
\param b2 forward filter coefficient
\param a1 feedback filter coefficient
\param a2 feedback filter coefficient
*/
uint_t aubio_filter_set_biquad (aubio_filter_t * f, lsmp_t b0, lsmp_t b1,
lsmp_t b2, lsmp_t a1, lsmp_t a2);
/** create biquad filter with `b0`, `b1`, `b2`, `a1`, `a2` coeffs
\param b0 forward filter coefficient
\param b1 forward filter coefficient
\param b2 forward filter coefficient
\param a1 feedback filter coefficient
\param a2 feedback filter coefficient
*/
aubio_filter_t *new_aubio_filter_biquad (lsmp_t b0, lsmp_t b1, lsmp_t b2,
lsmp_t a1, lsmp_t a2);
#ifdef __cplusplus
}
#endif
#endif /* AUBIO_FILTER_BIQUAD_H */
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