2 Copyright (C) 2003-2015 Paul Brossier <piem@aubio.org>
4 This file is part of aubio.
6 aubio is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 aubio is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with aubio. If not, see <http://www.gnu.org/licenses/>.
21 #ifndef AUBIO_FILTER_BIQUAD_H
22 #define AUBIO_FILTER_BIQUAD_H
26 Second order Infinite Impulse Response filter
28 This file implements a normalised biquad filter (second order IIR):
30 \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$
32 The filtfilt version runs the filter twice, forward and backward, to
33 compensate the phase shifting of the forward operation.
35 See also <a href="http://en.wikipedia.org/wiki/Digital_biquad_filter">Digital
36 biquad filter</a> on wikipedia.
38 \example temporal/test-biquad.c
46 /** set coefficients of a biquad filter
48 \param f filter object as returned by new_aubio_filter()
49 \param b0 forward filter coefficient
50 \param b1 forward filter coefficient
51 \param b2 forward filter coefficient
52 \param a1 feedback filter coefficient
53 \param a2 feedback filter coefficient
56 uint_t aubio_filter_set_biquad (aubio_filter_t * f, lsmp_t b0, lsmp_t b1,
57 lsmp_t b2, lsmp_t a1, lsmp_t a2);
59 /** create biquad filter with `b0`, `b1`, `b2`, `a1`, `a2` coeffs
61 \param b0 forward filter coefficient
62 \param b1 forward filter coefficient
63 \param b2 forward filter coefficient
64 \param a1 feedback filter coefficient
65 \param a2 feedback filter coefficient
68 aubio_filter_t *new_aubio_filter_biquad (lsmp_t b0, lsmp_t b1, lsmp_t b2,
69 lsmp_t a1, lsmp_t a2);
75 #endif /* AUBIO_FILTER_BIQUAD_H */