source: src/temporal/filter.h @ e9270a4

feature/autosinkfeature/cnnfeature/cnn_orgfeature/constantqfeature/crepefeature/crepe_orgfeature/pitchshiftfeature/pydocstringsfeature/timestretchfix/ffmpeg5pitchshiftsamplertimestretchyinfft+
Last change on this file since e9270a4 was b235c0e, checked in by Paul Brossier <piem@piem.org>, 10 years ago

src/: sync header defines, remove trailing spaces, update copyrights

Signed-off-by: Paul Brossier <piem@piem.org>

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1/*
2  Copyright (C) 2003-2013 Paul Brossier <piem@aubio.org>
3
4  This file is part of aubio.
5
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.
10
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.
15
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/>.
18
19*/
20
21#ifndef _AUBIO_FILTER_H
22#define _AUBIO_FILTER_H
23
24/** \file
25
26  Digital filter
27
28  This object stores a digital filter of order \f$n\f$.
29  It contains the following data:
30    - \f$ n*1 b_i \f$ feedforward coefficients
31    - \f$ n*1 a_i \f$ feedback coefficients
32    - \f$ n*c x_i \f$ input signal
33    - \f$ n*c y_i \f$ output signal
34
35  For convenience, the samplerate of the input signal is also stored in the
36  object.
37
38  Feedforward and feedback parameters can be modified using
39  aubio_filter_get_feedback() and aubio_filter_get_feedforward().
40
41  The function aubio_filter_do_outplace() computes the following output signal
42  \f$ y[n] \f$ from the input signal \f$ x[n] \f$:
43 
44  \f{eqnarray*}{
45     y[n] = b_0 x[n] & + & b_1 x[n-1] + b_2 x[n-2] + ... + b_P x[n-P] \\
46                     & - & a_1 y[n-1] - a_2 y[n-2] - ... - a_P y[n-P] \\
47  \f}
48
49  The function aubio_filter_do() executes the same computation but modifies
50  directly the input signal (in-place).
51
52  The function aubio_filter_do_filtfilt() version runs the filter twice, first
53  forward then backward, to compensate with the phase shifting of the forward
54  operation.
55
56  Some convenience functions are provided:
57    - new_aubio_filter_a_weighting() and aubio_filter_set_a_weighting(),
58    - new_aubio_filter_c_weighting() and aubio_filter_set_c_weighting().
59    - new_aubio_filter_biquad() and aubio_filter_set_biquad().
60
61  \example temporal/test-filter.c
62 
63*/
64
65#ifdef __cplusplus
66extern "C" {
67#endif
68
69/** Digital filter
70
71*/
72typedef struct _aubio_filter_t aubio_filter_t;
73
74/** filter input vector (in-place)
75
76  \param f filter object as returned by new_aubio_filter()
77  \param in input vector to filter
78
79*/
80void aubio_filter_do (aubio_filter_t * f, fvec_t * in);
81
82/** filter input vector (out-of-place)
83
84  \param f filter object as returned by new_aubio_filter()
85  \param in input vector to filter
86  \param out output vector to store filtered input
87
88*/
89void aubio_filter_do_outplace (aubio_filter_t * f, fvec_t * in, fvec_t * out);
90
91/** filter input vector forward and backward
92
93  \param f ::aubio_filter_t object as returned by new_aubio_filter()
94  \param in ::fvec_t input vector to filter
95  \param tmp memory space to use for computation
96
97*/
98void aubio_filter_do_filtfilt (aubio_filter_t * f, fvec_t * in, fvec_t * tmp);
99
100/** returns a pointer to feedback coefficients \f$ a_i \f$
101
102  \param f filter object to get parameters from
103
104  \return a pointer to the \f$ a_0 ... a_i ... a_P \f$ coefficients
105
106*/
107lvec_t *aubio_filter_get_feedback (aubio_filter_t * f);
108
109/** returns a pointer to feedforward coefficients \f$ b_i \f$
110
111  \param f filter object to get coefficients from
112
113  \return a pointer to the \f$ b_0 ... b_i ... b_P \f$ coefficients
114
115*/
116lvec_t *aubio_filter_get_feedforward (aubio_filter_t * f);
117
118/** get order of the filter
119
120  \param f filter to get order from
121
122  \return the order of the filter
123
124*/
125uint_t aubio_filter_get_order (aubio_filter_t * f);
126
127/** get sampling rate of the filter
128
129  \param f filter to get sampling rate from
130
131  \return the sampling rate of the filter, in Hz
132
133*/
134uint_t aubio_filter_get_samplerate (aubio_filter_t * f);
135
136/** get sampling rate of the filter
137
138  \param f filter to get sampling rate from
139  \param samplerate sample rate to set the filter to
140
141  \return the sampling rate of the filter, in Hz
142
143*/
144uint_t aubio_filter_set_samplerate (aubio_filter_t * f, uint_t samplerate);
145
146/** reset filter memory
147
148  \param f filter object as returned by new_aubio_filter()
149
150*/
151void aubio_filter_do_reset (aubio_filter_t * f);
152
153/** create new filter object
154
155  This function creates a new ::aubio_filter_t object, given the order of the
156  filter.
157
158  \param order order of the filter (number of coefficients)
159
160  \return the newly created filter object
161
162*/
163aubio_filter_t *new_aubio_filter (uint_t order);
164
165/** delete a filter object
166 
167  \param f filter object to delete
168
169*/
170void del_aubio_filter (aubio_filter_t * f);
171
172#ifdef __cplusplus
173}
174#endif
175
176#endif /* _AUBIO_FILTER_H */
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