aubio: temporal/filter.h Source File

aubio 0.4.9

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filter.h
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1/*
2 Copyright (C) 2003-2015 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$:
43
44 \f{eqnarray*}{
45 y[n] = b_0 x[n] & + & b_1 x[n-1] + b_2 x[n-2] + ... + b_P x[n-P] \\
46 & - & a_1 y[n-1] - a_2 y[n-2] - ... - a_P y[n-P] \\
47 \f}
48
49 The function aubio_filter_do() executes the same computation but modifies
50 directly the input signal (in-place).
51
52 The function aubio_filter_do_filtfilt() version runs the filter twice, first
53 forward then backward, to compensate with the phase shifting of the forward
54 operation.
55
56 Some convenience functions are provided:
57 - new_aubio_filter_a_weighting() and aubio_filter_set_a_weighting(),
58 - new_aubio_filter_c_weighting() and aubio_filter_set_c_weighting().
59 - new_aubio_filter_biquad() and aubio_filter_set_biquad().
60
61 \example temporal/test-filter.c
62
63*/
64
65#ifdef __cplusplus
66extern "C" {
67#endif
68
69/** Digital filter
70
71*/
72 typedef struct _aubio_filter_t aubio_filter_t;
73
74/** filter input vector (in-place)
75
76 \param f filter object as returned by new_aubio_filter()
77 \param in input vector to filter
78
79*/
80 void aubio_filter_do (aubio_filter_t * f, fvec_t * in);
81
82/** filter input vector (out-of-place)
83
84 \param f filter object as returned by new_aubio_filter()
85 \param in input vector to filter
86 \param out output vector to store filtered input
87
88*/
89 void aubio_filter_do_outplace (aubio_filter_t * f, const fvec_t * in, fvec_t * out);
90
91/** filter input vector forward and backward
92
93 \param f ::aubio_filter_t object as returned by new_aubio_filter()
94 \param in ::fvec_t input vector to filter
95 \param tmp memory space to use for computation
96
97*/
98 void aubio_filter_do_filtfilt (aubio_filter_t * f, fvec_t * in, fvec_t * tmp);
99
100/** returns a pointer to feedback coefficients \f$ 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*/
107 lvec_t *aubio_filter_get_feedback (const 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*/
116 lvec_t *aubio_filter_get_feedforward (const 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*/
125 uint_t aubio_filter_get_order (const 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*/
134 uint_t aubio_filter_get_samplerate (const 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*/
144 uint_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*/
151 void 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*/
163 aubio_filter_t *new_aubio_filter (uint_t order);
164
165/** delete a filter object
166
167 \param f filter object to delete
168
169*/
170 void del_aubio_filter (aubio_filter_t * f);
171
172#ifdef __cplusplus
173}
174#endif
175
176#endif /* AUBIO_FILTER_H */
aubio_filter_set_samplerate
uint_t aubio_filter_set_samplerate(aubio_filter_t *f, uint_t samplerate)
get sampling rate of the filter
new_aubio_filter
aubio_filter_t * new_aubio_filter(uint_t order)
create new filter object
aubio_filter_t
struct _aubio_filter_t aubio_filter_t
Digital filter.
Definition: filter.h:72
del_aubio_filter
void del_aubio_filter(aubio_filter_t *f)
delete a filter object
aubio_filter_get_order
uint_t aubio_filter_get_order(const aubio_filter_t *f)
get order of the filter
aubio_filter_get_feedback
lvec_t * aubio_filter_get_feedback(const aubio_filter_t *f)
returns a pointer to feedback coefficients
aubio_filter_get_samplerate
uint_t aubio_filter_get_samplerate(const aubio_filter_t *f)
get sampling rate of the filter
aubio_filter_get_feedforward
lvec_t * aubio_filter_get_feedforward(const aubio_filter_t *f)
returns a pointer to feedforward coefficients
aubio_filter_do
void aubio_filter_do(aubio_filter_t *f, fvec_t *in)
filter input vector (in-place)
aubio_filter_do_filtfilt
void aubio_filter_do_filtfilt(aubio_filter_t *f, fvec_t *in, fvec_t *tmp)
filter input vector forward and backward
aubio_filter_do_reset
void aubio_filter_do_reset(aubio_filter_t *f)
reset filter memory
aubio_filter_do_outplace
void aubio_filter_do_outplace(aubio_filter_t *f, const fvec_t *in, fvec_t *out)
filter input vector (out-of-place)
fvec_t
Buffer for real data.
Definition: fvec.h:67
lvec_t
Buffer for real data in double precision.
Definition: lvec.h:43
uint_t
unsigned int uint_t
unsigned integer
Definition: types.h:60