1/*
2 * IIR filter
3 * Copyright (c) 2008 Konstantin Shishkov
4 *
5 * This file is part of Libav.
6 *
7 * Libav is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * Libav is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22/**
23 * @file
24 * IIR filter interface
25 */
26
27#ifndef AVCODEC_IIRFILTER_H
28#define AVCODEC_IIRFILTER_H
29
30#include "avcodec.h"
31
32struct FFIIRFilterCoeffs;
33struct FFIIRFilterState;
34
35enum IIRFilterType{
36    FF_FILTER_TYPE_BESSEL,
37    FF_FILTER_TYPE_BIQUAD,
38    FF_FILTER_TYPE_BUTTERWORTH,
39    FF_FILTER_TYPE_CHEBYSHEV,
40    FF_FILTER_TYPE_ELLIPTIC,
41};
42
43enum IIRFilterMode{
44    FF_FILTER_MODE_LOWPASS,
45    FF_FILTER_MODE_HIGHPASS,
46    FF_FILTER_MODE_BANDPASS,
47    FF_FILTER_MODE_BANDSTOP,
48};
49
50/**
51 * Initialize filter coefficients.
52 *
53 * @param avc          a pointer to an arbitrary struct of which the first
54 *                     field is a pointer to an AVClass struct
55 * @param filt_type    filter type (e.g. Butterworth)
56 * @param filt_mode    filter mode (e.g. lowpass)
57 * @param order        filter order
58 * @param cutoff_ratio cutoff to input frequency ratio
59 * @param stopband     stopband to input frequency ratio (used by bandpass and bandstop filter modes)
60 * @param ripple       ripple factor (used only in Chebyshev filters)
61 *
62 * @return pointer to filter coefficients structure or NULL if filter cannot be created
63 */
64struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,
65                                                enum IIRFilterType filt_type,
66                                                enum IIRFilterMode filt_mode,
67                                                int order, float cutoff_ratio,
68                                                float stopband, float ripple);
69
70/**
71 * Create new filter state.
72 *
73 * @param order filter order
74 *
75 * @return pointer to new filter state or NULL if state creation fails
76 */
77struct FFIIRFilterState* ff_iir_filter_init_state(int order);
78
79/**
80 * Free filter coefficients.
81 *
82 * @param coeffs pointer allocated with ff_iir_filter_init_coeffs()
83 */
84void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs);
85
86/**
87 * Free filter state.
88 *
89 * @param state pointer allocated with ff_iir_filter_init_state()
90 */
91void ff_iir_filter_free_state(struct FFIIRFilterState *state);
92
93/**
94 * Perform IIR filtering on signed 16-bit input samples.
95 *
96 * @param coeffs pointer to filter coefficients
97 * @param state  pointer to filter state
98 * @param size   input length
99 * @param src    source samples
100 * @param sstep  source stride
101 * @param dst    filtered samples (destination may be the same as input)
102 * @param dstep  destination stride
103 */
104void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state,
105                   int size, const int16_t *src, int sstep, int16_t *dst, int dstep);
106
107/**
108 * Perform IIR filtering on floating-point input samples.
109 *
110 * @param coeffs pointer to filter coefficients
111 * @param state  pointer to filter state
112 * @param size   input length
113 * @param src    source samples
114 * @param sstep  source stride
115 * @param dst    filtered samples (destination may be the same as input)
116 * @param dstep  destination stride
117 */
118void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *coeffs,
119                       struct FFIIRFilterState *state, int size,
120                       const float *src, int sstep, float *dst, int dstep);
121
122#endif /* AVCODEC_IIRFILTER_H */
123