1/*
2 * IIR filter
3 * Copyright (c) 2008 Konstantin Shishkov
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg 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 * FFmpeg 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 FFmpeg; 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
50typedef struct FFIIRFilterContext {
51    /**
52    * Perform IIR filtering on floating-point input samples.
53    *
54    * @param coeffs pointer to filter coefficients
55    * @param state  pointer to filter state
56    * @param size   input length
57    * @param src    source samples
58    * @param sstep  source stride
59    * @param dst    filtered samples (destination may be the same as input)
60    * @param dstep  destination stride
61    */
62    void (*filter_flt)(const struct FFIIRFilterCoeffs *coeffs,
63                        struct FFIIRFilterState *state, int size,
64                        const float *src, int sstep, float *dst, int dstep);
65} FFIIRFilterContext;
66
67/**
68 * Initialize FFIIRFilterContext
69 */
70void ff_iir_filter_init(FFIIRFilterContext *f);
71void ff_iir_filter_init_mips(FFIIRFilterContext *f);
72
73/**
74 * Initialize filter coefficients.
75 *
76 * @param avc          a pointer to an arbitrary struct of which the first
77 *                     field is a pointer to an AVClass struct
78 * @param filt_type    filter type (e.g. Butterworth)
79 * @param filt_mode    filter mode (e.g. lowpass)
80 * @param order        filter order
81 * @param cutoff_ratio cutoff to input frequency ratio
82 * @param stopband     stopband to input frequency ratio (used by bandpass and bandstop filter modes)
83 * @param ripple       ripple factor (used only in Chebyshev filters)
84 *
85 * @return pointer to filter coefficients structure or NULL if filter cannot be created
86 */
87struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,
88                                                enum IIRFilterType filt_type,
89                                                enum IIRFilterMode filt_mode,
90                                                int order, float cutoff_ratio,
91                                                float stopband, float ripple);
92
93/**
94 * Create new filter state.
95 *
96 * @param order filter order
97 *
98 * @return pointer to new filter state or NULL if state creation fails
99 */
100struct FFIIRFilterState* ff_iir_filter_init_state(int order);
101
102/**
103 * Free filter coefficients.
104 *
105 * @param coeffs pointer allocated with ff_iir_filter_init_coeffs()
106 */
107void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs);
108
109/**
110 * Free filter state.
111 *
112 * @param state pointer allocated with ff_iir_filter_init_state()
113 */
114void ff_iir_filter_free_state(struct FFIIRFilterState *state);
115
116/**
117 * Perform IIR filtering on signed 16-bit input samples.
118 *
119 * @param coeffs pointer to filter coefficients
120 * @param state  pointer to filter state
121 * @param size   input length
122 * @param src    source samples
123 * @param sstep  source stride
124 * @param dst    filtered samples (destination may be the same as input)
125 * @param dstep  destination stride
126 */
127void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state,
128                   int size, const int16_t *src, int sstep, int16_t *dst, int dstep);
129
130/**
131 * Perform IIR filtering on floating-point input samples.
132 *
133 * @param coeffs pointer to filter coefficients
134 * @param state  pointer to filter state
135 * @param size   input length
136 * @param src    source samples
137 * @param sstep  source stride
138 * @param dst    filtered samples (destination may be the same as input)
139 * @param dstep  destination stride
140 */
141void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *coeffs,
142                       struct FFIIRFilterState *state, int size,
143                       const float *src, int sstep, float *dst, int dstep);
144
145#endif /* AVCODEC_IIRFILTER_H */
146