Simple lowpass filter implementation.
[libav.git] / libavcodec / lowpass.h
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1/*
2 * Lowpass 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 lowpass.h
24 * lowpass filter interface
25 */
26
27#ifndef FFMPEG_LOWPASS_H
28#define FFMPEG_LOWPASS_H
29
30#include "avcodec.h"
31
32struct FFLPFilterCoeffs;
33struct FFLPFilterState;
34
35/**
36 * Initialize filter coefficients.
37 *
38 * @param order filter order
39 * @param cutoff_ratio cutoff to input frequency ratio
40 *
41 * @return pointer to filter coefficients structure or NULL if filter cannot be created
42 */
43const struct FFLPFilterCoeffs* ff_lowpass_filter_init_coeffs(int order, float cutoff_ratio);
44
45/**
46 * Create new filter state.
47 *
48 * @param order filter order
49 *
50 * @return pointer to new filter state or NULL if state creation fails
51 */
52struct FFLPFilterState* ff_lowpass_filter_init_state(int order);
53
54#if 0 //enable with arbitrary order filter implementation, use av_free() for filter state only for now
55/**
56 * Free filter coefficients.
57 *
58 * @param coeffs pointer allocated with ff_lowpass_filter_init_coeffs()
59 */
60void ff_lowpass_filter_free_coeffs(struct FFLPFilterCoeffs *coeffs);
61
62/**
63 * Free filter state.
64 *
65 * @param state pointer allocated with ff_lowpass_filter_init_state()
66 */
67void ff_lowpass_filter_free_state(struct FFLPFilterState *state);
68#endif
69
70/**
71 * Perform lowpass filtering on input samples.
72 *
73 * @param coeffs pointer to filter coefficients
74 * @param state pointer to filter state
75 * @param size input length
76 * @param src source samples
77 * @param sstep source stride
78 * @param dst filtered samples (destination may be the same as input)
79 * @param dstep destination stride
80 */
81void ff_lowpass_filter(const struct FFLPFilterCoeffs *coeffs, struct FFLPFilterState *state, int size, int16_t *src, int sstep, int16_t *dst, int dstep);
82
83#endif /* FFMPEG_LOWPASS_H */