13e1598e399914f203ce37684b086861f2c45e97
[libav.git] / libavcodec / iirfilter.h
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
32 struct FFIIRFilterCoeffs;
33 struct FFIIRFilterState;
34
35 enum IIRFilterType{
36 FF_FILTER_TYPE_BESSEL,
37 FF_FILTER_TYPE_BUTTERWORTH,
38 FF_FILTER_TYPE_CHEBYSHEV,
39 FF_FILTER_TYPE_ELLIPTIC,
40 };
41
42 enum IIRFilterMode{
43 FF_FILTER_MODE_LOWPASS,
44 FF_FILTER_MODE_HIGHPASS,
45 FF_FILTER_MODE_BANDPASS,
46 FF_FILTER_MODE_BANDSTOP,
47 };
48
49 /**
50 * Initialize filter coefficients.
51 *
52 * @param avc a pointer to an arbitrary struct of which the first
53 * field is a pointer to an AVClass struct
54 * @param filt_type filter type (e.g. Butterworth)
55 * @param filt_mode filter mode (e.g. lowpass)
56 * @param order filter order
57 * @param cutoff_ratio cutoff to input frequency ratio
58 * @param stopband stopband to input frequency ratio (used by bandpass and bandstop filter modes)
59 * @param ripple ripple factor (used only in Chebyshev filters)
60 *
61 * @return pointer to filter coefficients structure or NULL if filter cannot be created
62 */
63 struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,
64 enum IIRFilterType filt_type,
65 enum IIRFilterMode filt_mode,
66 int order, float cutoff_ratio,
67 float stopband, float ripple);
68
69 /**
70 * Create new filter state.
71 *
72 * @param order filter order
73 *
74 * @return pointer to new filter state or NULL if state creation fails
75 */
76 struct FFIIRFilterState* ff_iir_filter_init_state(int order);
77
78 /**
79 * Free filter coefficients.
80 *
81 * @param coeffs pointer allocated with ff_iir_filter_init_coeffs()
82 */
83 void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs);
84
85 /**
86 * Free filter state.
87 *
88 * @param state pointer allocated with ff_iir_filter_init_state()
89 */
90 void ff_iir_filter_free_state(struct FFIIRFilterState *state);
91
92 /**
93 * Perform IIR filtering on signed 16-bit input samples.
94 *
95 * @param coeffs pointer to filter coefficients
96 * @param state pointer to filter state
97 * @param size input length
98 * @param src source samples
99 * @param sstep source stride
100 * @param dst filtered samples (destination may be the same as input)
101 * @param dstep destination stride
102 */
103 void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state,
104 int size, const int16_t *src, int sstep, int16_t *dst, int dstep);
105
106 /**
107 * Perform IIR filtering on floating-point input samples.
108 *
109 * @param coeffs pointer to filter coefficients
110 * @param state pointer to filter state
111 * @param size input length
112 * @param src source samples
113 * @param sstep source stride
114 * @param dst filtered samples (destination may be the same as input)
115 * @param dstep destination stride
116 */
117 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *coeffs,
118 struct FFIIRFilterState *state, int size,
119 const float *src, int sstep, void *dst, int dstep);
120
121 #endif /* AVCODEC_IIRFILTER_H */