1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
|
/*
* IIR filter
* Copyright (c) 2008 Konstantin Shishkov
*
* This file is part of Libav.
*
* Libav is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* Libav is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* IIR filter interface
*/
#ifndef AVCODEC_IIRFILTER_H
#define AVCODEC_IIRFILTER_H
#include <stddef.h>
#include <stdint.h>
struct FFIIRFilterCoeffs;
struct FFIIRFilterState;
enum IIRFilterType{
FF_FILTER_TYPE_BESSEL,
FF_FILTER_TYPE_BIQUAD,
FF_FILTER_TYPE_BUTTERWORTH,
FF_FILTER_TYPE_CHEBYSHEV,
FF_FILTER_TYPE_ELLIPTIC,
};
enum IIRFilterMode{
FF_FILTER_MODE_LOWPASS,
FF_FILTER_MODE_HIGHPASS,
FF_FILTER_MODE_BANDPASS,
FF_FILTER_MODE_BANDSTOP,
};
/**
* Initialize filter coefficients.
*
* @param avc a pointer to an arbitrary struct of which the first
* field is a pointer to an AVClass struct
* @param filt_type filter type (e.g. Butterworth)
* @param filt_mode filter mode (e.g. lowpass)
* @param order filter order
* @param cutoff_ratio cutoff to input frequency ratio
* @param stopband stopband to input frequency ratio (used by bandpass and bandstop filter modes)
* @param ripple ripple factor (used only in Chebyshev filters)
*
* @return pointer to filter coefficients structure or NULL if filter cannot be created
*/
struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,
enum IIRFilterType filt_type,
enum IIRFilterMode filt_mode,
int order, float cutoff_ratio,
float stopband, float ripple);
/**
* Create new filter state.
*
* @param order filter order
*
* @return pointer to new filter state or NULL if state creation fails
*/
struct FFIIRFilterState* ff_iir_filter_init_state(int order);
/**
* Free filter coefficients.
*
* @param coeffs pointer allocated with ff_iir_filter_init_coeffs()
*/
void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs);
/**
* Free filter state.
*
* @param state pointer allocated with ff_iir_filter_init_state()
*/
void ff_iir_filter_free_state(struct FFIIRFilterState *state);
/**
* Perform IIR filtering on signed 16-bit input samples.
*
* @param coeffs pointer to filter coefficients
* @param state pointer to filter state
* @param size input length
* @param src source samples
* @param sstep source stride
* @param dst filtered samples (destination may be the same as input)
* @param dstep destination stride
*/
void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state,
int size, const int16_t *src, ptrdiff_t sstep, int16_t *dst, ptrdiff_t dstep);
/**
* Perform IIR filtering on floating-point input samples.
*
* @param coeffs pointer to filter coefficients
* @param state pointer to filter state
* @param size input length
* @param src source samples
* @param sstep source stride
* @param dst filtered samples (destination may be the same as input)
* @param dstep destination stride
*/
void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *coeffs,
struct FFIIRFilterState *state, int size,
const float *src, ptrdiff_t sstep,
float *dst, ptrdiff_t dstep);
#endif /* AVCODEC_IIRFILTER_H */
|
