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iirfilter.h
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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 
41 };
42 
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  */
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  */
78 
79 /**
80  * Free filter coefficients.
81  *
82  * @param coeffs pointer allocated with ff_iir_filter_init_coeffs()
83  */
85 
86 /**
87  * Free filter state.
88  *
89  * @param state pointer allocated with ff_iir_filter_init_state()
90  */
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  */
104 void 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  */
118 void 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 */