3 * Copyright (c) 2008 Konstantin Shishkov
5 * This file is part of FFmpeg.
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.
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.
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
24 * IIR filter interface
27 #ifndef AVCODEC_IIRFILTER_H
28 #define AVCODEC_IIRFILTER_H
32 struct FFIIRFilterCoeffs;
33 struct FFIIRFilterState;
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,
44 FF_FILTER_MODE_LOWPASS,
45 FF_FILTER_MODE_HIGHPASS,
46 FF_FILTER_MODE_BANDPASS,
47 FF_FILTER_MODE_BANDSTOP,
50 typedef struct FFIIRFilterContext {
52 * Perform IIR filtering on floating-point input samples.
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
62 void (*filter_flt)(const struct FFIIRFilterCoeffs *coeffs,
63 struct FFIIRFilterState *state, int size,
64 const float *src, int sstep, float *dst, int dstep);
68 * Initialize FFIIRFilterContext
70 void ff_iir_filter_init(FFIIRFilterContext *f);
71 void ff_iir_filter_init_mips(FFIIRFilterContext *f);
74 * Initialize filter coefficients.
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)
85 * @return pointer to filter coefficients structure or NULL if filter cannot be created
87 struct 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);
94 * Create new filter state.
96 * @param order filter order
98 * @return pointer to new filter state or NULL if state creation fails
100 struct FFIIRFilterState* ff_iir_filter_init_state(int order);
103 * Free filter coefficients.
105 * @param coeffs pointer allocated with ff_iir_filter_init_coeffs()
107 void ff_iir_filter_free_coeffsp(struct FFIIRFilterCoeffs **coeffs);
110 * Free and zero filter state.
112 * @param state pointer to pointer allocated with ff_iir_filter_init_state()
114 void ff_iir_filter_free_statep(struct FFIIRFilterState **state);
117 * Perform IIR filtering on signed 16-bit input samples.
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
127 void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state,
128 int size, const int16_t *src, int sstep, int16_t *dst, int dstep);
131 * Perform IIR filtering on floating-point input samples.
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
141 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *coeffs,
142 struct FFIIRFilterState *state, int size,
143 const float *src, int sstep, float *dst, int dstep);
145 #endif /* AVCODEC_IIRFILTER_H */