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 32struct FFIIRFilterCoeffs; 33struct FFIIRFilterState; 34 35enum IIRFilterType{ 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, 41}; 42 43enum IIRFilterMode{ 44 FF_FILTER_MODE_LOWPASS, 45 FF_FILTER_MODE_HIGHPASS, 46 FF_FILTER_MODE_BANDPASS, 47 FF_FILTER_MODE_BANDSTOP, 48}; 49 50typedef struct FFIIRFilterContext { 51 /** 52 * Perform IIR filtering on floating-point input samples. 53 * 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 61 */ 62 void (*filter_flt)(const struct FFIIRFilterCoeffs *coeffs, 63 struct FFIIRFilterState *state, int size, 64 const float *src, int sstep, float *dst, int dstep); 65} FFIIRFilterContext; 66 67/** 68 * Initialize FFIIRFilterContext 69 */ 70void ff_iir_filter_init(FFIIRFilterContext *f); 71void ff_iir_filter_init_mips(FFIIRFilterContext *f); 72 73/** 74 * Initialize filter coefficients. 75 * 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) 84 * 85 * @return pointer to filter coefficients structure or NULL if filter cannot be created 86 */ 87struct 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); 92 93/** 94 * Create new filter state. 95 * 96 * @param order filter order 97 * 98 * @return pointer to new filter state or NULL if state creation fails 99 */ 100struct FFIIRFilterState* ff_iir_filter_init_state(int order); 101 102/** 103 * Free filter coefficients. 104 * 105 * @param coeffs pointer allocated with ff_iir_filter_init_coeffs() 106 */ 107void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs); 108 109/** 110 * Free filter state. 111 * 112 * @param state pointer allocated with ff_iir_filter_init_state() 113 */ 114void ff_iir_filter_free_state(struct FFIIRFilterState *state); 115 116/** 117 * Perform IIR filtering on signed 16-bit input samples. 118 * 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 126 */ 127void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state, 128 int size, const int16_t *src, int sstep, int16_t *dst, int dstep); 129 130/** 131 * Perform IIR filtering on floating-point input samples. 132 * 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 140 */ 141void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *coeffs, 142 struct FFIIRFilterState *state, int size, 143 const float *src, int sstep, float *dst, int dstep); 144 145#endif /* AVCODEC_IIRFILTER_H */ 146