1/* 2 * IIR filter 3 * Copyright (c) 2008 Konstantin Shishkov 4 * 5 * This file is part of Libav. 6 * 7 * Libav 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 * Libav 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 Libav; 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 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 */ 64struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc, 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 */ 77struct FFIIRFilterState* ff_iir_filter_init_state(int order); 78 79/** 80 * Free filter coefficients. 81 * 82 * @param coeffs pointer allocated with ff_iir_filter_init_coeffs() 83 */ 84void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs); 85 86/** 87 * Free filter state. 88 * 89 * @param state pointer allocated with ff_iir_filter_init_state() 90 */ 91void ff_iir_filter_free_state(struct FFIIRFilterState *state); 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 */ 104void 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 */ 118void 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 */ 123