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 <stddef.h> 31 #include <stdint.h> 32 33 struct FFIIRFilterCoeffs; 34 struct FFIIRFilterState; 35 36 enum IIRFilterType{ 37 FF_FILTER_TYPE_BESSEL, 38 FF_FILTER_TYPE_BIQUAD, 39 FF_FILTER_TYPE_BUTTERWORTH, 40 FF_FILTER_TYPE_CHEBYSHEV, 41 FF_FILTER_TYPE_ELLIPTIC, 42 }; 43 44 enum IIRFilterMode{ 45 FF_FILTER_MODE_LOWPASS, 46 FF_FILTER_MODE_HIGHPASS, 47 FF_FILTER_MODE_BANDPASS, 48 FF_FILTER_MODE_BANDSTOP, 49 }; 50 51 typedef struct FFIIRFilterContext { 52 /** 53 * Perform IIR filtering on floating-point input samples. 54 * 55 * @param coeffs pointer to filter coefficients 56 * @param state pointer to filter state 57 * @param size input length 58 * @param src source samples 59 * @param sstep source stride 60 * @param dst filtered samples (destination may be the same as input) 61 * @param dstep destination stride 62 */ 63 void (*filter_flt)(const struct FFIIRFilterCoeffs *coeffs, 64 struct FFIIRFilterState *state, int size, 65 const float *src, ptrdiff_t sstep, float *dst, ptrdiff_t dstep); 66 } FFIIRFilterContext; 67 68 /** 69 * Initialize FFIIRFilterContext 70 */ 71 void ff_iir_filter_init(FFIIRFilterContext *f); 72 void ff_iir_filter_init_mips(FFIIRFilterContext *f); 73 74 /** 75 * Initialize filter coefficients. 76 * 77 * @param avc a pointer to an arbitrary struct of which the first 78 * field is a pointer to an AVClass struct 79 * @param filt_type filter type (e.g. Butterworth) 80 * @param filt_mode filter mode (e.g. lowpass) 81 * @param order filter order 82 * @param cutoff_ratio cutoff to input frequency ratio 83 * @param stopband stopband to input frequency ratio (used by bandpass and bandstop filter modes) 84 * @param ripple ripple factor (used only in Chebyshev filters) 85 * 86 * @return pointer to filter coefficients structure or NULL if filter cannot be created 87 */ 88 struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc, 89 enum IIRFilterType filt_type, 90 enum IIRFilterMode filt_mode, 91 int order, float cutoff_ratio, 92 float stopband, float ripple); 93 94 /** 95 * Create new filter state. 96 * 97 * @param order filter order 98 * 99 * @return pointer to new filter state or NULL if state creation fails 100 */ 101 struct FFIIRFilterState* ff_iir_filter_init_state(int order); 102 103 /** 104 * Free filter coefficients. 105 * 106 * @param coeffs pointer allocated with ff_iir_filter_init_coeffs() 107 */ 108 void ff_iir_filter_free_coeffsp(struct FFIIRFilterCoeffs **coeffs); 109 110 /** 111 * Free and zero filter state. 112 * 113 * @param state pointer to pointer allocated with ff_iir_filter_init_state() 114 */ 115 void ff_iir_filter_free_statep(struct FFIIRFilterState **state); 116 117 /** 118 * Perform IIR filtering on signed 16-bit input samples. 119 * 120 * @param coeffs pointer to filter coefficients 121 * @param state pointer to filter state 122 * @param size input length 123 * @param src source samples 124 * @param sstep source stride 125 * @param dst filtered samples (destination may be the same as input) 126 * @param dstep destination stride 127 */ 128 void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state, 129 int size, const int16_t *src, ptrdiff_t sstep, int16_t *dst, ptrdiff_t dstep); 130 131 /** 132 * Perform IIR filtering on floating-point input samples. 133 * 134 * @param coeffs pointer to filter coefficients 135 * @param state pointer to filter state 136 * @param size input length 137 * @param src source samples 138 * @param sstep source stride 139 * @param dst filtered samples (destination may be the same as input) 140 * @param dstep destination stride 141 */ 142 void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *coeffs, 143 struct FFIIRFilterState *state, int size, 144 const float *src, ptrdiff_t sstep, 145 float *dst, ptrdiff_t dstep); 146 147 #endif /* AVCODEC_IIRFILTER_H */ 148