blob: 5ffa1ce53abd27a044dedbf7749989f77542420c
| 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 |