libavcodec/iirfilter.h

   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
  32 struct FFIIRFilterCoeffs;
  33 struct FFIIRFilterState;
  34
  35 enum 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
  43 enum 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  */
  64 struct 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  */
  77 struct 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  */
  84 void 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  */
  91 void 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  */
 104 void 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  */
 118 void 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 */