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ffmpeg / libavcodec / iirfilter.h @ d42dc217

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/*
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 * IIR filter
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 * Copyright (c) 2008 Konstantin Shishkov
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/**
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 * @file
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 * IIR filter interface
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 */
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#ifndef AVCODEC_IIRFILTER_H
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#define AVCODEC_IIRFILTER_H
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#include "avcodec.h"
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struct FFIIRFilterCoeffs;
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struct FFIIRFilterState;
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enum IIRFilterType{
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    FF_FILTER_TYPE_BESSEL,
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    FF_FILTER_TYPE_BUTTERWORTH,
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    FF_FILTER_TYPE_CHEBYSHEV,
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    FF_FILTER_TYPE_ELLIPTIC,
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};
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enum IIRFilterMode{
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    FF_FILTER_MODE_LOWPASS,
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    FF_FILTER_MODE_HIGHPASS,
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    FF_FILTER_MODE_BANDPASS,
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    FF_FILTER_MODE_BANDSTOP,
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};
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/**
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 * Initialize filter coefficients.
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 *
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 * @param avc          a pointer to an arbitrary struct of which the first
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 *                     field is a pointer to an AVClass struct
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 * @param filt_type    filter type (e.g. Butterworth)
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 * @param filt_mode    filter mode (e.g. lowpass)
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 * @param order        filter order
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 * @param cutoff_ratio cutoff to input frequency ratio
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 * @param stopband     stopband to input frequency ratio (used by bandpass and bandstop filter modes)
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 * @param ripple       ripple factor (used only in Chebyshev filters)
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 *
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 * @return pointer to filter coefficients structure or NULL if filter cannot be created
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 */
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struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,
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                                                enum IIRFilterType filt_type,
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                                                    enum IIRFilterMode filt_mode,
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                                                    int order, float cutoff_ratio,
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                                                    float stopband, float ripple);
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/**
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 * Create new filter state.
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 *
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 * @param order filter order
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 *
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 * @return pointer to new filter state or NULL if state creation fails
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 */
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struct FFIIRFilterState* ff_iir_filter_init_state(int order);
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/**
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 * Free filter coefficients.
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 *
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 * @param coeffs pointer allocated with ff_iir_filter_init_coeffs()
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 */
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void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs);
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/**
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 * Free filter state.
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 *
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 * @param state pointer allocated with ff_iir_filter_init_state()
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 */
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void ff_iir_filter_free_state(struct FFIIRFilterState *state);
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/**
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 * Perform IIR filtering on signed 16-bit input samples.
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 *
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 * @param coeffs pointer to filter coefficients
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 * @param state  pointer to filter state
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 * @param size   input length
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 * @param src    source samples
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 * @param sstep  source stride
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 * @param dst    filtered samples (destination may be the same as input)
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 * @param dstep  destination stride
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 */
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void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state,
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                   int size, const int16_t *src, int sstep, int16_t *dst, int dstep);
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/**
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 * Perform IIR filtering on floating-point input samples.
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 *
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 * @param coeffs pointer to filter coefficients
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 * @param state  pointer to filter state
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 * @param size   input length
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 * @param src    source samples
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 * @param sstep  source stride
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 * @param dst    filtered samples (destination may be the same as input)
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 * @param dstep  destination stride
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 */
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void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *coeffs,
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                       struct FFIIRFilterState *state, int size,
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                       const float *src, int sstep, void *dst, int dstep);
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#endif /* AVCODEC_IIRFILTER_H */