84 lines
2.5 KiB
C
84 lines
2.5 KiB
C
/*
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* Lowpass 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 lowpass.h
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* lowpass filter interface
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*/
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#ifndef FFMPEG_LOWPASS_H
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#define FFMPEG_LOWPASS_H
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#include "avcodec.h"
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struct FFLPFilterCoeffs;
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struct FFLPFilterState;
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/**
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* Initialize filter coefficients.
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*
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* @param order filter order
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* @param cutoff_ratio cutoff to input frequency ratio
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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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const struct FFLPFilterCoeffs* ff_lowpass_filter_init_coeffs(int order, float cutoff_ratio);
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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 FFLPFilterState* ff_lowpass_filter_init_state(int order);
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#if 0 //enable with arbitrary order filter implementation, use av_free() for filter state only for now
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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_lowpass_filter_init_coeffs()
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*/
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void ff_lowpass_filter_free_coeffs(struct FFLPFilterCoeffs *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_lowpass_filter_init_state()
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*/
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void ff_lowpass_filter_free_state(struct FFLPFilterState *state);
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#endif
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/**
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* Perform lowpass filtering on 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_lowpass_filter(const struct FFLPFilterCoeffs *coeffs, struct FFLPFilterState *state, int size, int16_t *src, int sstep, int16_t *dst, int dstep);
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#endif /* FFMPEG_LOWPASS_H */
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