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123 lines
3.9 KiB
C
123 lines
3.9 KiB
C
/*
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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 Libav.
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*
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* Libav 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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* Libav 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 Libav; 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_BIQUAD,
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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, float *dst, int dstep);
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#endif /* AVCODEC_IIRFILTER_H */
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