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103 lines
3.1 KiB
103 lines
3.1 KiB
/* |
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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 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(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 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_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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#endif /* AVCODEC_IIRFILTER_H */
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