120 lines
4.4 KiB
C
120 lines
4.4 KiB
C
/*
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* various filters for CELP-based codecs
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*
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* Copyright (c) 2008 Vladimir Voroshilov
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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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#ifndef AVCODEC_CELP_FILTERS_H
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#define AVCODEC_CELP_FILTERS_H
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#include <stdint.h>
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/**
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* Circularly convolve fixed vector with a phase dispersion impulse
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* response filter (D.6.2 of G.729 and 6.1.5 of AMR).
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* @param fc_out vector with filter applied
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* @param fc_in source vector
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* @param filter phase filter coefficients
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*
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* fc_out[n] = sum(i,0,len-1){ fc_in[i] * filter[(len + n - i)%len] }
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*
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* \note fc_in and fc_out should not overlap!
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*/
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void ff_celp_convolve_circ(int16_t *fc_out, const int16_t *fc_in,
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const int16_t *filter, int len);
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/**
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* Add an array to a rotated array.
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*
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* out[k] = in[k] + fac * lagged[k-lag] with wrap-around
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*
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* @param out result vector
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* @param in samples to be added unfiltered
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* @param lagged samples to be rotated, multiplied and added
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* @param lag lagged vector delay in the range [0, n]
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* @param fac scalefactor for lagged samples
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* @param n number of samples
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*/
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void ff_celp_circ_addf(float *out, const float *in,
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const float *lagged, int lag, float fac, int n);
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/**
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* LP synthesis filter.
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* @param[out] out pointer to output buffer
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* @param filter_coeffs filter coefficients (-0x8000 <= (3.12) < 0x8000)
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* @param in input signal
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* @param buffer_length amount of data to process
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* @param filter_length filter length (10 for 10th order LP filter)
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* @param stop_on_overflow 1 - return immediately if overflow occurs
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* 0 - ignore overflows
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* @param rounder the amount to add for rounding (usually 0x800 or 0xfff)
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*
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* @return 1 if overflow occurred, 0 - otherwise
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*
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* @note Output buffer must contain filter_length samples of past
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* speech data before pointer.
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*
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* Routine applies 1/A(z) filter to given speech data.
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*/
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int ff_celp_lp_synthesis_filter(int16_t *out, const int16_t *filter_coeffs,
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const int16_t *in, int buffer_length,
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int filter_length, int stop_on_overflow,
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int rounder);
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/**
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* LP synthesis filter.
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* @param[out] out pointer to output buffer
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* - the array out[-filter_length, -1] must
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* contain the previous result of this filter
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* @param filter_coeffs filter coefficients.
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* @param in input signal
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* @param buffer_length amount of data to process
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* @param filter_length filter length (10 for 10th order LP filter). Must be
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* greater than 4 and even.
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*
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* @note Output buffer must contain filter_length samples of past
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* speech data before pointer.
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*
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* Routine applies 1/A(z) filter to given speech data.
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*/
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void ff_celp_lp_synthesis_filterf(float *out, const float *filter_coeffs,
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const float *in, int buffer_length,
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int filter_length);
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/**
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* LP zero synthesis filter.
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* @param[out] out pointer to output buffer
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* @param filter_coeffs filter coefficients.
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* @param in input signal
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* - the array in[-filter_length, -1] must
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* contain the previous input of this filter
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* @param buffer_length amount of data to process
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* @param filter_length filter length (10 for 10th order LP filter)
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*
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* @note Output buffer must contain filter_length samples of past
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* speech data before pointer.
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*
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* Routine applies A(z) filter to given speech data.
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*/
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void ff_celp_lp_zero_synthesis_filterf(float *out, const float *filter_coeffs,
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const float *in, int buffer_length,
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int filter_length);
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#endif /* AVCODEC_CELP_FILTERS_H */
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