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105 lines
2.8 KiB
105 lines
2.8 KiB
/** |
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* LPC utility code |
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* Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com> |
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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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#ifndef AVCODEC_LPC_H |
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#define AVCODEC_LPC_H |
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#include <stdint.h> |
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#include "dsputil.h" |
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#define ORDER_METHOD_EST 0 |
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#define ORDER_METHOD_2LEVEL 1 |
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#define ORDER_METHOD_4LEVEL 2 |
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#define ORDER_METHOD_8LEVEL 3 |
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#define ORDER_METHOD_SEARCH 4 |
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#define ORDER_METHOD_LOG 5 |
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#define MIN_LPC_ORDER 1 |
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#define MAX_LPC_ORDER 32 |
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/** |
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* Calculate LPC coefficients for multiple orders |
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*/ |
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int ff_lpc_calc_coefs(DSPContext *s, |
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const int32_t *samples, int blocksize, int min_order, |
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int max_order, int precision, |
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int32_t coefs[][MAX_LPC_ORDER], int *shift, int use_lpc, |
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int omethod, int max_shift, int zero_shift); |
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void ff_lpc_compute_autocorr(const int32_t *data, int len, int lag, |
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double *autoc); |
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#ifdef LPC_USE_DOUBLE |
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#define LPC_TYPE double |
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#else |
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#define LPC_TYPE float |
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#endif |
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/** |
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* Levinson-Durbin recursion. |
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* Produce LPC coefficients from autocorrelation data. |
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*/ |
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static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order, |
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LPC_TYPE *lpc, int lpc_stride, int fail, |
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int normalize) |
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{ |
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int i, j; |
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LPC_TYPE err; |
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LPC_TYPE *lpc_last = lpc; |
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if (normalize) |
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err = *autoc++; |
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if (fail && (autoc[max_order - 1] == 0 || err <= 0)) |
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return -1; |
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for(i=0; i<max_order; i++) { |
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LPC_TYPE r = -autoc[i]; |
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if (normalize) { |
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for(j=0; j<i; j++) |
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r -= lpc_last[j] * autoc[i-j-1]; |
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r /= err; |
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err *= 1.0 - (r * r); |
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} |
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lpc[i] = r; |
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for(j=0; j < (i+1)>>1; j++) { |
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LPC_TYPE f = lpc_last[ j]; |
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LPC_TYPE b = lpc_last[i-1-j]; |
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lpc[ j] = f + r * b; |
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lpc[i-1-j] = b + r * f; |
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} |
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if (fail && err < 0) |
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return -1; |
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lpc_last = lpc; |
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lpc += lpc_stride; |
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} |
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return 0; |
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} |
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#endif /* AVCODEC_LPC_H */
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