/** * LPC utility code * Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com> * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #ifndef AVCODEC_LPC_H #define AVCODEC_LPC_H #include <stdint.h> #include "dsputil.h" #define ORDER_METHOD_EST 0 #define ORDER_METHOD_2LEVEL 1 #define ORDER_METHOD_4LEVEL 2 #define ORDER_METHOD_8LEVEL 3 #define ORDER_METHOD_SEARCH 4 #define ORDER_METHOD_LOG 5 #define MIN_LPC_ORDER 1 #define MAX_LPC_ORDER 32 /** * Calculate LPC coefficients for multiple orders */ int ff_lpc_calc_coefs(DSPContext *s, const int32_t *samples, int blocksize, int min_order, int max_order, int precision, int32_t coefs[][MAX_LPC_ORDER], int *shift, int use_lpc, int omethod, int max_shift, int zero_shift); #ifdef LPC_USE_DOUBLE #define LPC_TYPE double #else #define LPC_TYPE float #endif /** * Levinson-Durbin recursion. * Produces LPC coefficients from autocorrelation data. */ static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order, LPC_TYPE *lpc, int lpc_stride, int fail, int normalize) { int i, j; LPC_TYPE err; LPC_TYPE *lpc_last = lpc; if (normalize) err = *autoc++; if (fail && (autoc[max_order - 1] == 0 || err <= 0)) return -1; for(i=0; i<max_order; i++) { LPC_TYPE r = -autoc[i]; if (normalize) { for(j=0; j<i; j++) r -= lpc_last[j] * autoc[i-j-1]; r /= err; err *= 1.0 - (r * r); } lpc[i] = r; for(j=0; j < (i+1)>>1; j++) { LPC_TYPE f = lpc_last[ j]; LPC_TYPE b = lpc_last[i-1-j]; lpc[ j] = f + r * b; lpc[i-1-j] = b + r * f; } if (fail && err < 0) return -1; lpc_last = lpc; lpc += lpc_stride; } return 0; } #endif /* AVCODEC_LPC_H */