3 * Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com>
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
28 #define ORDER_METHOD_EST 0
29 #define ORDER_METHOD_2LEVEL 1
30 #define ORDER_METHOD_4LEVEL 2
31 #define ORDER_METHOD_8LEVEL 3
32 #define ORDER_METHOD_SEARCH 4
33 #define ORDER_METHOD_LOG 5
35 #define MIN_LPC_ORDER 1
36 #define MAX_LPC_ORDER 32
40 * Calculate LPC coefficients for multiple orders
42 int ff_lpc_calc_coefs(DSPContext *s,
43 const int32_t *samples, int blocksize, int min_order,
44 int max_order, int precision,
45 int32_t coefs[][MAX_LPC_ORDER], int *shift, int use_lpc,
46 int omethod, int max_shift, int zero_shift);
49 #define LPC_TYPE double
51 #define LPC_TYPE float
55 * Levinson-Durbin recursion.
56 * Produces LPC coefficients from autocorrelation data.
58 static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order,
59 LPC_TYPE *lpc, int lpc_stride, int fail,
64 LPC_TYPE *lpc_last = lpc;
69 if (fail && (autoc[max_order - 1] == 0 || err <= 0))
72 for(i=0; i<max_order; i++) {
73 LPC_TYPE r = -autoc[i];
77 r -= lpc_last[j] * autoc[i-j-1];
85 for(j=0; j < (i+1)>>1; j++) {
86 LPC_TYPE f = lpc_last[ j];
87 LPC_TYPE b = lpc_last[i-1-j];
89 lpc[i-1-j] = b + r * f;
102 #endif /* AVCODEC_LPC_H */