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
26 #include "libavutil/avassert.h"
29 #define ORDER_METHOD_EST 0
30 #define ORDER_METHOD_2LEVEL 1
31 #define ORDER_METHOD_4LEVEL 2
32 #define ORDER_METHOD_8LEVEL 3
33 #define ORDER_METHOD_SEARCH 4
34 #define ORDER_METHOD_LOG 5
36 #define MIN_LPC_ORDER 1
37 #define MAX_LPC_ORDER 32
43 FF_LPC_TYPE_DEFAULT = -1, ///< use the codec default LPC type
44 FF_LPC_TYPE_NONE = 0, ///< do not use LPC prediction or use all zero coefficients
45 FF_LPC_TYPE_FIXED = 1, ///< fixed LPC coefficients
46 FF_LPC_TYPE_LEVINSON = 2, ///< Levinson-Durbin recursion
47 FF_LPC_TYPE_CHOLESKY = 3, ///< Cholesky factorization
48 FF_LPC_TYPE_NB , ///< Not part of ABI
51 typedef struct LPCContext {
54 enum FFLPCType lpc_type;
55 double *windowed_buffer;
56 double *windowed_samples;
59 * Apply a Welch window to an array of input samples.
60 * The output samples have the same scale as the input, but are in double
62 * @param data input samples
63 * @param len number of input samples
64 * @param w_data output samples
66 void (*lpc_apply_welch_window)(const int32_t *data, int len,
69 * Perform autocorrelation on input samples with delay of 0 to lag.
70 * @param data input samples.
71 * constraints: no alignment needed, but must have have at
72 * least lag*sizeof(double) valid bytes preceding it, and
73 * size must be at least (len+1)*sizeof(double) if data is
74 * 16-byte aligned or (len+2)*sizeof(double) if data is
76 * @param len number of input samples to process
77 * @param lag maximum delay to calculate
78 * @param autoc output autocorrelation coefficients.
79 * constraints: array size must be at least lag+1.
81 void (*lpc_compute_autocorr)(const double *data, int len, int lag,
87 * Calculate LPC coefficients for multiple orders
89 int ff_lpc_calc_coefs(LPCContext *s,
90 const int32_t *samples, int blocksize, int min_order,
91 int max_order, int precision,
92 int32_t coefs[][MAX_LPC_ORDER], int *shift,
93 enum FFLPCType lpc_type, int lpc_passes,
94 int omethod, int max_shift, int zero_shift);
97 * Initialize LPCContext.
99 int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
100 enum FFLPCType lpc_type);
101 void ff_lpc_init_x86(LPCContext *s);
104 * Uninitialize LPCContext.
106 void ff_lpc_end(LPCContext *s);
108 #ifdef LPC_USE_DOUBLE
109 #define LPC_TYPE double
111 #define LPC_TYPE float
115 * Levinson-Durbin recursion.
116 * Produce LPC coefficients from autocorrelation data.
118 static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order,
119 LPC_TYPE *lpc, int lpc_stride, int fail,
124 LPC_TYPE *lpc_last = lpc;
126 av_assert2(normalize || !fail);
131 if (fail && (autoc[max_order - 1] == 0 || err <= 0))
134 for(i=0; i<max_order; i++) {
135 LPC_TYPE r = -autoc[i];
139 r -= lpc_last[j] * autoc[i-j-1];
142 err *= 1.0 - (r * r);
147 for(j=0; j < (i+1)>>1; j++) {
148 LPC_TYPE f = lpc_last[ j];
149 LPC_TYPE b = lpc_last[i-1-j];
151 lpc[i-1-j] = b + r * f;
164 #endif /* AVCODEC_LPC_H */