3 * Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com>
5 * This file is part of Libav.
7 * Libav 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 * Libav 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 Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
27 #define ORDER_METHOD_EST 0
28 #define ORDER_METHOD_2LEVEL 1
29 #define ORDER_METHOD_4LEVEL 2
30 #define ORDER_METHOD_8LEVEL 3
31 #define ORDER_METHOD_SEARCH 4
32 #define ORDER_METHOD_LOG 5
34 #define MIN_LPC_ORDER 1
35 #define MAX_LPC_ORDER 32
41 FF_LPC_TYPE_DEFAULT = -1, ///< use the codec default LPC type
42 FF_LPC_TYPE_NONE = 0, ///< do not use LPC prediction or use all zero coefficients
43 FF_LPC_TYPE_FIXED = 1, ///< fixed LPC coefficients
44 FF_LPC_TYPE_LEVINSON = 2, ///< Levinson-Durbin recursion
45 FF_LPC_TYPE_CHOLESKY = 3, ///< Cholesky factorization
46 FF_LPC_TYPE_NB , ///< Not part of ABI
49 typedef struct LPCContext {
52 enum FFLPCType lpc_type;
53 double *windowed_buffer;
54 double *windowed_samples;
57 * Apply a Welch window to an array of input samples.
58 * The output samples have the same scale as the input, but are in double
60 * @param data input samples
61 * @param len number of input samples
62 * @param w_data output samples
64 void (*lpc_apply_welch_window)(const int32_t *data, int len,
67 * Perform autocorrelation on input samples with delay of 0 to lag.
68 * @param data input samples.
69 * constraints: no alignment needed, but must have have at
70 * least lag*sizeof(double) valid bytes preceding it, and
71 * size must be at least (len+1)*sizeof(double) if data is
72 * 16-byte aligned or (len+2)*sizeof(double) if data is
74 * @param len number of input samples to process
75 * @param lag maximum delay to calculate
76 * @param autoc output autocorrelation coefficients.
77 * constraints: array size must be at least lag+1.
79 void (*lpc_compute_autocorr)(const double *data, int len, int lag,
85 * Calculate LPC coefficients for multiple orders
87 int ff_lpc_calc_coefs(LPCContext *s,
88 const int32_t *samples, int blocksize, int min_order,
89 int max_order, int precision,
90 int32_t coefs[][MAX_LPC_ORDER], int *shift,
91 enum FFLPCType lpc_type, int lpc_passes,
92 int omethod, int max_shift, int zero_shift);
94 int ff_lpc_calc_ref_coefs(LPCContext *s,
95 const int32_t *samples, int order, double *ref);
98 * Initialize LPCContext.
100 int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
101 enum FFLPCType lpc_type);
102 void ff_lpc_init_x86(LPCContext *s);
105 * Uninitialize LPCContext.
107 void ff_lpc_end(LPCContext *s);
109 #ifdef LPC_USE_DOUBLE
110 #define LPC_TYPE double
112 #define LPC_TYPE float
117 * Produces reflection coefficients from autocorrelation data.
119 static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order,
120 LPC_TYPE *ref, LPC_TYPE *error)
124 LPC_TYPE gen0[MAX_LPC_ORDER], gen1[MAX_LPC_ORDER];
126 for (i = 0; i < max_order; i++)
127 gen0[i] = gen1[i] = autoc[i + 1];
130 ref[0] = -gen1[0] / err;
131 err += gen1[0] * ref[0];
134 for (i = 1; i < max_order; i++) {
135 for (j = 0; j < max_order - i; j++) {
136 gen1[j] = gen1[j + 1] + ref[i - 1] * gen0[j];
137 gen0[j] = gen1[j + 1] * ref[i - 1] + gen0[j];
139 ref[i] = -gen1[0] / err;
140 err += gen1[0] * ref[i];
147 * Levinson-Durbin recursion.
148 * Produce LPC coefficients from autocorrelation data.
150 static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order,
151 LPC_TYPE *lpc, int lpc_stride, int fail,
156 LPC_TYPE *lpc_last = lpc;
161 if (fail && (autoc[max_order - 1] == 0 || err <= 0))
164 for(i=0; i<max_order; i++) {
165 LPC_TYPE r = -autoc[i];
169 r -= lpc_last[j] * autoc[i-j-1];
172 err *= 1.0 - (r * r);
177 for(j=0; j < (i+1)>>1; j++) {
178 LPC_TYPE f = lpc_last[ j];
179 LPC_TYPE b = lpc_last[i-1-j];
181 lpc[i-1-j] = b + r * f;
194 #endif /* AVCODEC_LPC_H */