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1/*
2 * LPC utility code
3 * Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com>
4 *
5 * This file is part of FFmpeg.
6 *
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.
11 *
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.
16 *
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
20 */
21
22#ifndef AVCODEC_LPC_H
23#define AVCODEC_LPC_H
24
25#include <stdint.h>
26#include "libavutil/avassert.h"
27#include "libavutil/lls.h"
28#include "aac_defines.h"
29
30#define ORDER_METHOD_EST 0
31#define ORDER_METHOD_2LEVEL 1
32#define ORDER_METHOD_4LEVEL 2
33#define ORDER_METHOD_8LEVEL 3
34#define ORDER_METHOD_SEARCH 4
35#define ORDER_METHOD_LOG 5
36
37#define MIN_LPC_ORDER 1
38#define MAX_LPC_ORDER 32
39
40/**
41 * LPC analysis type
42 */
43enum FFLPCType {
44 FF_LPC_TYPE_DEFAULT = -1, ///< use the codec default LPC type
45 FF_LPC_TYPE_NONE = 0, ///< do not use LPC prediction or use all zero coefficients
46 FF_LPC_TYPE_FIXED = 1, ///< fixed LPC coefficients
47 FF_LPC_TYPE_LEVINSON = 2, ///< Levinson-Durbin recursion
48 FF_LPC_TYPE_CHOLESKY = 3, ///< Cholesky factorization
49 FF_LPC_TYPE_NB , ///< Not part of ABI
50};
51
52typedef struct LPCContext {
53 int blocksize;
54 int max_order;
55 enum FFLPCType lpc_type;
56 double *windowed_buffer;
57 double *windowed_samples;
58
59 /**
60 * Apply a Welch window to an array of input samples.
61 * The output samples have the same scale as the input, but are in double
62 * sample format.
63 * @param data input samples
64 * @param len number of input samples
65 * @param w_data output samples
66 */
67 void (*lpc_apply_welch_window)(const int32_t *data, int len,
68 double *w_data);
69 /**
70 * Perform autocorrelation on input samples with delay of 0 to lag.
71 * @param data input samples.
72 * constraints: no alignment needed, but must have at
73 * least lag*sizeof(double) valid bytes preceding it, and
74 * size must be at least (len+1)*sizeof(double) if data is
75 * 16-byte aligned or (len+2)*sizeof(double) if data is
76 * unaligned.
77 * @param len number of input samples to process
78 * @param lag maximum delay to calculate
79 * @param autoc output autocorrelation coefficients.
80 * constraints: array size must be at least lag+1.
81 */
82 void (*lpc_compute_autocorr)(const double *data, int len, int lag,
83 double *autoc);
84
85 // TODO: these should be allocated to reduce ABI compatibility issues
86 LLSModel lls_models[2];
87} LPCContext;
88
89
90/**
91 * Calculate LPC coefficients for multiple orders
92 */
93int ff_lpc_calc_coefs(LPCContext *s,
94 const int32_t *samples, int blocksize, int min_order,
95 int max_order, int precision,
96 int32_t coefs[][MAX_LPC_ORDER], int *shift,
97 enum FFLPCType lpc_type, int lpc_passes,
98 int omethod, int min_shift, int max_shift, int zero_shift);
99
100int ff_lpc_calc_ref_coefs(LPCContext *s,
101 const int32_t *samples, int order, double *ref);
102
103double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len,
104 int order, double *ref);
105
106/**
107 * Initialize LPCContext.
108 */
109int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
110 enum FFLPCType lpc_type);
111void ff_lpc_init_x86(LPCContext *s);
112
113/**
114 * Uninitialize LPCContext.
115 */
116void ff_lpc_end(LPCContext *s);
117
118#if USE_FIXED
119typedef int LPC_TYPE;
120#else
121#ifdef LPC_USE_DOUBLE
122typedef double LPC_TYPE;
123#else
124typedef float LPC_TYPE;
125#endif
126#endif // USE_FIXED
127
128/**
129 * Schur recursion.
130 * Produces reflection coefficients from autocorrelation data.
131 */
132static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order,
133 LPC_TYPE *ref, LPC_TYPE *error)
134{
135 int i, j;
136 LPC_TYPE err;
137 LPC_TYPE gen0[MAX_LPC_ORDER], gen1[MAX_LPC_ORDER];
138
139 for (i = 0; i < max_order; i++)
140 gen0[i] = gen1[i] = autoc[i + 1];
141
142 err = autoc[0];
143 ref[0] = -gen1[0] / err;
144 err += gen1[0] * ref[0];
145 if (error)
146 error[0] = err;
147 for (i = 1; i < max_order; i++) {
148 for (j = 0; j < max_order - i; j++) {
149 gen1[j] = gen1[j + 1] + ref[i - 1] * gen0[j];
150 gen0[j] = gen1[j + 1] * ref[i - 1] + gen0[j];
151 }
152 ref[i] = -gen1[0] / err;
153 err += gen1[0] * ref[i];
154 if (error)
155 error[i] = err;
156 }
157}
158
159/**
160 * Levinson-Durbin recursion.
161 * Produce LPC coefficients from autocorrelation data.
162 */
163static inline int AAC_RENAME(compute_lpc_coefs)(const LPC_TYPE *autoc, int max_order,
164 LPC_TYPE *lpc, int lpc_stride, int fail,
165 int normalize)
166{
167 int i, j;
168 LPC_TYPE err = 0;
169 LPC_TYPE *lpc_last = lpc;
170
171 av_assert2(normalize || !fail);
172
173 if (normalize)
174 err = *autoc++;
175
176 if (fail && (autoc[max_order - 1] == 0 || err <= 0))
177 return -1;
178
179 for(i=0; i<max_order; i++) {
180 LPC_TYPE r = AAC_SRA_R(-autoc[i], 5);
181
182 if (normalize) {
183 for(j=0; j<i; j++)
184 r -= lpc_last[j] * autoc[i-j-1];
185
186 r /= err;
187 err *= FIXR(1.0) - (r * r);
188 }
189
190 lpc[i] = r;
191
192 for(j=0; j < (i+1)>>1; j++) {
193 LPC_TYPE f = lpc_last[ j];
194 LPC_TYPE b = lpc_last[i-1-j];
195 lpc[ j] = f + AAC_MUL26(r, b);
196 lpc[i-1-j] = b + AAC_MUL26(r, f);
197 }
198
199 if (fail && err < 0)
200 return -1;
201
202 lpc_last = lpc;
203 lpc += lpc_stride;
204 }
205
206 return 0;
207}
208
209#endif /* AVCODEC_LPC_H */
210
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