1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
|
/*
* 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 "libavutil/avassert.h"
#include "libavutil/lls.h"
#include "aac_defines.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
/**
* LPC analysis type
*/
enum FFLPCType {
FF_LPC_TYPE_DEFAULT = -1, ///< use the codec default LPC type
FF_LPC_TYPE_NONE = 0, ///< do not use LPC prediction or use all zero coefficients
FF_LPC_TYPE_FIXED = 1, ///< fixed LPC coefficients
FF_LPC_TYPE_LEVINSON = 2, ///< Levinson-Durbin recursion
FF_LPC_TYPE_CHOLESKY = 3, ///< Cholesky factorization
FF_LPC_TYPE_NB , ///< Not part of ABI
};
typedef struct LPCContext {
int blocksize;
int max_order;
enum FFLPCType lpc_type;
double *windowed_buffer;
double *windowed_samples;
/**
* Apply a Welch window to an array of input samples.
* The output samples have the same scale as the input, but are in double
* sample format.
* @param data input samples
* @param len number of input samples
* @param w_data output samples
*/
void (*lpc_apply_welch_window)(const int32_t *data, int len,
double *w_data);
/**
* Perform autocorrelation on input samples with delay of 0 to lag.
* @param data input samples.
* constraints: no alignment needed, but must have at
* least lag*sizeof(double) valid bytes preceding it, and
* size must be at least (len+1)*sizeof(double) if data is
* 16-byte aligned or (len+2)*sizeof(double) if data is
* unaligned.
* @param len number of input samples to process
* @param lag maximum delay to calculate
* @param autoc output autocorrelation coefficients.
* constraints: array size must be at least lag+1.
*/
void (*lpc_compute_autocorr)(const double *data, int len, int lag,
double *autoc);
// TODO: these should be allocated to reduce ABI compatibility issues
LLSModel lls_models[2];
} LPCContext;
/**
* Calculate LPC coefficients for multiple orders
*/
int ff_lpc_calc_coefs(LPCContext *s,
const int32_t *samples, int blocksize, int min_order,
int max_order, int precision,
int32_t coefs[][MAX_LPC_ORDER], int *shift,
enum FFLPCType lpc_type, int lpc_passes,
int omethod, int max_shift, int zero_shift);
int ff_lpc_calc_ref_coefs(LPCContext *s,
const int32_t *samples, int order, double *ref);
double ff_lpc_calc_ref_coefs_f(LPCContext *s, const float *samples, int len,
int order, double *ref);
/**
* Initialize LPCContext.
*/
int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
enum FFLPCType lpc_type);
void ff_lpc_init_x86(LPCContext *s);
/**
* Uninitialize LPCContext.
*/
void ff_lpc_end(LPCContext *s);
#if USE_FIXED
typedef int LPC_TYPE;
#else
#ifdef LPC_USE_DOUBLE
typedef double LPC_TYPE;
#else
typedef float LPC_TYPE;
#endif
#endif // USE_FIXED
/**
* Schur recursion.
* Produces reflection coefficients from autocorrelation data.
*/
static inline void compute_ref_coefs(const LPC_TYPE *autoc, int max_order,
LPC_TYPE *ref, LPC_TYPE *error)
{
int i, j;
LPC_TYPE err;
LPC_TYPE gen0[MAX_LPC_ORDER], gen1[MAX_LPC_ORDER];
for (i = 0; i < max_order; i++)
gen0[i] = gen1[i] = autoc[i + 1];
err = autoc[0];
ref[0] = -gen1[0] / err;
err += gen1[0] * ref[0];
if (error)
error[0] = err;
for (i = 1; i < max_order; i++) {
for (j = 0; j < max_order - i; j++) {
gen1[j] = gen1[j + 1] + ref[i - 1] * gen0[j];
gen0[j] = gen1[j + 1] * ref[i - 1] + gen0[j];
}
ref[i] = -gen1[0] / err;
err += gen1[0] * ref[i];
if (error)
error[i] = err;
}
}
/**
* Levinson-Durbin recursion.
* Produce LPC coefficients from autocorrelation data.
*/
static inline int AAC_RENAME(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 = 0;
LPC_TYPE *lpc_last = lpc;
av_assert2(normalize || !fail);
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 = AAC_SRA_R(-autoc[i], 5);
if (normalize) {
for(j=0; j<i; j++)
r -= lpc_last[j] * autoc[i-j-1];
r /= err;
err *= FIXR(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 + AAC_MUL26(r, b);
lpc[i-1-j] = b + AAC_MUL26(r, f);
}
if (fail && err < 0)
return -1;
lpc_last = lpc;
lpc += lpc_stride;
}
return 0;
}
#endif /* AVCODEC_LPC_H */
|
