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
|
/**
* LPC utility code
* Copyright (c) 2006 Justin Ruggles <justin.ruggles@gmail.com>
*
* This file is part of Libav.
*
* Libav 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.
*
* Libav 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 Libav; 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 "dsputil.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
typedef struct LPCContext {
int blocksize;
int max_order;
enum AVLPCType lpc_type;
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 have at
* least lag*sizeof(double) valid bytes preceeding 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);
} 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 AVLPCType lpc_type, int lpc_passes,
int omethod, int max_shift, int zero_shift);
/**
* Initialize LPCContext.
*/
int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
enum AVLPCType lpc_type);
void ff_lpc_init_x86(LPCContext *s);
/**
* Uninitialize LPCContext.
*/
void ff_lpc_end(LPCContext *s);
#ifdef LPC_USE_DOUBLE
#define LPC_TYPE double
#else
#define LPC_TYPE float
#endif
/**
* Levinson-Durbin recursion.
* Produce LPC coefficients from autocorrelation data.
*/
static inline int 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;
LPC_TYPE *lpc_last = lpc;
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 = -autoc[i];
if (normalize) {
for(j=0; j<i; j++)
r -= lpc_last[j] * autoc[i-j-1];
r /= err;
err *= 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 + r * b;
lpc[i-1-j] = b + r * f;
}
if (fail && err < 0)
return -1;
lpc_last = lpc;
lpc += lpc_stride;
}
return 0;
}
#endif /* AVCODEC_LPC_H */
|
