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
|
/**
* 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 "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
/**
* Calculate LPC coefficients for multiple orders
*/
int ff_lpc_calc_coefs(DSPContext *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);
void ff_lpc_compute_autocorr(const int32_t *data, int len, int lag,
double *autoc);
#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 */
|
