Statistics
| Branch: | Revision:

ffmpeg / libavcodec / lpc.h @ 3da11804

History | View | Annotate | Download (2.79 KB)

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 "dsputil.h"
27

    
28
#define ORDER_METHOD_EST     0
29
#define ORDER_METHOD_2LEVEL  1
30
#define ORDER_METHOD_4LEVEL  2
31
#define ORDER_METHOD_8LEVEL  3
32
#define ORDER_METHOD_SEARCH  4
33
#define ORDER_METHOD_LOG     5
34

    
35
#define MIN_LPC_ORDER        1
36
#define MAX_LPC_ORDER       32
37

    
38

    
39
/**
40
 * Calculate LPC coefficients for multiple orders
41
 */
42
int ff_lpc_calc_coefs(DSPContext *s,
43
                      const int32_t *samples, int blocksize, int min_order,
44
                      int max_order, int precision,
45
                      int32_t coefs[][MAX_LPC_ORDER], int *shift, int use_lpc,
46
                      int omethod, int max_shift, int zero_shift);
47

    
48
void ff_lpc_compute_autocorr(const int32_t *data, int len, int lag,
49
                             double *autoc);
50

    
51
#ifdef LPC_USE_DOUBLE
52
#define LPC_TYPE double
53
#else
54
#define LPC_TYPE float
55
#endif
56

    
57
/**
58
 * Levinson-Durbin recursion.
59
 * Produces LPC coefficients from autocorrelation data.
60
 */
61
static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order,
62
                                    LPC_TYPE *lpc, int lpc_stride, int fail,
63
                                    int normalize)
64
{
65
    int i, j;
66
    LPC_TYPE err;
67
    LPC_TYPE *lpc_last = lpc;
68

    
69
    if (normalize)
70
        err = *autoc++;
71

    
72
    if (fail && (autoc[max_order - 1] == 0 || err <= 0))
73
        return -1;
74

    
75
    for(i=0; i<max_order; i++) {
76
        LPC_TYPE r = -autoc[i];
77

    
78
        if (normalize) {
79
            for(j=0; j<i; j++)
80
                r -= lpc_last[j] * autoc[i-j-1];
81

    
82
            r /= err;
83
            err *= 1.0 - (r * r);
84
        }
85

    
86
        lpc[i] = r;
87

    
88
        for(j=0; j < (i+1)>>1; j++) {
89
            LPC_TYPE f = lpc_last[    j];
90
            LPC_TYPE b = lpc_last[i-1-j];
91
            lpc[    j] = f + r * b;
92
            lpc[i-1-j] = b + r * f;
93
        }
94

    
95
        if (fail && err < 0)
96
            return -1;
97

    
98
        lpc_last = lpc;
99
        lpc += lpc_stride;
100
    }
101

    
102
    return 0;
103
}
104

    
105
#endif /* AVCODEC_LPC_H */