Statistics
| Branch: | Revision:

ffmpeg / libavcodec / mlp.c @ ce15710f

History | View | Annotate | Download (3.38 KB)

1
/*
2
 * MLP codec common code
3
 * Copyright (c) 2007-2008 Ian Caulfield
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
#include <stdint.h>
23

    
24
#include "libavutil/crc.h"
25
#include "mlp.h"
26

    
27
const uint8_t ff_mlp_huffman_tables[3][18][2] = {
28
    {    /* Huffman table 0, -7 - +10 */
29
        {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
30
        {0x04, 3}, {0x05, 3}, {0x06, 3}, {0x07, 3},
31
        {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
32
    }, { /* Huffman table 1, -7 - +8 */
33
        {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
34
        {0x02, 2}, {0x03, 2},
35
        {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
36
    }, { /* Huffman table 2, -7 - +7 */
37
        {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
38
        {0x01, 1},
39
        {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
40
    }
41
};
42

    
43
static int crc_init = 0;
44
static AVCRC crc_63[1024];
45
static AVCRC crc_1D[1024];
46

    
47

    
48
static int crc_init_2D = 0;
49
static AVCRC crc_2D[1024];
50

    
51
int av_cold ff_mlp_init_crc2D(AVCodecParserContext *s)
52
{
53
    if (!crc_init_2D) {
54
        av_crc_init(crc_2D, 0, 16, 0x002D, sizeof(crc_2D));
55
        crc_init_2D = 1;
56
    }
57

    
58
    return 0;
59
}
60

    
61
void av_cold ff_mlp_init_crc()
62
{
63
    if (!crc_init) {
64
        av_crc_init(crc_63, 0,  8,   0x63, sizeof(crc_63));
65
        av_crc_init(crc_1D, 0,  8,   0x1D, sizeof(crc_1D));
66
        crc_init = 1;
67
    }
68
}
69

    
70
uint16_t ff_mlp_checksum16(const uint8_t *buf, unsigned int buf_size)
71
{
72
    uint16_t crc;
73

    
74
    crc = av_crc(crc_2D, 0, buf, buf_size - 2);
75
    crc ^= AV_RL16(buf + buf_size - 2);
76
    return crc;
77
}
78

    
79
uint8_t ff_mlp_checksum8(const uint8_t *buf, unsigned int buf_size)
80
{
81
    uint8_t checksum = av_crc(crc_63, 0x3c, buf, buf_size - 1); // crc_63[0xa2] == 0x3c
82
    checksum ^= buf[buf_size-1];
83
    return checksum;
84
}
85

    
86
uint8_t ff_mlp_restart_checksum(const uint8_t *buf, unsigned int bit_size)
87
{
88
    int i;
89
    int num_bytes = (bit_size + 2) / 8;
90

    
91
    int crc = crc_1D[buf[0] & 0x3f];
92
    crc = av_crc(crc_1D, crc, buf + 1, num_bytes - 2);
93
    crc ^= buf[num_bytes - 1];
94

    
95
    for (i = 0; i < ((bit_size + 2) & 7); i++) {
96
        crc <<= 1;
97
        if (crc & 0x100)
98
            crc ^= 0x11D;
99
        crc ^= (buf[num_bytes] >> (7 - i)) & 1;
100
    }
101

    
102
    return crc;
103
}
104

    
105
uint8_t ff_mlp_calculate_parity(const uint8_t *buf, unsigned int buf_size)
106
{
107
    uint32_t scratch = 0;
108
    const uint8_t *buf_end = buf + buf_size;
109

    
110
    for (; buf < buf_end - 3; buf += 4)
111
        scratch ^= *((const uint32_t*)buf);
112

    
113
    scratch ^= scratch >> 16;
114
    scratch ^= scratch >> 8;
115

    
116
    for (; buf < buf_end; buf++)
117
        scratch ^= *buf;
118

    
119
    return scratch;
120
}