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
|
/*
* Range coder
* Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
*
* 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
*/
/**
* @file
* Range coder.
*/
#ifndef AVCODEC_RANGECODER_H
#define AVCODEC_RANGECODER_H
#include <stdint.h>
#include "libavutil/common.h"
#include "libavutil/avassert.h"
typedef struct RangeCoder {
int low;
int range;
int outstanding_count;
int outstanding_byte;
uint8_t zero_state[256];
uint8_t one_state[256];
uint8_t *bytestream_start;
uint8_t *bytestream;
uint8_t *bytestream_end;
} RangeCoder;
void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size);
void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size);
int ff_rac_terminate(RangeCoder *c);
void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
static inline void renorm_encoder(RangeCoder *c)
{
// FIXME: optimize
while (c->range < 0x100) {
if (c->outstanding_byte < 0) {
c->outstanding_byte = c->low >> 8;
} else if (c->low <= 0xFF00) {
*c->bytestream++ = c->outstanding_byte;
for (; c->outstanding_count; c->outstanding_count--)
*c->bytestream++ = 0xFF;
c->outstanding_byte = c->low >> 8;
} else if (c->low >= 0x10000) {
*c->bytestream++ = c->outstanding_byte + 1;
for (; c->outstanding_count; c->outstanding_count--)
*c->bytestream++ = 0x00;
c->outstanding_byte = (c->low >> 8) & 0xFF;
} else {
c->outstanding_count++;
}
c->low = (c->low & 0xFF) << 8;
c->range <<= 8;
}
}
static inline int get_rac_count(RangeCoder *c)
{
int x = c->bytestream - c->bytestream_start + c->outstanding_count;
if (c->outstanding_byte >= 0)
x++;
return 8 * x - av_log2(c->range);
}
static inline void put_rac(RangeCoder *c, uint8_t *const state, int bit)
{
int range1 = (c->range * (*state)) >> 8;
av_assert2(*state);
av_assert2(range1 < c->range);
av_assert2(range1 > 0);
if (!bit) {
c->range -= range1;
*state = c->zero_state[*state];
} else {
c->low += c->range - range1;
c->range = range1;
*state = c->one_state[*state];
}
renorm_encoder(c);
}
static inline void refill(RangeCoder *c)
{
if (c->range < 0x100) {
c->range <<= 8;
c->low <<= 8;
if (c->bytestream < c->bytestream_end)
c->low += c->bytestream[0];
c->bytestream++;
}
}
static inline int get_rac(RangeCoder *c, uint8_t *const state)
{
int range1 = (c->range * (*state)) >> 8;
c->range -= range1;
if (c->low < c->range) {
*state = c->zero_state[*state];
refill(c);
return 0;
} else {
c->low -= c->range;
*state = c->one_state[*state];
c->range = range1;
refill(c);
return 1;
}
}
#endif /* AVCODEC_RANGECODER_H */
|
