Commit | Line | Data |
---|---|---|
2ba45a60 DM |
1 | /* |
2 | * Range coder | |
3 | * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at> | |
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 | /** | |
23 | * @file | |
24 | * Range coder. | |
25 | */ | |
26 | ||
27 | #ifndef AVCODEC_RANGECODER_H | |
28 | #define AVCODEC_RANGECODER_H | |
29 | ||
30 | #include <stdint.h> | |
31 | ||
32 | #include "libavutil/common.h" | |
33 | #include "libavutil/avassert.h" | |
34 | ||
35 | typedef struct RangeCoder { | |
36 | int low; | |
37 | int range; | |
38 | int outstanding_count; | |
39 | int outstanding_byte; | |
40 | uint8_t zero_state[256]; | |
41 | uint8_t one_state[256]; | |
42 | uint8_t *bytestream_start; | |
43 | uint8_t *bytestream; | |
44 | uint8_t *bytestream_end; | |
45 | } RangeCoder; | |
46 | ||
47 | void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size); | |
48 | void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size); | |
49 | int ff_rac_terminate(RangeCoder *c); | |
50 | void ff_build_rac_states(RangeCoder *c, int factor, int max_p); | |
51 | ||
52 | static inline void renorm_encoder(RangeCoder *c) | |
53 | { | |
54 | // FIXME: optimize | |
55 | while (c->range < 0x100) { | |
56 | if (c->outstanding_byte < 0) { | |
57 | c->outstanding_byte = c->low >> 8; | |
58 | } else if (c->low <= 0xFF00) { | |
59 | *c->bytestream++ = c->outstanding_byte; | |
60 | for (; c->outstanding_count; c->outstanding_count--) | |
61 | *c->bytestream++ = 0xFF; | |
62 | c->outstanding_byte = c->low >> 8; | |
63 | } else if (c->low >= 0x10000) { | |
64 | *c->bytestream++ = c->outstanding_byte + 1; | |
65 | for (; c->outstanding_count; c->outstanding_count--) | |
66 | *c->bytestream++ = 0x00; | |
67 | c->outstanding_byte = (c->low >> 8) & 0xFF; | |
68 | } else { | |
69 | c->outstanding_count++; | |
70 | } | |
71 | ||
72 | c->low = (c->low & 0xFF) << 8; | |
73 | c->range <<= 8; | |
74 | } | |
75 | } | |
76 | ||
77 | static inline int get_rac_count(RangeCoder *c) | |
78 | { | |
79 | int x = c->bytestream - c->bytestream_start + c->outstanding_count; | |
80 | if (c->outstanding_byte >= 0) | |
81 | x++; | |
82 | return 8 * x - av_log2(c->range); | |
83 | } | |
84 | ||
85 | static inline void put_rac(RangeCoder *c, uint8_t *const state, int bit) | |
86 | { | |
87 | int range1 = (c->range * (*state)) >> 8; | |
88 | ||
89 | av_assert2(*state); | |
90 | av_assert2(range1 < c->range); | |
91 | av_assert2(range1 > 0); | |
92 | if (!bit) { | |
93 | c->range -= range1; | |
94 | *state = c->zero_state[*state]; | |
95 | } else { | |
96 | c->low += c->range - range1; | |
97 | c->range = range1; | |
98 | *state = c->one_state[*state]; | |
99 | } | |
100 | ||
101 | renorm_encoder(c); | |
102 | } | |
103 | ||
104 | static inline void refill(RangeCoder *c) | |
105 | { | |
106 | if (c->range < 0x100) { | |
107 | c->range <<= 8; | |
108 | c->low <<= 8; | |
109 | if (c->bytestream < c->bytestream_end) | |
110 | c->low += c->bytestream[0]; | |
111 | c->bytestream++; | |
112 | } | |
113 | } | |
114 | ||
115 | static inline int get_rac(RangeCoder *c, uint8_t *const state) | |
116 | { | |
117 | int range1 = (c->range * (*state)) >> 8; | |
118 | ||
119 | c->range -= range1; | |
120 | #if 1 | |
121 | if (c->low < c->range) { | |
122 | *state = c->zero_state[*state]; | |
123 | refill(c); | |
124 | return 0; | |
125 | } else { | |
126 | c->low -= c->range; | |
127 | *state = c->one_state[*state]; | |
128 | c->range = range1; | |
129 | refill(c); | |
130 | return 1; | |
131 | } | |
132 | #else | |
133 | { | |
134 | int one_mask one_mask = (c->range - c->low - 1) >> 31; | |
135 | ||
136 | c->low -= c->range & one_mask; | |
137 | c->range += (range1 - c->range) & one_mask; | |
138 | ||
139 | *state = c->zero_state[(*state) + (256 & one_mask)]; | |
140 | } | |
141 | refill(c); | |
142 | ||
143 | return one_mask & 1; | |
144 | #endif | |
145 | } | |
146 | ||
147 | #endif /* AVCODEC_RANGECODER_H */ |