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rangecoder.h
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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;
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);
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 */
uint32_t low
Definition: mss3.c:64
uint8_t zero_state[256]
Definition: rangecoder.h:40
uint8_t * bytestream_end
Definition: rangecoder.h:44
uint32_t range
Definition: mss3.c:64
uint8_t one_state[256]
Definition: rangecoder.h:41
uint8_t
static int get_rac(RangeCoder *c, uint8_t *const state)
Definition: rangecoder.h:115
#define av_assert2(cond)
assert() equivalent, that does lie in speed critical code.
Definition: avassert.h:63
void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size)
Definition: rangecoder.c:42
void ff_build_rac_states(RangeCoder *c, int factor, int max_p)
Definition: rangecoder.c:62
static void put_rac(RangeCoder *c, uint8_t *const state, int bit)
Definition: rangecoder.h:85
static void renorm_encoder(RangeCoder *c)
Definition: rangecoder.h:52
simple assert() macros that are a bit more flexible than ISO C assert().
uint8_t * bytestream
Definition: rangecoder.h:43
static void refill(RangeCoder *c)
Definition: rangecoder.h:104
void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size)
Definition: rangecoder.c:53
static struct @197 state
int ff_rac_terminate(RangeCoder *c)
Definition: rangecoder.c:103
int outstanding_byte
Definition: rangecoder.h:39
void * buf
Definition: avisynth_c.h:553
static int get_rac_count(RangeCoder *c)
Definition: rangecoder.h:77
static const int factor[16]
Definition: vf_pp7.c:75
common internal and external API header
static double c[64]
int outstanding_count
Definition: rangecoder.h:38
uint8_t * bytestream_start
Definition: rangecoder.h:42
#define av_log2
Definition: intmath.h:105