Libav
cabac_functions.h
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1 /*
2  * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
3  * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
4  *
5  * This file is part of Libav.
6  *
7  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
27 #ifndef AVCODEC_CABAC_FUNCTIONS_H
28 #define AVCODEC_CABAC_FUNCTIONS_H
29 
30 #include <stdint.h>
31 
32 #include "cabac.h"
33 #include "config.h"
34 
35 #if ARCH_X86
36 # include "x86/cabac.h"
37 #endif
38 
39 extern uint8_t ff_h264_cabac_tables[512 + 4*2*64 + 4*64 + 63];
44 
45 static void refill(CABACContext *c){
46 #if CABAC_BITS == 16
47  c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
48 #else
49  c->low+= c->bytestream[0]<<1;
50 #endif
51  c->low -= CABAC_MASK;
52  if (c->bytestream < c->bytestream_end)
53  c->bytestream += CABAC_BITS / 8;
54 }
55 
56 static inline void renorm_cabac_decoder_once(CABACContext *c){
57  int shift= (uint32_t)(c->range - 0x100)>>31;
58  c->range<<= shift;
59  c->low <<= shift;
60  if(!(c->low & CABAC_MASK))
61  refill(c);
62 }
63 
64 #ifndef get_cabac_inline
65 static void refill2(CABACContext *c){
66  int i, x;
67 
68  x= c->low ^ (c->low-1);
69  i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
70 
71  x= -CABAC_MASK;
72 
73 #if CABAC_BITS == 16
74  x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
75 #else
76  x+= c->bytestream[0]<<1;
77 #endif
78 
79  c->low += x<<i;
80  if (c->bytestream < c->bytestream_end)
81  c->bytestream += CABAC_BITS/8;
82 }
83 
85  int s = *state;
86  int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
87  int bit, lps_mask;
88 
89  c->range -= RangeLPS;
90  lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
91 
92  c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
93  c->range += (RangeLPS - c->range) & lps_mask;
94 
95  s^=lps_mask;
96  *state= (ff_h264_mlps_state+128)[s];
97  bit= s&1;
98 
99  lps_mask= ff_h264_norm_shift[c->range];
100  c->range<<= lps_mask;
101  c->low <<= lps_mask;
102  if(!(c->low & CABAC_MASK))
103  refill2(c);
104  return bit;
105 }
106 #endif
107 
109  return get_cabac_inline(c,state);
110 }
111 
112 static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
113  return get_cabac_inline(c,state);
114 }
115 
116 #ifndef get_cabac_bypass
118  int range;
119  c->low += c->low;
120 
121  if(!(c->low & CABAC_MASK))
122  refill(c);
123 
124  range= c->range<<(CABAC_BITS+1);
125  if(c->low < range){
126  return 0;
127  }else{
128  c->low -= range;
129  return 1;
130  }
131 }
132 #endif
133 
134 #ifndef get_cabac_bypass_sign
136  int range, mask;
137  c->low += c->low;
138 
139  if(!(c->low & CABAC_MASK))
140  refill(c);
141 
142  range= c->range<<(CABAC_BITS+1);
143  c->low -= range;
144  mask= c->low >> 31;
145  range &= mask;
146  c->low += range;
147  return (val^mask)-mask;
148 }
149 #endif
150 
156  c->range -= 2;
157  if(c->low < c->range<<(CABAC_BITS+1)){
159  return 0;
160  }else{
161  return c->bytestream - c->bytestream_start;
162  }
163 }
164 
169 static av_unused const uint8_t* skip_bytes(CABACContext *c, int n) {
170  const uint8_t *ptr = c->bytestream;
171 
172  if (c->low & 0x1)
173  ptr--;
174 #if CABAC_BITS == 16
175  if (c->low & 0x1FF)
176  ptr--;
177 #endif
178  if ((int) (c->bytestream_end - ptr) < n)
179  return NULL;
180  ff_init_cabac_decoder(c, ptr + n, c->bytestream_end - ptr - n);
181 
182  return ptr;
183 }
184 
185 #endif /* AVCODEC_CABAC_FUNCTIONS_H */
const uint8_t * bytestream_end
Definition: cabac.h:47
#define CABAC_BITS
Definition: cabac.h:39
static uint8_t *const ff_h264_lps_range
static void renorm_cabac_decoder_once(CABACContext *c)
static uint8_t *const ff_h264_mlps_state
static int av_unused get_cabac(CABACContext *c, uint8_t *const state)
static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t *const state)
const uint8_t * bytestream
Definition: cabac.h:46
uint8_t ff_h264_cabac_tables[512+4 *2 *64+4 *64+63]
Definition: cabac.c:34
uint8_t
static av_unused const uint8_t * skip_bytes(CABACContext *c, int n)
Skip n bytes and reset the decoder.
static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t *const state)
static const uint16_t mask[17]
Definition: lzw.c:38
const uint8_t * bytestream_start
Definition: cabac.h:45
#define H264_LAST_COEFF_FLAG_OFFSET_8x8_OFFSET
Definition: cabac.h:37
static int av_unused get_cabac_terminate(CABACContext *c)
static void refill(CABACContext *c)
NULL
Definition: eval.c:55
static uint8_t *const ff_h264_norm_shift
int range
Definition: cabac.h:44
#define H264_MLPS_STATE_OFFSET
Definition: cabac.h:36
static uint32_t state
Definition: trasher.c:27
static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val)
static int av_unused get_cabac_bypass(CABACContext *c)
#define H264_NORM_SHIFT_OFFSET
Definition: cabac.h:34
int low
Definition: cabac.h:43
static void refill2(CABACContext *c)
void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size)
Definition: cabac.c:109
#define av_noinline
Definition: attributes.h:48
static uint8_t *const ff_h264_last_coeff_flag_offset_8x8
#define av_always_inline
Definition: attributes.h:40
#define CABAC_MASK
Definition: cabac.h:40
#define av_unused
Definition: attributes.h:86
Context Adaptive Binary Arithmetic Coder.
#define H264_LPS_RANGE_OFFSET
Definition: cabac.h:35