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 const uint8_t ff_h264_norm_shift[512];
40 extern uint8_t ff_h264_mlps_state[4*64];
41 extern uint8_t ff_h264_lps_range[4*2*64];
42 
43 static void refill(CABACContext *c){
44 #if CABAC_BITS == 16
45  c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
46 #else
47  c->low+= c->bytestream[0]<<1;
48 #endif
49  c->low -= CABAC_MASK;
50  c->bytestream+= CABAC_BITS/8;
51 }
52 
53 static inline void renorm_cabac_decoder_once(CABACContext *c){
54  int shift= (uint32_t)(c->range - 0x100)>>31;
55  c->range<<= shift;
56  c->low <<= shift;
57  if(!(c->low & CABAC_MASK))
58  refill(c);
59 }
60 
61 #ifndef get_cabac_inline
62 static void refill2(CABACContext *c){
63  int i, x;
64 
65  x= c->low ^ (c->low-1);
66  i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
67 
68  x= -CABAC_MASK;
69 
70 #if CABAC_BITS == 16
71  x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
72 #else
73  x+= c->bytestream[0]<<1;
74 #endif
75 
76  c->low += x<<i;
77  c->bytestream+= CABAC_BITS/8;
78 }
79 
80 static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
81  int s = *state;
82  int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
83  int bit, lps_mask;
84 
85  c->range -= RangeLPS;
86  lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
87 
88  c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
89  c->range += (RangeLPS - c->range) & lps_mask;
90 
91  s^=lps_mask;
92  *state= (ff_h264_mlps_state+128)[s];
93  bit= s&1;
94 
95  lps_mask= ff_h264_norm_shift[c->range];
96  c->range<<= lps_mask;
97  c->low <<= lps_mask;
98  if(!(c->low & CABAC_MASK))
99  refill2(c);
100  return bit;
101 }
102 #endif
103 
105  return get_cabac_inline(c,state);
106 }
107 
108 static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
109  return get_cabac_inline(c,state);
110 }
111 
113  int range;
114  c->low += c->low;
115 
116  if(!(c->low & CABAC_MASK))
117  refill(c);
118 
119  range= c->range<<(CABAC_BITS+1);
120  if(c->low < range){
121  return 0;
122  }else{
123  c->low -= range;
124  return 1;
125  }
126 }
127 
128 
129 #ifndef get_cabac_bypass_sign
131  int range, mask;
132  c->low += c->low;
133 
134  if(!(c->low & CABAC_MASK))
135  refill(c);
136 
137  range= c->range<<(CABAC_BITS+1);
138  c->low -= range;
139  mask= c->low >> 31;
140  range &= mask;
141  c->low += range;
142  return (val^mask)-mask;
143 }
144 #endif
145 
151  c->range -= 2;
152  if(c->low < c->range<<(CABAC_BITS+1)){
154  return 0;
155  }else{
156  return c->bytestream - c->bytestream_start;
157  }
158 }
159 
160 #endif /* AVCODEC_CABAC_FUNCTIONS_H */