FFmpeg
cabac.c
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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 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  * Context Adaptive Binary Arithmetic Coder.
25  */
26 
27 #include <string.h>
28 
29 #include "libavutil/common.h"
30 #include "libavutil/timer.h"
31 
32 #include "cabac.h"
33 #include "cabac_functions.h"
34 
35 DECLARE_ASM_ALIGNED(1, const uint8_t, ff_h264_cabac_tables)[512 + 4*2*64 + 4*64 + 63] = {
36  9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5,
37  4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
38  3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
39  3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
40  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
41  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
42  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
43  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
44  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
45  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
46  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
47  1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
48  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
49  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
50  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
51  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
52  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
53  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
54  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
55  0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
56  // LPS range
57  -128, -128, -128, -128, -128, -128, 123, 123,
58  116, 116, 111, 111, 105, 105, 100, 100,
59  95, 95, 90, 90, 85, 85, 81, 81,
60  77, 77, 73, 73, 69, 69, 66, 66,
61  62, 62, 59, 59, 56, 56, 53, 53,
62  51, 51, 48, 48, 46, 46, 43, 43,
63  41, 41, 39, 39, 37, 37, 35, 35,
64  33, 33, 32, 32, 30, 30, 29, 29,
65  27, 27, 26, 26, 24, 24, 23, 23,
66  22, 22, 21, 21, 20, 20, 19, 19,
67  18, 18, 17, 17, 16, 16, 15, 15,
68  14, 14, 14, 14, 13, 13, 12, 12,
69  12, 12, 11, 11, 11, 11, 10, 10,
70  10, 10, 9, 9, 9, 9, 8, 8,
71  8, 8, 7, 7, 7, 7, 7, 7,
72  6, 6, 6, 6, 6, 6, 2, 2,
73  -80, -80, -89, -89, -98, -98, -106, -106,
74  -114, -114, -121, -121, -128, -128, 122, 122,
75  116, 116, 110, 110, 104, 104, 99, 99,
76  94, 94, 89, 89, 85, 85, 80, 80,
77  76, 76, 72, 72, 69, 69, 65, 65,
78  62, 62, 59, 59, 56, 56, 53, 53,
79  50, 50, 48, 48, 45, 45, 43, 43,
80  41, 41, 39, 39, 37, 37, 35, 35,
81  33, 33, 31, 31, 30, 30, 28, 28,
82  27, 27, 26, 26, 24, 24, 23, 23,
83  22, 22, 21, 21, 20, 20, 19, 19,
84  18, 18, 17, 17, 16, 16, 15, 15,
85  14, 14, 14, 14, 13, 13, 12, 12,
86  12, 12, 11, 11, 11, 11, 10, 10,
87  9, 9, 9, 9, 9, 9, 8, 8,
88  8, 8, 7, 7, 7, 7, 2, 2,
89  -48, -48, -59, -59, -69, -69, -78, -78,
90  -87, -87, -96, -96, -104, -104, -112, -112,
91  -119, -119, -126, -126, 123, 123, 117, 117,
92  111, 111, 105, 105, 100, 100, 95, 95,
93  90, 90, 86, 86, 81, 81, 77, 77,
94  73, 73, 69, 69, 66, 66, 63, 63,
95  59, 59, 56, 56, 54, 54, 51, 51,
96  48, 48, 46, 46, 43, 43, 41, 41,
97  39, 39, 37, 37, 35, 35, 33, 33,
98  32, 32, 30, 30, 29, 29, 27, 27,
99  26, 26, 25, 25, 23, 23, 22, 22,
100  21, 21, 20, 20, 19, 19, 18, 18,
101  17, 17, 16, 16, 15, 15, 15, 15,
102  14, 14, 13, 13, 12, 12, 12, 12,
103  11, 11, 11, 11, 10, 10, 10, 10,
104  9, 9, 9, 9, 8, 8, 2, 2,
105  -16, -16, -29, -29, -40, -40, -51, -51,
106  -61, -61, -71, -71, -81, -81, -90, -90,
107  -98, -98, -106, -106, -114, -114, -121, -121,
108  -128, -128, 122, 122, 116, 116, 110, 110,
109  104, 104, 99, 99, 94, 94, 89, 89,
110  85, 85, 80, 80, 76, 76, 72, 72,
111  69, 69, 65, 65, 62, 62, 59, 59,
112  56, 56, 53, 53, 50, 50, 48, 48,
113  45, 45, 43, 43, 41, 41, 39, 39,
114  37, 37, 35, 35, 33, 33, 31, 31,
115  30, 30, 28, 28, 27, 27, 25, 25,
116  24, 24, 23, 23, 22, 22, 21, 21,
117  20, 20, 19, 19, 18, 18, 17, 17,
118  16, 16, 15, 15, 14, 14, 14, 14,
119  13, 13, 12, 12, 12, 12, 11, 11,
120  11, 11, 10, 10, 9, 9, 2, 2,
121  // mlps state
122  127, 126, 77, 76, 77, 76, 75, 74,
123  75, 74, 75, 74, 73, 72, 73, 72,
124  73, 72, 71, 70, 71, 70, 71, 70,
125  69, 68, 69, 68, 67, 66, 67, 66,
126  67, 66, 65, 64, 65, 64, 63, 62,
127  61, 60, 61, 60, 61, 60, 59, 58,
128  59, 58, 57, 56, 55, 54, 55, 54,
129  53, 52, 53, 52, 51, 50, 49, 48,
130  49, 48, 47, 46, 45, 44, 45, 44,
131  43, 42, 43, 42, 39, 38, 39, 38,
132  37, 36, 37, 36, 33, 32, 33, 32,
133  31, 30, 31, 30, 27, 26, 27, 26,
134  25, 24, 23, 22, 23, 22, 19, 18,
135  19, 18, 17, 16, 15, 14, 13, 12,
136  11, 10, 9, 8, 9, 8, 5, 4,
137  5, 4, 3, 2, 1, 0, 0, 1,
138  2, 3, 4, 5, 6, 7, 8, 9,
139  10, 11, 12, 13, 14, 15, 16, 17,
140  18, 19, 20, 21, 22, 23, 24, 25,
141  26, 27, 28, 29, 30, 31, 32, 33,
142  34, 35, 36, 37, 38, 39, 40, 41,
143  42, 43, 44, 45, 46, 47, 48, 49,
144  50, 51, 52, 53, 54, 55, 56, 57,
145  58, 59, 60, 61, 62, 63, 64, 65,
146  66, 67, 68, 69, 70, 71, 72, 73,
147  74, 75, 76, 77, 78, 79, 80, 81,
148  82, 83, 84, 85, 86, 87, 88, 89,
149  90, 91, 92, 93, 94, 95, 96, 97,
150  98, 99, 100, 101, 102, 103, 104, 105,
151  106, 107, 108, 109, 110, 111, 112, 113,
152  114, 115, 116, 117, 118, 119, 120, 121,
153  122, 123, 124, 125, 124, 125, 126, 127,
154  // last_coeff_flag_offset_8x8
155  0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
156  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
157  3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
158  5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8
159 };
160 
161 /**
162  * @param buf_size size of buf in bits
163  */
165  init_put_bits(&c->pb, buf, buf_size);
166 
167  c->low= 0;
168  c->range= 0x1FE;
169  c->outstanding_count= 0;
170  c->pb.bit_left++; //avoids firstBitFlag
171 }
172 
173 /**
174  *
175  * @param buf_size size of buf in bits
176  */
177 int ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
178  c->bytestream_start=
179  c->bytestream= buf;
180  c->bytestream_end= buf + buf_size;
181 
182 #if CABAC_BITS == 16
183  c->low = (*c->bytestream++)<<18;
184  c->low+= (*c->bytestream++)<<10;
185  // Keep our fetches on a 2-byte boundary as this should avoid ever having to
186  // do unaligned loads if the compiler (or asm) optimises the double byte
187  // load into a single instruction
188  if(((uintptr_t)c->bytestream & 1) == 0) {
189  c->low += (1 << 9);
190  }
191  else {
192  c->low += ((*c->bytestream++) << 2) + 2;
193  }
194 #else
195  c->low = (*c->bytestream++)<<10;
196  c->low+= ((*c->bytestream++)<<2) + 2;
197 #endif
198  c->range= 0x1FE;
199  if ((c->range<<(CABAC_BITS+1)) < c->low)
200  return AVERROR_INVALIDDATA;
201  return 0;
202 }
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
const uint8_t * bytestream_end
Definition: cabac.h:49
#define CABAC_BITS
Definition: cabac.h:40
const uint8_t * bytestream
Definition: cabac.h:48
uint8_t
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
high precision timer, useful to profile code
const uint8_t * bytestream_start
Definition: cabac.h:47
int ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size)
Definition: cabac.c:177
Context Adaptive Binary Arithmetic Coder inline functions.
void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size)
Definition: cabac.c:164
int bit_left
Definition: put_bits.h:37
int outstanding_count
Definition: cabac.h:46
void * buf
Definition: avisynth_c.h:766
int range
Definition: cabac.h:45
DECLARE_ASM_ALIGNED(1, const uint8_t, ff_h264_cabac_tables)[512+4 *2 *64+4 *64+63]
PutBitContext pb
Definition: cabac.h:50
int low
Definition: cabac.h:44
const uint8_t ff_h264_cabac_tables[512+4 *2 *64+4 *64+63]
common internal and external API header
static void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
Initialize the PutBitContext s.
Definition: put_bits.h:48
Context Adaptive Binary Arithmetic Coder.