Libav
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 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 #include <string.h>
28 
29 #include "libavutil/common.h"
30 #include "get_bits.h"
31 #include "cabac.h"
32 #include "cabac_functions.h"
33 
34 uint8_t ff_h264_cabac_tables[512 + 4*2*64 + 4*64 + 63] = {
35  9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5,
36  4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
37  3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
38  3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
39  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
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  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,
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  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,
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 };
56 
57 static const uint8_t lps_range[64][4]= {
58 {128,176,208,240}, {128,167,197,227}, {128,158,187,216}, {123,150,178,205},
59 {116,142,169,195}, {111,135,160,185}, {105,128,152,175}, {100,122,144,166},
60 { 95,116,137,158}, { 90,110,130,150}, { 85,104,123,142}, { 81, 99,117,135},
61 { 77, 94,111,128}, { 73, 89,105,122}, { 69, 85,100,116}, { 66, 80, 95,110},
62 { 62, 76, 90,104}, { 59, 72, 86, 99}, { 56, 69, 81, 94}, { 53, 65, 77, 89},
63 { 51, 62, 73, 85}, { 48, 59, 69, 80}, { 46, 56, 66, 76}, { 43, 53, 63, 72},
64 { 41, 50, 59, 69}, { 39, 48, 56, 65}, { 37, 45, 54, 62}, { 35, 43, 51, 59},
65 { 33, 41, 48, 56}, { 32, 39, 46, 53}, { 30, 37, 43, 50}, { 29, 35, 41, 48},
66 { 27, 33, 39, 45}, { 26, 31, 37, 43}, { 24, 30, 35, 41}, { 23, 28, 33, 39},
67 { 22, 27, 32, 37}, { 21, 26, 30, 35}, { 20, 24, 29, 33}, { 19, 23, 27, 31},
68 { 18, 22, 26, 30}, { 17, 21, 25, 28}, { 16, 20, 23, 27}, { 15, 19, 22, 25},
69 { 14, 18, 21, 24}, { 14, 17, 20, 23}, { 13, 16, 19, 22}, { 12, 15, 18, 21},
70 { 12, 14, 17, 20}, { 11, 14, 16, 19}, { 11, 13, 15, 18}, { 10, 12, 15, 17},
71 { 10, 12, 14, 16}, { 9, 11, 13, 15}, { 9, 11, 12, 14}, { 8, 10, 12, 14},
72 { 8, 9, 11, 13}, { 7, 9, 11, 12}, { 7, 9, 10, 12}, { 7, 8, 10, 11},
73 { 6, 8, 9, 11}, { 6, 7, 9, 10}, { 6, 7, 8, 9}, { 2, 2, 2, 2},
74 };
75 
76 static const uint8_t mps_state[64]= {
77  1, 2, 3, 4, 5, 6, 7, 8,
78  9,10,11,12,13,14,15,16,
79  17,18,19,20,21,22,23,24,
80  25,26,27,28,29,30,31,32,
81  33,34,35,36,37,38,39,40,
82  41,42,43,44,45,46,47,48,
83  49,50,51,52,53,54,55,56,
84  57,58,59,60,61,62,62,63,
85 };
86 
87 static const uint8_t lps_state[64]= {
88  0, 0, 1, 2, 2, 4, 4, 5,
89  6, 7, 8, 9, 9,11,11,12,
90  13,13,15,15,16,16,18,18,
91  19,19,21,21,22,22,23,24,
92  24,25,26,26,27,27,28,29,
93  29,30,30,30,31,32,32,33,
94  33,33,34,34,35,35,35,36,
95  36,36,37,37,37,38,38,63,
96 };
97 
98 static const uint8_t last_coeff_flag_offset_8x8[63] = {
99  0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
100  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
101  3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4,
102  5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 8, 8, 8
103 };
104 
109 void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
110  c->bytestream_start=
111  c->bytestream= buf;
112  c->bytestream_end= buf + buf_size;
113 
114 #if CABAC_BITS == 16
115  c->low = (*c->bytestream++)<<18;
116  c->low+= (*c->bytestream++)<<10;
117 #else
118  c->low = (*c->bytestream++)<<10;
119 #endif
120  c->low+= ((*c->bytestream++)<<2) + 2;
121  c->range= 0x1FE;
122 }
123 
125 {
126  int i, j;
127  static int initialized = 0;
128 
129  if (initialized)
130  return;
131 
132  for(i=0; i<64; i++){
133  for(j=0; j<4; j++){ //FIXME check if this is worth the 1 shift we save
134  ff_h264_lps_range[j*2*64+2*i+0]=
135  ff_h264_lps_range[j*2*64+2*i+1]= lps_range[i][j];
136  }
137 
138  ff_h264_mlps_state[128 + 2 * i + 0] = 2 * mps_state[i] + 0;
139  ff_h264_mlps_state[128 + 2 * i + 1] = 2 * mps_state[i] + 1;
140 
141  if( i ){
142  ff_h264_mlps_state[128-2*i-1]= 2*lps_state[i]+0;
143  ff_h264_mlps_state[128-2*i-2]= 2*lps_state[i]+1;
144  }else{
145  ff_h264_mlps_state[128-2*i-1]= 1;
146  ff_h264_mlps_state[128-2*i-2]= 0;
147  }
148  }
149  for(i=0; i< 63; i++){
151  }
152 
153  initialized = 1;
154 }