50f086e6f314564f37a775af0017c0b11857e2e3
[libav.git] / libavcodec / cabac.c
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
22 /**
23 * @file
24 * Context Adaptive Binary Arithmetic Coder.
25 */
26
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
105 /**
106 *
107 * @param buf_size size of buf in bits
108 */
109 void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size){
110 init_put_bits(&c->pb, buf, buf_size);
111
112 c->low= 0;
113 c->range= 0x1FE;
114 c->outstanding_count= 0;
115 c->pb.bit_left++; //avoids firstBitFlag
116 }
117
118 /**
119 *
120 * @param buf_size size of buf in bits
121 */
122 void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
123 c->bytestream_start=
124 c->bytestream= buf;
125 c->bytestream_end= buf + buf_size;
126
127 #if CABAC_BITS == 16
128 c->low = (*c->bytestream++)<<18;
129 c->low+= (*c->bytestream++)<<10;
130 #else
131 c->low = (*c->bytestream++)<<10;
132 #endif
133 c->low+= ((*c->bytestream++)<<2) + 2;
134 c->range= 0x1FE;
135 }
136
137 void ff_init_cabac_states(void)
138 {
139 int i, j;
140
141 for(i=0; i<64; i++){
142 for(j=0; j<4; j++){ //FIXME check if this is worth the 1 shift we save
143 ff_h264_lps_range[j*2*64+2*i+0]=
144 ff_h264_lps_range[j*2*64+2*i+1]= lps_range[i][j];
145 }
146
147 ff_h264_mlps_state[128 + 2 * i + 0] = 2 * mps_state[i] + 0;
148 ff_h264_mlps_state[128 + 2 * i + 1] = 2 * mps_state[i] + 1;
149
150 if( i ){
151 ff_h264_mlps_state[128-2*i-1]= 2*lps_state[i]+0;
152 ff_h264_mlps_state[128-2*i-2]= 2*lps_state[i]+1;
153 }else{
154 ff_h264_mlps_state[128-2*i-1]= 1;
155 ff_h264_mlps_state[128-2*i-2]= 0;
156 }
157 }
158 for(i=0; i< 63; i++){
159 ff_h264_last_coeff_flag_offset_8x8[i] = last_coeff_flag_offset_8x8[i];
160 }
161 }