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 static const uint8_t lps_range[64][4]= {
35 {128,176,208,240}, {128,167,197,227}, {128,158,187,216}, {123,150,178,205},
36 {116,142,169,195}, {111,135,160,185}, {105,128,152,175}, {100,122,144,166},
37 { 95,116,137,158}, { 90,110,130,150}, { 85,104,123,142}, { 81, 99,117,135},
38 { 77, 94,111,128}, { 73, 89,105,122}, { 69, 85,100,116}, { 66, 80, 95,110},
39 { 62, 76, 90,104}, { 59, 72, 86, 99}, { 56, 69, 81, 94}, { 53, 65, 77, 89},
40 { 51, 62, 73, 85}, { 48, 59, 69, 80}, { 46, 56, 66, 76}, { 43, 53, 63, 72},
41 { 41, 50, 59, 69}, { 39, 48, 56, 65}, { 37, 45, 54, 62}, { 35, 43, 51, 59},
42 { 33, 41, 48, 56}, { 32, 39, 46, 53}, { 30, 37, 43, 50}, { 29, 35, 41, 48},
43 { 27, 33, 39, 45}, { 26, 31, 37, 43}, { 24, 30, 35, 41}, { 23, 28, 33, 39},
44 { 22, 27, 32, 37}, { 21, 26, 30, 35}, { 20, 24, 29, 33}, { 19, 23, 27, 31},
45 { 18, 22, 26, 30}, { 17, 21, 25, 28}, { 16, 20, 23, 27}, { 15, 19, 22, 25},
46 { 14, 18, 21, 24}, { 14, 17, 20, 23}, { 13, 16, 19, 22}, { 12, 15, 18, 21},
47 { 12, 14, 17, 20}, { 11, 14, 16, 19}, { 11, 13, 15, 18}, { 10, 12, 15, 17},
48 { 10, 12, 14, 16}, { 9, 11, 13, 15}, { 9, 11, 12, 14}, { 8, 10, 12, 14},
49 { 8, 9, 11, 13}, { 7, 9, 11, 12}, { 7, 9, 10, 12}, { 7, 8, 10, 11},
50 { 6, 8, 9, 11}, { 6, 7, 9, 10}, { 6, 7, 8, 9}, { 2, 2, 2, 2},
51 };
52 
53 uint8_t ff_h264_mlps_state[4*64];
54 uint8_t ff_h264_lps_range[4*2*64];
55 static uint8_t h264_mps_state[2 * 64];
56 
57 static const uint8_t mps_state[64]= {
58  1, 2, 3, 4, 5, 6, 7, 8,
59  9,10,11,12,13,14,15,16,
60  17,18,19,20,21,22,23,24,
61  25,26,27,28,29,30,31,32,
62  33,34,35,36,37,38,39,40,
63  41,42,43,44,45,46,47,48,
64  49,50,51,52,53,54,55,56,
65  57,58,59,60,61,62,62,63,
66 };
67 
68 static const uint8_t lps_state[64]= {
69  0, 0, 1, 2, 2, 4, 4, 5,
70  6, 7, 8, 9, 9,11,11,12,
71  13,13,15,15,16,16,18,18,
72  19,19,21,21,22,22,23,24,
73  24,25,26,26,27,27,28,29,
74  29,30,30,30,31,32,32,33,
75  33,33,34,34,35,35,35,36,
76  36,36,37,37,37,38,38,63,
77 };
78 
79 const uint8_t ff_h264_norm_shift[512]= {
80  9,8,7,7,6,6,6,6,5,5,5,5,5,5,5,5,
81  4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
82  3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
83  3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,
84  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
85  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
86  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
87  2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
88  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,
89  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,
90  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,
91  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,
92  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,
93  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,
94  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,
95  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,
96  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,
97  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,
98  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,
99  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,
100 };
101 
106 void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size){
107  init_put_bits(&c->pb, buf, buf_size);
108 
109  c->low= 0;
110  c->range= 0x1FE;
111  c->outstanding_count= 0;
112  c->pb.bit_left++; //avoids firstBitFlag
113 }
114 
119 void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size){
120  c->bytestream_start=
121  c->bytestream= buf;
122  c->bytestream_end= buf + buf_size;
123 
124 #if CABAC_BITS == 16
125  c->low = (*c->bytestream++)<<18;
126  c->low+= (*c->bytestream++)<<10;
127 #else
128  c->low = (*c->bytestream++)<<10;
129 #endif
130  c->low+= ((*c->bytestream++)<<2) + 2;
131  c->range= 0x1FE;
132 }
133 
135  int i, j;
136 
137  for(i=0; i<64; i++){
138  for(j=0; j<4; j++){ //FIXME check if this is worth the 1 shift we save
139  ff_h264_lps_range[j*2*64+2*i+0]=
140  ff_h264_lps_range[j*2*64+2*i+1]= lps_range[i][j];
141  }
142 
143  ff_h264_mlps_state[128+2*i+0]=
144  h264_mps_state[2 * i + 0] = 2 * mps_state[i] + 0;
145  ff_h264_mlps_state[128+2*i+1]=
146  h264_mps_state[2 * i + 1] = 2 * mps_state[i] + 1;
147 
148  if( i ){
149  ff_h264_mlps_state[128-2*i-1]= 2*lps_state[i]+0;
150  ff_h264_mlps_state[128-2*i-2]= 2*lps_state[i]+1;
151  }else{
152  ff_h264_mlps_state[128-2*i-1]= 1;
153  ff_h264_mlps_state[128-2*i-2]= 0;
154  }
155  }
156 }
157 
158 #ifdef TEST
159 #define SIZE 10240
160 
161 #include "libavutil/lfg.h"
162 #include "avcodec.h"
163 #include "cabac.h"
164 
165 static inline void put_cabac_bit(CABACContext *c, int b){
166  put_bits(&c->pb, 1, b);
167  for(;c->outstanding_count; c->outstanding_count--){
168  put_bits(&c->pb, 1, 1-b);
169  }
170 }
171 
172 static inline void renorm_cabac_encoder(CABACContext *c){
173  while(c->range < 0x100){
174  //FIXME optimize
175  if(c->low<0x100){
176  put_cabac_bit(c, 0);
177  }else if(c->low<0x200){
178  c->outstanding_count++;
179  c->low -= 0x100;
180  }else{
181  put_cabac_bit(c, 1);
182  c->low -= 0x200;
183  }
184 
185  c->range+= c->range;
186  c->low += c->low;
187  }
188 }
189 
190 static void put_cabac(CABACContext *c, uint8_t * const state, int bit){
191  int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + *state];
192 
193  if(bit == ((*state)&1)){
194  c->range -= RangeLPS;
195  *state = h264_mps_state[*state];
196  }else{
197  c->low += c->range - RangeLPS;
198  c->range = RangeLPS;
199  }
200 
201  renorm_cabac_encoder(c);
202 }
203 
207 static void put_cabac_bypass(CABACContext *c, int bit){
208  c->low += c->low;
209 
210  if(bit){
211  c->low += c->range;
212  }
213 //FIXME optimize
214  if(c->low<0x200){
215  put_cabac_bit(c, 0);
216  }else if(c->low<0x400){
217  c->outstanding_count++;
218  c->low -= 0x200;
219  }else{
220  put_cabac_bit(c, 1);
221  c->low -= 0x400;
222  }
223 }
224 
229 static int put_cabac_terminate(CABACContext *c, int bit){
230  c->range -= 2;
231 
232  if(!bit){
233  renorm_cabac_encoder(c);
234  }else{
235  c->low += c->range;
236  c->range= 2;
237 
238  renorm_cabac_encoder(c);
239 
240  assert(c->low <= 0x1FF);
241  put_cabac_bit(c, c->low>>9);
242  put_bits(&c->pb, 2, ((c->low>>7)&3)|1);
243 
244  flush_put_bits(&c->pb); //FIXME FIXME FIXME XXX wrong
245  }
246 
247  return (put_bits_count(&c->pb)+7)>>3;
248 }
249 
250 int main(void){
251  CABACContext c;
252  uint8_t b[9*SIZE];
253  uint8_t r[9*SIZE];
254  int i;
255  uint8_t state[10]= {0};
256  AVLFG prng;
257 
258  av_lfg_init(&prng, 1);
259  ff_init_cabac_encoder(&c, b, SIZE);
261 
262  for(i=0; i<SIZE; i++){
263  r[i] = av_lfg_get(&prng) % 7;
264  }
265 
266  for(i=0; i<SIZE; i++){
268  put_cabac_bypass(&c, r[i]&1);
269 STOP_TIMER("put_cabac_bypass")
270  }
271 
272  for(i=0; i<SIZE; i++){
274  put_cabac(&c, state, r[i]&1);
275 STOP_TIMER("put_cabac")
276  }
277 
278  put_cabac_terminate(&c, 1);
279 
280  ff_init_cabac_decoder(&c, b, SIZE);
281 
282  memset(state, 0, sizeof(state));
283 
284  for(i=0; i<SIZE; i++){
286  if( (r[i]&1) != get_cabac_bypass(&c) )
287  av_log(NULL, AV_LOG_ERROR, "CABAC bypass failure at %d\n", i);
288 STOP_TIMER("get_cabac_bypass")
289  }
290 
291  for(i=0; i<SIZE; i++){
293  if( (r[i]&1) != get_cabac(&c, state) )
294  av_log(NULL, AV_LOG_ERROR, "CABAC failure at %d\n", i);
295 STOP_TIMER("get_cabac")
296  }
297  if(!get_cabac_terminate(&c))
298  av_log(NULL, AV_LOG_ERROR, "where's the Terminator?\n");
299 
300  return 0;
301 }
302 
303 #endif /* TEST */