BRANCHLESS_CABAD --> BRANCHLESS_CABAC_DECODER
[libav.git] / libavcodec / cabac.h
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 /**
24 * @file cabac.h
25 * Context Adaptive Binary Arithmetic Coder.
26 */
27
28
29 //#undef NDEBUG
30 #include <assert.h>
31
32 #define CABAC_BITS 16
33 #define CABAC_MASK ((1<<CABAC_BITS)-1)
34 #define BRANCHLESS_CABAC_DECODER 1
35
36 typedef struct CABACContext{
37 int low;
38 int range;
39 int outstanding_count;
40 #ifdef STRICT_LIMITS
41 int symCount;
42 #endif
43 uint8_t lps_range[2*65][4]; ///< rangeTabLPS
44 uint8_t lps_state[2*64]; ///< transIdxLPS
45 uint8_t mps_state[2*64]; ///< transIdxMPS
46 const uint8_t *bytestream_start;
47 const uint8_t *bytestream;
48 const uint8_t *bytestream_end;
49 PutBitContext pb;
50 }CABACContext;
51
52 extern const uint8_t ff_h264_lps_range[64][4];
53 extern const uint8_t ff_h264_mps_state[64];
54 extern const uint8_t ff_h264_lps_state[64];
55 extern const uint8_t ff_h264_norm_shift[128];
56
57
58 void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size);
59 void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size);
60 void ff_init_cabac_states(CABACContext *c, uint8_t const (*lps_range)[4],
61 uint8_t const *mps_state, uint8_t const *lps_state, int state_count);
62
63
64 static inline void put_cabac_bit(CABACContext *c, int b){
65 put_bits(&c->pb, 1, b);
66 for(;c->outstanding_count; c->outstanding_count--){
67 put_bits(&c->pb, 1, 1-b);
68 }
69 }
70
71 static inline void renorm_cabac_encoder(CABACContext *c){
72 while(c->range < 0x100){
73 //FIXME optimize
74 if(c->low<0x100){
75 put_cabac_bit(c, 0);
76 }else if(c->low<0x200){
77 c->outstanding_count++;
78 c->low -= 0x100;
79 }else{
80 put_cabac_bit(c, 1);
81 c->low -= 0x200;
82 }
83
84 c->range+= c->range;
85 c->low += c->low;
86 }
87 }
88
89 static void put_cabac(CABACContext *c, uint8_t * const state, int bit){
90 int RangeLPS= c->lps_range[*state][c->range>>6];
91
92 if(bit == ((*state)&1)){
93 c->range -= RangeLPS;
94 *state= c->mps_state[*state];
95 }else{
96 c->low += c->range - RangeLPS;
97 c->range = RangeLPS;
98 *state= c->lps_state[*state];
99 }
100
101 renorm_cabac_encoder(c);
102
103 #ifdef STRICT_LIMITS
104 c->symCount++;
105 #endif
106 }
107
108 static void put_cabac_static(CABACContext *c, int RangeLPS, int bit){
109 assert(c->range > RangeLPS);
110
111 if(!bit){
112 c->range -= RangeLPS;
113 }else{
114 c->low += c->range - RangeLPS;
115 c->range = RangeLPS;
116 }
117
118 renorm_cabac_encoder(c);
119
120 #ifdef STRICT_LIMITS
121 c->symCount++;
122 #endif
123 }
124
125 /**
126 * @param bit 0 -> write zero bit, !=0 write one bit
127 */
128 static void put_cabac_bypass(CABACContext *c, int bit){
129 c->low += c->low;
130
131 if(bit){
132 c->low += c->range;
133 }
134 //FIXME optimize
135 if(c->low<0x200){
136 put_cabac_bit(c, 0);
137 }else if(c->low<0x400){
138 c->outstanding_count++;
139 c->low -= 0x200;
140 }else{
141 put_cabac_bit(c, 1);
142 c->low -= 0x400;
143 }
144
145 #ifdef STRICT_LIMITS
146 c->symCount++;
147 #endif
148 }
149
150 /**
151 *
152 * @return the number of bytes written
153 */
154 static int put_cabac_terminate(CABACContext *c, int bit){
155 c->range -= 2;
156
157 if(!bit){
158 renorm_cabac_encoder(c);
159 }else{
160 c->low += c->range;
161 c->range= 2;
162
163 renorm_cabac_encoder(c);
164
165 assert(c->low <= 0x1FF);
166 put_cabac_bit(c, c->low>>9);
167 put_bits(&c->pb, 2, ((c->low>>7)&3)|1);
168
169 flush_put_bits(&c->pb); //FIXME FIXME FIXME XXX wrong
170 }
171
172 #ifdef STRICT_LIMITS
173 c->symCount++;
174 #endif
175
176 return (put_bits_count(&c->pb)+7)>>3;
177 }
178
179 /**
180 * put (truncated) unary binarization.
181 */
182 static void put_cabac_u(CABACContext *c, uint8_t * state, int v, int max, int max_index, int truncated){
183 int i;
184
185 assert(v <= max);
186
187 #if 1
188 for(i=0; i<v; i++){
189 put_cabac(c, state, 1);
190 if(i < max_index) state++;
191 }
192 if(truncated==0 || v<max)
193 put_cabac(c, state, 0);
194 #else
195 if(v <= max_index){
196 for(i=0; i<v; i++){
197 put_cabac(c, state+i, 1);
198 }
199 if(truncated==0 || v<max)
200 put_cabac(c, state+i, 0);
201 }else{
202 for(i=0; i<=max_index; i++){
203 put_cabac(c, state+i, 1);
204 }
205 for(; i<v; i++){
206 put_cabac(c, state+max_index, 1);
207 }
208 if(truncated==0 || v<max)
209 put_cabac(c, state+max_index, 0);
210 }
211 #endif
212 }
213
214 /**
215 * put unary exp golomb k-th order binarization.
216 */
217 static void put_cabac_ueg(CABACContext *c, uint8_t * state, int v, int max, int is_signed, int k, int max_index){
218 int i;
219
220 if(v==0)
221 put_cabac(c, state, 0);
222 else{
223 const int sign= v < 0;
224
225 if(is_signed) v= ABS(v);
226
227 if(v<max){
228 for(i=0; i<v; i++){
229 put_cabac(c, state, 1);
230 if(i < max_index) state++;
231 }
232
233 put_cabac(c, state, 0);
234 }else{
235 int m= 1<<k;
236
237 for(i=0; i<max; i++){
238 put_cabac(c, state, 1);
239 if(i < max_index) state++;
240 }
241
242 v -= max;
243 while(v >= m){ //FIXME optimize
244 put_cabac_bypass(c, 1);
245 v-= m;
246 m+= m;
247 }
248 put_cabac_bypass(c, 0);
249 while(m>>=1){
250 put_cabac_bypass(c, v&m);
251 }
252 }
253
254 if(is_signed)
255 put_cabac_bypass(c, sign);
256 }
257 }
258
259 static void refill(CABACContext *c){
260 #if CABAC_BITS == 16
261 c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
262 #else
263 c->low+= c->bytestream[0]<<1;
264 #endif
265 c->low -= CABAC_MASK;
266 c->bytestream+= CABAC_BITS/8;
267 }
268
269 static void refill2(CABACContext *c){
270 int i, x;
271
272 x= c->low ^ (c->low-1);
273 i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS+1)];
274
275 x= -CABAC_MASK;
276
277 #if CABAC_BITS == 16
278 x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
279 #else
280 x+= c->bytestream[0]<<1;
281 #endif
282
283 c->low += x<<i;
284 c->bytestream+= CABAC_BITS/8;
285 }
286
287 static inline void renorm_cabac_decoder(CABACContext *c){
288 while(c->range < (0x200 << CABAC_BITS)){
289 c->range+= c->range;
290 c->low+= c->low;
291 if(!(c->low & CABAC_MASK))
292 refill(c);
293 }
294 }
295
296 static inline void renorm_cabac_decoder_once(CABACContext *c){
297 #ifdef ARCH_X86_DISABLED
298 int temp;
299 #if 0
300 //P3:683 athlon:475
301 asm(
302 "lea -0x2000000(%0), %2 \n\t"
303 "shr $31, %2 \n\t" //FIXME 31->63 for x86-64
304 "shl %%cl, %0 \n\t"
305 "shl %%cl, %1 \n\t"
306 : "+r"(c->range), "+r"(c->low), "+c"(temp)
307 );
308 #elif 0
309 //P3:680 athlon:474
310 asm(
311 "cmp $0x2000000, %0 \n\t"
312 "setb %%cl \n\t" //FIXME 31->63 for x86-64
313 "shl %%cl, %0 \n\t"
314 "shl %%cl, %1 \n\t"
315 : "+r"(c->range), "+r"(c->low), "+c"(temp)
316 );
317 #elif 1
318 int temp2;
319 //P3:665 athlon:517
320 asm(
321 "lea -0x2000000(%0), %%eax \n\t"
322 "cdq \n\t"
323 "mov %0, %%eax \n\t"
324 "and %%edx, %0 \n\t"
325 "and %1, %%edx \n\t"
326 "add %%eax, %0 \n\t"
327 "add %%edx, %1 \n\t"
328 : "+r"(c->range), "+r"(c->low), "+a"(temp), "+d"(temp2)
329 );
330 #elif 0
331 int temp2;
332 //P3:673 athlon:509
333 asm(
334 "cmp $0x2000000, %0 \n\t"
335 "sbb %%edx, %%edx \n\t"
336 "mov %0, %%eax \n\t"
337 "and %%edx, %0 \n\t"
338 "and %1, %%edx \n\t"
339 "add %%eax, %0 \n\t"
340 "add %%edx, %1 \n\t"
341 : "+r"(c->range), "+r"(c->low), "+a"(temp), "+d"(temp2)
342 );
343 #else
344 int temp2;
345 //P3:677 athlon:511
346 asm(
347 "cmp $0x2000000, %0 \n\t"
348 "lea (%0, %0), %%eax \n\t"
349 "lea (%1, %1), %%edx \n\t"
350 "cmovb %%eax, %0 \n\t"
351 "cmovb %%edx, %1 \n\t"
352 : "+r"(c->range), "+r"(c->low), "+a"(temp), "+d"(temp2)
353 );
354 #endif
355 #else
356 //P3:675 athlon:476
357 int shift= (uint32_t)(c->range - (0x200 << CABAC_BITS))>>31;
358 c->range<<= shift;
359 c->low <<= shift;
360 #endif
361 if(!(c->low & CABAC_MASK))
362 refill(c);
363 }
364
365 static int get_cabac(CABACContext *c, uint8_t * const state){
366 //FIXME gcc generates duplicate load/stores for c->low and c->range
367 #ifdef ARCH_X86
368 int bit;
369
370 #define LOW "0"
371 #define RANGE "4"
372 #define LPS_RANGE "12"
373 #define LPS_STATE "12+2*65*4"
374 #define MPS_STATE "12+2*65*4+2*64"
375 #define BYTESTART "12+2*65*4+4*64"
376 #define BYTE "16+2*65*4+4*64"
377 #define BYTEEND "20+2*65*4+4*64"
378 #ifndef BRANCHLESS_CABAC_DECODER
379 asm volatile(
380 "movzbl (%1), %%eax \n\t"
381 "movl "RANGE "(%2), %%ebx \n\t"
382 "movl "RANGE "(%2), %%edx \n\t"
383 "shrl $23, %%ebx \n\t"
384 "leal "LPS_RANGE"(%2, %%eax, 4), %%esi \n\t"
385 "movzbl (%%ebx, %%esi), %%esi \n\t"
386 "shll $17, %%esi \n\t"
387 "movl "LOW "(%2), %%ebx \n\t"
388 //eax:state ebx:low, edx:range, esi:RangeLPS
389 "subl %%esi, %%edx \n\t"
390 "cmpl %%edx, %%ebx \n\t"
391 " ja 1f \n\t"
392 "cmp $0x2000000, %%edx \n\t" //FIXME avoidable
393 "setb %%cl \n\t"
394 "shl %%cl, %%edx \n\t"
395 "shl %%cl, %%ebx \n\t"
396 "movzbl "MPS_STATE"(%2, %%eax), %%ecx \n\t"
397 "movb %%cl, (%1) \n\t"
398 //eax:state ebx:low, edx:range, esi:RangeLPS
399 "test %%bx, %%bx \n\t"
400 " jnz 2f \n\t"
401 "movl "BYTE "(%2), %%esi \n\t"
402 "subl $0xFFFF, %%ebx \n\t"
403 "movzwl (%%esi), %%ecx \n\t"
404 "bswap %%ecx \n\t"
405 "shrl $15, %%ecx \n\t"
406 "addl $2, %%esi \n\t"
407 "addl %%ecx, %%ebx \n\t"
408 "movl %%esi, "BYTE "(%2) \n\t"
409 "jmp 2f \n\t"
410 "1: \n\t"
411 //eax:state ebx:low, edx:range, esi:RangeLPS
412 "subl %%edx, %%ebx \n\t"
413 "movl %%esi, %%edx \n\t"
414 "shr $19, %%esi \n\t"
415 "movzbl " MANGLE(ff_h264_norm_shift) "(%%esi), %%ecx \n\t"
416 "shll %%cl, %%ebx \n\t"
417 "shll %%cl, %%edx \n\t"
418 "movzbl "LPS_STATE"(%2, %%eax), %%ecx \n\t"
419 "movb %%cl, (%1) \n\t"
420 "addl $1, %%eax \n\t"
421 "test %%bx, %%bx \n\t"
422 " jnz 2f \n\t"
423
424 "movl "BYTE "(%2), %%ecx \n\t"
425 "movzwl (%%ecx), %%esi \n\t"
426 "bswap %%esi \n\t"
427 "shrl $15, %%esi \n\t"
428 "subl $0xFFFF, %%esi \n\t"
429 "addl $2, %%ecx \n\t"
430 "movl %%ecx, "BYTE "(%2) \n\t"
431
432 "leal -1(%%ebx), %%ecx \n\t"
433 "xorl %%ebx, %%ecx \n\t"
434 "shrl $17, %%ecx \n\t"
435 "movzbl " MANGLE(ff_h264_norm_shift) "(%%ecx), %%ecx \n\t"
436 "neg %%cl \n\t"
437 "add $7, %%cl \n\t"
438
439 "shll %%cl , %%esi \n\t"
440 "addl %%esi, %%ebx \n\t"
441 "2: \n\t"
442 "movl %%edx, "RANGE "(%2) \n\t"
443 "movl %%ebx, "LOW "(%2) \n\t"
444 :"=&a"(bit) //FIXME this is fragile gcc either runs out of registers or misscompiles it (for example if "+a"(bit) or "+m"(*state) is used
445 :"r"(state), "r"(c)
446 : "%ecx", "%ebx", "%edx", "%esi"
447 );
448 bit&=1;
449 #else
450 asm volatile(
451 "movzbl (%1), %%eax \n\t"
452 "movl "RANGE "(%2), %%ebx \n\t"
453 "movl "RANGE "(%2), %%edx \n\t"
454 "shrl $23, %%ebx \n\t"
455 "leal "LPS_RANGE"(%2, %%eax, 4), %%esi \n\t"
456 "movzbl (%%ebx, %%esi), %%esi \n\t"
457 "shll $17, %%esi \n\t"
458 "movl "LOW "(%2), %%ebx \n\t"
459 //eax:state ebx:low, edx:range, esi:RangeLPS
460 "subl %%esi, %%edx \n\t"
461 #ifdef CMOV_IS_FAST //FIXME actually define this somewhere
462 "cmpl %%ebx, %%edx \n\t"
463 "cmova %%edx, %%esi \n\t"
464 "sbbl %%ecx, %%ecx \n\t"
465 "andl %%ecx, %%edx \n\t"
466 "subl %%edx, %%ebx \n\t"
467 "xorl %%ecx, %%eax \n\t"
468 #else
469 "movl %%edx, %%ecx \n\t"
470 "subl %%ebx, %%edx \n\t"
471 "sarl $31, %%edx \n\t" //lps_mask
472 "subl %%ecx, %%esi \n\t" //RangeLPS - range
473 "andl %%edx, %%esi \n\t" //(RangeLPS - range)&lps_mask
474 "addl %%ecx, %%esi \n\t" //new range
475 "andl %%edx, %%ecx \n\t"
476 "subl %%ecx, %%ebx \n\t"
477 "xorl %%edx, %%eax \n\t"
478 #endif
479
480 //eax:state ebx:low edx:mask esi:range
481 "movzbl "MPS_STATE"(%2, %%eax), %%ecx \n\t"
482 "movb %%cl, (%1) \n\t"
483
484 "movl %%esi, %%edx \n\t"
485 //eax:bit ebx:low edx:range esi:range
486
487 "shr $19, %%esi \n\t"
488 "movzbl " MANGLE(ff_h264_norm_shift) "(%%esi), %%ecx \n\t"
489 "shll %%cl, %%ebx \n\t"
490 "shll %%cl, %%edx \n\t"
491 "test %%bx, %%bx \n\t"
492 " jnz 1f \n\t"
493
494 "movl "BYTE "(%2), %%ecx \n\t"
495 "movzwl (%%ecx), %%esi \n\t"
496 "bswap %%esi \n\t"
497 "shrl $15, %%esi \n\t"
498 "subl $0xFFFF, %%esi \n\t"
499 "addl $2, %%ecx \n\t"
500 "movl %%ecx, "BYTE "(%2) \n\t"
501
502 "leal -1(%%ebx), %%ecx \n\t"
503 "xorl %%ebx, %%ecx \n\t"
504 "shrl $17, %%ecx \n\t"
505 "movzbl " MANGLE(ff_h264_norm_shift) "(%%ecx), %%ecx \n\t"
506 "neg %%cl \n\t"
507 "add $7, %%cl \n\t"
508
509 "shll %%cl , %%esi \n\t"
510 "addl %%esi, %%ebx \n\t"
511 "1: \n\t"
512 "movl %%edx, "RANGE "(%2) \n\t"
513 "movl %%ebx, "LOW "(%2) \n\t"
514 :"=&a"(bit)
515 :"r"(state), "r"(c)
516 : "%ecx", "%ebx", "%edx", "%esi"
517 );
518 bit&=1;
519 #endif
520 #else
521 int s = *state;
522 int RangeLPS= c->lps_range[s][c->range>>(CABAC_BITS+7)]<<(CABAC_BITS+1);
523 int bit, lps_mask attribute_unused;
524
525 c->range -= RangeLPS;
526 #ifndef BRANCHLESS_CABAC_DECODER
527 if(c->low < c->range){
528 bit= s&1;
529 *state= c->mps_state[s];
530 renorm_cabac_decoder_once(c);
531 }else{
532 bit= ff_h264_norm_shift[RangeLPS>>19];
533 c->low -= c->range;
534 *state= c->lps_state[s];
535 c->range = RangeLPS<<bit;
536 c->low <<= bit;
537 bit= (s&1)^1;
538
539 if(!(c->low & 0xFFFF)){
540 refill2(c);
541 }
542 }
543 #else
544 lps_mask= (c->range - c->low)>>31;
545
546 c->low -= c->range & lps_mask;
547 c->range += (RangeLPS - c->range) & lps_mask;
548
549 s^=lps_mask;
550 *state= c->mps_state[s];
551 bit= s&1;
552
553 lps_mask= ff_h264_norm_shift[c->range>>(CABAC_BITS+3)];
554 c->range<<= lps_mask;
555 c->low <<= lps_mask;
556 if(!(c->low & CABAC_MASK))
557 refill2(c);
558 #endif
559 #endif
560 return bit;
561 }
562
563 static int get_cabac_bypass(CABACContext *c){
564 c->low += c->low;
565
566 if(!(c->low & CABAC_MASK))
567 refill(c);
568
569 if(c->low < c->range){
570 return 0;
571 }else{
572 c->low -= c->range;
573 return 1;
574 }
575 }
576
577 /**
578 *
579 * @return the number of bytes read or 0 if no end
580 */
581 static int get_cabac_terminate(CABACContext *c){
582 c->range -= 4<<CABAC_BITS;
583 if(c->low < c->range){
584 renorm_cabac_decoder_once(c);
585 return 0;
586 }else{
587 return c->bytestream - c->bytestream_start;
588 }
589 }
590
591 /**
592 * get (truncated) unnary binarization.
593 */
594 static int get_cabac_u(CABACContext *c, uint8_t * state, int max, int max_index, int truncated){
595 int i;
596
597 for(i=0; i<max; i++){
598 if(get_cabac(c, state)==0)
599 return i;
600
601 if(i< max_index) state++;
602 }
603
604 return truncated ? max : -1;
605 }
606
607 /**
608 * get unary exp golomb k-th order binarization.
609 */
610 static int get_cabac_ueg(CABACContext *c, uint8_t * state, int max, int is_signed, int k, int max_index){
611 int i, v;
612 int m= 1<<k;
613
614 if(get_cabac(c, state)==0)
615 return 0;
616
617 if(0 < max_index) state++;
618
619 for(i=1; i<max; i++){
620 if(get_cabac(c, state)==0){
621 if(is_signed && get_cabac_bypass(c)){
622 return -i;
623 }else
624 return i;
625 }
626
627 if(i < max_index) state++;
628 }
629
630 while(get_cabac_bypass(c)){
631 i+= m;
632 m+= m;
633 }
634
635 v=0;
636 while(m>>=1){
637 v+= v + get_cabac_bypass(c);
638 }
639 i += v;
640
641 if(is_signed && get_cabac_bypass(c)){
642 return -i;
643 }else
644 return i;
645 }