libavcodec/bitstream.h

   1 /*
   2  * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 /**
  22  * @file bitstream.h
  23  * bitstream api header.
  24  */
  25
  26 #ifndef AVCODEC_BITSTREAM_H
  27 #define AVCODEC_BITSTREAM_H
  28
  29 #include <stdint.h>
  30 #include <stdlib.h>
  31 #include <assert.h>
  32 #include "libavutil/bswap.h"
  33 #include "libavutil/common.h"
  34 #include "libavutil/intreadwrite.h"
  35 #include "libavutil/log.h"
  36
  37 #if defined(ALT_BITSTREAM_READER_LE) && !defined(ALT_BITSTREAM_READER)
  38 #   define ALT_BITSTREAM_READER
  39 #endif
  40
  41 //#define ALT_BITSTREAM_WRITER
  42 //#define ALIGNED_BITSTREAM_WRITER
  43 #if !defined(LIBMPEG2_BITSTREAM_READER) && !defined(A32_BITSTREAM_READER) && !defined(ALT_BITSTREAM_READER)
  44 #   ifdef ARCH_ARMV4L
  45 #       define A32_BITSTREAM_READER
  46 #   else
  47 #       define ALT_BITSTREAM_READER
  48 //#define LIBMPEG2_BITSTREAM_READER
  49 //#define A32_BITSTREAM_READER
  50 #   endif
  51 #endif
  52
  53 extern const uint8_t ff_reverse[256];
  54
  55 #if defined(ARCH_X86)
  56 // avoid +32 for shift optimization (gcc should do that ...)
  57 static inline  int32_t NEG_SSR32( int32_t a, int8_t s){
  58     __asm__ ("sarl %1, %0\n\t"
  59          : "+r" (a)
  60          : "ic" ((uint8_t)(-s))
  61     );
  62     return a;
  63 }
  64 static inline uint32_t NEG_USR32(uint32_t a, int8_t s){
  65     __asm__ ("shrl %1, %0\n\t"
  66          : "+r" (a)
  67          : "ic" ((uint8_t)(-s))
  68     );
  69     return a;
  70 }
  71 #else
  72 #    define NEG_SSR32(a,s) ((( int32_t)(a))>>(32-(s)))
  73 #    define NEG_USR32(a,s) (((uint32_t)(a))>>(32-(s)))
  74 #endif
  75
  76 /* bit output */
  77
  78 /* buf and buf_end must be present and used by every alternative writer. */
  79 typedef struct PutBitContext {
  80 #ifdef ALT_BITSTREAM_WRITER
  81     uint8_t *buf, *buf_end;
  82     int index;
  83 #else
  84     uint32_t bit_buf;
  85     int bit_left;
  86     uint8_t *buf, *buf_ptr, *buf_end;
  87 #endif
  88 } PutBitContext;
  89
  90 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
  91 {
  92     if(buffer_size < 0) {
  93         buffer_size = 0;
  94         buffer = NULL;
  95     }
  96
  97     s->buf = buffer;
  98     s->buf_end = s->buf + buffer_size;
  99 #ifdef ALT_BITSTREAM_WRITER
 100     s->index=0;
 101     ((uint32_t*)(s->buf))[0]=0;
 102 //    memset(buffer, 0, buffer_size);
 103 #else
 104     s->buf_ptr = s->buf;
 105     s->bit_left=32;
 106     s->bit_buf=0;
 107 #endif
 108 }
 109
 110 /* return the number of bits output */
 111 static inline int put_bits_count(PutBitContext *s)
 112 {
 113 #ifdef ALT_BITSTREAM_WRITER
 114     return s->index;
 115 #else
 116     return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
 117 #endif
 118 }
 119
 120 /* pad the end of the output stream with zeros */
 121 static inline void flush_put_bits(PutBitContext *s)
 122 {
 123 #ifdef ALT_BITSTREAM_WRITER
 124     align_put_bits(s);
 125 #else
 126 #ifndef BITSTREAM_WRITER_LE
 127     s->bit_buf<<= s->bit_left;
 128 #endif
 129     while (s->bit_left < 32) {
 130         /* XXX: should test end of buffer */
 131 #ifdef BITSTREAM_WRITER_LE
 132         *s->buf_ptr++=s->bit_buf;
 133         s->bit_buf>>=8;
 134 #else
 135         *s->buf_ptr++=s->bit_buf >> 24;
 136         s->bit_buf<<=8;
 137 #endif
 138         s->bit_left+=8;
 139     }
 140     s->bit_left=32;
 141     s->bit_buf=0;
 142 #endif
 143 }
 144
 145 void align_put_bits(PutBitContext *s);
 146 void ff_put_string(PutBitContext * pbc, const char *s, int put_zero);
 147 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
 148
 149 /* bit input */
 150 /* buffer, buffer_end and size_in_bits must be present and used by every reader */
 151 typedef struct GetBitContext {
 152     const uint8_t *buffer, *buffer_end;
 153 #ifdef ALT_BITSTREAM_READER
 154     int index;
 155 #elif defined LIBMPEG2_BITSTREAM_READER
 156     uint8_t *buffer_ptr;
 157     uint32_t cache;
 158     int bit_count;
 159 #elif defined A32_BITSTREAM_READER
 160     uint32_t *buffer_ptr;
 161     uint32_t cache0;
 162     uint32_t cache1;
 163     int bit_count;
 164 #endif
 165     int size_in_bits;
 166 } GetBitContext;
 167
 168 #define VLC_TYPE int16_t
 169
 170 typedef struct VLC {
 171     int bits;
 172     VLC_TYPE (*table)[2]; ///< code, bits
 173     int table_size, table_allocated;
 174 } VLC;
 175
 176 typedef struct RL_VLC_ELEM {
 177     int16_t level;
 178     int8_t len;
 179     uint8_t run;
 180 } RL_VLC_ELEM;
 181
 182 #if defined(ARCH_SPARC) || defined(ARCH_ARMV4L) || defined(ARCH_MIPS) || defined(ARCH_BFIN)
 183 #define UNALIGNED_STORES_ARE_BAD
 184 #endif
 185
 186 #ifndef ALT_BITSTREAM_WRITER
 187 static inline void put_bits(PutBitContext *s, int n, unsigned int value)
 188 {
 189     unsigned int bit_buf;
 190     int bit_left;
 191
 192     //    printf("put_bits=%d %x\n", n, value);
 193     assert(n == 32 || value < (1U << n));
 194
 195     bit_buf = s->bit_buf;
 196     bit_left = s->bit_left;
 197
 198     //    printf("n=%d value=%x cnt=%d buf=%x\n", n, value, bit_cnt, bit_buf);
 199     /* XXX: optimize */
 200 #ifdef BITSTREAM_WRITER_LE
 201     bit_buf |= value << (32 - bit_left);
 202     if (n >= bit_left) {
 203 #ifdef UNALIGNED_STORES_ARE_BAD
 204         if (3 & (intptr_t) s->buf_ptr) {
 205             s->buf_ptr[0] = bit_buf      ;
 206             s->buf_ptr[1] = bit_buf >>  8;
 207             s->buf_ptr[2] = bit_buf >> 16;
 208             s->buf_ptr[3] = bit_buf >> 24;
 209         } else
 210 #endif
 211         *(uint32_t *)s->buf_ptr = le2me_32(bit_buf);
 212         s->buf_ptr+=4;
 213         bit_buf = (bit_left==32)?0:value >> bit_left;
 214         bit_left+=32;
 215     }
 216     bit_left-=n;
 217 #else
 218     if (n < bit_left) {
 219         bit_buf = (bit_buf<<n) | value;
 220         bit_left-=n;
 221     } else {
 222         bit_buf<<=bit_left;
 223         bit_buf |= value >> (n - bit_left);
 224 #ifdef UNALIGNED_STORES_ARE_BAD
 225         if (3 & (intptr_t) s->buf_ptr) {
 226             s->buf_ptr[0] = bit_buf >> 24;
 227             s->buf_ptr[1] = bit_buf >> 16;
 228             s->buf_ptr[2] = bit_buf >>  8;
 229             s->buf_ptr[3] = bit_buf      ;
 230         } else
 231 #endif
 232         *(uint32_t *)s->buf_ptr = be2me_32(bit_buf);
 233         //printf("bitbuf = %08x\n", bit_buf);
 234         s->buf_ptr+=4;
 235         bit_left+=32 - n;
 236         bit_buf = value;
 237     }
 238 #endif
 239
 240     s->bit_buf = bit_buf;
 241     s->bit_left = bit_left;
 242 }
 243 #endif
 244
 245
 246 #ifdef ALT_BITSTREAM_WRITER
 247 static inline void put_bits(PutBitContext *s, int n, unsigned int value)
 248 {
 249 #    ifdef ALIGNED_BITSTREAM_WRITER
 250 #        if defined(ARCH_X86)
 251     __asm__ volatile(
 252         "movl %0, %%ecx                 \n\t"
 253         "xorl %%eax, %%eax              \n\t"
 254         "shrdl %%cl, %1, %%eax          \n\t"
 255         "shrl %%cl, %1                  \n\t"
 256         "movl %0, %%ecx                 \n\t"
 257         "shrl $3, %%ecx                 \n\t"
 258         "andl $0xFFFFFFFC, %%ecx        \n\t"
 259         "bswapl %1                      \n\t"
 260         "orl %1, (%2, %%ecx)            \n\t"
 261         "bswapl %%eax                   \n\t"
 262         "addl %3, %0                    \n\t"
 263         "movl %%eax, 4(%2, %%ecx)       \n\t"
 264         : "=&r" (s->index), "=&r" (value)
 265         : "r" (s->buf), "r" (n), "0" (s->index), "1" (value<<(-n))
 266         : "%eax", "%ecx"
 267     );
 268 #        else
 269     int index= s->index;
 270     uint32_t *ptr= ((uint32_t *)s->buf)+(index>>5);
 271
 272     value<<= 32-n;
 273
 274     ptr[0] |= be2me_32(value>>(index&31));
 275     ptr[1]  = be2me_32(value<<(32-(index&31)));
 276 //if(n>24) printf("%d %d\n", n, value);
 277     index+= n;
 278     s->index= index;
 279 #        endif
 280 #    else //ALIGNED_BITSTREAM_WRITER
 281 #        if defined(ARCH_X86)
 282     __asm__ volatile(
 283         "movl $7, %%ecx                 \n\t"
 284         "andl %0, %%ecx                 \n\t"
 285         "addl %3, %%ecx                 \n\t"
 286         "negl %%ecx                     \n\t"
 287         "shll %%cl, %1                  \n\t"
 288         "bswapl %1                      \n\t"
 289         "movl %0, %%ecx                 \n\t"
 290         "shrl $3, %%ecx                 \n\t"
 291         "orl %1, (%%ecx, %2)            \n\t"
 292         "addl %3, %0                    \n\t"
 293         "movl $0, 4(%%ecx, %2)          \n\t"
 294         : "=&r" (s->index), "=&r" (value)
 295         : "r" (s->buf), "r" (n), "0" (s->index), "1" (value)
 296         : "%ecx"
 297     );
 298 #        else
 299     int index= s->index;
 300     uint32_t *ptr= (uint32_t*)(((uint8_t *)s->buf)+(index>>3));
 301
 302     ptr[0] |= be2me_32(value<<(32-n-(index&7) ));
 303     ptr[1] = 0;
 304 //if(n>24) printf("%d %d\n", n, value);
 305     index+= n;
 306     s->index= index;
 307 #        endif
 308 #    endif //!ALIGNED_BITSTREAM_WRITER
 309 }
 310 #endif
 311
 312 static inline void put_sbits(PutBitContext *pb, int bits, int32_t val)
 313 {
 314     assert(bits >= 0 && bits <= 31);
 315
 316     put_bits(pb, bits, val & ((1<<bits)-1));
 317 }
 318
 319
 320 static inline uint8_t* pbBufPtr(PutBitContext *s)
 321 {
 322 #ifdef ALT_BITSTREAM_WRITER
 323         return s->buf + (s->index>>3);
 324 #else
 325         return s->buf_ptr;
 326 #endif
 327 }
 328
 329 /**
 330  *
 331  * PutBitContext must be flushed & aligned to a byte boundary before calling this.
 332  */
 333 static inline void skip_put_bytes(PutBitContext *s, int n){
 334         assert((put_bits_count(s)&7)==0);
 335 #ifdef ALT_BITSTREAM_WRITER
 336         FIXME may need some cleaning of the buffer
 337         s->index += n<<3;
 338 #else
 339         assert(s->bit_left==32);
 340         s->buf_ptr += n;
 341 #endif
 342 }
 343
 344 /**
 345  * Skips the given number of bits.
 346  * Must only be used if the actual values in the bitstream do not matter.
 347  */
 348 static inline void skip_put_bits(PutBitContext *s, int n){
 349 #ifdef ALT_BITSTREAM_WRITER
 350     s->index += n;
 351 #else
 352     s->bit_left -= n;
 353     s->buf_ptr-= s->bit_left>>5;
 354     s->bit_left &= 31;
 355 #endif
 356 }
 357
 358 /**
 359  * Changes the end of the buffer.
 360  */
 361 static inline void set_put_bits_buffer_size(PutBitContext *s, int size){
 362     s->buf_end= s->buf + size;
 363 }
 364
 365 /* Bitstream reader API docs:
 366 name
 367     arbitrary name which is used as prefix for the internal variables
 368
 369 gb
 370     getbitcontext
 371
 372 OPEN_READER(name, gb)
 373     loads gb into local variables
 374
 375 CLOSE_READER(name, gb)
 376     stores local vars in gb
 377
 378 UPDATE_CACHE(name, gb)
 379     refills the internal cache from the bitstream
 380     after this call at least MIN_CACHE_BITS will be available,
 381
 382 GET_CACHE(name, gb)
 383     will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)
 384
 385 SHOW_UBITS(name, gb, num)
 386     will return the next num bits
 387
 388 SHOW_SBITS(name, gb, num)
 389     will return the next num bits and do sign extension
 390
 391 SKIP_BITS(name, gb, num)
 392     will skip over the next num bits
 393     note, this is equivalent to SKIP_CACHE; SKIP_COUNTER
 394
 395 SKIP_CACHE(name, gb, num)
 396     will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)
 397
 398 SKIP_COUNTER(name, gb, num)
 399     will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)
 400
 401 LAST_SKIP_CACHE(name, gb, num)
 402     will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing
 403
 404 LAST_SKIP_BITS(name, gb, num)
 405     is equivalent to SKIP_LAST_CACHE; SKIP_COUNTER
 406
 407 for examples see get_bits, show_bits, skip_bits, get_vlc
 408 */
 409
 410 #ifdef ALT_BITSTREAM_READER
 411 #   define MIN_CACHE_BITS 25
 412
 413 #   define OPEN_READER(name, gb)\
 414         int name##_index= (gb)->index;\
 415         int name##_cache= 0;\
 416
 417 #   define CLOSE_READER(name, gb)\
 418         (gb)->index= name##_index;\
 419
 420 # ifdef ALT_BITSTREAM_READER_LE
 421 #   define UPDATE_CACHE(name, gb)\
 422         name##_cache= AV_RL32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) >> (name##_index&0x07);\
 423
 424 #   define SKIP_CACHE(name, gb, num)\
 425         name##_cache >>= (num);
 426 # else
 427 #   define UPDATE_CACHE(name, gb)\
 428         name##_cache= AV_RB32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) << (name##_index&0x07);\
 429
 430 #   define SKIP_CACHE(name, gb, num)\
 431         name##_cache <<= (num);
 432 # endif
 433
 434 // FIXME name?
 435 #   define SKIP_COUNTER(name, gb, num)\
 436         name##_index += (num);\
 437
 438 #   define SKIP_BITS(name, gb, num)\
 439         {\
 440             SKIP_CACHE(name, gb, num)\
 441             SKIP_COUNTER(name, gb, num)\
 442         }\
 443
 444 #   define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
 445 #   define LAST_SKIP_CACHE(name, gb, num) ;
 446
 447 # ifdef ALT_BITSTREAM_READER_LE
 448 #   define SHOW_UBITS(name, gb, num)\
 449         ((name##_cache) & (NEG_USR32(0xffffffff,num)))
 450
 451 #   define SHOW_SBITS(name, gb, num)\
 452         NEG_SSR32((name##_cache)<<(32-(num)), num)
 453 # else
 454 #   define SHOW_UBITS(name, gb, num)\
 455         NEG_USR32(name##_cache, num)
 456
 457 #   define SHOW_SBITS(name, gb, num)\
 458         NEG_SSR32(name##_cache, num)
 459 # endif
 460
 461 #   define GET_CACHE(name, gb)\
 462         ((uint32_t)name##_cache)
 463
 464 static inline int get_bits_count(GetBitContext *s){
 465     return s->index;
 466 }
 467
 468 static inline void skip_bits_long(GetBitContext *s, int n){
 469     s->index += n;
 470 }
 471
 472 #elif defined LIBMPEG2_BITSTREAM_READER
 473 //libmpeg2 like reader
 474
 475 #   define MIN_CACHE_BITS 17
 476
 477 #   define OPEN_READER(name, gb)\
 478         int name##_bit_count=(gb)->bit_count;\
 479         int name##_cache= (gb)->cache;\
 480         uint8_t * name##_buffer_ptr=(gb)->buffer_ptr;\
 481
 482 #   define CLOSE_READER(name, gb)\
 483         (gb)->bit_count= name##_bit_count;\
 484         (gb)->cache= name##_cache;\
 485         (gb)->buffer_ptr= name##_buffer_ptr;\
 486
 487 #   define UPDATE_CACHE(name, gb)\
 488     if(name##_bit_count >= 0){\
 489         name##_cache+= AV_RB16(name##_buffer_ptr) << name##_bit_count; \
 490         name##_buffer_ptr+=2;\
 491         name##_bit_count-= 16;\
 492     }\
 493
 494 #   define SKIP_CACHE(name, gb, num)\
 495         name##_cache <<= (num);\
 496
 497 #   define SKIP_COUNTER(name, gb, num)\
 498         name##_bit_count += (num);\
 499
 500 #   define SKIP_BITS(name, gb, num)\
 501         {\
 502             SKIP_CACHE(name, gb, num)\
 503             SKIP_COUNTER(name, gb, num)\
 504         }\
 505
 506 #   define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
 507 #   define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
 508
 509 #   define SHOW_UBITS(name, gb, num)\
 510         NEG_USR32(name##_cache, num)
 511
 512 #   define SHOW_SBITS(name, gb, num)\
 513         NEG_SSR32(name##_cache, num)
 514
 515 #   define GET_CACHE(name, gb)\
 516         ((uint32_t)name##_cache)
 517
 518 static inline int get_bits_count(GetBitContext *s){
 519     return (s->buffer_ptr - s->buffer)*8 - 16 + s->bit_count;
 520 }
 521
 522 static inline void skip_bits_long(GetBitContext *s, int n){
 523     OPEN_READER(re, s)
 524     re_bit_count += n;
 525     re_buffer_ptr += 2*(re_bit_count>>4);
 526     re_bit_count &= 15;
 527     re_cache = ((re_buffer_ptr[-2]<<8) + re_buffer_ptr[-1]) << (16+re_bit_count);
 528     UPDATE_CACHE(re, s)
 529     CLOSE_READER(re, s)
 530 }
 531
 532 #elif defined A32_BITSTREAM_READER
 533
 534 #   define MIN_CACHE_BITS 32
 535
 536 #   define OPEN_READER(name, gb)\
 537         int name##_bit_count=(gb)->bit_count;\
 538         uint32_t name##_cache0= (gb)->cache0;\
 539         uint32_t name##_cache1= (gb)->cache1;\
 540         uint32_t * name##_buffer_ptr=(gb)->buffer_ptr;\
 541
 542 #   define CLOSE_READER(name, gb)\
 543         (gb)->bit_count= name##_bit_count;\
 544         (gb)->cache0= name##_cache0;\
 545         (gb)->cache1= name##_cache1;\
 546         (gb)->buffer_ptr= name##_buffer_ptr;\
 547
 548 #   define UPDATE_CACHE(name, gb)\
 549     if(name##_bit_count > 0){\
 550         const uint32_t next= be2me_32( *name##_buffer_ptr );\
 551         name##_cache0 |= NEG_USR32(next,name##_bit_count);\
 552         name##_cache1 |= next<<name##_bit_count;\
 553         name##_buffer_ptr++;\
 554         name##_bit_count-= 32;\
 555     }\
 556
 557 #if defined(ARCH_X86)
 558 #   define SKIP_CACHE(name, gb, num)\
 559         __asm__(\
 560             "shldl %2, %1, %0          \n\t"\
 561             "shll %2, %1               \n\t"\
 562             : "+r" (name##_cache0), "+r" (name##_cache1)\
 563             : "Ic" ((uint8_t)(num))\
 564            );
 565 #else
 566 #   define SKIP_CACHE(name, gb, num)\
 567         name##_cache0 <<= (num);\
 568         name##_cache0 |= NEG_USR32(name##_cache1,num);\
 569         name##_cache1 <<= (num);
 570 #endif
 571
 572 #   define SKIP_COUNTER(name, gb, num)\
 573         name##_bit_count += (num);\
 574
 575 #   define SKIP_BITS(name, gb, num)\
 576         {\
 577             SKIP_CACHE(name, gb, num)\
 578             SKIP_COUNTER(name, gb, num)\
 579         }\
 580
 581 #   define LAST_SKIP_BITS(name, gb, num) SKIP_BITS(name, gb, num)
 582 #   define LAST_SKIP_CACHE(name, gb, num) SKIP_CACHE(name, gb, num)
 583
 584 #   define SHOW_UBITS(name, gb, num)\
 585         NEG_USR32(name##_cache0, num)
 586
 587 #   define SHOW_SBITS(name, gb, num)\
 588         NEG_SSR32(name##_cache0, num)
 589
 590 #   define GET_CACHE(name, gb)\
 591         (name##_cache0)
 592
 593 static inline int get_bits_count(GetBitContext *s){
 594     return ((uint8_t*)s->buffer_ptr - s->buffer)*8 - 32 + s->bit_count;
 595 }
 596
 597 static inline void skip_bits_long(GetBitContext *s, int n){
 598     OPEN_READER(re, s)
 599     re_bit_count += n;
 600     re_buffer_ptr += re_bit_count>>5;
 601     re_bit_count &= 31;
 602     re_cache0 = be2me_32( re_buffer_ptr[-1] ) << re_bit_count;
 603     re_cache1 = 0;
 604     UPDATE_CACHE(re, s)
 605     CLOSE_READER(re, s)
 606 }
 607
 608 #endif
 609
 610 /**
 611  * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
 612  * if MSB not set it is negative
 613  * @param n length in bits
 614  * @author BERO
 615  */
 616 static inline int get_xbits(GetBitContext *s, int n){
 617     register int sign;
 618     register int32_t cache;
 619     OPEN_READER(re, s)
 620     UPDATE_CACHE(re, s)
 621     cache = GET_CACHE(re,s);
 622     sign=(~cache)>>31;
 623     LAST_SKIP_BITS(re, s, n)
 624     CLOSE_READER(re, s)
 625     return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
 626 }
 627
 628 static inline int get_sbits(GetBitContext *s, int n){
 629     register int tmp;
 630     OPEN_READER(re, s)
 631     UPDATE_CACHE(re, s)
 632     tmp= SHOW_SBITS(re, s, n);
 633     LAST_SKIP_BITS(re, s, n)
 634     CLOSE_READER(re, s)
 635     return tmp;
 636 }
 637
 638 /**
 639  * reads 1-17 bits.
 640  * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
 641  */
 642 static inline unsigned int get_bits(GetBitContext *s, int n){
 643     register int tmp;
 644     OPEN_READER(re, s)
 645     UPDATE_CACHE(re, s)
 646     tmp= SHOW_UBITS(re, s, n);
 647     LAST_SKIP_BITS(re, s, n)
 648     CLOSE_READER(re, s)
 649     return tmp;
 650 }
 651
 652 /**
 653  * shows 1-17 bits.
 654  * Note, the alt bitstream reader can read up to 25 bits, but the libmpeg2 reader can't
 655  */
 656 static inline unsigned int show_bits(GetBitContext *s, int n){
 657     register int tmp;
 658     OPEN_READER(re, s)
 659     UPDATE_CACHE(re, s)
 660     tmp= SHOW_UBITS(re, s, n);
 661 //    CLOSE_READER(re, s)
 662     return tmp;
 663 }
 664
 665 static inline void skip_bits(GetBitContext *s, int n){
 666  //Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
 667     OPEN_READER(re, s)
 668     UPDATE_CACHE(re, s)
 669     LAST_SKIP_BITS(re, s, n)
 670     CLOSE_READER(re, s)
 671 }
 672
 673 static inline unsigned int get_bits1(GetBitContext *s){
 674 #ifdef ALT_BITSTREAM_READER
 675     int index= s->index;
 676     uint8_t result= s->buffer[ index>>3 ];
 677 #ifdef ALT_BITSTREAM_READER_LE
 678     result>>= (index&0x07);
 679     result&= 1;
 680 #else
 681     result<<= (index&0x07);
 682     result>>= 8 - 1;
 683 #endif
 684     index++;
 685     s->index= index;
 686
 687     return result;
 688 #else
 689     return get_bits(s, 1);
 690 #endif
 691 }
 692
 693 static inline unsigned int show_bits1(GetBitContext *s){
 694     return show_bits(s, 1);
 695 }
 696
 697 static inline void skip_bits1(GetBitContext *s){
 698     skip_bits(s, 1);
 699 }
 700
 701 /**
 702  * reads 0-32 bits.
 703  */
 704 static inline unsigned int get_bits_long(GetBitContext *s, int n){
 705     if(n<=17) return get_bits(s, n);
 706     else{
 707 #ifdef ALT_BITSTREAM_READER_LE
 708         int ret= get_bits(s, 16);
 709         return ret | (get_bits(s, n-16) << 16);
 710 #else
 711         int ret= get_bits(s, 16) << (n-16);
 712         return ret | get_bits(s, n-16);
 713 #endif
 714     }
 715 }
 716
 717 /**
 718  * shows 0-32 bits.
 719  */
 720 static inline unsigned int show_bits_long(GetBitContext *s, int n){
 721     if(n<=17) return show_bits(s, n);
 722     else{
 723         GetBitContext gb= *s;
 724         int ret= get_bits_long(s, n);
 725         *s= gb;
 726         return ret;
 727     }
 728 }
 729
 730 static inline int check_marker(GetBitContext *s, const char *msg)
 731 {
 732     int bit= get_bits1(s);
 733     if(!bit)
 734         av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
 735
 736     return bit;
 737 }
 738
 739 /**
 740  * init GetBitContext.
 741  * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
 742  * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
 743  * @param bit_size the size of the buffer in bits
 744  */
 745 static inline void init_get_bits(GetBitContext *s,
 746                    const uint8_t *buffer, int bit_size)
 747 {
 748     int buffer_size= (bit_size+7)>>3;
 749     if(buffer_size < 0 || bit_size < 0) {
 750         buffer_size = bit_size = 0;
 751         buffer = NULL;
 752     }
 753
 754     s->buffer= buffer;
 755     s->size_in_bits= bit_size;
 756     s->buffer_end= buffer + buffer_size;
 757 #ifdef ALT_BITSTREAM_READER
 758     s->index=0;
 759 #elif defined LIBMPEG2_BITSTREAM_READER
 760     s->buffer_ptr = (uint8_t*)((intptr_t)buffer&(~1));
 761     s->bit_count = 16 + 8*((intptr_t)buffer&1);
 762     skip_bits_long(s, 0);
 763 #elif defined A32_BITSTREAM_READER
 764     s->buffer_ptr = (uint32_t*)((intptr_t)buffer&(~3));
 765     s->bit_count = 32 + 8*((intptr_t)buffer&3);
 766     skip_bits_long(s, 0);
 767 #endif
 768 }
 769
 770 static inline void align_get_bits(GetBitContext *s)
 771 {
 772     int n= (-get_bits_count(s)) & 7;
 773     if(n) skip_bits(s, n);
 774 }
 775
 776 #define init_vlc(vlc, nb_bits, nb_codes,\
 777                  bits, bits_wrap, bits_size,\
 778                  codes, codes_wrap, codes_size,\
 779                  flags)\
 780         init_vlc_sparse(vlc, nb_bits, nb_codes,\
 781                  bits, bits_wrap, bits_size,\
 782                  codes, codes_wrap, codes_size,\
 783                  NULL, 0, 0, flags)
 784
 785 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
 786              const void *bits, int bits_wrap, int bits_size,
 787              const void *codes, int codes_wrap, int codes_size,
 788              const void *symbols, int symbols_wrap, int symbols_size,
 789              int flags);
 790 #define INIT_VLC_USE_STATIC 1 ///< VERY strongly deprecated and forbidden
 791 #define INIT_VLC_LE         2
 792 #define INIT_VLC_USE_NEW_STATIC 4
 793 void free_vlc(VLC *vlc);
 794
 795 #define INIT_VLC_STATIC(vlc, bits, a,b,c,d,e,f,g, static_size)\
 796 {\
 797     static VLC_TYPE table[static_size][2];\
 798     (vlc)->table= table;\
 799     (vlc)->table_allocated= static_size;\
 800     init_vlc(vlc, bits, a,b,c,d,e,f,g, INIT_VLC_USE_NEW_STATIC);\
 801 }
 802
 803
 804 /**
 805  *
 806  * if the vlc code is invalid and max_depth=1 than no bits will be removed
 807  * if the vlc code is invalid and max_depth>1 than the number of bits removed
 808  * is undefined
 809  */
 810 #define GET_VLC(code, name, gb, table, bits, max_depth)\
 811 {\
 812     int n, index, nb_bits;\
 813 \
 814     index= SHOW_UBITS(name, gb, bits);\
 815     code = table[index][0];\
 816     n    = table[index][1];\
 817 \
 818     if(max_depth > 1 && n < 0){\
 819         LAST_SKIP_BITS(name, gb, bits)\
 820         UPDATE_CACHE(name, gb)\
 821 \
 822         nb_bits = -n;\
 823 \
 824         index= SHOW_UBITS(name, gb, nb_bits) + code;\
 825         code = table[index][0];\
 826         n    = table[index][1];\
 827         if(max_depth > 2 && n < 0){\
 828             LAST_SKIP_BITS(name, gb, nb_bits)\
 829             UPDATE_CACHE(name, gb)\
 830 \
 831             nb_bits = -n;\
 832 \
 833             index= SHOW_UBITS(name, gb, nb_bits) + code;\
 834             code = table[index][0];\
 835             n    = table[index][1];\
 836         }\
 837     }\
 838     SKIP_BITS(name, gb, n)\
 839 }
 840
 841 #define GET_RL_VLC(level, run, name, gb, table, bits, max_depth, need_update)\
 842 {\
 843     int n, index, nb_bits;\
 844 \
 845     index= SHOW_UBITS(name, gb, bits);\
 846     level = table[index].level;\
 847     n     = table[index].len;\
 848 \
 849     if(max_depth > 1 && n < 0){\
 850         SKIP_BITS(name, gb, bits)\
 851         if(need_update){\
 852             UPDATE_CACHE(name, gb)\
 853         }\
 854 \
 855         nb_bits = -n;\
 856 \
 857         index= SHOW_UBITS(name, gb, nb_bits) + level;\
 858         level = table[index].level;\
 859         n     = table[index].len;\
 860     }\
 861     run= table[index].run;\
 862     SKIP_BITS(name, gb, n)\
 863 }
 864
 865
 866 /**
 867  * parses a vlc code, faster then get_vlc()
 868  * @param bits is the number of bits which will be read at once, must be
 869  *             identical to nb_bits in init_vlc()
 870  * @param max_depth is the number of times bits bits must be read to completely
 871  *                  read the longest vlc code
 872  *                  = (max_vlc_length + bits - 1) / bits
 873  */
 874 static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
 875                                   int bits, int max_depth)
 876 {
 877     int code;
 878
 879     OPEN_READER(re, s)
 880     UPDATE_CACHE(re, s)
 881
 882     GET_VLC(code, re, s, table, bits, max_depth)
 883
 884     CLOSE_READER(re, s)
 885     return code;
 886 }
 887
 888 //#define TRACE
 889
 890 #ifdef TRACE
 891 static inline void print_bin(int bits, int n){
 892     int i;
 893
 894     for(i=n-1; i>=0; i--){
 895         av_log(NULL, AV_LOG_DEBUG, "%d", (bits>>i)&1);
 896     }
 897     for(i=n; i<24; i++)
 898         av_log(NULL, AV_LOG_DEBUG, " ");
 899 }
 900
 901 static inline int get_bits_trace(GetBitContext *s, int n, char *file, const char *func, int line){
 902     int r= get_bits(s, n);
 903
 904     print_bin(r, n);
 905     av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n", r, n, r, get_bits_count(s)-n, file, func, line);
 906     return r;
 907 }
 908 static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2], int bits, int max_depth, char *file, const char *func, int line){
 909     int show= show_bits(s, 24);
 910     int pos= get_bits_count(s);
 911     int r= get_vlc2(s, table, bits, max_depth);
 912     int len= get_bits_count(s) - pos;
 913     int bits2= show>>(24-len);
 914
 915     print_bin(bits2, len);
 916
 917     av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n", bits2, len, r, pos, file, func, line);
 918     return r;
 919 }
 920 static inline int get_xbits_trace(GetBitContext *s, int n, char *file, const char *func, int line){
 921     int show= show_bits(s, n);
 922     int r= get_xbits(s, n);
 923
 924     print_bin(show, n);
 925     av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n", show, n, r, get_bits_count(s)-n, file, func, line);
 926     return r;
 927 }
 928
 929 #define get_bits(s, n)  get_bits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
 930 #define get_bits1(s)    get_bits_trace(s, 1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
 931 #define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
 932 #define get_vlc(s, vlc)            get_vlc_trace(s, (vlc)->table, (vlc)->bits, 3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
 933 #define get_vlc2(s, tab, bits, max) get_vlc_trace(s, tab, bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
 934
 935 #define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
 936
 937 #else //TRACE
 938 #define tprintf(p, ...) {}
 939 #endif
 940
 941 static inline int decode012(GetBitContext *gb){
 942     int n;
 943     n = get_bits1(gb);
 944     if (n == 0)
 945         return 0;
 946     else
 947         return get_bits1(gb) + 1;
 948 }
 949
 950 static inline int decode210(GetBitContext *gb){
 951     if (get_bits1(gb))
 952         return 0;
 953     else
 954         return 2 - get_bits1(gb);
 955 }
 956
 957 #endif /* AVCODEC_BITSTREAM_H */