libavcodec/bitstream.c

   1 /*
   2  * Common bit i/o utils
   3  * Copyright (c) 2000, 2001 Fabrice Bellard
   4  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
   5  *
   6  * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
   7  *
   8  * This file is part of FFmpeg.
   9  *
  10  * FFmpeg is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU Lesser General Public
  12  * License as published by the Free Software Foundation; either
  13  * version 2.1 of the License, or (at your option) any later version.
  14  *
  15  * FFmpeg is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * Lesser General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public
  21  * License along with FFmpeg; if not, write to the Free Software
  22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  23  */
  24
  25 /**
  26  * @file libavcodec/bitstream.c
  27  * bitstream api.
  28  */
  29
  30 #include "avcodec.h"
  31 #include "get_bits.h"
  32 #include "put_bits.h"
  33
  34 const uint8_t ff_log2_run[32]={
  35  0, 0, 0, 0, 1, 1, 1, 1,
  36  2, 2, 2, 2, 3, 3, 3, 3,
  37  4, 4, 5, 5, 6, 6, 7, 7,
  38  8, 9,10,11,12,13,14,15
  39 };
  40
  41 #if LIBAVCODEC_VERSION_MAJOR < 53
  42 /**
  43  * Same as av_mallocz_static(), but does a realloc.
  44  *
  45  * @param[in] ptr The block of memory to reallocate.
  46  * @param[in] size The requested size.
  47  * @return Block of memory of requested size.
  48  * @deprecated. Code which uses ff_realloc_static is broken/misdesigned
  49  * and should correctly use static arrays
  50  */
  51 attribute_deprecated av_alloc_size(2)
  52 static void *ff_realloc_static(void *ptr, unsigned int size);
  53
  54 static void *ff_realloc_static(void *ptr, unsigned int size)
  55 {
  56     return av_realloc(ptr, size);
  57 }
  58 #endif
  59
  60 void align_put_bits(PutBitContext *s)
  61 {
  62 #ifdef ALT_BITSTREAM_WRITER
  63     put_bits(s,(  - s->index) & 7,0);
  64 #else
  65     put_bits(s,s->bit_left & 7,0);
  66 #endif
  67 }
  68
  69 void ff_put_string(PutBitContext * pbc, const char *s, int terminate_string)
  70 {
  71     while(*s){
  72         put_bits(pbc, 8, *s);
  73         s++;
  74     }
  75     if(terminate_string)
  76         put_bits(pbc, 8, 0);
  77 }
  78
  79 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
  80 {
  81     int words= length>>4;
  82     int bits= length&15;
  83     int i;
  84
  85     if(length==0) return;
  86
  87     if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){
  88         for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i));
  89     }else{
  90         for(i=0; put_bits_count(pb)&31; i++)
  91             put_bits(pb, 8, src[i]);
  92         flush_put_bits(pb);
  93         memcpy(put_bits_ptr(pb), src+i, 2*words-i);
  94         skip_put_bytes(pb, 2*words-i);
  95     }
  96
  97     put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits));
  98 }
  99
 100 /* VLC decoding */
 101
 102 //#define DEBUG_VLC
 103
 104 #define GET_DATA(v, table, i, wrap, size) \
 105 {\
 106     const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
 107     switch(size) {\
 108     case 1:\
 109         v = *(const uint8_t *)ptr;\
 110         break;\
 111     case 2:\
 112         v = *(const uint16_t *)ptr;\
 113         break;\
 114     default:\
 115         v = *(const uint32_t *)ptr;\
 116         break;\
 117     }\
 118 }
 119
 120
 121 static int alloc_table(VLC *vlc, int size, int use_static)
 122 {
 123     int index;
 124     index = vlc->table_size;
 125     vlc->table_size += size;
 126     if (vlc->table_size > vlc->table_allocated) {
 127         if(use_static>1)
 128             abort(); //cant do anything, init_vlc() is used with too little memory
 129         vlc->table_allocated += (1 << vlc->bits);
 130         if(use_static)
 131             vlc->table = ff_realloc_static(vlc->table,
 132                                            sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 133         else
 134             vlc->table = av_realloc(vlc->table,
 135                                     sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 136         if (!vlc->table)
 137             return -1;
 138     }
 139     return index;
 140 }
 141
 142 static int build_table(VLC *vlc, int table_nb_bits,
 143                        int nb_codes,
 144                        const void *bits, int bits_wrap, int bits_size,
 145                        const void *codes, int codes_wrap, int codes_size,
 146                        const void *symbols, int symbols_wrap, int symbols_size,
 147                        uint32_t code_prefix, int n_prefix, int flags)
 148 {
 149     int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2, symbol;
 150     uint32_t code;
 151     VLC_TYPE (*table)[2];
 152
 153     table_size = 1 << table_nb_bits;
 154     table_index = alloc_table(vlc, table_size, flags & (INIT_VLC_USE_STATIC|INIT_VLC_USE_NEW_STATIC));
 155 #ifdef DEBUG_VLC
 156     av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d code_prefix=%x n=%d\n",
 157            table_index, table_size, code_prefix, n_prefix);
 158 #endif
 159     if (table_index < 0)
 160         return -1;
 161     table = &vlc->table[table_index];
 162
 163     for(i=0;i<table_size;i++) {
 164         table[i][1] = 0; //bits
 165         table[i][0] = -1; //codes
 166     }
 167
 168     /* first pass: map codes and compute auxillary table sizes */
 169     for(i=0;i<nb_codes;i++) {
 170         GET_DATA(n, bits, i, bits_wrap, bits_size);
 171         GET_DATA(code, codes, i, codes_wrap, codes_size);
 172         /* we accept tables with holes */
 173         if (n <= 0)
 174             continue;
 175         if (!symbols)
 176             symbol = i;
 177         else
 178             GET_DATA(symbol, symbols, i, symbols_wrap, symbols_size);
 179 #if defined(DEBUG_VLC) && 0
 180         av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
 181 #endif
 182         /* if code matches the prefix, it is in the table */
 183         n -= n_prefix;
 184         if(flags & INIT_VLC_LE)
 185             code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
 186         else
 187             code_prefix2= code >> n;
 188         if (n > 0 && code_prefix2 == code_prefix) {
 189             if (n <= table_nb_bits) {
 190                 /* no need to add another table */
 191                 j = (code << (table_nb_bits - n)) & (table_size - 1);
 192                 nb = 1 << (table_nb_bits - n);
 193                 for(k=0;k<nb;k++) {
 194                     if(flags & INIT_VLC_LE)
 195                         j = (code >> n_prefix) + (k<<n);
 196 #ifdef DEBUG_VLC
 197                     av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
 198                            j, i, n);
 199 #endif
 200                     if (table[j][1] /*bits*/ != 0) {
 201                         av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
 202                         return -1;
 203                     }
 204                     table[j][1] = n; //bits
 205                     table[j][0] = symbol;
 206                     j++;
 207                 }
 208             } else {
 209                 n -= table_nb_bits;
 210                 j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
 211 #ifdef DEBUG_VLC
 212                 av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
 213                        j, n);
 214 #endif
 215                 /* compute table size */
 216                 n1 = -table[j][1]; //bits
 217                 if (n > n1)
 218                     n1 = n;
 219                 table[j][1] = -n1; //bits
 220             }
 221         }
 222     }
 223
 224     /* second pass : fill auxillary tables recursively */
 225     for(i=0;i<table_size;i++) {
 226         n = table[i][1]; //bits
 227         if (n < 0) {
 228             n = -n;
 229             if (n > table_nb_bits) {
 230                 n = table_nb_bits;
 231                 table[i][1] = -n; //bits
 232             }
 233             index = build_table(vlc, n, nb_codes,
 234                                 bits, bits_wrap, bits_size,
 235                                 codes, codes_wrap, codes_size,
 236                                 symbols, symbols_wrap, symbols_size,
 237                                 (flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
 238                                 n_prefix + table_nb_bits, flags);
 239             if (index < 0)
 240                 return -1;
 241             /* note: realloc has been done, so reload tables */
 242             table = &vlc->table[table_index];
 243             table[i][0] = index; //code
 244         }
 245     }
 246     return table_index;
 247 }
 248
 249
 250 /* Build VLC decoding tables suitable for use with get_vlc().
 251
 252    'nb_bits' set thee decoding table size (2^nb_bits) entries. The
 253    bigger it is, the faster is the decoding. But it should not be too
 254    big to save memory and L1 cache. '9' is a good compromise.
 255
 256    'nb_codes' : number of vlcs codes
 257
 258    'bits' : table which gives the size (in bits) of each vlc code.
 259
 260    'codes' : table which gives the bit pattern of of each vlc code.
 261
 262    'symbols' : table which gives the values to be returned from get_vlc().
 263
 264    'xxx_wrap' : give the number of bytes between each entry of the
 265    'bits' or 'codes' tables.
 266
 267    'xxx_size' : gives the number of bytes of each entry of the 'bits'
 268    or 'codes' tables.
 269
 270    'wrap' and 'size' allows to use any memory configuration and types
 271    (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
 272
 273    'use_static' should be set to 1 for tables, which should be freed
 274    with av_free_static(), 0 if free_vlc() will be used.
 275 */
 276 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
 277              const void *bits, int bits_wrap, int bits_size,
 278              const void *codes, int codes_wrap, int codes_size,
 279              const void *symbols, int symbols_wrap, int symbols_size,
 280              int flags)
 281 {
 282     vlc->bits = nb_bits;
 283     if(flags & INIT_VLC_USE_NEW_STATIC){
 284         if(vlc->table_size && vlc->table_size == vlc->table_allocated){
 285             return 0;
 286         }else if(vlc->table_size){
 287             abort(); // fatal error, we are called on a partially initialized table
 288         }
 289     }else if(!(flags & INIT_VLC_USE_STATIC)) {
 290         vlc->table = NULL;
 291         vlc->table_allocated = 0;
 292         vlc->table_size = 0;
 293     } else {
 294         /* Static tables are initially always NULL, return
 295            if vlc->table != NULL to avoid double allocation */
 296         if(vlc->table)
 297             return 0;
 298     }
 299
 300 #ifdef DEBUG_VLC
 301     av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
 302 #endif
 303
 304     if (build_table(vlc, nb_bits, nb_codes,
 305                     bits, bits_wrap, bits_size,
 306                     codes, codes_wrap, codes_size,
 307                     symbols, symbols_wrap, symbols_size,
 308                     0, 0, flags) < 0) {
 309         av_freep(&vlc->table);
 310         return -1;
 311     }
 312     if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
 313         av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
 314     return 0;
 315 }
 316
 317
 318 void free_vlc(VLC *vlc)
 319 {
 320     av_freep(&vlc->table);
 321 }
 322