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 bitstream.c
  27  * bitstream api.
  28  */
  29
  30 #include "avcodec.h"
  31 #include "bitstream.h"
  32
  33 /**
  34  * Same as av_mallocz_static(), but does a realloc.
  35  *
  36  * @param[in] ptr The block of memory to reallocate.
  37  * @param[in] size The requested size.
  38  * @return Block of memory of requested size.
  39  * @deprecated. Code which uses ff_realloc_static is broken/misdesigned
  40  * and should correctly use static arrays
  41  */
  42 attribute_deprecated void *ff_realloc_static(void *ptr, unsigned int size);
  43
  44 void align_put_bits(PutBitContext *s)
  45 {
  46 #ifdef ALT_BITSTREAM_WRITER
  47     put_bits(s,(  - s->index) & 7,0);
  48 #else
  49     put_bits(s,s->bit_left & 7,0);
  50 #endif
  51 }
  52
  53 void ff_put_string(PutBitContext * pbc, const char *s, int put_zero)
  54 {
  55     while(*s){
  56         put_bits(pbc, 8, *s);
  57         s++;
  58     }
  59     if(put_zero)
  60         put_bits(pbc, 8, 0);
  61 }
  62
  63 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
  64 {
  65     const uint16_t *srcw= (const uint16_t*)src;
  66     int words= length>>4;
  67     int bits= length&15;
  68     int i;
  69
  70     if(length==0) return;
  71
  72     if(ENABLE_SMALL || words < 16 || put_bits_count(pb)&7){
  73         for(i=0; i<words; i++) put_bits(pb, 16, be2me_16(srcw[i]));
  74     }else{
  75         for(i=0; put_bits_count(pb)&31; i++)
  76             put_bits(pb, 8, src[i]);
  77         flush_put_bits(pb);
  78         memcpy(pbBufPtr(pb), src+i, 2*words-i);
  79         skip_put_bytes(pb, 2*words-i);
  80     }
  81
  82     put_bits(pb, bits, be2me_16(srcw[words])>>(16-bits));
  83 }
  84
  85 /* VLC decoding */
  86
  87 //#define DEBUG_VLC
  88
  89 #define GET_DATA(v, table, i, wrap, size) \
  90 {\
  91     const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
  92     switch(size) {\
  93     case 1:\
  94         v = *(const uint8_t *)ptr;\
  95         break;\
  96     case 2:\
  97         v = *(const uint16_t *)ptr;\
  98         break;\
  99     default:\
 100         v = *(const uint32_t *)ptr;\
 101         break;\
 102     }\
 103 }
 104
 105
 106 static int alloc_table(VLC *vlc, int size, int use_static)
 107 {
 108     int index;
 109     index = vlc->table_size;
 110     vlc->table_size += size;
 111     if (vlc->table_size > vlc->table_allocated) {
 112         vlc->table_allocated += (1 << vlc->bits);
 113         if(use_static)
 114             vlc->table = ff_realloc_static(vlc->table,
 115                                            sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 116         else
 117             vlc->table = av_realloc(vlc->table,
 118                                     sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 119         if (!vlc->table)
 120             return -1;
 121     }
 122     return index;
 123 }
 124
 125 static int build_table(VLC *vlc, int table_nb_bits,
 126                        int nb_codes,
 127                        const void *bits, int bits_wrap, int bits_size,
 128                        const void *codes, int codes_wrap, int codes_size,
 129                        const void *symbols, int symbols_wrap, int symbols_size,
 130                        uint32_t code_prefix, int n_prefix, int flags)
 131 {
 132     int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2, symbol;
 133     uint32_t code;
 134     VLC_TYPE (*table)[2];
 135
 136     table_size = 1 << table_nb_bits;
 137     table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_STATIC);
 138 #ifdef DEBUG_VLC
 139     av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d code_prefix=%x n=%d\n",
 140            table_index, table_size, code_prefix, n_prefix);
 141 #endif
 142     if (table_index < 0)
 143         return -1;
 144     table = &vlc->table[table_index];
 145
 146     for(i=0;i<table_size;i++) {
 147         table[i][1] = 0; //bits
 148         table[i][0] = -1; //codes
 149     }
 150
 151     /* first pass: map codes and compute auxillary table sizes */
 152     for(i=0;i<nb_codes;i++) {
 153         GET_DATA(n, bits, i, bits_wrap, bits_size);
 154         GET_DATA(code, codes, i, codes_wrap, codes_size);
 155         /* we accept tables with holes */
 156         if (n <= 0)
 157             continue;
 158         if (!symbols)
 159             symbol = i;
 160         else
 161             GET_DATA(symbol, symbols, i, symbols_wrap, symbols_size);
 162 #if defined(DEBUG_VLC) && 0
 163         av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
 164 #endif
 165         /* if code matches the prefix, it is in the table */
 166         n -= n_prefix;
 167         if(flags & INIT_VLC_LE)
 168             code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
 169         else
 170             code_prefix2= code >> n;
 171         if (n > 0 && code_prefix2 == code_prefix) {
 172             if (n <= table_nb_bits) {
 173                 /* no need to add another table */
 174                 j = (code << (table_nb_bits - n)) & (table_size - 1);
 175                 nb = 1 << (table_nb_bits - n);
 176                 for(k=0;k<nb;k++) {
 177                     if(flags & INIT_VLC_LE)
 178                         j = (code >> n_prefix) + (k<<n);
 179 #ifdef DEBUG_VLC
 180                     av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
 181                            j, i, n);
 182 #endif
 183                     if (table[j][1] /*bits*/ != 0) {
 184                         av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
 185                         return -1;
 186                     }
 187                     table[j][1] = n; //bits
 188                     table[j][0] = symbol;
 189                     j++;
 190                 }
 191             } else {
 192                 n -= table_nb_bits;
 193                 j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
 194 #ifdef DEBUG_VLC
 195                 av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
 196                        j, n);
 197 #endif
 198                 /* compute table size */
 199                 n1 = -table[j][1]; //bits
 200                 if (n > n1)
 201                     n1 = n;
 202                 table[j][1] = -n1; //bits
 203             }
 204         }
 205     }
 206
 207     /* second pass : fill auxillary tables recursively */
 208     for(i=0;i<table_size;i++) {
 209         n = table[i][1]; //bits
 210         if (n < 0) {
 211             n = -n;
 212             if (n > table_nb_bits) {
 213                 n = table_nb_bits;
 214                 table[i][1] = -n; //bits
 215             }
 216             index = build_table(vlc, n, nb_codes,
 217                                 bits, bits_wrap, bits_size,
 218                                 codes, codes_wrap, codes_size,
 219                                 symbols, symbols_wrap, symbols_size,
 220                                 (flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
 221                                 n_prefix + table_nb_bits, flags);
 222             if (index < 0)
 223                 return -1;
 224             /* note: realloc has been done, so reload tables */
 225             table = &vlc->table[table_index];
 226             table[i][0] = index; //code
 227         }
 228     }
 229     return table_index;
 230 }
 231
 232
 233 /* Build VLC decoding tables suitable for use with get_vlc().
 234
 235    'nb_bits' set thee decoding table size (2^nb_bits) entries. The
 236    bigger it is, the faster is the decoding. But it should not be too
 237    big to save memory and L1 cache. '9' is a good compromise.
 238
 239    'nb_codes' : number of vlcs codes
 240
 241    'bits' : table which gives the size (in bits) of each vlc code.
 242
 243    'codes' : table which gives the bit pattern of of each vlc code.
 244
 245    'symbols' : table which gives the values to be returned from get_vlc().
 246
 247    'xxx_wrap' : give the number of bytes between each entry of the
 248    'bits' or 'codes' tables.
 249
 250    'xxx_size' : gives the number of bytes of each entry of the 'bits'
 251    or 'codes' tables.
 252
 253    'wrap' and 'size' allows to use any memory configuration and types
 254    (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
 255
 256    'use_static' should be set to 1 for tables, which should be freed
 257    with av_free_static(), 0 if free_vlc() will be used.
 258 */
 259 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
 260              const void *bits, int bits_wrap, int bits_size,
 261              const void *codes, int codes_wrap, int codes_size,
 262              const void *symbols, int symbols_wrap, int symbols_size,
 263              int flags)
 264 {
 265     vlc->bits = nb_bits;
 266     if(!(flags & INIT_VLC_USE_STATIC)) {
 267         vlc->table = NULL;
 268         vlc->table_allocated = 0;
 269         vlc->table_size = 0;
 270     } else {
 271         /* Static tables are initially always NULL, return
 272            if vlc->table != NULL to avoid double allocation */
 273         if(vlc->table)
 274             return 0;
 275     }
 276
 277 #ifdef DEBUG_VLC
 278     av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
 279 #endif
 280
 281     if (build_table(vlc, nb_bits, nb_codes,
 282                     bits, bits_wrap, bits_size,
 283                     codes, codes_wrap, codes_size,
 284                     symbols, symbols_wrap, symbols_size,
 285                     0, 0, flags) < 0) {
 286         av_freep(&vlc->table);
 287         return -1;
 288     }
 289     return 0;
 290 }
 291
 292
 293 void free_vlc(VLC *vlc)
 294 {
 295     av_freep(&vlc->table);
 296 }
 297