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 void align_put_bits(PutBitContext *s)
  42 {
  43 #ifdef ALT_BITSTREAM_WRITER
  44     put_bits(s,(  - s->index) & 7,0);
  45 #else
  46     put_bits(s,s->bit_left & 7,0);
  47 #endif
  48 }
  49
  50 void ff_put_string(PutBitContext * pbc, const char *s, int terminate_string)
  51 {
  52     while(*s){
  53         put_bits(pbc, 8, *s);
  54         s++;
  55     }
  56     if(terminate_string)
  57         put_bits(pbc, 8, 0);
  58 }
  59
  60 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
  61 {
  62     int words= length>>4;
  63     int bits= length&15;
  64     int i;
  65
  66     if(length==0) return;
  67
  68     if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){
  69         for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i));
  70     }else{
  71         for(i=0; put_bits_count(pb)&31; i++)
  72             put_bits(pb, 8, src[i]);
  73         flush_put_bits(pb);
  74         memcpy(put_bits_ptr(pb), src+i, 2*words-i);
  75         skip_put_bytes(pb, 2*words-i);
  76     }
  77
  78     put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits));
  79 }
  80
  81 /* VLC decoding */
  82
  83 //#define DEBUG_VLC
  84
  85 #define GET_DATA(v, table, i, wrap, size) \
  86 {\
  87     const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
  88     switch(size) {\
  89     case 1:\
  90         v = *(const uint8_t *)ptr;\
  91         break;\
  92     case 2:\
  93         v = *(const uint16_t *)ptr;\
  94         break;\
  95     default:\
  96         v = *(const uint32_t *)ptr;\
  97         break;\
  98     }\
  99 }
 100
 101
 102 static int alloc_table(VLC *vlc, int size, int use_static)
 103 {
 104     int index;
 105     index = vlc->table_size;
 106     vlc->table_size += size;
 107     if (vlc->table_size > vlc->table_allocated) {
 108         if(use_static)
 109             abort(); //cant do anything, init_vlc() is used with too little memory
 110         vlc->table_allocated += (1 << vlc->bits);
 111         vlc->table = av_realloc(vlc->table,
 112                                 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 113         if (!vlc->table)
 114             return -1;
 115     }
 116     return index;
 117 }
 118
 119 static int build_table(VLC *vlc, int table_nb_bits,
 120                        int nb_codes,
 121                        const void *bits, int bits_wrap, int bits_size,
 122                        const void *codes, int codes_wrap, int codes_size,
 123                        const void *symbols, int symbols_wrap, int symbols_size,
 124                        uint32_t code_prefix, int n_prefix, int flags)
 125 {
 126     int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2, symbol;
 127     uint32_t code;
 128     VLC_TYPE (*table)[2];
 129
 130     table_size = 1 << table_nb_bits;
 131     table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
 132 #ifdef DEBUG_VLC
 133     av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d code_prefix=%x n=%d\n",
 134            table_index, table_size, code_prefix, n_prefix);
 135 #endif
 136     if (table_index < 0)
 137         return -1;
 138     table = &vlc->table[table_index];
 139
 140     for(i=0;i<table_size;i++) {
 141         table[i][1] = 0; //bits
 142         table[i][0] = -1; //codes
 143     }
 144
 145     /* first pass: map codes and compute auxillary table sizes */
 146     for(i=0;i<nb_codes;i++) {
 147         GET_DATA(n, bits, i, bits_wrap, bits_size);
 148         GET_DATA(code, codes, i, codes_wrap, codes_size);
 149         /* we accept tables with holes */
 150         if (n <= 0)
 151             continue;
 152         if (!symbols)
 153             symbol = i;
 154         else
 155             GET_DATA(symbol, symbols, i, symbols_wrap, symbols_size);
 156 #if defined(DEBUG_VLC) && 0
 157         av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
 158 #endif
 159         /* if code matches the prefix, it is in the table */
 160         n -= n_prefix;
 161         if(flags & INIT_VLC_LE)
 162             code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
 163         else
 164             code_prefix2= code >> n;
 165         if (n > 0 && code_prefix2 == code_prefix) {
 166             if (n <= table_nb_bits) {
 167                 /* no need to add another table */
 168                 j = (code << (table_nb_bits - n)) & (table_size - 1);
 169                 nb = 1 << (table_nb_bits - n);
 170                 for(k=0;k<nb;k++) {
 171                     if(flags & INIT_VLC_LE)
 172                         j = (code >> n_prefix) + (k<<n);
 173 #ifdef DEBUG_VLC
 174                     av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
 175                            j, i, n);
 176 #endif
 177                     if (table[j][1] /*bits*/ != 0) {
 178                         av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
 179                         return -1;
 180                     }
 181                     table[j][1] = n; //bits
 182                     table[j][0] = symbol;
 183                     j++;
 184                 }
 185             } else {
 186                 n -= table_nb_bits;
 187                 j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
 188 #ifdef DEBUG_VLC
 189                 av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
 190                        j, n);
 191 #endif
 192                 /* compute table size */
 193                 n1 = -table[j][1]; //bits
 194                 if (n > n1)
 195                     n1 = n;
 196                 table[j][1] = -n1; //bits
 197             }
 198         }
 199     }
 200
 201     /* second pass : fill auxillary tables recursively */
 202     for(i=0;i<table_size;i++) {
 203         n = table[i][1]; //bits
 204         if (n < 0) {
 205             n = -n;
 206             if (n > table_nb_bits) {
 207                 n = table_nb_bits;
 208                 table[i][1] = -n; //bits
 209             }
 210             index = build_table(vlc, n, nb_codes,
 211                                 bits, bits_wrap, bits_size,
 212                                 codes, codes_wrap, codes_size,
 213                                 symbols, symbols_wrap, symbols_size,
 214                                 (flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
 215                                 n_prefix + table_nb_bits, flags);
 216             if (index < 0)
 217                 return -1;
 218             /* note: realloc has been done, so reload tables */
 219             table = &vlc->table[table_index];
 220             table[i][0] = index; //code
 221         }
 222     }
 223     return table_index;
 224 }
 225
 226
 227 /* Build VLC decoding tables suitable for use with get_vlc().
 228
 229    'nb_bits' set thee decoding table size (2^nb_bits) entries. The
 230    bigger it is, the faster is the decoding. But it should not be too
 231    big to save memory and L1 cache. '9' is a good compromise.
 232
 233    'nb_codes' : number of vlcs codes
 234
 235    'bits' : table which gives the size (in bits) of each vlc code.
 236
 237    'codes' : table which gives the bit pattern of of each vlc code.
 238
 239    'symbols' : table which gives the values to be returned from get_vlc().
 240
 241    'xxx_wrap' : give the number of bytes between each entry of the
 242    'bits' or 'codes' tables.
 243
 244    'xxx_size' : gives the number of bytes of each entry of the 'bits'
 245    or 'codes' tables.
 246
 247    'wrap' and 'size' allows to use any memory configuration and types
 248    (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
 249
 250    'use_static' should be set to 1 for tables, which should be freed
 251    with av_free_static(), 0 if free_vlc() will be used.
 252 */
 253 int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
 254              const void *bits, int bits_wrap, int bits_size,
 255              const void *codes, int codes_wrap, int codes_size,
 256              const void *symbols, int symbols_wrap, int symbols_size,
 257              int flags)
 258 {
 259     vlc->bits = nb_bits;
 260     if(flags & INIT_VLC_USE_NEW_STATIC){
 261         if(vlc->table_size && vlc->table_size == vlc->table_allocated){
 262             return 0;
 263         }else if(vlc->table_size){
 264             abort(); // fatal error, we are called on a partially initialized table
 265         }
 266     }else {
 267         vlc->table = NULL;
 268         vlc->table_allocated = 0;
 269         vlc->table_size = 0;
 270     }
 271
 272 #ifdef DEBUG_VLC
 273     av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
 274 #endif
 275
 276     if (build_table(vlc, nb_bits, nb_codes,
 277                     bits, bits_wrap, bits_size,
 278                     codes, codes_wrap, codes_size,
 279                     symbols, symbols_wrap, symbols_size,
 280                     0, 0, flags) < 0) {
 281         av_freep(&vlc->table);
 282         return -1;
 283     }
 284     if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
 285         av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
 286     return 0;
 287 }
 288
 289
 290 void free_vlc(VLC *vlc)
 291 {
 292     av_freep(&vlc->table);
 293 }
 294