libavcodec/common.c

   1 /*
   2  * Common bit i/o utils
   3  * Copyright (c) 2000, 2001 Fabrice Bellard.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  *
  19  * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
  20  */
  21
  22 /**
  23  * @file common.c
  24  * common internal api.
  25  */
  26
  27 #include "avcodec.h"
  28
  29 const uint8_t ff_sqrt_tab[128]={
  30         0, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5,
  31         5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
  32         8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
  33         9, 9, 9, 9,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,11,11,11,11,11,11,11
  34 };
  35
  36 const uint8_t ff_log2_tab[256]={
  37         0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
  38         5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
  39         6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
  40         6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
  41         7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  42         7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  43         7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
  44         7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
  45 };
  46
  47 void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
  48 {
  49     s->buf = buffer;
  50     s->buf_end = s->buf + buffer_size;
  51     s->data_out_size = 0;
  52 #ifdef ALT_BITSTREAM_WRITER
  53     s->index=0;
  54     ((uint32_t*)(s->buf))[0]=0;
  55 //    memset(buffer, 0, buffer_size);
  56 #else
  57     s->buf_ptr = s->buf;
  58     s->bit_left=32;
  59     s->bit_buf=0;
  60 #endif
  61 }
  62
  63 #ifdef CONFIG_ENCODERS
  64
  65 /* return the number of bits output */
  66 int64_t get_bit_count(PutBitContext *s)
  67 {
  68 #ifdef ALT_BITSTREAM_WRITER
  69     return s->data_out_size * 8 + s->index;
  70 #else
  71     return (s->buf_ptr - s->buf + s->data_out_size) * 8 + 32 - (int64_t)s->bit_left;
  72 #endif
  73 }
  74
  75 void align_put_bits(PutBitContext *s)
  76 {
  77 #ifdef ALT_BITSTREAM_WRITER
  78     put_bits(s,(  - s->index) & 7,0);
  79 #else
  80     put_bits(s,s->bit_left & 7,0);
  81 #endif
  82 }
  83
  84 #endif //CONFIG_ENCODERS
  85
  86 /* pad the end of the output stream with zeros */
  87 void flush_put_bits(PutBitContext *s)
  88 {
  89 #ifdef ALT_BITSTREAM_WRITER
  90     align_put_bits(s);
  91 #else
  92     s->bit_buf<<= s->bit_left;
  93     while (s->bit_left < 32) {
  94         /* XXX: should test end of buffer */
  95         *s->buf_ptr++=s->bit_buf >> 24;
  96         s->bit_buf<<=8;
  97         s->bit_left+=8;
  98     }
  99     s->bit_left=32;
 100     s->bit_buf=0;
 101 #endif
 102 }
 103
 104 #ifdef CONFIG_ENCODERS
 105
 106 void put_string(PutBitContext * pbc, char *s)
 107 {
 108     while(*s){
 109         put_bits(pbc, 8, *s);
 110         s++;
 111     }
 112     put_bits(pbc, 8, 0);
 113 }
 114
 115 /* bit input functions */
 116
 117 #endif //CONFIG_ENCODERS
 118
 119 /**
 120  * init GetBitContext.
 121  * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
 122  * because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
 123  * @param bit_size the size of the buffer in bits
 124  */
 125 void init_get_bits(GetBitContext *s,
 126                    const uint8_t *buffer, int bit_size)
 127 {
 128     const int buffer_size= (bit_size+7)>>3;
 129
 130     s->buffer= buffer;
 131     s->size_in_bits= bit_size;
 132     s->buffer_end= buffer + buffer_size;
 133 #ifdef ALT_BITSTREAM_READER
 134     s->index=0;
 135 #elif defined LIBMPEG2_BITSTREAM_READER
 136 #ifdef LIBMPEG2_BITSTREAM_READER_HACK
 137   if ((int)buffer&1) {
 138      /* word alignment */
 139     s->cache = (*buffer++)<<24;
 140     s->buffer_ptr = buffer;
 141     s->bit_count = 16-8;
 142   } else
 143 #endif
 144   {
 145     s->buffer_ptr = buffer;
 146     s->bit_count = 16;
 147     s->cache = 0;
 148   }
 149 #elif defined A32_BITSTREAM_READER
 150     s->buffer_ptr = (uint32_t*)buffer;
 151     s->bit_count = 32;
 152     s->cache0 = 0;
 153     s->cache1 = 0;
 154 #endif
 155     {
 156         OPEN_READER(re, s)
 157         UPDATE_CACHE(re, s)
 158         UPDATE_CACHE(re, s)
 159         CLOSE_READER(re, s)
 160     }
 161 #ifdef A32_BITSTREAM_READER
 162     s->cache1 = 0;
 163 #endif
 164 }
 165
 166 /**
 167  * reads 0-32 bits.
 168  */
 169 unsigned int get_bits_long(GetBitContext *s, int n){
 170     if(n<=17) return get_bits(s, n);
 171     else{
 172         int ret= get_bits(s, 16) << (n-16);
 173         return ret | get_bits(s, n-16);
 174     }
 175 }
 176
 177 /**
 178  * shows 0-32 bits.
 179  */
 180 unsigned int show_bits_long(GetBitContext *s, int n){
 181     if(n<=17) return show_bits(s, n);
 182     else{
 183         GetBitContext gb= *s;
 184         int ret= get_bits_long(s, n);
 185         *s= gb;
 186         return ret;
 187     }
 188 }
 189
 190 void align_get_bits(GetBitContext *s)
 191 {
 192     int n= (-get_bits_count(s)) & 7;
 193     if(n) skip_bits(s, n);
 194 }
 195
 196 int check_marker(GetBitContext *s, const char *msg)
 197 {
 198     int bit= get_bits1(s);
 199     if(!bit) printf("Marker bit missing %s\n", msg);
 200
 201     return bit;
 202 }
 203
 204 /* VLC decoding */
 205
 206 //#define DEBUG_VLC
 207
 208 #define GET_DATA(v, table, i, wrap, size) \
 209 {\
 210     const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
 211     switch(size) {\
 212     case 1:\
 213         v = *(const uint8_t *)ptr;\
 214         break;\
 215     case 2:\
 216         v = *(const uint16_t *)ptr;\
 217         break;\
 218     default:\
 219         v = *(const uint32_t *)ptr;\
 220         break;\
 221     }\
 222 }
 223
 224
 225 static int alloc_table(VLC *vlc, int size)
 226 {
 227     int index;
 228     index = vlc->table_size;
 229     vlc->table_size += size;
 230     if (vlc->table_size > vlc->table_allocated) {
 231         vlc->table_allocated += (1 << vlc->bits);
 232         vlc->table = av_realloc(vlc->table,
 233                                 sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
 234         if (!vlc->table)
 235             return -1;
 236     }
 237     return index;
 238 }
 239
 240 static int build_table(VLC *vlc, int table_nb_bits,
 241                        int nb_codes,
 242                        const void *bits, int bits_wrap, int bits_size,
 243                        const void *codes, int codes_wrap, int codes_size,
 244                        uint32_t code_prefix, int n_prefix)
 245 {
 246     int i, j, k, n, table_size, table_index, nb, n1, index;
 247     uint32_t code;
 248     VLC_TYPE (*table)[2];
 249
 250     table_size = 1 << table_nb_bits;
 251     table_index = alloc_table(vlc, table_size);
 252 #ifdef DEBUG_VLC
 253     printf("new table index=%d size=%d code_prefix=%x n=%d\n",
 254            table_index, table_size, code_prefix, n_prefix);
 255 #endif
 256     if (table_index < 0)
 257         return -1;
 258     table = &vlc->table[table_index];
 259
 260     for(i=0;i<table_size;i++) {
 261         table[i][1] = 0; //bits
 262         table[i][0] = -1; //codes
 263     }
 264
 265     /* first pass: map codes and compute auxillary table sizes */
 266     for(i=0;i<nb_codes;i++) {
 267         GET_DATA(n, bits, i, bits_wrap, bits_size);
 268         GET_DATA(code, codes, i, codes_wrap, codes_size);
 269         /* we accept tables with holes */
 270         if (n <= 0)
 271             continue;
 272 #if defined(DEBUG_VLC) && 0
 273         printf("i=%d n=%d code=0x%x\n", i, n, code);
 274 #endif
 275         /* if code matches the prefix, it is in the table */
 276         n -= n_prefix;
 277         if (n > 0 && (code >> n) == code_prefix) {
 278             if (n <= table_nb_bits) {
 279                 /* no need to add another table */
 280                 j = (code << (table_nb_bits - n)) & (table_size - 1);
 281                 nb = 1 << (table_nb_bits - n);
 282                 for(k=0;k<nb;k++) {
 283 #ifdef DEBUG_VLC
 284                     printf("%4x: code=%d n=%d\n",
 285                            j, i, n);
 286 #endif
 287                     if (table[j][1] /*bits*/ != 0) {
 288                         fprintf(stderr, "incorrect codes\n");
 289                         av_abort();
 290                     }
 291                     table[j][1] = n; //bits
 292                     table[j][0] = i; //code
 293                     j++;
 294                 }
 295             } else {
 296                 n -= table_nb_bits;
 297                 j = (code >> n) & ((1 << table_nb_bits) - 1);
 298 #ifdef DEBUG_VLC
 299                 printf("%4x: n=%d (subtable)\n",
 300                        j, n);
 301 #endif
 302                 /* compute table size */
 303                 n1 = -table[j][1]; //bits
 304                 if (n > n1)
 305                     n1 = n;
 306                 table[j][1] = -n1; //bits
 307             }
 308         }
 309     }
 310
 311     /* second pass : fill auxillary tables recursively */
 312     for(i=0;i<table_size;i++) {
 313         n = table[i][1]; //bits
 314         if (n < 0) {
 315             n = -n;
 316             if (n > table_nb_bits) {
 317                 n = table_nb_bits;
 318                 table[i][1] = -n; //bits
 319             }
 320             index = build_table(vlc, n, nb_codes,
 321                                 bits, bits_wrap, bits_size,
 322                                 codes, codes_wrap, codes_size,
 323                                 (code_prefix << table_nb_bits) | i,
 324                                 n_prefix + table_nb_bits);
 325             if (index < 0)
 326                 return -1;
 327             /* note: realloc has been done, so reload tables */
 328             table = &vlc->table[table_index];
 329             table[i][0] = index; //code
 330         }
 331     }
 332     return table_index;
 333 }
 334
 335
 336 /* Build VLC decoding tables suitable for use with get_vlc().
 337
 338    'nb_bits' set thee decoding table size (2^nb_bits) entries. The
 339    bigger it is, the faster is the decoding. But it should not be too
 340    big to save memory and L1 cache. '9' is a good compromise.
 341
 342    'nb_codes' : number of vlcs codes
 343
 344    'bits' : table which gives the size (in bits) of each vlc code.
 345
 346    'codes' : table which gives the bit pattern of of each vlc code.
 347
 348    'xxx_wrap' : give the number of bytes between each entry of the
 349    'bits' or 'codes' tables.
 350
 351    'xxx_size' : gives the number of bytes of each entry of the 'bits'
 352    or 'codes' tables.
 353
 354    'wrap' and 'size' allows to use any memory configuration and types
 355    (byte/word/long) to store the 'bits' and 'codes' tables.
 356 */
 357 int init_vlc(VLC *vlc, int nb_bits, int nb_codes,
 358              const void *bits, int bits_wrap, int bits_size,
 359              const void *codes, int codes_wrap, int codes_size)
 360 {
 361     vlc->bits = nb_bits;
 362     vlc->table = NULL;
 363     vlc->table_allocated = 0;
 364     vlc->table_size = 0;
 365 #ifdef DEBUG_VLC
 366     printf("build table nb_codes=%d\n", nb_codes);
 367 #endif
 368
 369     if (build_table(vlc, nb_bits, nb_codes,
 370                     bits, bits_wrap, bits_size,
 371                     codes, codes_wrap, codes_size,
 372                     0, 0) < 0) {
 373         av_free(vlc->table);
 374         return -1;
 375     }
 376     return 0;
 377 }
 378
 379
 380 void free_vlc(VLC *vlc)
 381 {
 382     av_free(vlc->table);
 383 }
 384
 385 int64_t ff_gcd(int64_t a, int64_t b){
 386     if(b) return ff_gcd(b, a%b);
 387     else  return a;
 388 }
 389
 390 void ff_float2fraction(int *nom_arg, int *denom_arg, double f, int max){
 391     double best_diff=1E10, diff;
 392     int best_denom=1, best_nom=1;
 393     int nom, denom, gcd;
 394
 395     //brute force here, perhaps we should try continued fractions if we need large max ...
 396     for(denom=1; denom<=max; denom++){
 397         nom= (int)(f*denom + 0.5);
 398         if(nom<=0 || nom>max) continue;
 399
 400         diff= ABS( f - (double)nom / (double)denom );
 401         if(diff < best_diff){
 402             best_diff= diff;
 403             best_nom= nom;
 404             best_denom= denom;
 405         }
 406     }
 407
 408     gcd= ff_gcd(best_nom, best_denom);
 409     best_nom   /= gcd;
 410     best_denom /= gcd;
 411
 412     *nom_arg= best_nom;
 413     *denom_arg= best_denom;
 414 }