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 * Copyright (c) 2010 Loren Merritt 6 * 7 * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at> 8 * 9 * This file is part of FFmpeg. 10 * 11 * FFmpeg is free software; you can redistribute it and/or 12 * modify it under the terms of the GNU Lesser General Public 13 * License as published by the Free Software Foundation; either 14 * version 2.1 of the License, or (at your option) any later version. 15 * 16 * FFmpeg is distributed in the hope that it will be useful, 17 * but WITHOUT ANY WARRANTY; without even the implied warranty of 18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 19 * Lesser General Public License for more details. 20 * 21 * You should have received a copy of the GNU Lesser General Public 22 * License along with FFmpeg; if not, write to the Free Software 23 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 24 */ 25 26/** 27 * @file 28 * bitstream api. 29 */ 30 31#include "avcodec.h" 32#include "get_bits.h" 33#include "put_bits.h" 34 35const uint8_t ff_log2_run[32]={ 36 0, 0, 0, 0, 1, 1, 1, 1, 37 2, 2, 2, 2, 3, 3, 3, 3, 38 4, 4, 5, 5, 6, 6, 7, 7, 39 8, 9,10,11,12,13,14,15 40}; 41 42void align_put_bits(PutBitContext *s) 43{ 44#ifdef ALT_BITSTREAM_WRITER 45 put_bits(s,( - s->index) & 7,0); 46#else 47 put_bits(s,s->bit_left & 7,0); 48#endif 49} 50 51void ff_put_string(PutBitContext *pb, const char *string, int terminate_string) 52{ 53 while(*string){ 54 put_bits(pb, 8, *string); 55 string++; 56 } 57 if(terminate_string) 58 put_bits(pb, 8, 0); 59} 60 61void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length) 62{ 63 int words= length>>4; 64 int bits= length&15; 65 int i; 66 67 if(length==0) return; 68 69 if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){ 70 for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i)); 71 }else{ 72 for(i=0; put_bits_count(pb)&31; i++) 73 put_bits(pb, 8, src[i]); 74 flush_put_bits(pb); 75 memcpy(put_bits_ptr(pb), src+i, 2*words-i); 76 skip_put_bytes(pb, 2*words-i); 77 } 78 79 put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits)); 80} 81 82/* VLC decoding */ 83 84//#define DEBUG_VLC 85 86#define GET_DATA(v, table, i, wrap, size) \ 87{\ 88 const uint8_t *ptr = (const uint8_t *)table + i * wrap;\ 89 switch(size) {\ 90 case 1:\ 91 v = *(const uint8_t *)ptr;\ 92 break;\ 93 case 2:\ 94 v = *(const uint16_t *)ptr;\ 95 break;\ 96 default:\ 97 v = *(const uint32_t *)ptr;\ 98 break;\ 99 }\ 100} 101 102 103static int alloc_table(VLC *vlc, int size, int use_static) 104{ 105 int index; 106 index = vlc->table_size; 107 vlc->table_size += size; 108 if (vlc->table_size > vlc->table_allocated) { 109 if(use_static) 110 abort(); //cant do anything, init_vlc() is used with too little memory 111 vlc->table_allocated += (1 << vlc->bits); 112 vlc->table = av_realloc(vlc->table, 113 sizeof(VLC_TYPE) * 2 * vlc->table_allocated); 114 if (!vlc->table) 115 return -1; 116 } 117 return index; 118} 119 120static av_always_inline uint32_t bitswap_32(uint32_t x) { 121 return av_reverse[x&0xFF]<<24 122 | av_reverse[(x>>8)&0xFF]<<16 123 | av_reverse[(x>>16)&0xFF]<<8 124 | av_reverse[x>>24]; 125} 126 127typedef struct { 128 uint8_t bits; 129 uint16_t symbol; 130 /** codeword, with the first bit-to-be-read in the msb 131 * (even if intended for a little-endian bitstream reader) */ 132 uint32_t code; 133} VLCcode; 134 135static int compare_vlcspec(const void *a, const void *b) 136{ 137 const VLCcode *sa=a, *sb=b; 138 return (sa->code >> 1) - (sb->code >> 1); 139} 140 141/** 142 * Build VLC decoding tables suitable for use with get_vlc(). 143 * 144 * @param vlc the context to be initted 145 * 146 * @param table_nb_bits max length of vlc codes to store directly in this table 147 * (Longer codes are delegated to subtables.) 148 * 149 * @param nb_codes number of elements in codes[] 150 * 151 * @param codes descriptions of the vlc codes 152 * These must be ordered such that codes going into the same subtable are contiguous. 153 * Sorting by VLCcode.code is sufficient, though not necessary. 154 */ 155static int build_table(VLC *vlc, int table_nb_bits, int nb_codes, 156 VLCcode *codes, int flags) 157{ 158 int table_size, table_index, index, code_prefix, symbol, subtable_bits; 159 int i, j, k, n, nb, inc; 160 uint32_t code; 161 VLC_TYPE (*table)[2]; 162 163 table_size = 1 << table_nb_bits; 164 table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC); 165#ifdef DEBUG_VLC 166 av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d\n", 167 table_index, table_size); 168#endif 169 if (table_index < 0) 170 return -1; 171 table = &vlc->table[table_index]; 172 173 for (i = 0; i < table_size; i++) { 174 table[i][1] = 0; //bits 175 table[i][0] = -1; //codes 176 } 177 178 /* first pass: map codes and compute auxillary table sizes */ 179 for (i = 0; i < nb_codes; i++) { 180 n = codes[i].bits; 181 code = codes[i].code; 182 symbol = codes[i].symbol; 183#if defined(DEBUG_VLC) && 0 184 av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code); 185#endif 186 if (n <= table_nb_bits) { 187 /* no need to add another table */ 188 j = code >> (32 - table_nb_bits); 189 nb = 1 << (table_nb_bits - n); 190 inc = 1; 191 if (flags & INIT_VLC_LE) { 192 j = bitswap_32(code); 193 inc = 1 << n; 194 } 195 for (k = 0; k < nb; k++) { 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 += inc; 207 } 208 } else { 209 /* fill auxiliary table recursively */ 210 n -= table_nb_bits; 211 code_prefix = code >> (32 - table_nb_bits); 212 subtable_bits = n; 213 codes[i].bits = n; 214 codes[i].code = code << table_nb_bits; 215 for (k = i+1; k < nb_codes; k++) { 216 n = codes[k].bits - table_nb_bits; 217 if (n <= 0) 218 break; 219 code = codes[k].code; 220 if (code >> (32 - table_nb_bits) != code_prefix) 221 break; 222 codes[k].bits = n; 223 codes[k].code = code << table_nb_bits; 224 subtable_bits = FFMAX(subtable_bits, n); 225 } 226 subtable_bits = FFMIN(subtable_bits, table_nb_bits); 227 j = (flags & INIT_VLC_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix; 228 table[j][1] = -subtable_bits; 229#ifdef DEBUG_VLC 230 av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n", 231 j, codes[i].bits + table_nb_bits); 232#endif 233 index = build_table(vlc, subtable_bits, k-i, codes+i, flags); 234 if (index < 0) 235 return -1; 236 /* note: realloc has been done, so reload tables */ 237 table = &vlc->table[table_index]; 238 table[j][0] = index; //code 239 i = k-1; 240 } 241 } 242 return table_index; 243} 244 245 246/* Build VLC decoding tables suitable for use with get_vlc(). 247 248 'nb_bits' set thee decoding table size (2^nb_bits) entries. The 249 bigger it is, the faster is the decoding. But it should not be too 250 big to save memory and L1 cache. '9' is a good compromise. 251 252 'nb_codes' : number of vlcs codes 253 254 'bits' : table which gives the size (in bits) of each vlc code. 255 256 'codes' : table which gives the bit pattern of of each vlc code. 257 258 'symbols' : table which gives the values to be returned from get_vlc(). 259 260 'xxx_wrap' : give the number of bytes between each entry of the 261 'bits' or 'codes' tables. 262 263 'xxx_size' : gives the number of bytes of each entry of the 'bits' 264 or 'codes' tables. 265 266 'wrap' and 'size' allows to use any memory configuration and types 267 (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables. 268 269 'use_static' should be set to 1 for tables, which should be freed 270 with av_free_static(), 0 if free_vlc() will be used. 271*/ 272int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes, 273 const void *bits, int bits_wrap, int bits_size, 274 const void *codes, int codes_wrap, int codes_size, 275 const void *symbols, int symbols_wrap, int symbols_size, 276 int flags) 277{ 278 VLCcode buf[nb_codes]; 279 int i, j; 280 281 vlc->bits = nb_bits; 282 if(flags & INIT_VLC_USE_NEW_STATIC){ 283 if(vlc->table_size && vlc->table_size == vlc->table_allocated){ 284 return 0; 285 }else if(vlc->table_size){ 286 abort(); // fatal error, we are called on a partially initialized table 287 } 288 }else { 289 vlc->table = NULL; 290 vlc->table_allocated = 0; 291 vlc->table_size = 0; 292 } 293 294#ifdef DEBUG_VLC 295 av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes); 296#endif 297 298 assert(symbols_size <= 2 || !symbols); 299 j = 0; 300#define COPY(condition)\ 301 for (i = 0; i < nb_codes; i++) {\ 302 GET_DATA(buf[j].bits, bits, i, bits_wrap, bits_size);\ 303 if (!(condition))\ 304 continue;\ 305 GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size);\ 306 if (flags & INIT_VLC_LE)\ 307 buf[j].code = bitswap_32(buf[j].code);\ 308 else\ 309 buf[j].code <<= 32 - buf[j].bits;\ 310 if (symbols)\ 311 GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size)\ 312 else\ 313 buf[j].symbol = i;\ 314 j++;\ 315 } 316 COPY(buf[j].bits > nb_bits); 317 // qsort is the slowest part of init_vlc, and could probably be improved or avoided 318 qsort(buf, j, sizeof(VLCcode), compare_vlcspec); 319 COPY(buf[j].bits && buf[j].bits <= nb_bits); 320 nb_codes = j; 321 322 if (build_table(vlc, nb_bits, nb_codes, buf, flags) < 0) { 323 av_freep(&vlc->table); 324 return -1; 325 } 326 if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated) 327 av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated); 328 return 0; 329} 330 331 332void free_vlc(VLC *vlc) 333{ 334 av_freep(&vlc->table); 335} 336 337