vlc.h (14980B)
1 /* 2 * This file is part of FFmpeg. 3 * 4 * FFmpeg is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU Lesser General Public 6 * License as published by the Free Software Foundation; either 7 * version 2.1 of the License, or (at your option) any later version. 8 * 9 * FFmpeg is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 * Lesser General Public License for more details. 13 * 14 * You should have received a copy of the GNU Lesser General Public 15 * License along with FFmpeg; if not, write to the Free Software 16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 17 */ 18 19 #ifndef AVCODEC_VLC_H 20 #define AVCODEC_VLC_H 21 22 #include <stddef.h> 23 #include <stdint.h> 24 25 #include "libavutil/macros.h" 26 27 #define VLC_MULTI_MAX_SYMBOLS 6 28 29 // When changing this, be sure to also update tableprint_vlc.h accordingly. 30 typedef int16_t VLCBaseType; 31 32 typedef struct VLCElem { 33 VLCBaseType sym, len; 34 } VLCElem; 35 36 typedef struct VLC { 37 int bits; 38 VLCElem *table; 39 int table_size, table_allocated; 40 } VLC; 41 42 typedef struct VLC_MULTI_ELEM { 43 union { 44 uint8_t val8[VLC_MULTI_MAX_SYMBOLS]; 45 uint16_t val16[VLC_MULTI_MAX_SYMBOLS / 2]; 46 }; 47 int8_t len; // -31,32 48 uint8_t num; 49 } VLC_MULTI_ELEM; 50 51 typedef struct VLC_MULTI { 52 VLC_MULTI_ELEM *table; 53 int table_size, table_allocated; 54 } VLC_MULTI; 55 56 typedef struct RL_VLC_ELEM { 57 int16_t level; 58 int8_t len; 59 uint8_t run; 60 } RL_VLC_ELEM; 61 62 #define vlc_init(vlc, nb_bits, nb_codes, \ 63 bits, bits_wrap, bits_size, \ 64 codes, codes_wrap, codes_size, \ 65 flags) \ 66 ff_vlc_init_sparse(vlc, nb_bits, nb_codes, \ 67 bits, bits_wrap, bits_size, \ 68 codes, codes_wrap, codes_size, \ 69 NULL, 0, 0, flags) 70 71 /** 72 * Build VLC decoding tables suitable for use with get_vlc2(). 73 * 74 * @param[in,out] vlc The VLC to be initialized; table and table_allocated 75 * must have been set when initializing a static VLC, 76 * otherwise this will be treated as uninitialized. 77 * @param[in] nb_bits The number of bits to use for the VLC table; 78 * higher values take up more memory and cache, but 79 * allow to read codes with fewer reads. 80 * Corresponds to the `bits` parameter of get_vlc2(). 81 * @param[in] nb_codes The number of provided bits, codes and (if supplied) 82 * symbol entries. 83 * @param[in] bits The lengths (in bits) of the codes. Entries > 0 84 * correspond to valid codes; entries == 0 will be skipped. 85 * @param[in] bits_wrap Stride (in bytes) of the bits table. 86 * @param[in] codes_size Size of the bits. 1, 2 and 4 are supported. 87 * @param[in] codes Table which gives the bit pattern of of each vlc code. 88 * @param[in] codes_wrap Stride (in bytes) of the codes table. 89 * @param[in] codes_size Size of the codes. 1, 2 and 4 are supported. 90 * @param[in] symbols The symbols, i.e. what is returned from get_vlc2() 91 * when the corresponding code is encountered. 92 * May be NULL, then 0, 1, 2, 3, 4,... will be used. 93 * @param[in] symbols_wrap Stride (in bytes) of the symbols table. 94 * @param[in] symbols_size Size of the symbols. 1 and 2 are supported. 95 * @param[in] flags A combination of the VLC_INIT_* flags. 96 * 97 * 'wrap' and 'size' make it possible to use any memory configuration and types 98 * (byte/word/int) to store the 'bits', 'codes', and 'symbols' tables. 99 */ 100 int ff_vlc_init_sparse(VLC *vlc, int nb_bits, int nb_codes, 101 const void *bits, int bits_wrap, int bits_size, 102 const void *codes, int codes_wrap, int codes_size, 103 const void *symbols, int symbols_wrap, int symbols_size, 104 int flags); 105 106 /** 107 * Build VLC decoding tables suitable for use with get_vlc2() 108 * 109 * This function takes lengths and symbols and calculates the codes from them. 110 * For this the input lengths and symbols have to be sorted according to "left 111 * nodes in the corresponding tree first". 112 * 113 * @param[in,out] vlc The VLC to be initialized; table and table_allocated 114 * must have been set when initializing a static VLC, 115 * otherwise this will be treated as uninitialized. 116 * @param[in] nb_bits The number of bits to use for the VLC table; 117 * higher values take up more memory and cache, but 118 * allow to read codes with fewer reads. 119 * @param[in] nb_codes The number of provided length and (if supplied) symbol 120 * entries. 121 * @param[in] lens The lengths of the codes. Entries > 0 correspond to 122 * valid codes; entries == 0 will be skipped and entries 123 * with len < 0 indicate that the tree is incomplete and 124 * has an open end of length -len at this position. 125 * @param[in] lens_wrap Stride (in bytes) of the lengths. 126 * @param[in] symbols The symbols, i.e. what is returned from get_vlc2() 127 * when the corresponding code is encountered. 128 * May be NULL, then 0, 1, 2, 3, 4,... will be used. 129 * @param[in] symbols_wrap Stride (in bytes) of the symbols. 130 * @param[in] symbols_size Size of the symbols. 1 and 2 are supported. 131 * @param[in] offset An offset to apply to all the valid symbols. 132 * @param[in] flags A combination of the VLC_INIT_* flags; notice that 133 * VLC_INIT_INPUT_LE is pointless and ignored. 134 */ 135 int ff_vlc_init_from_lengths(VLC *vlc, int nb_bits, int nb_codes, 136 const int8_t *lens, int lens_wrap, 137 const void *symbols, int symbols_wrap, int symbols_size, 138 int offset, int flags, void *logctx); 139 140 /** 141 * Build VLC decoding tables suitable for use with get_vlc_multi() 142 * 143 * This function takes lengths and symbols and calculates the codes from them. 144 * For this the input lengths and symbols have to be sorted according to "left 145 * nodes in the corresponding tree first". 146 * 147 * @param[in,out] vlc The VLC to be initialized; table and table_allocated 148 * must have been set when initializing a static VLC, 149 * otherwise this will be treated as uninitialized. 150 * @param[in,out] multi The VLC_MULTI to be initialized; table and table_allocated 151 * must have been set when initializing a static VLC, 152 * otherwise this will be treated as uninitialized. 153 * @param[in] nb_bits The number of bits to use for the VLC table; 154 * higher values take up more memory and cache, but 155 * allow to read codes with fewer reads. 156 * @param[in] nb_elems The max possible number of elements. 157 * @param[in] nb_codes The number of provided length and (if supplied) symbol 158 * entries. 159 * @param[in] lens The lengths of the codes. Entries > 0 correspond to 160 * valid codes; entries == 0 will be skipped and entries 161 * with len < 0 indicate that the tree is incomplete and 162 * has an open end of length -len at this position. 163 * @param[in] lens_wrap Stride (in bytes) of the lengths. 164 * @param[in] symbols The symbols, i.e. what is returned from get_vlc2() 165 * when the corresponding code is encountered. 166 * May be NULL, then 0, 1, 2, 3, 4,... will be used. 167 * @param[in] symbols_wrap Stride (in bytes) of the symbols. 168 * @param[in] symbols_size Size of the symbols. 1 and 2 are supported. 169 * @param[in] offset An offset to apply to all the valid symbols. 170 * @param[in] flags A combination of the VLC_INIT_* flags; notice that 171 * VLC_INIT_INPUT_LE is pointless and ignored. 172 */ 173 int ff_vlc_init_multi_from_lengths(VLC *vlc, VLC_MULTI *multi, int nb_bits, int nb_elems, 174 int nb_codes, const int8_t *lens, int lens_wrap, 175 const void *symbols, int symbols_wrap, int symbols_size, 176 int offset, int flags, void *logctx); 177 178 179 void ff_vlc_free_multi(VLC_MULTI *vlc); 180 void ff_vlc_free(VLC *vlc); 181 182 #define VLC_INIT_USE_STATIC 1 183 #define VLC_INIT_STATIC_OVERLONG (2 | VLC_INIT_USE_STATIC) 184 /* If VLC_INIT_INPUT_LE is set, the LSB bit of the codes used to 185 * initialize the VLC table is the first bit to be read. */ 186 #define VLC_INIT_INPUT_LE 4 187 /* If set the VLC is intended for a little endian bitstream reader. */ 188 #define VLC_INIT_OUTPUT_LE 8 189 #define VLC_INIT_LE (VLC_INIT_INPUT_LE | VLC_INIT_OUTPUT_LE) 190 191 /** 192 * For static VLCs, the number of bits can often be hardcoded 193 * at each get_vlc2() callsite. Then using a full VLC would be uneconomical, 194 * because only VLC.table would ever be accessed after initialization. 195 * The following functions provide wrappers around the relevant ff_vlc_init_* 196 * functions suitable for said task. 197 * 198 * The ff_vlc_init_tables_* functions are intended to be used for initializing 199 * a series of VLCs. The user initializes a VLCInitState with the details 200 * about the underlying array of VLCElem; it is automatically updated by 201 * the ff_vlc_init_tables_* functions (i.e. table is incremented and size 202 * decremented by the number of elements of the current table). 203 * The VLC_INIT_STATIC_OVERLONG flag is also automatically added. 204 * These functions return a pointer to the table just initialized, 205 * potentially to be used in arrays of pointer to VLC tables. 206 * 207 * The ff_vlc_init_table_* functions are intended to be used for initializing 208 * a single VLC table, given by table and table_size. The VLC_INIT_USE_STATIC 209 * flag is automatically added. 210 */ 211 212 typedef struct VLCInitState { 213 VLCElem *table; ///< points to where the next VLC table will be placed 214 unsigned size; ///< remaining number of elements in table 215 } VLCInitState; 216 217 #define VLC_INIT_STATE(_table) { .table = (_table), .size = FF_ARRAY_ELEMS(_table) } 218 219 void ff_vlc_init_table_from_lengths(VLCElem table[], int table_size, 220 int nb_bits, int nb_codes, 221 const int8_t *lens, int lens_wrap, 222 const void *symbols, int symbols_wrap, int symbols_size, 223 int offset, int flags); 224 225 const VLCElem *ff_vlc_init_tables_from_lengths(VLCInitState *state, 226 int nb_bits, int nb_codes, 227 const int8_t *lens, int lens_wrap, 228 const void *symbols, int symbols_wrap, int symbols_size, 229 int offset, int flags); 230 231 void ff_vlc_init_table_sparse(VLCElem table[], int table_size, 232 int nb_bits, int nb_codes, 233 const void *bits, int bits_wrap, int bits_size, 234 const void *codes, int codes_wrap, int codes_size, 235 const void *symbols, int symbols_wrap, int symbols_size, 236 int flags); 237 238 const VLCElem *ff_vlc_init_tables_sparse(VLCInitState *state, 239 int nb_bits, int nb_codes, 240 const void *bits, int bits_wrap, int bits_size, 241 const void *codes, int codes_wrap, int codes_size, 242 const void *symbols, int symbols_wrap, int symbols_size, 243 int flags); 244 245 static inline 246 const VLCElem *ff_vlc_init_tables(VLCInitState *state, 247 int nb_bits, int nb_codes, 248 const void *bits, int bits_wrap, int bits_size, 249 const void *codes, int codes_wrap, int codes_size, 250 int flags) 251 { 252 return ff_vlc_init_tables_sparse(state, nb_bits, nb_codes, 253 bits, bits_wrap, bits_size, 254 codes, codes_wrap, codes_size, 255 NULL, 0, 0, flags); 256 } 257 258 #define VLC_INIT_STATIC_SPARSE_TABLE(vlc_table, nb_bits, nb_codes, \ 259 bits, bits_wrap, bits_size, \ 260 codes, codes_wrap, codes_size, \ 261 symbols, symbols_wrap, symbols_size, \ 262 flags) \ 263 ff_vlc_init_table_sparse(vlc_table, FF_ARRAY_ELEMS(vlc_table), \ 264 (nb_bits), (nb_codes), \ 265 (bits), (bits_wrap), (bits_size), \ 266 (codes), (codes_wrap), (codes_size), \ 267 (symbols), (symbols_wrap), (symbols_size), \ 268 (flags)) 269 270 #define VLC_INIT_STATIC_TABLE(vlc_table, nb_bits, nb_codes, \ 271 bits, bits_wrap, bits_size, \ 272 codes, codes_wrap, codes_size, \ 273 flags) \ 274 ff_vlc_init_table_sparse(vlc_table, FF_ARRAY_ELEMS(vlc_table), \ 275 (nb_bits), (nb_codes), \ 276 (bits), (bits_wrap), (bits_size), \ 277 (codes), (codes_wrap), (codes_size), \ 278 NULL, 0, 0, (flags)) 279 280 #define VLC_INIT_STATIC_TABLE_FROM_LENGTHS(vlc_table, nb_bits, nb_codes, \ 281 lens, lens_wrap, \ 282 syms, syms_wrap, syms_size, \ 283 offset, flags) \ 284 ff_vlc_init_table_from_lengths(vlc_table, FF_ARRAY_ELEMS(vlc_table), \ 285 (nb_bits), (nb_codes), \ 286 (lens), (lens_wrap), \ 287 (syms), (syms_wrap), (syms_size), \ 288 (offset), (flags)) 289 290 #endif /* AVCODEC_VLC_H */