git.sesse.net Git - ffmpeg/blob - libavcodec/vlc.h

   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 <stdint.h>
  23
  24 #define VLC_TYPE int16_t
  25
  26 typedef struct VLC {
  27     int bits;
  28     VLC_TYPE (*table)[2]; ///< code, bits
  29     int table_size, table_allocated;
  30 } VLC;
  31
  32 typedef struct RL_VLC_ELEM {
  33     int16_t level;
  34     int8_t len;
  35     uint8_t run;
  36 } RL_VLC_ELEM;
  37
  38 #define init_vlc(vlc, nb_bits, nb_codes,                \
  39                  bits, bits_wrap, bits_size,            \
  40                  codes, codes_wrap, codes_size,         \
  41                  flags)                                 \
  42     ff_init_vlc_sparse(vlc, nb_bits, nb_codes,          \
  43                        bits, bits_wrap, bits_size,      \
  44                        codes, codes_wrap, codes_size,   \
  45                        NULL, 0, 0, flags)
  46
  47 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
  48                        const void *bits, int bits_wrap, int bits_size,
  49                        const void *codes, int codes_wrap, int codes_size,
  50                        const void *symbols, int symbols_wrap, int symbols_size,
  51                        int flags);
  52
  53 /**
  54  * Build VLC decoding tables suitable for use with get_vlc2()
  55  *
  56  * This function takes lengths and symbols and calculates the codes from them.
  57  * For this the input lengths and symbols have to be sorted according to "left
  58  * nodes in the corresponding tree first".
  59  *
  60  * @param[in,out] vlc      The VLC to be initialized; table and table_allocated
  61  *                         must have been set when initializing a static VLC,
  62  *                         otherwise this will be treated as uninitialized.
  63  * @param[in] nb_bits      The number of bits to use for the VLC table;
  64  *                         higher values take up more memory and cache, but
  65  *                         allow to read codes with fewer reads.
  66  * @param[in] nb_codes     The number of provided length and (if supplied) symbol
  67  *                         entries.
  68  * @param[in] lens         The lengths of the codes. Entries > 0 correspond to
  69  *                         valid codes; entries == 0 will be skipped and entries
  70  *                         with len < 0 indicate that the tree is incomplete and
  71  *                         has an open end of length -len at this position.
  72  * @param[in] lens_wrap    Stride (in bytes) of the lengths.
  73  * @param[in] symbols      The symbols, i.e. what is returned from get_vlc2()
  74  *                         when the corresponding code is encountered.
  75  *                         May be NULL, then 0, 1, 2, 3, 4,... will be used.
  76  * @param[in] symbols_wrap Stride (in bytes) of the symbols.
  77  * @param[in] symbols_size Size of the symbols. 1 and 2 are supported.
  78  * @param[in] offset       An offset to apply to all the valid symbols.
  79  * @param[in] flags        A combination of the INIT_VLC_* flags; notice that
  80  *                         INIT_VLC_INPUT_LE is pointless and ignored.
  81  */
  82 int ff_init_vlc_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
  83                              const int8_t *lens, int lens_wrap,
  84                              const void *symbols, int symbols_wrap, int symbols_size,
  85                              int offset, int flags, void *logctx);
  86
  87 void ff_free_vlc(VLC *vlc);
  88
  89 /* If INIT_VLC_INPUT_LE is set, the LSB bit of the codes used to
  90  * initialize the VLC table is the first bit to be read. */
  91 #define INIT_VLC_INPUT_LE       2
  92 /* If set the VLC is intended for a little endian bitstream reader. */
  93 #define INIT_VLC_OUTPUT_LE      8
  94 #define INIT_VLC_LE             (INIT_VLC_INPUT_LE | INIT_VLC_OUTPUT_LE)
  95 #define INIT_VLC_USE_NEW_STATIC 4
  96 #define INIT_VLC_STATIC_OVERLONG (1 | INIT_VLC_USE_NEW_STATIC)
  97
  98 #define INIT_CUSTOM_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g,      \
  99                                       h, i, j, flags, static_size)         \
 100     do {                                                                   \
 101         static VLC_TYPE table[static_size][2];                             \
 102         (vlc)->table           = table;                                    \
 103         (vlc)->table_allocated = static_size;                              \
 104         ff_init_vlc_sparse(vlc, bits, a, b, c, d, e, f, g, h, i, j,        \
 105                            flags | INIT_VLC_USE_NEW_STATIC);               \
 106     } while (0)
 107
 108 #define INIT_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, h, i, j, static_size) \
 109     INIT_CUSTOM_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g,          \
 110                                   h, i, j, 0, static_size)
 111
 112 #define INIT_LE_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, h, i, j, static_size) \
 113     INIT_CUSTOM_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g,          \
 114                                   h, i, j, INIT_VLC_LE, static_size)
 115
 116 #define INIT_CUSTOM_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, flags, static_size) \
 117     INIT_CUSTOM_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g,          \
 118                                   NULL, 0, 0, flags, static_size)
 119
 120 #define INIT_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size)       \
 121     INIT_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, NULL, 0, 0, static_size)
 122
 123 #define INIT_LE_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
 124     INIT_LE_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, NULL, 0, 0, static_size)
 125
 126 #define INIT_VLC_STATIC_FROM_LENGTHS(vlc, bits, nb_codes, lens, len_wrap,  \
 127                                      symbols, symbols_wrap, symbols_size,  \
 128                                      offset, flags, static_size)           \
 129     do {                                                                   \
 130         static VLC_TYPE table[static_size][2];                             \
 131         (vlc)->table           = table;                                    \
 132         (vlc)->table_allocated = static_size;                              \
 133         ff_init_vlc_from_lengths(vlc, bits, nb_codes, lens, len_wrap,      \
 134                                  symbols, symbols_wrap, symbols_size,      \
 135                                  offset, flags | INIT_VLC_USE_NEW_STATIC,  \
 136                                  NULL);                                    \
 137     } while (0)
 138
 139 #endif /* AVCODEC_VLC_H */