FFmpeg
vlc.h
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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
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 */
RL_VLC_ELEM::run
uint8_t run
Definition: vlc.h:35
VLC_TYPE
#define VLC_TYPE
Definition: vlc.h:24
ff_init_vlc_from_lengths
int ff_init_vlc_from_lengths(VLC *vlc, int nb_bits, int nb_codes, const int8_t *lens, int lens_wrap, const void *symbols, int symbols_wrap, int symbols_size, int offset, int flags, void *logctx)
Build VLC decoding tables suitable for use with get_vlc2()
Definition: bitstream.c:370
bits
uint8_t bits
Definition: vp3data.h:141
ff_free_vlc
void ff_free_vlc(VLC *vlc)
Definition: bitstream.c:420
RL_VLC_ELEM::len
int8_t len
Definition: vlc.h:34
VLC::table_allocated
int table_allocated
Definition: vlc.h:29
RL_VLC_ELEM
Definition: vlc.h:32
offset
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf offset
Definition: writing_filters.txt:86
ff_init_vlc_sparse
int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes, const void *bits, int bits_wrap, int bits_size, const void *codes, int codes_wrap, int codes_size, const void *symbols, int symbols_wrap, int symbols_size, int flags)
Definition: bitstream.c:312
VLC::bits
int bits
Definition: vlc.h:27
VLC
Definition: vlc.h:26
VLC::table_size
int table_size
Definition: vlc.h:29
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:561
VLC::table
VLC_TYPE(* table)[2]
code, bits
Definition: vlc.h:28
RL_VLC_ELEM::level
int16_t level
Definition: vlc.h:33