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 // When changing this, be sure to also update tableprint_vlc.h accordingly.
25 typedef int16_t VLCBaseType;
26 
27 typedef struct VLCElem {
29 } VLCElem;
30 
31 typedef struct VLC {
32  int bits;
35 } VLC;
36 
37 typedef struct RL_VLC_ELEM {
38  int16_t level;
39  int8_t len;
40  uint8_t run;
41 } RL_VLC_ELEM;
42 
43 #define init_vlc(vlc, nb_bits, nb_codes, \
44  bits, bits_wrap, bits_size, \
45  codes, codes_wrap, codes_size, \
46  flags) \
47  ff_init_vlc_sparse(vlc, nb_bits, nb_codes, \
48  bits, bits_wrap, bits_size, \
49  codes, codes_wrap, codes_size, \
50  NULL, 0, 0, flags)
51 
52 int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
53  const void *bits, int bits_wrap, int bits_size,
54  const void *codes, int codes_wrap, int codes_size,
55  const void *symbols, int symbols_wrap, int symbols_size,
56  int flags);
57 
58 /**
59  * Build VLC decoding tables suitable for use with get_vlc2()
60  *
61  * This function takes lengths and symbols and calculates the codes from them.
62  * For this the input lengths and symbols have to be sorted according to "left
63  * nodes in the corresponding tree first".
64  *
65  * @param[in,out] vlc The VLC to be initialized; table and table_allocated
66  * must have been set when initializing a static VLC,
67  * otherwise this will be treated as uninitialized.
68  * @param[in] nb_bits The number of bits to use for the VLC table;
69  * higher values take up more memory and cache, but
70  * allow to read codes with fewer reads.
71  * @param[in] nb_codes The number of provided length and (if supplied) symbol
72  * entries.
73  * @param[in] lens The lengths of the codes. Entries > 0 correspond to
74  * valid codes; entries == 0 will be skipped and entries
75  * with len < 0 indicate that the tree is incomplete and
76  * has an open end of length -len at this position.
77  * @param[in] lens_wrap Stride (in bytes) of the lengths.
78  * @param[in] symbols The symbols, i.e. what is returned from get_vlc2()
79  * when the corresponding code is encountered.
80  * May be NULL, then 0, 1, 2, 3, 4,... will be used.
81  * @param[in] symbols_wrap Stride (in bytes) of the symbols.
82  * @param[in] symbols_size Size of the symbols. 1 and 2 are supported.
83  * @param[in] offset An offset to apply to all the valid symbols.
84  * @param[in] flags A combination of the INIT_VLC_* flags; notice that
85  * INIT_VLC_INPUT_LE is pointless and ignored.
86  */
87 int ff_init_vlc_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
88  const int8_t *lens, int lens_wrap,
89  const void *symbols, int symbols_wrap, int symbols_size,
90  int offset, int flags, void *logctx);
91 
92 void ff_free_vlc(VLC *vlc);
93 
94 /* If INIT_VLC_INPUT_LE is set, the LSB bit of the codes used to
95  * initialize the VLC table is the first bit to be read. */
96 #define INIT_VLC_INPUT_LE 2
97 /* If set the VLC is intended for a little endian bitstream reader. */
98 #define INIT_VLC_OUTPUT_LE 8
99 #define INIT_VLC_LE (INIT_VLC_INPUT_LE | INIT_VLC_OUTPUT_LE)
100 #define INIT_VLC_USE_NEW_STATIC 4
101 #define INIT_VLC_STATIC_OVERLONG (1 | INIT_VLC_USE_NEW_STATIC)
102 
103 #define INIT_CUSTOM_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, \
104  h, i, j, flags, static_size) \
105  do { \
106  static VLCElem table[static_size]; \
107  (vlc)->table = table; \
108  (vlc)->table_allocated = static_size; \
109  ff_init_vlc_sparse(vlc, bits, a, b, c, d, e, f, g, h, i, j, \
110  flags | INIT_VLC_USE_NEW_STATIC); \
111  } while (0)
112 
113 #define INIT_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, h, i, j, static_size) \
114  INIT_CUSTOM_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, \
115  h, i, j, 0, static_size)
116 
117 #define INIT_LE_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, h, i, j, static_size) \
118  INIT_CUSTOM_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, \
119  h, i, j, INIT_VLC_LE, static_size)
120 
121 #define INIT_CUSTOM_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, flags, static_size) \
122  INIT_CUSTOM_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, \
123  NULL, 0, 0, flags, static_size)
124 
125 #define INIT_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
126  INIT_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, NULL, 0, 0, static_size)
127 
128 #define INIT_LE_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size) \
129  INIT_LE_VLC_SPARSE_STATIC(vlc, bits, a, b, c, d, e, f, g, NULL, 0, 0, static_size)
130 
131 #define INIT_VLC_STATIC_FROM_LENGTHS(vlc, bits, nb_codes, lens, len_wrap, \
132  symbols, symbols_wrap, symbols_size, \
133  offset, flags, static_size) \
134  do { \
135  static VLCElem table[static_size]; \
136  (vlc)->table = table; \
137  (vlc)->table_allocated = static_size; \
138  ff_init_vlc_from_lengths(vlc, bits, nb_codes, lens, len_wrap, \
139  symbols, symbols_wrap, symbols_size, \
140  offset, flags | INIT_VLC_USE_NEW_STATIC, \
141  NULL); \
142  } while (0)
143 
144 #endif /* AVCODEC_VLC_H */
RL_VLC_ELEM::run
uint8_t run
Definition: vlc.h:40
VLCElem::len
VLCBaseType len
Definition: vlc.h:28
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: vlc.c:328
VLCElem::sym
VLCBaseType sym
Definition: vlc.h:28
bits
uint8_t bits
Definition: vp3data.h:128
ff_free_vlc
void ff_free_vlc(VLC *vlc)
Definition: vlc.c:375
RL_VLC_ELEM::len
int8_t len
Definition: vlc.h:39
VLC::table_allocated
int table_allocated
Definition: vlc.h:34
RL_VLC_ELEM
Definition: vlc.h:37
VLCElem
Definition: vlc.h:27
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: vlc.c:272
VLC::bits
int bits
Definition: vlc.h:32
VLC
Definition: vlc.h:31
VLC::table
VLCElem * table
Definition: vlc.h:33
VLC::table_size
int table_size
Definition: vlc.h:34
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:561
VLCBaseType
int16_t VLCBaseType
Definition: vlc.h:25
RL_VLC_ELEM::level
int16_t level
Definition: vlc.h:38