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 <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 {
34 } VLCElem;
35 
36 typedef struct VLC {
37  int bits;
40 } VLC;
41 
42 typedef struct VLC_MULTI_ELEM {
43  union {
46  };
47  int8_t len; // -31,32
48  uint8_t num;
50 
51 typedef struct VLC_MULTI {
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 
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 
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
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 */
VLCInitState::table
VLCElem * table
points to where the next VLC table will be placed
Definition: vlc.h:213
VLC_MULTI_ELEM
Definition: vlc.h:42
table
static const uint16_t table[]
Definition: prosumer.c:203
RL_VLC_ELEM::run
uint8_t run
Definition: vlc.h:59
VLCElem::len
VLCBaseType len
Definition: vlc.h:33
ff_vlc_free_multi
void ff_vlc_free_multi(VLC_MULTI *vlc)
Definition: vlc.c:575
macros.h
VLCElem::sym
VLCBaseType sym
Definition: vlc.h:33
VLCInitState
For static VLCs, the number of bits can often be hardcoded at each get_vlc2() callsite.
Definition: vlc.h:212
VLC_MULTI::table_size
int table_size
Definition: vlc.h:53
ff_vlc_free
void ff_vlc_free(VLC *vlc)
Definition: vlc.c:580
VLC_MULTI
Definition: vlc.h:51
bits
uint8_t bits
Definition: vp3data.h:128
VLC_MULTI_ELEM::num
uint8_t num
Definition: vlc.h:48
ff_vlc_init_from_lengths
int ff_vlc_init_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:306
ff_vlc_init_multi_from_lengths
int ff_vlc_init_multi_from_lengths(VLC *vlc, VLC_MULTI *multi, int nb_bits, int nb_elems, 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_vlc_multi()
Definition: vlc.c:517
NULL
#define NULL
Definition: coverity.c:32
ff_vlc_init_tables_from_lengths
const VLCElem * ff_vlc_init_tables_from_lengths(VLCInitState *state, 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)
Definition: vlc.c:366
VLC_MULTI_MAX_SYMBOLS
#define VLC_MULTI_MAX_SYMBOLS
Definition: vlc.h:27
RL_VLC_ELEM::len
int8_t len
Definition: vlc.h:58
VLC::table_allocated
int table_allocated
Definition: vlc.h:39
RL_VLC_ELEM
Definition: vlc.h:56
VLCElem
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_vlc_init_table_from_lengths
void ff_vlc_init_table_from_lengths(VLCElem table[], int table_size, 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)
Definition: vlc.c:353
VLC_MULTI_ELEM::val8
uint8_t val8[VLC_MULTI_MAX_SYMBOLS]
Definition: vlc.h:44
state
static struct @416 state
VLC::bits
int bits
Definition: vlc.h:37
VLC_MULTI_ELEM::len
int8_t len
Definition: vlc.h:47
ff_vlc_init_tables_sparse
const VLCElem * ff_vlc_init_tables_sparse(VLCInitState *state, 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:400
VLC_MULTI::table
VLC_MULTI_ELEM * table
Definition: vlc.h:52
bits_size
#define bits_size
Definition: bitstream.h:113
VLC
Definition: vlc.h:36
VLC::table
VLCElem * table
Definition: vlc.h:38
VLC::table_size
int table_size
Definition: vlc.h:39
ff_vlc_init_tables
static const VLCElem * ff_vlc_init_tables(VLCInitState *state, int nb_bits, int nb_codes, const void *bits, int bits_wrap, int bits_size, const void *codes, int codes_wrap, int codes_size, int flags)
Definition: vlc.h:246
ff_vlc_init_sparse
int ff_vlc_init_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)
Build VLC decoding tables suitable for use with get_vlc2().
Definition: vlc.c:250
ff_vlc_init_table_sparse
void ff_vlc_init_table_sparse(VLCElem table[], int table_size, 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:384
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:474
VLC_MULTI::table_allocated
int table_allocated
Definition: vlc.h:53
VLCBaseType
int16_t VLCBaseType
Definition: vlc.h:30
VLCInitState::size
unsigned size
remaining number of elements in table
Definition: vlc.h:214
VLC_MULTI_ELEM::val16
uint16_t val16[VLC_MULTI_MAX_SYMBOLS/2]
Definition: vlc.h:45
RL_VLC_ELEM::level
int16_t level
Definition: vlc.h:57