xref: /third_party/ffmpeg/libavcodec/rl.c (revision cabdff1a) 
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#include <stdint.h>
20#include <string.h>
21
22#include "libavutil/attributes.h"
23#include "libavutil/avassert.h"
24
25#include "rl.h"
26
27av_cold void ff_rl_init(RLTable *rl,
28                        uint8_t static_store[2][2 * MAX_RUN + MAX_LEVEL + 3])
29{
30    int last, run, level, start, end, i;
31
32    /* compute max_level[], max_run[] and index_run[] */
33    for (last = 0; last < 2; last++) {
34        int8_t *max_level  = static_store[last];
35        int8_t *max_run    = static_store[last] + MAX_RUN + 1;
36        uint8_t *index_run = static_store[last] + MAX_RUN + 1 + MAX_LEVEL + 1;
37        if (last == 0) {
38            start = 0;
39            end = rl->last;
40        } else {
41            start = rl->last;
42            end = rl->n;
43        }
44
45        memset(index_run, rl->n, MAX_RUN + 1);
46        for (i = start; i < end; i++) {
47            run   = rl->table_run[i];
48            level = rl->table_level[i];
49            if (index_run[run] == rl->n)
50                index_run[run] = i;
51            if (level > max_level[run])
52                max_level[run] = level;
53            if (run > max_run[level])
54                max_run[level] = run;
55        }
56        rl->max_level[last] = max_level;
57        rl->max_run[last]   = max_run;
58        rl->index_run[last] = index_run;
59    }
60}
61
62av_cold void ff_rl_init_vlc(RLTable *rl, unsigned static_size)
63{
64    int i, q;
65    VLCElem table[1500] = { 0 };
66    VLC vlc = { .table = table, .table_allocated = static_size };
67    av_assert0(static_size <= FF_ARRAY_ELEMS(table));
68    init_vlc(&vlc, 9, rl->n + 1, &rl->table_vlc[0][1], 4, 2, &rl->table_vlc[0][0], 4, 2, INIT_VLC_USE_NEW_STATIC);
69
70    for (q = 0; q < 32; q++) {
71        int qmul = q * 2;
72        int qadd = (q - 1) | 1;
73
74        if (!rl->rl_vlc[q])
75            return;
76
77        if (q == 0) {
78            qmul = 1;
79            qadd = 0;
80        }
81        for (i = 0; i < vlc.table_size; i++) {
82            int code = vlc.table[i].sym;
83            int len  = vlc.table[i].len;
84            int level, run;
85
86            if (len == 0) { // illegal code
87                run   = 66;
88                level = MAX_LEVEL;
89            } else if (len < 0) { // more bits needed
90                run   = 0;
91                level = code;
92            } else {
93                if (code == rl->n) { // esc
94                    run   = 66;
95                    level =  0;
96                } else {
97                    run   = rl->table_run[code] + 1;
98                    level = rl->table_level[code] * qmul + qadd;
99                    if (code >= rl->last) run += 192;
100                }
101            }
102            rl->rl_vlc[q][i].len   = len;
103            rl->rl_vlc[q][i].level = level;
104            rl->rl_vlc[q][i].run   = run;
105        }
106    }
107}
108