1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
|
/*
* Copyright (c) 2006 Konstantin Shishkov
* Copyright (c) 2007 Loren Merritt
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* huffman tree builder and VLC generator
*/
#include <stdint.h>
#include "libavutil/qsort.h"
#include "libavutil/common.h"
#include "huffman.h"
#include "vlc.h"
/* symbol for Huffman tree node */
#define HNODE -1
typedef struct HeapElem {
uint64_t val;
int name;
} HeapElem;
static void heap_sift(HeapElem *h, int root, int size)
{
while (root * 2 + 1 < size) {
int child = root * 2 + 1;
if (child < size - 1 && h[child].val > h[child+1].val)
child++;
if (h[root].val > h[child].val) {
FFSWAP(HeapElem, h[root], h[child]);
root = child;
} else
break;
}
}
int ff_huff_gen_len_table(uint8_t *dst, const uint64_t *stats, int stats_size, int skip0)
{
HeapElem *h = av_malloc_array(sizeof(*h), stats_size);
int *up = av_malloc_array(sizeof(*up) * 2, stats_size);
uint8_t *len = av_malloc_array(sizeof(*len) * 2, stats_size);
uint16_t *map= av_malloc_array(sizeof(*map), stats_size);
int offset, i, next;
int size = 0;
int ret = 0;
if (!h || !up || !len || !map) {
ret = AVERROR(ENOMEM);
goto end;
}
for (i = 0; i<stats_size; i++) {
dst[i] = 255;
if (stats[i] || !skip0)
map[size++] = i;
}
for (offset = 1; ; offset <<= 1) {
for (i=0; i < size; i++) {
h[i].name = i;
h[i].val = (stats[map[i]] << 14) + offset;
}
for (i = size / 2 - 1; i >= 0; i--)
heap_sift(h, i, size);
for (next = size; next < size * 2 - 1; next++) {
// merge the two smallest entries, and put it back in the heap
uint64_t min1v = h[0].val;
up[h[0].name] = next;
h[0].val = INT64_MAX;
heap_sift(h, 0, size);
up[h[0].name] = next;
h[0].name = next;
h[0].val += min1v;
heap_sift(h, 0, size);
}
len[2 * size - 2] = 0;
for (i = 2 * size - 3; i >= size; i--)
len[i] = len[up[i]] + 1;
for (i = 0; i < size; i++) {
dst[map[i]] = len[up[i]] + 1;
if (dst[map[i]] >= 32) break;
}
if (i==size) break;
}
end:
av_free(h);
av_free(up);
av_free(len);
av_free(map);
return ret;
}
static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t *xlat,
Node *nodes, int node,
uint32_t pfx, int pl, int *pos, int no_zero_count)
{
int s;
s = nodes[node].sym;
if (s != HNODE || (no_zero_count && !nodes[node].count)) {
bits[*pos] = pfx;
lens[*pos] = pl;
xlat[*pos] = s;
(*pos)++;
} else {
pfx <<= 1;
pl++;
get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl,
pos, no_zero_count);
pfx |= 1;
get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0 + 1, pfx, pl,
pos, no_zero_count);
}
}
static int build_huff_tree(VLC *vlc, Node *nodes, int head, int flags, int nb_bits)
{
int no_zero_count = !(flags & FF_HUFFMAN_FLAG_ZERO_COUNT);
uint32_t bits[256];
int16_t lens[256];
uint8_t xlat[256];
int pos = 0;
get_tree_codes(bits, lens, xlat, nodes, head, 0, 0,
&pos, no_zero_count);
return ff_init_vlc_sparse(vlc, nb_bits, pos, lens, 2, 2, bits, 4, 4, xlat, 1, 1, 0);
}
/**
* nodes size must be 2*nb_codes
* first nb_codes nodes.count must be set
*/
int ff_huff_build_tree(void *logctx, VLC *vlc, int nb_codes, int nb_bits,
Node *nodes, HuffCmp cmp, int flags)
{
int i, j;
int cur_node;
int64_t sum = 0;
for (i = 0; i < nb_codes; i++) {
nodes[i].sym = i;
nodes[i].n0 = -2;
sum += nodes[i].count;
}
if (sum >> 31) {
av_log(logctx, AV_LOG_ERROR,
"Too high symbol frequencies. "
"Tree construction is not possible\n");
return -1;
}
AV_QSORT(nodes, nb_codes, Node, cmp);
cur_node = nb_codes;
nodes[nb_codes*2-1].count = 0;
for (i = 0; i < nb_codes * 2 - 1; i += 2) {
uint32_t cur_count = nodes[i].count + nodes[i+1].count;
// find correct place to insert new node, and
// make space for the new node while at it
for(j = cur_node; j > i + 2; j--){
if(cur_count > nodes[j-1].count ||
(cur_count == nodes[j-1].count &&
!(flags & FF_HUFFMAN_FLAG_HNODE_FIRST)))
break;
nodes[j] = nodes[j - 1];
}
nodes[j].sym = HNODE;
nodes[j].count = cur_count;
nodes[j].n0 = i;
cur_node++;
}
if (build_huff_tree(vlc, nodes, nb_codes * 2 - 2, flags, nb_bits) < 0) {
av_log(logctx, AV_LOG_ERROR, "Error building tree\n");
return -1;
}
return 0;
}
|
