2 * Copyright (c) 2006 Konstantin Shishkov
3 * Copyright (c) 2007 Loren Merritt
5 * This file is part of Libav.
7 * Libav is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * Libav is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with Libav; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 * huffman tree builder and VLC generator
29 #include"libavutil/common.h"
35 /* symbol for Huffman tree node */
38 typedef struct HeapElem {
43 static void heap_sift(HeapElem *h, int root, int size)
45 while (root * 2 + 1 < size) {
46 int child = root * 2 + 1;
47 if (child < size - 1 && h[child].val > h[child+1].val)
49 if (h[root].val > h[child].val) {
50 FFSWAP(HeapElem, h[root], h[child]);
57 void ff_huff_gen_len_table(uint8_t *dst, const uint64_t *stats)
65 for (offset = 1; ; offset <<= 1) {
66 for (i=0; i < size; i++) {
68 h[i].val = (stats[i] << 8) + offset;
70 for (i = size / 2 - 1; i >= 0; i--)
71 heap_sift(h, i, size);
73 for (next = size; next < size * 2 - 1; next++) {
74 // merge the two smallest entries, and put it back in the heap
75 uint64_t min1v = h[0].val;
78 heap_sift(h, 0, size);
82 heap_sift(h, 0, size);
85 len[2 * size - 2] = 0;
86 for (i = 2 * size - 3; i >= size; i--)
87 len[i] = len[up[i]] + 1;
88 for (i = 0; i < size; i++) {
89 dst[i] = len[up[i]] + 1;
90 if (dst[i] >= 32) break;
96 static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t *xlat,
97 Node *nodes, int node,
98 uint32_t pfx, int pl, int *pos, int no_zero_count)
103 if (s != HNODE || (no_zero_count && !nodes[node].count)) {
111 get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl,
114 get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0 + 1, pfx, pl,
119 static int build_huff_tree(VLC *vlc, Node *nodes, int head, int flags, int nb_bits)
121 int no_zero_count = !(flags & FF_HUFFMAN_FLAG_ZERO_COUNT);
127 get_tree_codes(bits, lens, xlat, nodes, head, 0, 0,
128 &pos, no_zero_count);
129 return ff_init_vlc_sparse(vlc, nb_bits, pos, lens, 2, 2, bits, 4, 4, xlat, 1, 1, 0);
134 * nodes size must be 2*nb_codes
135 * first nb_codes nodes.count must be set
137 int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes, int nb_bits,
138 Node *nodes, HuffCmp cmp, int flags)
144 for (i = 0; i < nb_codes; i++) {
147 sum += nodes[i].count;
151 av_log(avctx, AV_LOG_ERROR,
152 "Too high symbol frequencies. "
153 "Tree construction is not possible\n");
156 qsort(nodes, nb_codes, sizeof(Node), cmp);
158 nodes[nb_codes*2-1].count = 0;
159 for (i = 0; i < nb_codes * 2 - 1; i += 2) {
160 nodes[cur_node].sym = HNODE;
161 nodes[cur_node].count = nodes[i].count + nodes[i + 1].count;
162 nodes[cur_node].n0 = i;
163 for (j = cur_node; j > 0; j--) {
164 if (nodes[j].count > nodes[j - 1].count ||
165 (nodes[j].count == nodes[j - 1].count &&
166 (!(flags & FF_HUFFMAN_FLAG_HNODE_FIRST) ||
167 nodes[j].n0 == j - 1 || nodes[j].n0 == j - 2 ||
168 (nodes[j].sym!=HNODE && nodes[j-1].sym!=HNODE))))
170 FFSWAP(Node, nodes[j], nodes[j - 1]);
174 if (build_huff_tree(vlc, nodes, nb_codes * 2 - 2, flags, nb_bits) < 0) {
175 av_log(avctx, AV_LOG_ERROR, "Error building tree\n");