2 * Copyright (c) 2006 Konstantin Shishkov
3 * Copyright (c) 2007 Loren Merritt
5 * This file is part of FFmpeg.
7 * FFmpeg 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 * FFmpeg 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 FFmpeg; 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
33 /* symbol for Huffman tree node */
41 static void heap_sift(HeapElem *h, int root, int size)
43 while (root * 2 + 1 < size) {
44 int child = root * 2 + 1;
45 if (child < size - 1 && h[child].val > h[child+1].val)
47 if (h[root].val > h[child].val) {
48 FFSWAP(HeapElem, h[root], h[child]);
55 int ff_huff_gen_len_table(uint8_t *dst, const uint64_t *stats, int size)
57 HeapElem *h = av_malloc_array(sizeof(*h), size);
58 int *up = av_malloc_array(sizeof(*up) * 2, size);
59 uint8_t *len = av_malloc_array(sizeof(*len) * 2, size);
63 if (!h || !up || !len) {
64 ret = AVERROR(ENOMEM);
68 for (offset = 1; ; offset <<= 1) {
69 for (i=0; i < size; i++) {
71 h[i].val = (stats[i] << 14) + offset;
73 for (i = size / 2 - 1; i >= 0; i--)
74 heap_sift(h, i, size);
76 for (next = size; next < size * 2 - 1; next++) {
77 // merge the two smallest entries, and put it back in the heap
78 uint64_t min1v = h[0].val;
81 heap_sift(h, 0, size);
85 heap_sift(h, 0, size);
88 len[2 * size - 2] = 0;
89 for (i = 2 * size - 3; i >= size; i--)
90 len[i] = len[up[i]] + 1;
91 for (i = 0; i < size; i++) {
92 dst[i] = len[up[i]] + 1;
93 if (dst[i] >= 32) break;
104 static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t *xlat,
105 Node *nodes, int node,
106 uint32_t pfx, int pl, int *pos, int no_zero_count)
111 if (s != HNODE || (no_zero_count && !nodes[node].count)) {
119 get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl,
122 get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0 + 1, pfx, pl,
127 static int build_huff_tree(VLC *vlc, Node *nodes, int head, int flags, int nb_bits)
129 int no_zero_count = !(flags & FF_HUFFMAN_FLAG_ZERO_COUNT);
135 get_tree_codes(bits, lens, xlat, nodes, head, 0, 0,
136 &pos, no_zero_count);
137 return ff_init_vlc_sparse(vlc, nb_bits, pos, lens, 2, 2, bits, 4, 4, xlat, 1, 1, 0);
142 * nodes size must be 2*nb_codes
143 * first nb_codes nodes.count must be set
145 int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes, int nb_bits,
146 Node *nodes, HuffCmp cmp, int flags)
152 for (i = 0; i < nb_codes; i++) {
155 sum += nodes[i].count;
159 av_log(avctx, AV_LOG_ERROR,
160 "Too high symbol frequencies. "
161 "Tree construction is not possible\n");
164 qsort(nodes, nb_codes, sizeof(Node), cmp);
166 nodes[nb_codes*2-1].count = 0;
167 for (i = 0; i < nb_codes * 2 - 1; i += 2) {
168 uint32_t cur_count = nodes[i].count + nodes[i+1].count;
169 // find correct place to insert new node, and
170 // make space for the new node while at it
171 for(j = cur_node; j > i + 2; j--){
172 if(cur_count > nodes[j-1].count ||
173 (cur_count == nodes[j-1].count &&
174 !(flags & FF_HUFFMAN_FLAG_HNODE_FIRST)))
176 nodes[j] = nodes[j - 1];
178 nodes[j].sym = HNODE;
179 nodes[j].count = cur_count;
183 if (build_huff_tree(vlc, nodes, nb_codes * 2 - 2, flags, nb_bits) < 0) {
184 av_log(avctx, AV_LOG_ERROR, "Error building tree\n");