3 * huffman tree builder and VLC generator
4 * Copyright (c) 2006 Konstantin Shishkov
6 * This file is part of FFmpeg.
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 #include "bitstream.h"
27 /* symbol for Huffman tree node */
31 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)
36 if(s != HNODE || !nodes[node].count){
44 get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl, pos);
46 get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0+1, pfx, pl, pos);
50 static int build_huff_tree(VLC *vlc, Node *nodes, int head)
57 get_tree_codes(bits, lens, xlat, nodes, head, 0, 0, &pos);
58 return init_vlc_sparse(vlc, 9, pos, lens, 2, 2, bits, 4, 4, xlat, 1, 1, 0);
63 * nodes size must be 2*nb_codes
64 * first nb_codes nodes.count must be set
66 int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes,
67 Node *nodes, huff_cmp_t cmp, int hnode_first)
73 for(i = 0; i < nb_codes; i++){
76 sum += nodes[i].count;
80 av_log(avctx, AV_LOG_ERROR, "Too high symbol frequencies. Tree construction is not possible\n");
83 qsort(nodes, nb_codes, sizeof(Node), cmp);
85 nodes[nb_codes*2-1].count = 0;
86 for(i = 0; i < nb_codes*2-1; i += 2){
87 nodes[cur_node].sym = HNODE;
88 nodes[cur_node].count = nodes[i].count + nodes[i+1].count;
89 nodes[cur_node].n0 = i;
90 for(j = cur_node; j > 0; j--){
91 if(nodes[j].count > nodes[j-1].count ||
92 (nodes[j].count == nodes[j-1].count &&
93 (!hnode_first || nodes[j].n0==j-1 || nodes[j].n0==j-2 ||
94 (nodes[j].sym!=HNODE && nodes[j-1].sym!=HNODE))))
96 FFSWAP(Node, nodes[j], nodes[j-1]);
100 if(build_huff_tree(vlc, nodes, nb_codes*2-2) < 0){
101 av_log(avctx, AV_LOG_ERROR, "Error building tree\n");