1/* 2 * Copyright (c) 2006 Konstantin Shishkov 3 * 4 * This file is part of Libav. 5 * 6 * Libav is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU Lesser General Public 8 * License as published by the Free Software Foundation; either 9 * version 2.1 of the License, or (at your option) any later version. 10 * 11 * Libav is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 * Lesser General Public License for more details. 15 * 16 * You should have received a copy of the GNU Lesser General Public 17 * License along with Libav; if not, write to the Free Software 18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 19 */ 20 21/** 22 * @file 23 * huffman tree builder and VLC generator 24 */ 25 26#include "avcodec.h" 27#include "get_bits.h" 28#include "huffman.h" 29 30/* symbol for Huffman tree node */ 31#define HNODE -1 32 33 34static 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) 35{ 36 int s; 37 38 s = nodes[node].sym; 39 if(s != HNODE || (no_zero_count && !nodes[node].count)){ 40 bits[*pos] = pfx; 41 lens[*pos] = pl; 42 xlat[*pos] = s; 43 (*pos)++; 44 }else{ 45 pfx <<= 1; 46 pl++; 47 get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl, pos, 48 no_zero_count); 49 pfx |= 1; 50 get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0+1, pfx, pl, pos, 51 no_zero_count); 52 } 53} 54 55static int build_huff_tree(VLC *vlc, Node *nodes, int head, int flags) 56{ 57 int no_zero_count = !(flags & FF_HUFFMAN_FLAG_ZERO_COUNT); 58 uint32_t bits[256]; 59 int16_t lens[256]; 60 uint8_t xlat[256]; 61 int pos = 0; 62 63 get_tree_codes(bits, lens, xlat, nodes, head, 0, 0, &pos, no_zero_count); 64 return ff_init_vlc_sparse(vlc, 9, pos, lens, 2, 2, bits, 4, 4, xlat, 1, 1, 0); 65} 66 67 68/** 69 * nodes size must be 2*nb_codes 70 * first nb_codes nodes.count must be set 71 */ 72int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes, 73 Node *nodes, HuffCmp cmp, int flags) 74{ 75 int i, j; 76 int cur_node; 77 int64_t sum = 0; 78 79 for(i = 0; i < nb_codes; i++){ 80 nodes[i].sym = i; 81 nodes[i].n0 = -2; 82 sum += nodes[i].count; 83 } 84 85 if(sum >> 31) { 86 av_log(avctx, AV_LOG_ERROR, "Too high symbol frequencies. Tree construction is not possible\n"); 87 return -1; 88 } 89 qsort(nodes, nb_codes, sizeof(Node), cmp); 90 cur_node = nb_codes; 91 nodes[nb_codes*2-1].count = 0; 92 for(i = 0; i < nb_codes*2-1; i += 2){ 93 nodes[cur_node].sym = HNODE; 94 nodes[cur_node].count = nodes[i].count + nodes[i+1].count; 95 nodes[cur_node].n0 = i; 96 for(j = cur_node; j > 0; j--){ 97 if(nodes[j].count > nodes[j-1].count || 98 (nodes[j].count == nodes[j-1].count && 99 (!(flags & FF_HUFFMAN_FLAG_HNODE_FIRST) || 100 nodes[j].n0==j-1 || nodes[j].n0==j-2 || 101 (nodes[j].sym!=HNODE && nodes[j-1].sym!=HNODE)))) 102 break; 103 FFSWAP(Node, nodes[j], nodes[j-1]); 104 } 105 cur_node++; 106 } 107 if(build_huff_tree(vlc, nodes, nb_codes*2-2, flags) < 0){ 108 av_log(avctx, AV_LOG_ERROR, "Error building tree\n"); 109 return -1; 110 } 111 return 0; 112} 113