1/* 2 * Copyright (c) 2006 Konstantin Shishkov 3 * Copyright (c) 2007 Loren Merritt 4 * 5 * This file is part of FFmpeg. 6 * 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. 11 * 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. 16 * 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 20 */ 21 22/** 23 * @file 24 * huffman tree builder and VLC generator 25 */ 26 27#include <stdint.h> 28 29#include "avcodec.h" 30#include "get_bits.h" 31#include "huffman.h" 32 33/* symbol for Huffman tree node */ 34#define HNODE -1 35 36typedef struct { 37 uint64_t val; 38 int name; 39} HeapElem; 40 41static void heap_sift(HeapElem *h, int root, int size) 42{ 43 while (root * 2 + 1 < size) { 44 int child = root * 2 + 1; 45 if (child < size - 1 && h[child].val > h[child+1].val) 46 child++; 47 if (h[root].val > h[child].val) { 48 FFSWAP(HeapElem, h[root], h[child]); 49 root = child; 50 } else 51 break; 52 } 53} 54 55int ff_huff_gen_len_table(uint8_t *dst, const uint64_t *stats, int stats_size, int skip0) 56{ 57 HeapElem *h = av_malloc_array(sizeof(*h), stats_size); 58 int *up = av_malloc_array(sizeof(*up) * 2, stats_size); 59 uint8_t *len = av_malloc_array(sizeof(*len) * 2, stats_size); 60 uint16_t *map= av_malloc_array(sizeof(*map), stats_size); 61 int offset, i, next; 62 int size = 0; 63 int ret = 0; 64 65 if (!h || !up || !len) { 66 ret = AVERROR(ENOMEM); 67 goto end; 68 } 69 70 for (i = 0; i<stats_size; i++) { 71 dst[i] = 255; 72 if (stats[i] || !skip0) 73 map[size++] = i; 74 } 75 76 for (offset = 1; ; offset <<= 1) { 77 for (i=0; i < size; i++) { 78 h[i].name = i; 79 h[i].val = (stats[map[i]] << 14) + offset; 80 } 81 for (i = size / 2 - 1; i >= 0; i--) 82 heap_sift(h, i, size); 83 84 for (next = size; next < size * 2 - 1; next++) { 85 // merge the two smallest entries, and put it back in the heap 86 uint64_t min1v = h[0].val; 87 up[h[0].name] = next; 88 h[0].val = INT64_MAX; 89 heap_sift(h, 0, size); 90 up[h[0].name] = next; 91 h[0].name = next; 92 h[0].val += min1v; 93 heap_sift(h, 0, size); 94 } 95 96 len[2 * size - 2] = 0; 97 for (i = 2 * size - 3; i >= size; i--) 98 len[i] = len[up[i]] + 1; 99 for (i = 0; i < size; i++) { 100 dst[map[i]] = len[up[i]] + 1; 101 if (dst[map[i]] >= 32) break; 102 } 103 if (i==size) break; 104 } 105end: 106 av_free(h); 107 av_free(up); 108 av_free(len); 109 av_free(map); 110 return ret; 111} 112 113static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t *xlat, 114 Node *nodes, int node, 115 uint32_t pfx, int pl, int *pos, int no_zero_count) 116{ 117 int s; 118 119 s = nodes[node].sym; 120 if (s != HNODE || (no_zero_count && !nodes[node].count)) { 121 bits[*pos] = pfx; 122 lens[*pos] = pl; 123 xlat[*pos] = s; 124 (*pos)++; 125 } else { 126 pfx <<= 1; 127 pl++; 128 get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl, 129 pos, no_zero_count); 130 pfx |= 1; 131 get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0 + 1, pfx, pl, 132 pos, no_zero_count); 133 } 134} 135 136static int build_huff_tree(VLC *vlc, Node *nodes, int head, int flags, int nb_bits) 137{ 138 int no_zero_count = !(flags & FF_HUFFMAN_FLAG_ZERO_COUNT); 139 uint32_t bits[256]; 140 int16_t lens[256]; 141 uint8_t xlat[256]; 142 int pos = 0; 143 144 get_tree_codes(bits, lens, xlat, nodes, head, 0, 0, 145 &pos, no_zero_count); 146 return ff_init_vlc_sparse(vlc, nb_bits, pos, lens, 2, 2, bits, 4, 4, xlat, 1, 1, 0); 147} 148 149 150/** 151 * nodes size must be 2*nb_codes 152 * first nb_codes nodes.count must be set 153 */ 154int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes, int nb_bits, 155 Node *nodes, HuffCmp cmp, int flags) 156{ 157 int i, j; 158 int cur_node; 159 int64_t sum = 0; 160 161 for (i = 0; i < nb_codes; i++) { 162 nodes[i].sym = i; 163 nodes[i].n0 = -2; 164 sum += nodes[i].count; 165 } 166 167 if (sum >> 31) { 168 av_log(avctx, AV_LOG_ERROR, 169 "Too high symbol frequencies. " 170 "Tree construction is not possible\n"); 171 return -1; 172 } 173 qsort(nodes, nb_codes, sizeof(Node), cmp); 174 cur_node = nb_codes; 175 nodes[nb_codes*2-1].count = 0; 176 for (i = 0; i < nb_codes * 2 - 1; i += 2) { 177 uint32_t cur_count = nodes[i].count + nodes[i+1].count; 178 // find correct place to insert new node, and 179 // make space for the new node while at it 180 for(j = cur_node; j > i + 2; j--){ 181 if(cur_count > nodes[j-1].count || 182 (cur_count == nodes[j-1].count && 183 !(flags & FF_HUFFMAN_FLAG_HNODE_FIRST))) 184 break; 185 nodes[j] = nodes[j - 1]; 186 } 187 nodes[j].sym = HNODE; 188 nodes[j].count = cur_count; 189 nodes[j].n0 = i; 190 cur_node++; 191 } 192 if (build_huff_tree(vlc, nodes, nb_codes * 2 - 2, flags, nb_bits) < 0) { 193 av_log(avctx, AV_LOG_ERROR, "Error building tree\n"); 194 return -1; 195 } 196 return 0; 197} 198