yading@10: /*
yading@10:  * Copyright (c) 2006 Konstantin Shishkov
yading@10:  * Copyright (c) 2007 Loren Merritt
yading@10:  *
yading@10:  * This file is part of FFmpeg.
yading@10:  *
yading@10:  * FFmpeg is free software; you can redistribute it and/or
yading@10:  * modify it under the terms of the GNU Lesser General Public
yading@10:  * License as published by the Free Software Foundation; either
yading@10:  * version 2.1 of the License, or (at your option) any later version.
yading@10:  *
yading@10:  * FFmpeg is distributed in the hope that it will be useful,
yading@10:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@10:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@10:  * Lesser General Public License for more details.
yading@10:  *
yading@10:  * You should have received a copy of the GNU Lesser General Public
yading@10:  * License along with FFmpeg; if not, write to the Free Software
yading@10:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@10:  */
yading@10: 
yading@10: /**
yading@10:  * @file
yading@10:  * huffman tree builder and VLC generator
yading@10:  */
yading@10: 
yading@10: #include "avcodec.h"
yading@10: #include "get_bits.h"
yading@10: #include "huffman.h"
yading@10: 
yading@10: /* symbol for Huffman tree node */
yading@10: #define HNODE -1
yading@10: 
yading@10: typedef struct {
yading@10:     uint64_t val;
yading@10:     int name;
yading@10: } HeapElem;
yading@10: 
yading@10: static void heap_sift(HeapElem *h, int root, int size)
yading@10: {
yading@10:     while (root * 2 + 1 < size) {
yading@10:         int child = root * 2 + 1;
yading@10:         if (child < size - 1 && h[child].val > h[child+1].val)
yading@10:             child++;
yading@10:         if (h[root].val > h[child].val) {
yading@10:             FFSWAP(HeapElem, h[root], h[child]);
yading@10:             root = child;
yading@10:         } else
yading@10:             break;
yading@10:     }
yading@10: }
yading@10: 
yading@10: void ff_huff_gen_len_table(uint8_t *dst, const uint64_t *stats)
yading@10: {
yading@10:     HeapElem h[256];
yading@10:     int up[2*256];
yading@10:     int len[2*256];
yading@10:     int offset, i, next;
yading@10:     int size = 256;
yading@10: 
yading@10:     for (offset = 1; ; offset <<= 1) {
yading@10:         for (i=0; i < size; i++) {
yading@10:             h[i].name = i;
yading@10:             h[i].val = (stats[i] << 8) + offset;
yading@10:         }
yading@10:         for (i = size / 2 - 1; i >= 0; i--)
yading@10:             heap_sift(h, i, size);
yading@10: 
yading@10:         for (next = size; next < size * 2 - 1; next++) {
yading@10:             // merge the two smallest entries, and put it back in the heap
yading@10:             uint64_t min1v = h[0].val;
yading@10:             up[h[0].name] = next;
yading@10:             h[0].val = INT64_MAX;
yading@10:             heap_sift(h, 0, size);
yading@10:             up[h[0].name] = next;
yading@10:             h[0].name = next;
yading@10:             h[0].val += min1v;
yading@10:             heap_sift(h, 0, size);
yading@10:         }
yading@10: 
yading@10:         len[2 * size - 2] = 0;
yading@10:         for (i = 2 * size - 3; i >= size; i--)
yading@10:             len[i] = len[up[i]] + 1;
yading@10:         for (i = 0; i < size; i++) {
yading@10:             dst[i] = len[up[i]] + 1;
yading@10:             if (dst[i] >= 32) break;
yading@10:         }
yading@10:         if (i==size) break;
yading@10:     }
yading@10: }
yading@10: 
yading@10: static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t *xlat,
yading@10:                            Node *nodes, int node,
yading@10:                            uint32_t pfx, int pl, int *pos, int no_zero_count)
yading@10: {
yading@10:     int s;
yading@10: 
yading@10:     s = nodes[node].sym;
yading@10:     if (s != HNODE || (no_zero_count && !nodes[node].count)) {
yading@10:         bits[*pos] = pfx;
yading@10:         lens[*pos] = pl;
yading@10:         xlat[*pos] = s;
yading@10:         (*pos)++;
yading@10:     } else {
yading@10:         pfx <<= 1;
yading@10:         pl++;
yading@10:         get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl,
yading@10:                        pos, no_zero_count);
yading@10:         pfx |= 1;
yading@10:         get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0 + 1, pfx, pl,
yading@10:                        pos, no_zero_count);
yading@10:     }
yading@10: }
yading@10: 
yading@10: static int build_huff_tree(VLC *vlc, Node *nodes, int head, int flags)
yading@10: {
yading@10:     int no_zero_count = !(flags & FF_HUFFMAN_FLAG_ZERO_COUNT);
yading@10:     uint32_t bits[256];
yading@10:     int16_t lens[256];
yading@10:     uint8_t xlat[256];
yading@10:     int pos = 0;
yading@10: 
yading@10:     get_tree_codes(bits, lens, xlat, nodes, head, 0, 0,
yading@10:                    &pos, no_zero_count);
yading@10:     return ff_init_vlc_sparse(vlc, 9, pos, lens, 2, 2, bits, 4, 4, xlat, 1, 1, 0);
yading@10: }
yading@10: 
yading@10: 
yading@10: /**
yading@10:  * nodes size must be 2*nb_codes
yading@10:  * first nb_codes nodes.count must be set
yading@10:  */
yading@10: int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes,
yading@10:                        Node *nodes, HuffCmp cmp, int flags)
yading@10: {
yading@10:     int i, j;
yading@10:     int cur_node;
yading@10:     int64_t sum = 0;
yading@10: 
yading@10:     for (i = 0; i < nb_codes; i++) {
yading@10:         nodes[i].sym = i;
yading@10:         nodes[i].n0 = -2;
yading@10:         sum += nodes[i].count;
yading@10:     }
yading@10: 
yading@10:     if (sum >> 31) {
yading@10:         av_log(avctx, AV_LOG_ERROR,
yading@10:                "Too high symbol frequencies. "
yading@10:                "Tree construction is not possible\n");
yading@10:         return -1;
yading@10:     }
yading@10:     qsort(nodes, nb_codes, sizeof(Node), cmp);
yading@10:     cur_node = nb_codes;
yading@10:     nodes[nb_codes*2-1].count = 0;
yading@10:     for (i = 0; i < nb_codes * 2 - 1; i += 2) {
yading@10:         uint32_t cur_count = nodes[i].count + nodes[i+1].count;
yading@10:         // find correct place to insert new node, and
yading@10:         // make space for the new node while at it
yading@10:         for(j = cur_node; j > i + 2; j--){
yading@10:             if(cur_count > nodes[j-1].count ||
yading@10:                (cur_count == nodes[j-1].count &&
yading@10:                 !(flags & FF_HUFFMAN_FLAG_HNODE_FIRST)))
yading@10:                 break;
yading@10:             nodes[j] = nodes[j - 1];
yading@10:         }
yading@10:         nodes[j].sym = HNODE;
yading@10:         nodes[j].count = cur_count;
yading@10:         nodes[j].n0 = i;
yading@10:         cur_node++;
yading@10:     }
yading@10:     if (build_huff_tree(vlc, nodes, nb_codes * 2 - 2, flags) < 0) {
yading@10:         av_log(avctx, AV_LOG_ERROR, "Error building tree\n");
yading@10:         return -1;
yading@10:     }
yading@10:     return 0;
yading@10: }