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