Libav
huffman.c
Go to the documentation of this file.
1 /*
2  * Copyright (c) 2006 Konstantin Shishkov
3  * Copyright (c) 2007 Loren Merritt
4  *
5  * This file is part of Libav.
6  *
7  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
27 #include <stdint.h>
28 
29 #include"libavutil/common.h"
30 
31 #include "avcodec.h"
32 #include "huffman.h"
33 #include "vlc.h"
34 
35 /* symbol for Huffman tree node */
36 #define HNODE -1
37 
38 typedef struct HeapElem {
39  uint64_t val;
40  int name;
41 } HeapElem;
42 
43 static void heap_sift(HeapElem *h, int root, int size)
44 {
45  while (root * 2 + 1 < size) {
46  int child = root * 2 + 1;
47  if (child < size - 1 && h[child].val > h[child+1].val)
48  child++;
49  if (h[root].val > h[child].val) {
50  FFSWAP(HeapElem, h[root], h[child]);
51  root = child;
52  } else
53  break;
54  }
55 }
56 
57 void ff_huff_gen_len_table(uint8_t *dst, const uint64_t *stats)
58 {
59  HeapElem h[256];
60  int up[2*256];
61  int len[2*256];
62  int offset, i, next;
63  int size = 256;
64 
65  for (offset = 1; ; offset <<= 1) {
66  for (i=0; i < size; i++) {
67  h[i].name = i;
68  h[i].val = (stats[i] << 8) + offset;
69  }
70  for (i = size / 2 - 1; i >= 0; i--)
71  heap_sift(h, i, size);
72 
73  for (next = size; next < size * 2 - 1; next++) {
74  // merge the two smallest entries, and put it back in the heap
75  uint64_t min1v = h[0].val;
76  up[h[0].name] = next;
77  h[0].val = INT64_MAX;
78  heap_sift(h, 0, size);
79  up[h[0].name] = next;
80  h[0].name = next;
81  h[0].val += min1v;
82  heap_sift(h, 0, size);
83  }
84 
85  len[2 * size - 2] = 0;
86  for (i = 2 * size - 3; i >= size; i--)
87  len[i] = len[up[i]] + 1;
88  for (i = 0; i < size; i++) {
89  dst[i] = len[up[i]] + 1;
90  if (dst[i] >= 32) break;
91  }
92  if (i==size) break;
93  }
94 }
95 
96 static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t *xlat,
97  Node *nodes, int node,
98  uint32_t pfx, int pl, int *pos, int no_zero_count)
99 {
100  int s;
101 
102  s = nodes[node].sym;
103  if (s != HNODE || (no_zero_count && !nodes[node].count)) {
104  bits[*pos] = pfx;
105  lens[*pos] = pl;
106  xlat[*pos] = s;
107  (*pos)++;
108  } else {
109  pfx <<= 1;
110  pl++;
111  get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl,
112  pos, no_zero_count);
113  pfx |= 1;
114  get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0 + 1, pfx, pl,
115  pos, no_zero_count);
116  }
117 }
118 
119 static int build_huff_tree(VLC *vlc, Node *nodes, int head, int flags, int nb_bits)
120 {
121  int no_zero_count = !(flags & FF_HUFFMAN_FLAG_ZERO_COUNT);
122  uint32_t bits[256];
123  int16_t lens[256];
124  uint8_t xlat[256];
125  int pos = 0;
126 
127  get_tree_codes(bits, lens, xlat, nodes, head, 0, 0,
128  &pos, no_zero_count);
129  return ff_init_vlc_sparse(vlc, nb_bits, pos, lens, 2, 2, bits, 4, 4, xlat, 1, 1, 0);
130 }
131 
132 
137 int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes, int nb_bits,
138  Node *nodes, HuffCmp cmp, int flags)
139 {
140  int i, j;
141  int cur_node;
142  int64_t sum = 0;
143 
144  for (i = 0; i < nb_codes; i++) {
145  nodes[i].sym = i;
146  nodes[i].n0 = -2;
147  sum += nodes[i].count;
148  }
149 
150  if (sum >> 31) {
151  av_log(avctx, AV_LOG_ERROR,
152  "Too high symbol frequencies. "
153  "Tree construction is not possible\n");
154  return -1;
155  }
156  qsort(nodes, nb_codes, sizeof(Node), cmp);
157  cur_node = nb_codes;
158  nodes[nb_codes*2-1].count = 0;
159  for (i = 0; i < nb_codes * 2 - 1; i += 2) {
160  nodes[cur_node].sym = HNODE;
161  nodes[cur_node].count = nodes[i].count + nodes[i + 1].count;
162  nodes[cur_node].n0 = i;
163  for (j = cur_node; j > 0; j--) {
164  if (nodes[j].count > nodes[j - 1].count ||
165  (nodes[j].count == nodes[j - 1].count &&
166  (!(flags & FF_HUFFMAN_FLAG_HNODE_FIRST) ||
167  nodes[j].n0 == j - 1 || nodes[j].n0 == j - 2 ||
168  (nodes[j].sym!=HNODE && nodes[j-1].sym!=HNODE))))
169  break;
170  FFSWAP(Node, nodes[j], nodes[j - 1]);
171  }
172  cur_node++;
173  }
174  if (build_huff_tree(vlc, nodes, nb_codes * 2 - 2, flags, nb_bits) < 0) {
175  av_log(avctx, AV_LOG_ERROR, "Error building tree\n");
176  return -1;
177  }
178  return 0;
179 }
#define FF_HUFFMAN_FLAG_HNODE_FIRST
Definition: huffman.h:38
int size
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, int no_zero_count)
Definition: huffman.c:96
int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes, int nb_bits, Node *nodes, HuffCmp cmp, int flags)
nodes size must be 2*nb_codes first nb_codes nodes.count must be set
Definition: huffman.c:137
av_log(ac->avr, AV_LOG_TRACE, "%d samples - audio_convert: %s to %s (%s)\, len, av_get_sample_fmt_name(ac->in_fmt), av_get_sample_fmt_name(ac->out_fmt), use_generic ? ac->func_descr_generic :ac->func_descr)
void ff_huff_gen_len_table(uint8_t *dst, const uint64_t *stats)
Definition: huffman.c:57
Definition: huffman.h:32
static int build_huff_tree(VLC *vlc, Node *nodes, int head, int flags, int nb_bits)
Definition: huffman.c:119
int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes, const void *bits, int bits_wrap, int bits_size, const void *codes, int codes_wrap, int codes_size, const void *symbols, int symbols_wrap, int symbols_size, int flags)
Definition: bitstream.c:267
uint8_t bits
Definition: crc.c:252
uint8_t
static int flags
Definition: log.c:50
static void heap_sift(HeapElem *h, int root, int size)
Definition: huffman.c:43
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:124
#define HNODE
Definition: huffman.c:36
#define FF_HUFFMAN_FLAG_ZERO_COUNT
Definition: huffman.h:39
uint64_t val
Definition: huffman.c:39
Definition: vlc.h:26
int name
Definition: huffman.c:40
static av_always_inline int cmp(MpegEncContext *s, const int x, const int y, const int subx, const int suby, const int size, const int h, int ref_index, int src_index, me_cmp_func cmp_func, me_cmp_func chroma_cmp_func, const int flags)
compares a block (either a full macroblock or a partition thereof) against a proposed motion-compensa...
Definition: motion_est.c:257
Libavcodec external API header.
main external API structure.
Definition: avcodec.h:1409
int16_t n0
Definition: huffman.h:34
huffman tree builder and VLC generator
int16_t sym
Definition: huffman.h:33
common internal and external API header
int len
uint32_t count
Definition: huffman.h:35
#define FFSWAP(type, a, b)
Definition: common.h:69
int(* HuffCmp)(const void *va, const void *vb)
Definition: huffman.h:42