/media/libvpx/vp8/common/treecoder.h

 1/*
 2 *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
 3 *
 4 *  Use of this source code is governed by a BSD-style license
 5 *  that can be found in the LICENSE file in the root of the source
 6 *  tree. An additional intellectual property rights grant can be found
 7 *  in the file PATENTS.  All contributing project authors may
 8 *  be found in the AUTHORS file in the root of the source tree.
 9 */
10
11
12#ifndef __INC_TREECODER_H
13#define __INC_TREECODER_H
14
15typedef unsigned char vp8bc_index_t; /* probability index */
16
17
18typedef unsigned char vp8_prob;
19
20#define vp8_prob_half ( (vp8_prob) 128)
21
22typedef signed char vp8_tree_index;
23struct bool_coder_spec;
24
25typedef struct bool_coder_spec bool_coder_spec;
26typedef struct bool_writer bool_writer;
27typedef struct bool_reader bool_reader;
28
29typedef const bool_coder_spec c_bool_coder_spec;
30typedef const bool_writer c_bool_writer;
31typedef const bool_reader c_bool_reader;
32
33
34
35# define vp8_complement( x) (255 - x)
36
37
38/* We build coding trees compactly in arrays.
39   Each node of the tree is a pair of vp8_tree_indices.
40   Array index often references a corresponding probability table.
41   Index <= 0 means done encoding/decoding and value = -Index,
42   Index > 0 means need another bit, specification at index.
43   Nonnegative indices are always even;  processing begins at node 0. */
44
45typedef const vp8_tree_index vp8_tree[], *vp8_tree_p;
46
47
48typedef const struct vp8_token_struct
49{
50    int value;
51    int Len;
52} vp8_token;
53
54/* Construct encoding array from tree. */
55
56void vp8_tokens_from_tree(struct vp8_token_struct *, vp8_tree);
57void vp8_tokens_from_tree_offset(struct vp8_token_struct *, vp8_tree,
58                                 int offset);
59
60
61/* Convert array of token occurrence counts into a table of probabilities
62   for the associated binary encoding tree.  Also writes count of branches
63   taken for each node on the tree; this facilitiates decisions as to
64   probability updates. */
65
66void vp8_tree_probs_from_distribution(
67    int n,                      /* n = size of alphabet */
68    vp8_token tok               [ /* n */ ],
69    vp8_tree tree,
70    vp8_prob probs          [ /* n-1 */ ],
71    unsigned int branch_ct       [ /* n-1 */ ] [2],
72    const unsigned int num_events[ /* n */ ],
73    unsigned int Pfactor,
74    int Round
75);
76
77/* Variant of above using coder spec rather than hardwired 8-bit probs. */
78
79void vp8bc_tree_probs_from_distribution(
80    int n,                      /* n = size of alphabet */
81    vp8_token tok               [ /* n */ ],
82    vp8_tree tree,
83    vp8_prob probs          [ /* n-1 */ ],
84    unsigned int branch_ct       [ /* n-1 */ ] [2],
85    const unsigned int num_events[ /* n */ ],
86    c_bool_coder_spec *s
87);
88
89
90#endif