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 VP8_ENCODER_TREEWRITER_H_
13 #define VP8_ENCODER_TREEWRITER_H_
14
15 /* Trees map alphabets into huffman-like codes suitable for an arithmetic
16 bit coder. Timothy S Murphy 11 October 2004 */
17
18 #include "vp8/common/treecoder.h"
19
20 #include "boolhuff.h" /* for now */
21
22 #ifdef __cplusplus
23 extern "C" {
24 #endif
25
26 typedef BOOL_CODER vp8_writer;
27
28 #define vp8_write vp8_encode_bool
29 #define vp8_write_literal vp8_encode_value
30 #define vp8_write_bit( W, V) vp8_write( W, V, vp8_prob_half)
31
32 #define vp8bc_write vp8bc_write_bool
33 #define vp8bc_write_literal vp8bc_write_bits
34 #define vp8bc_write_bit( W, V) vp8bc_write_bits( W, V, 1)
35
36
37 /* Approximate length of an encoded bool in 256ths of a bit at given prob */
38
39 #define vp8_cost_zero( x) ( vp8_prob_cost[x])
40 #define vp8_cost_one( x) vp8_cost_zero( vp8_complement(x))
41
42 #define vp8_cost_bit( x, b) vp8_cost_zero( (b)? vp8_complement(x) : (x) )
43
44 /* VP8BC version is scaled by 2^20 rather than 2^8; see bool_coder.h */
45
46
47 /* Both of these return bits, not scaled bits. */
48
vp8_cost_branch(const unsigned int ct[2],vp8_prob p)49 static unsigned int vp8_cost_branch(const unsigned int ct[2], vp8_prob p)
50 {
51 /* Imitate existing calculation */
52
53 return ((ct[0] * vp8_cost_zero(p))
54 + (ct[1] * vp8_cost_one(p))) >> 8;
55 }
56
57 /* Small functions to write explicit values and tokens, as well as
58 estimate their lengths. */
59
vp8_treed_write(vp8_writer * const w,vp8_tree t,const vp8_prob * const p,int v,int n)60 static void vp8_treed_write
61 (
62 vp8_writer *const w,
63 vp8_tree t,
64 const vp8_prob *const p,
65 int v,
66 int n /* number of bits in v, assumed nonzero */
67 )
68 {
69 vp8_tree_index i = 0;
70
71 do
72 {
73 const int b = (v >> --n) & 1;
74 vp8_write(w, b, p[i>>1]);
75 i = t[i+b];
76 }
77 while (n);
78 }
vp8_write_token(vp8_writer * const w,vp8_tree t,const vp8_prob * const p,vp8_token * const x)79 static void vp8_write_token
80 (
81 vp8_writer *const w,
82 vp8_tree t,
83 const vp8_prob *const p,
84 vp8_token *const x
85 )
86 {
87 vp8_treed_write(w, t, p, x->value, x->Len);
88 }
89
vp8_treed_cost(vp8_tree t,const vp8_prob * const p,int v,int n)90 static int vp8_treed_cost(
91 vp8_tree t,
92 const vp8_prob *const p,
93 int v,
94 int n /* number of bits in v, assumed nonzero */
95 )
96 {
97 int c = 0;
98 vp8_tree_index i = 0;
99
100 do
101 {
102 const int b = (v >> --n) & 1;
103 c += vp8_cost_bit(p[i>>1], b);
104 i = t[i+b];
105 }
106 while (n);
107
108 return c;
109 }
vp8_cost_token(vp8_tree t,const vp8_prob * const p,vp8_token * const x)110 static int vp8_cost_token
111 (
112 vp8_tree t,
113 const vp8_prob *const p,
114 vp8_token *const x
115 )
116 {
117 return vp8_treed_cost(t, p, x->value, x->Len);
118 }
119
120 /* Fill array of costs for all possible token values. */
121
122 void vp8_cost_tokens(
123 int *Costs, const vp8_prob *, vp8_tree
124 );
125
126 void vp8_cost_tokens2(
127 int *Costs, const vp8_prob *, vp8_tree, int
128 );
129
130 #ifdef __cplusplus
131 } // extern "C"
132 #endif
133
134 #endif // VP8_ENCODER_TREEWRITER_H_
135