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 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 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 } 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 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 } 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
