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 15 typedef unsigned char vp8bc_index_t; /* probability index */ 16 17 18 typedef unsigned char vp8_prob; 19 20 #define vp8_prob_half ( (vp8_prob) 128) 21 22 typedef signed char vp8_tree_index; 23 struct bool_coder_spec; 24 25 typedef struct bool_coder_spec bool_coder_spec; 26 typedef struct bool_writer bool_writer; 27 typedef struct bool_reader bool_reader; 28 29 typedef const bool_coder_spec c_bool_coder_spec; 30 typedef const bool_writer c_bool_writer; 31 typedef 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 45 typedef const vp8_tree_index vp8_tree[], *vp8_tree_p; 46 47 48 typedef const struct vp8_token_struct 49 { 50 int value; 51 int Len; 52 } vp8_token; 53 54 /* Construct encoding array from tree. */ 55 56 void vp8_tokens_from_tree(struct vp8_token_struct *, vp8_tree); 57 void 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 66 void 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 79 void 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 91