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 #ifndef VPX_VP8_COMMON_TREECODER_H_ 12 #define VPX_VP8_COMMON_TREECODER_H_ 13 14 #ifdef __cplusplus 15 extern "C" { 16 #endif 17 18 typedef unsigned char vp8bc_index_t; /* probability index */ 19 20 typedef unsigned char vp8_prob; 21 22 #define vp8_prob_half ((vp8_prob)128) 23 24 typedef signed char vp8_tree_index; 25 struct bool_coder_spec; 26 27 typedef struct bool_coder_spec bool_coder_spec; 28 typedef struct bool_writer bool_writer; 29 typedef struct bool_reader bool_reader; 30 31 typedef const bool_coder_spec c_bool_coder_spec; 32 typedef const bool_writer c_bool_writer; 33 typedef const bool_reader c_bool_reader; 34 35 #define vp8_complement(x) (255 - (x)) 36 37 /* We build coding trees compactly in arrays. 38 Each node of the tree is a pair of vp8_tree_indices. 39 Array index often references a corresponding probability table. 40 Index <= 0 means done encoding/decoding and value = -Index, 41 Index > 0 means need another bit, specification at index. 42 Nonnegative indices are always even; processing begins at node 0. */ 43 44 typedef const vp8_tree_index vp8_tree[], *vp8_tree_p; 45 46 typedef const struct vp8_token_struct { 47 int value; 48 int Len; 49 } vp8_token; 50 51 /* Construct encoding array from tree. */ 52 53 void vp8_tokens_from_tree(struct vp8_token_struct *, vp8_tree); 54 void vp8_tokens_from_tree_offset(struct vp8_token_struct *, vp8_tree, 55 int offset); 56 57 /* Convert array of token occurrence counts into a table of probabilities 58 for the associated binary encoding tree. Also writes count of branches 59 taken for each node on the tree; this facilitiates decisions as to 60 probability updates. */ 61 62 void vp8_tree_probs_from_distribution(int n, /* n = size of alphabet */ 63 vp8_token tok[/* n */], vp8_tree tree, 64 vp8_prob probs[/* n-1 */], 65 unsigned int branch_ct[/* n-1 */][2], 66 const unsigned int num_events[/* n */], 67 unsigned int Pfactor, int Round); 68 69 /* Variant of above using coder spec rather than hardwired 8-bit probs. */ 70 71 void vp8bc_tree_probs_from_distribution(int n, /* n = size of alphabet */ 72 vp8_token tok[/* n */], vp8_tree tree, 73 vp8_prob probs[/* n-1 */], 74 unsigned int branch_ct[/* n-1 */][2], 75 const unsigned int num_events[/* n */], 76 c_bool_coder_spec *s); 77 78 #ifdef __cplusplus 79 } // extern "C" 80 #endif 81 82 #endif // VPX_VP8_COMMON_TREECODER_H_ 83