ref: 0c7a9925d620e44a4131e76494c25253dcfed13a
dir: /vp8/common/treecoder.h/
/*
* Copyright (c) 2010 The WebM project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef VP8_COMMON_TREECODER_H_
#define VP8_COMMON_TREECODER_H_
#ifdef __cplusplus
extern "C" {
#endif
typedef unsigned char vp8bc_index_t; /* probability index */
typedef unsigned char vp8_prob;
#define vp8_prob_half ( (vp8_prob) 128)
typedef signed char vp8_tree_index;
struct bool_coder_spec;
typedef struct bool_coder_spec bool_coder_spec;
typedef struct bool_writer bool_writer;
typedef struct bool_reader bool_reader;
typedef const bool_coder_spec c_bool_coder_spec;
typedef const bool_writer c_bool_writer;
typedef const bool_reader c_bool_reader;
# define vp8_complement( x) (255 - x)
/* We build coding trees compactly in arrays.
Each node of the tree is a pair of vp8_tree_indices.
Array index often references a corresponding probability table.
Index <= 0 means done encoding/decoding and value = -Index,
Index > 0 means need another bit, specification at index.
Nonnegative indices are always even; processing begins at node 0. */
typedef const vp8_tree_index vp8_tree[], *vp8_tree_p;
typedef const struct vp8_token_struct
{
int value;
int Len;
} vp8_token;
/* Construct encoding array from tree. */
void vp8_tokens_from_tree(struct vp8_token_struct *, vp8_tree);
void vp8_tokens_from_tree_offset(struct vp8_token_struct *, vp8_tree,
int offset);
/* Convert array of token occurrence counts into a table of probabilities
for the associated binary encoding tree. Also writes count of branches
taken for each node on the tree; this facilitiates decisions as to
probability updates. */
void vp8_tree_probs_from_distribution(
int n, /* n = size of alphabet */
vp8_token tok [ /* n */ ],
vp8_tree tree,
vp8_prob probs [ /* n-1 */ ],
unsigned int branch_ct [ /* n-1 */ ] [2],
const unsigned int num_events[ /* n */ ],
unsigned int Pfactor,
int Round
);
/* Variant of above using coder spec rather than hardwired 8-bit probs. */
void vp8bc_tree_probs_from_distribution(
int n, /* n = size of alphabet */
vp8_token tok [ /* n */ ],
vp8_tree tree,
vp8_prob probs [ /* n-1 */ ],
unsigned int branch_ct [ /* n-1 */ ] [2],
const unsigned int num_events[ /* n */ ],
c_bool_coder_spec *s
);
#ifdef __cplusplus
} // extern "C"
#endif
#endif // VP8_COMMON_TREECODER_H_