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/*
* Copyright (c) 2010 The VP8 project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license and patent
* grant that can be found in the LICENSE file in the root of the source
* tree. All contributing project authors may be found in the AUTHORS
* file in the root of the source tree.
*/
#ifndef __INC_TREEWRITER_H
#define __INC_TREEWRITER_H
/* Trees map alphabets into huffman-like codes suitable for an arithmetic
bit coder. Timothy S Murphy 11 October 2004 */
#include "treecoder.h"
#include "boolhuff.h" /* for now */
typedef BOOL_CODER vp8_writer;
#define vp8_write vp8_encode_bool
#define vp8_write_literal vp8_encode_value
#define vp8_write_bit( W, V) vp8_write( W, V, vp8_prob_half)
#define vp8bc_write vp8bc_write_bool
#define vp8bc_write_literal vp8bc_write_bits
#define vp8bc_write_bit( W, V) vp8bc_write_bits( W, V, 1)
/* Approximate length of an encoded bool in 256ths of a bit at given prob */
#define vp8_cost_zero( x) ( vp8_prob_cost[x])
#define vp8_cost_one( x) vp8_cost_zero( vp8_complement(x))
#define vp8_cost_bit( x, b) vp8_cost_zero( (b)? vp8_complement(x) : (x) )
/* VP8BC version is scaled by 2^20 rather than 2^8; see bool_coder.h */
/* Both of these return bits, not scaled bits. */
static __inline unsigned int vp8_cost_branch(const unsigned int ct[2], vp8_prob p)
{
/* Imitate existing calculation */
return ((ct[0] * vp8_cost_zero(p))
+ (ct[1] * vp8_cost_one(p))) >> 8;
}
/* Small functions to write explicit values and tokens, as well as
estimate their lengths. */
static __inline void vp8_treed_write
(
vp8_writer *const w,
vp8_tree t,
const vp8_prob *const p,
int v,
int n /* number of bits in v, assumed nonzero */
)
{
vp8_tree_index i = 0;
do
{
const int b = (v >> --n) & 1;
vp8_write(w, b, p[i>>1]);
i = t[i+b];
}
while (n);
}
static __inline void vp8_write_token
(
vp8_writer *const w,
vp8_tree t,
const vp8_prob *const p,
vp8_token *const x
)
{
vp8_treed_write(w, t, p, x->value, x->Len);
}
static __inline int vp8_treed_cost(
vp8_tree t,
const vp8_prob *const p,
int v,
int n /* number of bits in v, assumed nonzero */
)
{
int c = 0;
vp8_tree_index i = 0;
do
{
const int b = (v >> --n) & 1;
c += vp8_cost_bit(p[i>>1], b);
i = t[i+b];
}
while (n);
return c;
}
static __inline int vp8_cost_token
(
vp8_tree t,
const vp8_prob *const p,
vp8_token *const x
)
{
return vp8_treed_cost(t, p, x->value, x->Len);
}
/* Fill array of costs for all possible token values. */
void vp8_cost_tokens(
int *Costs, const vp8_prob *, vp8_tree
);
#endif