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      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 VP8_ENCODER_TREEWRITER_H_
     12 #define VP8_ENCODER_TREEWRITER_H_
     13 
     14 /* Trees map alphabets into huffman-like codes suitable for an arithmetic
     15    bit coder.  Timothy S Murphy  11 October 2004 */
     16 
     17 #include "./vpx_config.h"
     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 /* Approximate length of an encoded bool in 256ths of a bit at given prob */
     37 
     38 #define vp8_cost_zero(x) (vp8_prob_cost[x])
     39 #define vp8_cost_one(x) vp8_cost_zero(vp8_complement(x))
     40 
     41 #define vp8_cost_bit(x, b) vp8_cost_zero((b) ? vp8_complement(x) : (x))
     42 
     43 /* VP8BC version is scaled by 2^20 rather than 2^8; see bool_coder.h */
     44 
     45 /* Both of these return bits, not scaled bits. */
     46 
     47 static INLINE unsigned int vp8_cost_branch(const unsigned int ct[2],
     48                                            vp8_prob p) {
     49   /* Imitate existing calculation */
     50 
     51   return ((ct[0] * vp8_cost_zero(p)) + (ct[1] * vp8_cost_one(p))) >> 8;
     52 }
     53 
     54 /* Small functions to write explicit values and tokens, as well as
     55    estimate their lengths. */
     56 
     57 static void vp8_treed_write(vp8_writer *const w, vp8_tree t,
     58                             const vp8_prob *const p, int v,
     59                             int n /* number of bits in v, assumed nonzero */
     60                             ) {
     61   vp8_tree_index i = 0;
     62 
     63   do {
     64     const int b = (v >> --n) & 1;
     65     vp8_write(w, b, p[i >> 1]);
     66     i = t[i + b];
     67   } while (n);
     68 }
     69 static INLINE void vp8_write_token(vp8_writer *const w, vp8_tree t,
     70                                    const vp8_prob *const p,
     71                                    vp8_token *const x) {
     72   vp8_treed_write(w, t, p, x->value, x->Len);
     73 }
     74 
     75 static int vp8_treed_cost(vp8_tree t, const vp8_prob *const p, int v,
     76                           int n /* number of bits in v, assumed nonzero */
     77                           ) {
     78   int c = 0;
     79   vp8_tree_index i = 0;
     80 
     81   do {
     82     const int b = (v >> --n) & 1;
     83     c += vp8_cost_bit(p[i >> 1], b);
     84     i = t[i + b];
     85   } while (n);
     86 
     87   return c;
     88 }
     89 static INLINE int vp8_cost_token(vp8_tree t, const vp8_prob *const p,
     90                                  vp8_token *const x) {
     91   return vp8_treed_cost(t, p, x->value, x->Len);
     92 }
     93 
     94 /* Fill array of costs for all possible token values. */
     95 
     96 void vp8_cost_tokens(int *Costs, const vp8_prob *, vp8_tree);
     97 
     98 void vp8_cost_tokens2(int *Costs, const vp8_prob *, vp8_tree, int);
     99 
    100 #ifdef __cplusplus
    101 }  // extern "C"
    102 #endif
    103 
    104 #endif  // VP8_ENCODER_TREEWRITER_H_
    105