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 /*

  *  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 VP9_COMMON_VP9_TREECODER_H_

 #define VP9_COMMON_VP9_TREECODER_H_

 #include "./vpx_config.h"

 #include "vpx/vpx_integer.h"

 #include "vp9/common/vp9_common.h"

 typedef uint8_t vp9_prob;

 #define vp9_prob_half ((vp9_prob) 128)

 typedef int8_t vp9_tree_index;

 #define TREE_SIZE(leaf_count) (2 * (leaf_count) - 2)

 #define vp9_complement(x) (255 - x)

 /* We build coding trees compactly in arrays.

    Each node of the tree is a pair of vp9_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 vp9_tree_index vp9_tree[];

 struct vp9_token {

   int value;

   int len;

 };

 /* Construct encoding array from tree. */

 void vp9_tokens_from_tree(struct vp9_token*, vp9_tree);

 /* 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 vp9_tree_probs_from_distribution(vp9_tree tree,

                                       unsigned int branch_ct[ /* n - 1 */ ][2],

                                       const unsigned int num_events[ /* n */ ]);

 static INLINE vp9_prob clip_prob(int p) {

   return (p > 255) ? 255u : (p < 1) ? 1u : p;

 }

 // int64 is not needed for normal frame level calculations.

 // However when outputing entropy stats accumulated over many frames

 // or even clips we can overflow int math.

 #ifdef ENTROPY_STATS

 static INLINE vp9_prob get_prob(int num, int den) {

   return (den == 0) ? 128u : clip_prob(((int64_t)num * 256 + (den >> 1)) / den);

 }

 #else

 static INLINE vp9_prob get_prob(int num, int den) {

   return (den == 0) ? 128u : clip_prob((num * 256 + (den >> 1)) / den);

 }

 #endif

 static INLINE vp9_prob get_binary_prob(int n0, int n1) {

   return get_prob(n0, n0 + n1);

 }

 /* this function assumes prob1 and prob2 are already within [1,255] range */

 static INLINE vp9_prob weighted_prob(int prob1, int prob2, int factor) {

   return ROUND_POWER_OF_TWO(prob1 * (256 - factor) + prob2 * factor, 8);

 }

 static INLINE vp9_prob merge_probs(vp9_prob pre_prob,

                                    const unsigned int ct[2],

                                    unsigned int count_sat,

                                    unsigned int max_update_factor) {

   const vp9_prob prob = get_binary_prob(ct[0], ct[1]);

   const unsigned int count = MIN(ct[0] + ct[1], count_sat);

   const unsigned int factor = max_update_factor * count / count_sat;

   return weighted_prob(pre_prob, prob, factor);

 }

 static unsigned int tree_merge_probs_impl(unsigned int i,

                                           const vp9_tree_index *tree,

                                           const vp9_prob *pre_probs,

                                           const unsigned int *counts,

                                           unsigned int count_sat,

                                           unsigned int max_update_factor,

                                           vp9_prob *probs) {

   const int l = tree[i];

   const unsigned int left_count = (l <= 0)

                  ? counts[-l]

                  : tree_merge_probs_impl(l, tree, pre_probs, counts,

                                          count_sat, max_update_factor, probs);

   const int r = tree[i + 1];

   const unsigned int right_count = (r <= 0)

                  ? counts[-r]

                  : tree_merge_probs_impl(r, tree, pre_probs, counts,

                                          count_sat, max_update_factor, probs);

   const unsigned int ct[2] = { left_count, right_count };

   probs[i >> 1] = merge_probs(pre_probs[i >> 1], ct,

                               count_sat, max_update_factor);

   return left_count + right_count;

 }

 static void tree_merge_probs(const vp9_tree_index *tree,

                              const vp9_prob *pre_probs,

                              const unsigned int *counts,

                              unsigned int count_sat,

                              unsigned int max_update_factor, vp9_prob *probs) {

   tree_merge_probs_impl(0, tree, pre_probs, counts,

                         count_sat, max_update_factor, probs);

 }

 #endif  // VP9_COMMON_VP9_TREECODER_H_