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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_
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