117 lines
4.5 KiB
C
117 lines
4.5 KiB
C
/*
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* Copyright (c) 2010 The WebM project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef VP9_COMMON_VP9_TREECODER_H_
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#define VP9_COMMON_VP9_TREECODER_H_
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#include "./vpx_config.h"
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#include "vpx/vpx_integer.h"
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#include "vp9/common/vp9_common.h"
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typedef uint8_t vp9_prob;
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#define vp9_prob_half ((vp9_prob) 128)
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typedef int8_t vp9_tree_index;
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#define TREE_SIZE(leaf_count) (2 * (leaf_count) - 2)
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#define vp9_complement(x) (255 - x)
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/* We build coding trees compactly in arrays.
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Each node of the tree is a pair of vp9_tree_indices.
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Array index often references a corresponding probability table.
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Index <= 0 means done encoding/decoding and value = -Index,
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Index > 0 means need another bit, specification at index.
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Nonnegative indices are always even; processing begins at node 0. */
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typedef const vp9_tree_index vp9_tree[];
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/* Convert array of token occurrence counts into a table of probabilities
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for the associated binary encoding tree. Also writes count of branches
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taken for each node on the tree; this facilitiates decisions as to
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probability updates. */
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void vp9_tree_probs_from_distribution(vp9_tree tree,
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unsigned int branch_ct[ /* n - 1 */ ][2],
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const unsigned int num_events[ /* n */ ]);
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static INLINE vp9_prob clip_prob(int p) {
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return (p > 255) ? 255u : (p < 1) ? 1u : p;
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}
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// int64 is not needed for normal frame level calculations.
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// However when outputing entropy stats accumulated over many frames
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// or even clips we can overflow int math.
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#ifdef ENTROPY_STATS
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static INLINE vp9_prob get_prob(int num, int den) {
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return (den == 0) ? 128u : clip_prob(((int64_t)num * 256 + (den >> 1)) / den);
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}
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#else
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static INLINE vp9_prob get_prob(int num, int den) {
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return (den == 0) ? 128u : clip_prob((num * 256 + (den >> 1)) / den);
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}
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#endif
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static INLINE vp9_prob get_binary_prob(int n0, int n1) {
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return get_prob(n0, n0 + n1);
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}
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/* this function assumes prob1 and prob2 are already within [1,255] range */
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static INLINE vp9_prob weighted_prob(int prob1, int prob2, int factor) {
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return ROUND_POWER_OF_TWO(prob1 * (256 - factor) + prob2 * factor, 8);
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}
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static INLINE vp9_prob merge_probs(vp9_prob pre_prob,
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const unsigned int ct[2],
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unsigned int count_sat,
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unsigned int max_update_factor) {
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const vp9_prob prob = get_binary_prob(ct[0], ct[1]);
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const unsigned int count = MIN(ct[0] + ct[1], count_sat);
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const unsigned int factor = max_update_factor * count / count_sat;
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return weighted_prob(pre_prob, prob, factor);
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}
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static unsigned int tree_merge_probs_impl(unsigned int i,
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const vp9_tree_index *tree,
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const vp9_prob *pre_probs,
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const unsigned int *counts,
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unsigned int count_sat,
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unsigned int max_update_factor,
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vp9_prob *probs) {
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const int l = tree[i];
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const unsigned int left_count = (l <= 0)
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? counts[-l]
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: tree_merge_probs_impl(l, tree, pre_probs, counts,
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count_sat, max_update_factor, probs);
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const int r = tree[i + 1];
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const unsigned int right_count = (r <= 0)
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? counts[-r]
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: tree_merge_probs_impl(r, tree, pre_probs, counts,
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count_sat, max_update_factor, probs);
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const unsigned int ct[2] = { left_count, right_count };
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probs[i >> 1] = merge_probs(pre_probs[i >> 1], ct,
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count_sat, max_update_factor);
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return left_count + right_count;
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}
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static void tree_merge_probs(const vp9_tree_index *tree,
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const vp9_prob *pre_probs,
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const unsigned int *counts,
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unsigned int count_sat,
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unsigned int max_update_factor, vp9_prob *probs) {
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tree_merge_probs_impl(0, tree, pre_probs, counts,
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count_sat, max_update_factor, probs);
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}
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#endif // VP9_COMMON_VP9_TREECODER_H_
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