aom/aom_dsp/prob.h

/*
 * Copyright (c) 2016, Alliance for Open Media. All rights reserved
 *
 * This source code is subject to the terms of the BSD 2 Clause License and
 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
 * was not distributed with this source code in the LICENSE file, you can
 * obtain it at www.aomedia.org/license/software. If the Alliance for Open
 * Media Patent License 1.0 was not distributed with this source code in the
 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
 */

#ifndef AOM_DSP_PROB_H_
#define AOM_DSP_PROB_H_

#include "./aom_config.h"
#include "./aom_dsp_common.h"

#include "aom_ports/mem.h"

#ifdef __cplusplus
extern "C" {
#endif

typedef uint8_t aom_prob;

#define MAX_PROB 255

#define aom_prob_half ((aom_prob)128)

typedef int8_t aom_tree_index;

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

#define aom_complement(x) (255 - x)

#define MODE_MV_COUNT_SAT 20

/* We build coding trees compactly in arrays.
   Each node of the tree is a pair of aom_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 aom_tree_index aom_tree[];

static INLINE aom_prob clip_prob(int p) {
  return (p > 255) ? 255 : (p < 1) ? 1 : p;
}

static INLINE aom_prob get_prob(int num, int den) {
  return (den == 0) ? 128u : clip_prob(((int64_t)num * 256 + (den >> 1)) / den);
}

static INLINE aom_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 aom_prob weighted_prob(int prob1, int prob2, int factor) {
  return ROUND_POWER_OF_TWO(prob1 * (256 - factor) + prob2 * factor, 8);
}

static INLINE aom_prob merge_probs(aom_prob pre_prob, const unsigned int ct[2],
                                   unsigned int count_sat,
                                   unsigned int max_update_factor) {
  const aom_prob prob = get_binary_prob(ct[0], ct[1]);
  const unsigned int count = AOMMIN(ct[0] + ct[1], count_sat);
  const unsigned int factor = max_update_factor * count / count_sat;
  return weighted_prob(pre_prob, prob, factor);
}

// MODE_MV_MAX_UPDATE_FACTOR (128) * count / MODE_MV_COUNT_SAT;
static const int count_to_update_factor[MODE_MV_COUNT_SAT + 1] = {
  0,  6,  12, 19, 25, 32,  38,  44,  51,  57, 64,
  70, 76, 83, 89, 96, 102, 108, 115, 121, 128
};

static INLINE aom_prob mode_mv_merge_probs(aom_prob pre_prob,
                                           const unsigned int ct[2]) {
  const unsigned int den = ct[0] + ct[1];
  if (den == 0) {
    return pre_prob;
  } else {
    const unsigned int count = AOMMIN(den, MODE_MV_COUNT_SAT);
    const unsigned int factor = count_to_update_factor[count];
    const aom_prob prob =
        clip_prob(((int64_t)(ct[0]) * 256 + (den >> 1)) / den);
    return weighted_prob(pre_prob, prob, factor);
  }
}

void aom_tree_merge_probs(const aom_tree_index *tree, const aom_prob *pre_probs,
                          const unsigned int *counts, aom_prob *probs);

DECLARE_ALIGNED(16, extern const uint8_t, aom_norm[256]);

#ifdef __cplusplus
}  // extern "C"
#endif

#endif  // AOM_DSP_PROB_H_