modules/audio_processing/transient/wpd_tree.h

/*
 *  Copyright (c) 2013 The WebRTC 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 MODULES_AUDIO_PROCESSING_TRANSIENT_WPD_TREE_H_
#define MODULES_AUDIO_PROCESSING_TRANSIENT_WPD_TREE_H_

#include <stddef.h>

#include <memory>

#include "modules/audio_processing/transient/wpd_node.h"

namespace webrtc {

// Tree of a Wavelet Packet Decomposition (WPD).
//
// The root node contains all the data provided; for each node in the tree, the
// left child contains the approximation coefficients extracted from the node,
// and the right child contains the detail coefficients.
// It preserves its state, so it can be multiple-called.
//
// The number of nodes in the tree will be 2 ^ levels - 1.
//
// Implementation details: Since the tree always will be a complete binary tree,
// it is implemented using a single linear array instead of managing the
// relationships in each node. For convience is better to use a array that
// starts in 1 (instead of 0). Taking that into account, the following formulas
// apply:
// Root node index: 1.
// Node(Level, Index in that level): 2 ^ Level + (Index in that level).
// Left Child: Current node index * 2.
// Right Child: Current node index * 2 + 1.
// Parent: Current Node Index / 2 (Integer division).
class WPDTree {
 public:
  // Creates a WPD tree using the data length and coefficients provided.
  WPDTree(size_t data_length,
          const float* high_pass_coefficients,
          const float* low_pass_coefficients,
          size_t coefficients_length,
          int levels);
  ~WPDTree();

  // Returns the number of nodes at any given level.
  static int NumberOfNodesAtLevel(int level) { return 1 << level; }

  // Returns a pointer to the node at the given level and index(of that level).
  // Level goes from 0 to levels().
  // Index goes from 0 to the number of NumberOfNodesAtLevel(level) - 1.
  //
  // You can use the following formulas to get any node within the tree:
  // Notation: (Level, Index of node in that level).
  // Root node: (0/0).
  // Left Child: (Current node level + 1, Current node index * 2).
  // Right Child: (Current node level + 1, Current node index * 2 + 1).
  // Parent: (Current node level - 1, Current node index / 2) (Integer division)
  //
  // If level or index are out of bounds the function will return NULL.
  WPDNode* NodeAt(int level, int index);

  // Updates all the nodes of the tree with the new data. |data_length| must be
  // teh same that was used for the creation of the tree.
  // Returns 0 if correct, and -1 otherwise.
  int Update(const float* data, size_t data_length);

  // Returns the total number of levels below the root. Root is cosidered level
  // 0.
  int levels() const { return levels_; }

  // Returns the total number of nodes.
  int num_nodes() const { return num_nodes_; }

  // Returns the total number of leaves.
  int num_leaves() const { return 1 << levels_; }

 private:
  size_t data_length_;
  int levels_;
  int num_nodes_;
  std::unique_ptr<std::unique_ptr<WPDNode>[]> nodes_;
};

}  // namespace webrtc

#endif  // MODULES_AUDIO_PROCESSING_TRANSIENT_WPD_TREE_H_