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* 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.
#include <stddef.h>
#include <deque>
#include <memory>
#include "modules/audio_processing/transient/moving_moments.h"
#include "modules/audio_processing/transient/wpd_tree.h"
namespace webrtc {
// This is an implementation of the transient detector described in "Causal
// Wavelet based transient detector".
// Calculates the log-likelihood of a transient to happen on a signal at any
// given time based on the previous samples; it uses a WPD tree to analyze the
// signal. It preserves its state, so it can be multiple-called.
class TransientDetector {
// TODO(chadan): The only supported wavelet is Daubechies 8 using a WPD tree
// of 3 levels. Make an overloaded constructor to allow different wavelets and
// depths of the tree. When needed.
// Creates a wavelet based transient detector.
TransientDetector(int sample_rate_hz);
// Calculates the log-likelihood of the existence of a transient in `data`.
// `data_length` has to be equal to `samples_per_chunk_`.
// Returns a value between 0 and 1, as a non linear representation of this
// likelihood.
// Returns a negative value on error.
float Detect(const float* data,
size_t data_length,
const float* reference_data,
size_t reference_length);
bool using_reference() { return using_reference_; }
float ReferenceDetectionValue(const float* data, size_t length);
static const size_t kLevels = 3;
static const size_t kLeaves = 1 << kLevels;
size_t samples_per_chunk_;
std::unique_ptr<WPDTree> wpd_tree_;
size_t tree_leaves_data_length_;
// A MovingMoments object is needed for each leaf in the WPD tree.
std::unique_ptr<MovingMoments> moving_moments_[kLeaves];
std::unique_ptr<float[]> first_moments_;
std::unique_ptr<float[]> second_moments_;
// Stores the last calculated moments from the previous detection.
float last_first_moment_[kLeaves];
float last_second_moment_[kLeaves];
// We keep track of the previous results from the previous chunks, so it can
// be used to effectively give results according to the `transient_length`.
std::deque<float> previous_results_;
// Number of chunks that are going to return only zeros at the beginning of
// the detection. It helps to avoid infs and nans due to the lack of
// information.
int chunks_at_startup_left_to_delete_;
float reference_energy_;
bool using_reference_;
} // namespace webrtc