Line data    Source code

       1             : /*
       2             :  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
       3             :  *
       4             :  *  Use of this source code is governed by a BSD-style license
       5             :  *  that can be found in the LICENSE file in the root of the source
       6             :  *  tree. An additional intellectual property rights grant can be found
       7             :  *  in the file PATENTS.  All contributing project authors may
       8             :  *  be found in the AUTHORS file in the root of the source tree.
       9             :  */
      10             : 
      11             : #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_TRANSIENT_DETECTOR_H_
      12             : #define WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_TRANSIENT_DETECTOR_H_
      13             : 
      14             : #include <deque>
      15             : #include <memory>
      16             : 
      17             : #include "webrtc/modules/audio_processing/transient/moving_moments.h"
      18             : #include "webrtc/modules/audio_processing/transient/wpd_tree.h"
      19             : 
      20             : namespace webrtc {
      21             : 
      22             : // This is an implementation of the transient detector described in "Causal
      23             : // Wavelet based transient detector".
      24             : // Calculates the log-likelihood of a transient to happen on a signal at any
      25             : // given time based on the previous samples; it uses a WPD tree to analyze the
      26             : // signal.  It preserves its state, so it can be multiple-called.
      27             : class TransientDetector {
      28             :  public:
      29             :   // TODO(chadan): The only supported wavelet is Daubechies 8 using a WPD tree
      30             :   // of 3 levels. Make an overloaded constructor to allow different wavelets and
      31             :   // depths of the tree. When needed.
      32             : 
      33             :   // Creates a wavelet based transient detector.
      34             :   TransientDetector(int sample_rate_hz);
      35             : 
      36             :   ~TransientDetector();
      37             : 
      38             :   // Calculates the log-likelihood of the existence of a transient in |data|.
      39             :   // |data_length| has to be equal to |samples_per_chunk_|.
      40             :   // Returns a value between 0 and 1, as a non linear representation of this
      41             :   // likelihood.
      42             :   // Returns a negative value on error.
      43             :   float Detect(const float* data,
      44             :                size_t data_length,
      45             :                const float* reference_data,
      46             :                size_t reference_length);
      47             : 
      48           0 :   bool using_reference() { return using_reference_; }
      49             : 
      50             :  private:
      51             :   float ReferenceDetectionValue(const float* data, size_t length);
      52             : 
      53             :   static const size_t kLevels = 3;
      54             :   static const size_t kLeaves = 1 << kLevels;
      55             : 
      56             :   size_t samples_per_chunk_;
      57             : 
      58             :   std::unique_ptr<WPDTree> wpd_tree_;
      59             :   size_t tree_leaves_data_length_;
      60             : 
      61             :   // A MovingMoments object is needed for each leaf in the WPD tree.
      62             :   std::unique_ptr<MovingMoments> moving_moments_[kLeaves];
      63             : 
      64             :   std::unique_ptr<float[]> first_moments_;
      65             :   std::unique_ptr<float[]> second_moments_;
      66             : 
      67             :   // Stores the last calculated moments from the previous detection.
      68             :   float last_first_moment_[kLeaves];
      69             :   float last_second_moment_[kLeaves];
      70             : 
      71             :   // We keep track of the previous results from the previous chunks, so it can
      72             :   // be used to effectively give results according to the |transient_length|.
      73             :   std::deque<float> previous_results_;
      74             : 
      75             :   // Number of chunks that are going to return only zeros at the beginning of
      76             :   // the detection. It helps to avoid infs and nans due to the lack of
      77             :   // information.
      78             :   int chunks_at_startup_left_to_delete_;
      79             : 
      80             :   float reference_energy_;
      81             : 
      82             :   bool using_reference_;
      83             : };
      84             : 
      85             : }  // namespace webrtc
      86             : 
      87             : #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_TRANSIENT_DETECTOR_H_