Pull the Voice Activity Detector out from the AGC

webrtc/modules/audio_processing/agc/circular_buffer.h

-/*
- *  Copyright (c) 2012 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 WEBRTC_MODULES_AUDIO_PROCESSING_AGC_CIRCULAR_BUFFER_H_
-#define WEBRTC_MODULES_AUDIO_PROCESSING_AGC_CIRCULAR_BUFFER_H_
-
-#include "webrtc/base/scoped_ptr.h"
-
-namespace webrtc {
-
-// A circular buffer tailored to the need of this project. It stores last
-// K samples of the input, and keeps track of the mean of the last samples.
-//
-// It is used in class "PitchBasedActivity" to keep track of posterior
-// probabilities in the past few seconds. The posterior probabilities are used
-// to recursively update prior probabilities.
-class AgcCircularBuffer {
- public:
-  static AgcCircularBuffer* Create(int buffer_size);
-  ~AgcCircularBuffer();
-
-  // If buffer is wrapped around.
-  bool is_full() const { return is_full_; }
-  // Get the oldest entry in the buffer.
-  double Oldest() const;
-  // Insert new value into the buffer.
-  void Insert(double value);
-  // Reset buffer, forget the past, start fresh.
-  void Reset();
-
-  // The mean value of the elements in the buffer. The return value is zero if
-  // buffer is empty, i.e. no value is inserted.
-  double Mean();
-  // Remove transients. If the values exceed |val_threshold| for a period
-  // shorter then or equal to |width_threshold|, then that period is considered
-  // transient and set to zero.
-  int RemoveTransient(int width_threshold, double val_threshold);
-
- private:
-  explicit AgcCircularBuffer(int buffer_size);
-  // Get previous values. |index = 0| corresponds to the most recent
-  // insertion. |index = 1| is the one before the most recent insertion, and
-  // so on.
-  int Get(int index, double* value) const;
-  // Set a given position to |value|. |index| is interpreted as above.
-  int Set(int index, double value);
-  // Return the number of valid elements in the buffer.
-  int BufferLevel();
-
-  // Convert an index with the interpretation as get() method to the
-  // corresponding linear index.
-  int ConvertToLinearIndex(int* index) const;
-
-  rtc::scoped_ptr<double[]> buffer_;
-  bool is_full_;
-  int index_;
-  int buffer_size_;
-  double sum_;
-};
-
-}  // namespace webrtc
-#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AGC_CIRCULAR_BUFFER_H_