Add algorithm for Residual Echo Detector.

webrtc/modules/audio_processing/echo_detector/echo_detector.h

 /*
  *  Copyright (c) 2016 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_ECHO_DETECTOR_ECHO_DETECTOR_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_ECHO_DETECTOR_ECHO_DETECTOR_H_
 
-#include <stddef.h>
+#include <vector>
+
 #include "webrtc/base/array_view.h"
+#include "webrtc/modules/audio_processing/echo_detector/circular_buffer.h"
+#include "webrtc/modules/audio_processing/echo_detector/mean_variance_estimator.h"
+#include "webrtc/modules/audio_processing/echo_detector/normalized_covariance_estimator.h"
 
 namespace webrtc {
 
 class EchoDetector {
  public:
-  EchoDetector() {}
-  ~EchoDetector() {}
+  EchoDetector();
+  ~EchoDetector();
 
-  void BufferFarend(const rtc::ArrayView<const float>& farend);
+  void BufferRender(rtc::ArrayView<const float> render);
 
-  void Process(const rtc::ArrayView<const float>& nearend);
+  void Process(rtc::ArrayView<const float> capture);
 
-  void Initialize(int sample_rate_hz);
+  void Initialize();
+
+  float echo_likelihood() const { return echo_likelihood_; }
+
+ private:
+  static constexpr size_t kLookbackFrames = 650;
+  // TODO(ivoc): Verify the size of this buffer.

[peah-webrtc, 2016/10/20 15:08:24]

Do these two constants need to be in the header file?

[ivoc, 2016/10/21 12:21:15]

Not anymore, I will move them to the cc file.

+  static constexpr size_t kRenderBufferSize = 30;
+
+  // Keep track if this is the first call to Process().
+  bool first_process_call_ = true;
+
+  // Buffer for storing the power of incoming farend buffers. This is needed for
+  // cases where calls to BufferFarend and Process are jittery.
+  CircularBuffer render_buffer_;
+  // Count how long ago it was that the size of |render_buffer_| was zero.
+  size_t render_buffer_zero_ = 0;

[peah-webrtc, 2016/10/20 15:08:24]

I think this variable would benefit of being more specifically named, such as
frames_since_zero_buffer_length_
or zero_length_buffer_frame_counter_

As it is now, the name is not self-explanatory and you need the comment in order
to tell what the variable stores.

[ivoc, 2016/10/21 12:21:15]

I changed it to frames_since_zero_buffer_size_.

+
+  // Circular buffers containing delayed versions of the power, mean and
+  // standard deviation, for calculating the delayed covariance values.
+  std::vector<float> render_power_;
+  std::vector<float> render_power_mean_;
+  std::vector<float> render_power_std_dev_;
+  // Covariance estimates for different delay values.
+  std::vector<NormalizedCovarianceEstimator> covariances_;
+  // Index where next element should be inserted in all of the above circular
+  // buffers.
+  size_t next_insertion_index_ = 0;
+
+  MeanVarianceEstimator render_statistics_;
+  MeanVarianceEstimator capture_statistics_;
+  // Current echo likelihood.
+  float echo_likelihood_ = 0.f;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_AUDIO_PROCESSING_ECHO_DETECTOR_ECHO_DETECTOR_H_