Add algorithm for Residual Echo Detector.

webrtc/modules/audio_processing/residual_echo_detector.h

Index: webrtc/modules/audio_processing/residual_echo_detector.h
diff --git a/webrtc/modules/audio_processing/residual_echo_detector.h b/webrtc/modules/audio_processing/residual_echo_detector.h
index 723371c7ce68c57756420ed7b1cf7aa21a31e2ae..37aa283b0869487e08a498961e292667f458c71e 100644
--- a/webrtc/modules/audio_processing/residual_echo_detector.h
+++ b/webrtc/modules/audio_processing/residual_echo_detector.h
@@ -11,10 +11,12 @@
 #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_RESIDUAL_ECHO_DETECTOR_H_
 #define WEBRTC_MODULES_AUDIO_PROCESSING_RESIDUAL_ECHO_DETECTOR_H_
 
-#include <memory>
 #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 {
 
@@ -27,7 +29,7 @@ class ResidualEchoDetector {
   ~ResidualEchoDetector();
 
   // This function should be called while holding the render lock.
-  void AnalyzeRenderAudio(rtc::ArrayView<const float> render_audio) const;
+  void AnalyzeRenderAudio(rtc::ArrayView<const float> render_audio);
 
   // This function should be called while holding the capture lock.
   void AnalyzeCaptureAudio(rtc::ArrayView<const float> capture_audio);
@@ -39,7 +41,36 @@ class ResidualEchoDetector {
                                     std::vector<float>* packed_buffer);
 
   // This function should be called while holding the capture lock.
-  float get_echo_likelihood() const;
+  float echo_likelihood() const { return echo_likelihood_; }
+
+ private:
+  // Keep track if the |Process| function has been previously called.
+  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. This
+  // value is also reset to zero when clock drift is detected and a value from
+  // the renderbuffer is discarded, even though the buffer is not actually zero
+  // at that point. This is done to avoid repeatedly removing elements in this
+  // situation.
+  size_t frames_since_zero_buffer_size_ = 0;
+
+  // 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