Add algorithm for Residual Echo Detector.

webrtc/modules/audio_processing/echo_detector/echo_detector.h

Index: webrtc/modules/audio_processing/echo_detector/echo_detector.h
diff --git a/webrtc/modules/audio_processing/echo_detector/echo_detector.h b/webrtc/modules/audio_processing/echo_detector/echo_detector.h
index d9c8bd5d18799c23d277c3883126759a3566f20d..215932ed6667ed6f5b4eaff7d3e2fcf6faeadbe8 100644
--- a/webrtc/modules/audio_processing/echo_detector/echo_detector.h
+++ b/webrtc/modules/audio_processing/echo_detector/echo_detector.h
@@ -11,21 +11,54 @@
 #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 BufferRender(rtc::ArrayView<const float> render);
+
+  void Process(rtc::ArrayView<const float> nearend);
+
+  void Initialize();
+
+  float echo_likelihood() const { return echo_likelihood_; }
+
+ private:
+  static constexpr size_t kLookbackFrames = 650;
+  // TODO(ivoc): Verify the size of this buffer.
+  static constexpr size_t kRenderBufferSize = 30;
 
-  void BufferFarend(const rtc::ArrayView<const float>& farend);
+  // 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_ = CircularBuffer(kRenderBufferSize);
 
-  void Process(const rtc::ArrayView<const float>& nearend);
+  // 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>(kLookbackFrames);

[peah-webrtc, 2016/10/19 14:45:25]

Can't you just write std::vector<float> render_power_(kLookbackFrames) ? (you
may have to do it in the initializer list though).

[ivoc, 2016/10/20 14:04:35]

Ok, I'll do that in the initializer list.

+  std::vector<float> render_power_mean_ = std::vector<float>(kLookbackFrames);
+  std::vector<float> render_power_std_dev_ =
+      std::vector<float>(kLookbackFrames);
+  // Covariance estimates for different delay values.
+  std::vector<NormalizedCovarianceEstimator> covariance_ =
+      std::vector<NormalizedCovarianceEstimator>(kLookbackFrames);
+  // Index where next element should be inserted in all of the above circular
+  // buffers.
+  size_t next_insertion_index_ = 0;
 
-  void Initialize(int sample_rate_hz);
+  MeanVarianceEstimator render_variance_;
+  MeanVarianceEstimator capture_variance_;

[peah-webrtc, 2016/10/19 14:45:25]

Since you use render_variance_ and capture_variance_ both for computing the mean
and variances, these variable names are misleading I think. What about the names
render_statistics_ and capture_statistics_?

[ivoc, 2016/10/20 14:04:35]

Done.

+  // Current echo likelihood.
+  float echo_likelihood_ = 0.f;
 };
 
 }  // namespace webrtc