Adding fraction of filter divergence in AEC metrics.

webrtc/modules/audio_processing/utility/mean_calculator.h

Index: webrtc/modules/audio_processing/utility/mean_calculator.h
diff --git a/webrtc/modules/audio_processing/utility/mean_calculator.h b/webrtc/modules/audio_processing/utility/mean_calculator.h
new file mode 100644
index 0000000000000000000000000000000000000000..c9184ab211688ffec9ae3b4febfc9fd3af68f402
--- /dev/null
+++ b/webrtc/modules/audio_processing/utility/mean_calculator.h
@@ -0,0 +1,60 @@
+/*
+ *  Copyright 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_UTILITY_MEAN_CALCULATOR_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_UTILITY_MEAN_CALCULATOR_H_
+
+#include <stddef.h>
+#include <vector>
+
+#include "webrtc/base/criticalsection.h"
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/base/optional.h"
+
+namespace webrtc {
+
+// MeanCalculator calculates the mean of a sample sequence of a certain length.
+class MeanCalculator {
+ public:
+  explicit MeanCalculator(size_t window_length);
+
+  // Add one sample to the sequence.
+  void AddSample(float sample);
+
+  // Get the mean of the latest samples. Returns the mean if it is available,
+  // otherwise null, which happens when the added samples have not fully filled
+  // the window.
+  rtc::Optional<float> GetMean() const;
+
+  // Clear all samples added.
+  void Clear();
+
+  // Determines if the window is full. This is a quick way of checking if the
+  // mean is ready.
+  bool IsWindowFull() const;
+
+ private:
+  // Update |sum_| and |compensation_| using Kahan algorithm.
+  void KahanSum(float sample);
+
+  rtc::CriticalSection crit_;
+  size_t window_length_ GUARDED_BY(crit_);
+  std::vector<float> buffer_ GUARDED_BY(crit_);
+  size_t head_ GUARDED_BY(crit_);
+  bool full_ GUARDED_BY(crit_);
+  float sum_ GUARDED_BY(crit_);
+  float compensation_ GUARDED_BY(crit_);
+
+  RTC_DISALLOW_COPY_AND_ASSIGN(MeanCalculator);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_UTILITY_MEAN_CALCULATOR_H