Adding fraction of filter divergence in AEC metrics.

webrtc/modules/audio_processing/utility/mean_calculator.cc

Index: webrtc/modules/audio_processing/utility/mean_calculator.cc
diff --git a/webrtc/modules/audio_processing/utility/mean_calculator.cc b/webrtc/modules/audio_processing/utility/mean_calculator.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0b3b46d8cb189d57e2e7540bc55ae5ee771ecacd
--- /dev/null
+++ b/webrtc/modules/audio_processing/utility/mean_calculator.cc
@@ -0,0 +1,74 @@
+/*
+ *  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.
+ */
+
+#include "webrtc/modules/audio_processing/utility/mean_calculator.h"
+
+namespace webrtc {
+
+MeanCalculator::MeanCalculator(size_t window_length)
+    : window_length_(window_length),
+      head_(0),
+      full_(false),
+      sum_(0.0f),
+      compensation_(0.0f) {
+  buffer_.resize(window_length);
+}
+
+// MeanCalculator::~MeanCalculator() = default;
+
+// Add one sample to the sequence.
+void MeanCalculator::AddSample(float sample) {
+  rtc::CritScope cs(&crit_);
+  if (full_)
+    KahanSum(-buffer_[head_]);
+  buffer_[head_] = sample;
+  KahanSum(buffer_[head_]);
+  head_ = (head_ + 1) % window_length_;
+  if (!full_ && head_ == 0)
+    full_ = true;
+}
+
+// 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> MeanCalculator::GetMean() const {
+  rtc::CritScope cs(&crit_);
+  if (full_) {
+    return rtc::Optional<float>(sum_ / window_length_);
+  } else {
+    return rtc::Optional<float>();
+  }
+}
+
+// Flush all samples added.
+void MeanCalculator::Clear() {
+  rtc::CritScope cs(&crit_);
+  head_ = 0;
+  full_ = false;
+  sum_ = 0.0f;
+  compensation_ = 0.0f;
+}
+
+// Determines if the window is full. This is a quick way of checking if the
+// mean is ready.
+bool MeanCalculator::IsWindowFull() const {
+  rtc::CritScope cs(&crit_);
+  return full_;
+}
+
+void MeanCalculator::KahanSum(float sample) {
+  rtc::CritScope cs(&crit_);
+  const float compensated_sample = sample - compensation_;
+  const float temp_sum = sum_ + compensated_sample;
+  compensation_ = (temp_sum - sum_) - compensated_sample;
+  sum_ = temp_sum;
+}
+
+}  // namespace webrtc