Adding BlockMeanCalculator for AEC.

webrtc/modules/audio_processing/utility/mean_calculator.cc

+/*
+ *  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 {
+
+BlockMeanCalculator::BlockMeanCalculator(size_t block_length)
+    : block_length_(block_length),
+      count_(0),
+      sum_(0.0),
+      mean_(0.0) {
+}
+
+void BlockMeanCalculator::Reset() {
+  Clear();
+  mean_ = 0.0;
+}
+
+void BlockMeanCalculator::AddSample(float sample) {
+  sum_ += sample;
+  ++count_;
+  if (count_ == block_length_) {
+    mean_ = sum_ / block_length_;
+    Clear();
+  }
+}
+
+size_t BlockMeanCalculator::SamplesSinceLastUpdate() const {
+  return count_;
+}
+
+float BlockMeanCalculator::GetLatestMean() const {
+  return mean_;
+}
+
+// Flush all samples added.
+void BlockMeanCalculator::Clear() {
+  count_ = 0;
+  sum_ = 0.0;
+}
+
+}  // namespace webrtc