Added a new echo likelihood stat that reports the maximum value from a previous time period.

webrtc/modules/audio_processing/echo_detector/moving_max.cc

+/*
+ *  Copyright (c) 2017 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/echo_detector/moving_max.h"
+
+#include <algorithm>

[the sun, 2017/01/13 14:51:23]

Not needed

[ivoc, 2017/01/13 15:08:41]

Good point, removed.

+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+
+MovingMax::MovingMax(size_t window_size) : window_size_(window_size) {
+  RTC_DCHECK_GT(window_size, 0);
+}
+
+MovingMax::~MovingMax() {}
+
+void MovingMax::Update(float value) {
+  if (counter_ >= window_size_) {
+    max_value_ *= 0.99f;

[the sun, 2017/01/13 14:51:23]

Pull the constant out into a constexpr and add rationale or function used to
compute it.

[ivoc, 2017/01/13 15:08:41]

Done. This made me rethink the value and realize that it's too high.

+  }
+  if (value > max_value_) {
+    max_value_ = value;
+    counter_ = 0;
+  }
+  ++counter_;

[the sun, 2017/01/13 14:51:23]

Counter may wrap. If you really need the peak hold, don't increment once you've
reached window_size_.

[ivoc, 2017/01/13 15:08:41]

Done.

+}
+
+float MovingMax::max() const {
+  return max_value_;
+}
+
+void MovingMax::Clear() {
+  max_value_ = 0.f;
+  counter_ = 0;
+}
+
+}  // namespace webrtc