New module for the adaptive level controlling functionality in the audio processing module

webrtc/modules/audio_processing/level_controller/saturating_gain_estimator.cc

+/*
+ *  Copyright (c) 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/level_controller/saturating_gain_estimator.h"
+
+#include <math.h>
+#include <algorithm>
+
+#include "webrtc/modules/audio_processing/level_controller/lc_constants.h"
+#include "webrtc/modules/audio_processing/logging/apm_data_dumper.h"
+
+namespace webrtc {
+
+SaturatingGainEstimator::SaturatingGainEstimator() {
+  Initialize();
+}
+
+SaturatingGainEstimator::~SaturatingGainEstimator() {}
+
+void SaturatingGainEstimator::Initialize() {
+  saturating_gain_ = 1000.f;
+  saturating_gain_hold_counter_ = 0;
+}
+
+void SaturatingGainEstimator::Update(float gain, int num_saturations) {
+  bool too_many_saturations = (num_saturations > 2);
+
+  if (too_many_saturations) {
+    saturating_gain_ = 0.95f * gain;
+    saturating_gain_hold_counter_ = 1000;
+  } else {
+    saturating_gain_hold_counter_ =
+        std::max(0, saturating_gain_hold_counter_ - 1);
+    if (saturating_gain_hold_counter_ == 0) {
+      saturating_gain_ *= 1.001f;
+      saturating_gain_ = std::min(kMaxLcGain, saturating_gain_);
+    }
+  }
+}
+
+}  // namespace webrtc