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

webrtc/modules/audio_processing/level_controller/noise_level_estimator.h

+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_MODULES_AUDIO_PROCESSING_LEVEL_CONTROLLER_NOISE_LEVEL_ESTIMATOR_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_LEVEL_CONTROLLER_NOISE_LEVEL_ESTIMATOR_H_
+
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/modules/audio_processing/level_controller/signal_classifier.h"
+
+namespace webrtc {
+
+class NoiseLevelEstimator {
+ public:
+  NoiseLevelEstimator();
+  ~NoiseLevelEstimator();
+  void Initialize(int sample_rate_hz);
+  float Analyze(SignalClassifier::SignalType signal_type, float frame_energy);
+
+ private:
+  float min_noise_energy_ = 0.f;
+  bool first_update_;
+  float noise_energy_;
+  int noise_energy_hold_counter_;
+
+  RTC_DISALLOW_COPY_AND_ASSIGN(NoiseLevelEstimator);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_LEVEL_CONTROLLER_NOISE_LEVEL_ESTIMATOR_H_