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

webrtc/modules/audio_processing/level_controller/down_sampler.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_DOWN_SAMPLER_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_LEVEL_CONTROLLER_DOWN_SAMPLER_H_
+
+#include "webrtc/base/array_view.h"
+#include "webrtc/base/constructormagic.h"
+#include "webrtc/modules/audio_processing/level_controller/biquad_filter.h"
+
+namespace webrtc {
+
+class ApmDataDumper;
+
+class DownSampler {
+ public:
+  explicit DownSampler(ApmDataDumper* data_dumper);
+  void Initialize(int sample_rate_hz);
+
+  void DownSample(rtc::ArrayView<const float> in, rtc::ArrayView<float> out);
+
+ private:
+  ApmDataDumper* data_dumper_;
+  int sample_rate_hz_;
+  int down_sampling_factor_;
+  BiQuadFilter low_pass_filter_;
+
+  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(DownSampler);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_LEVEL_CONTROLLER_DOWN_SAMPLER_H_