Move smoothing filter to common audio and exp_filter to base/analytics.

webrtc/base/exp_filter.h

-/*
- *  Copyright (c) 2011 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_BASE_EXP_FILTER_H_
-#define WEBRTC_BASE_EXP_FILTER_H_
-
-namespace rtc {
-
-// This class can be used, for example, for smoothing the result of bandwidth
-// estimation and packet loss estimation.
-
-class ExpFilter {
- public:
-  static const float kValueUndefined;
-
-  explicit ExpFilter(float alpha, float max = kValueUndefined)
-      : max_(max) {
-    Reset(alpha);
-  }
-
-  // Resets the filter to its initial state, and resets filter factor base to
-  // the given value |alpha|.
-  void Reset(float alpha);
-
-  // Applies the filter with a given exponent on the provided sample:
-  // y(k) = min(alpha_^ exp * y(k-1) + (1 - alpha_^ exp) * sample, max_).
-  float Apply(float exp, float sample);
-
-  // Returns current filtered value.
-  float filtered() const { return filtered_; }
-
-  // Changes the filter factor base to the given value |alpha|.
-  void UpdateBase(float alpha);
-
- private:
-  float alpha_;  // Filter factor base.
-  float filtered_;  // Current filter output.
-  const float max_;
-};
-}  // namespace rtc
-
-#endif  // WEBRTC_BASE_EXP_FILTER_H_