Revert of Reland "Move smoothing filter to common audio".

webrtc/base/exp_filter.h

Index: webrtc/base/exp_filter.h
diff --git a/webrtc/base/exp_filter.h b/webrtc/base/exp_filter.h
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index 0000000000000000000000000000000000000000..174159b45f8291af985cef4552a8cca02411079e
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+++ b/webrtc/base/exp_filter.h
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+/*
+ *  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_