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

webrtc/base/exp_filter.cc

Index: webrtc/base/exp_filter.cc
diff --git a/webrtc/base/exp_filter.cc b/webrtc/base/exp_filter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9529480061aee23c62bcb28c94d7f63bcf6864b2
--- /dev/null
+++ b/webrtc/base/exp_filter.cc
@@ -0,0 +1,43 @@
+/*
+ *  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.
+ */
+
+#include "webrtc/base/exp_filter.h"
+
+#include <math.h>
+
+namespace rtc {
+
+const float ExpFilter::kValueUndefined = -1.0f;
+
+void ExpFilter::Reset(float alpha) {
+  alpha_ = alpha;
+  filtered_ = kValueUndefined;
+}
+
+float ExpFilter::Apply(float exp, float sample) {
+  if (filtered_ == kValueUndefined) {
+    // Initialize filtered value.
+    filtered_ = sample;
+  } else if (exp == 1.0) {
+    filtered_ = alpha_ * filtered_ + (1 - alpha_) * sample;
+  } else {
+    float alpha = pow(alpha_, exp);
+    filtered_ = alpha * filtered_ + (1 - alpha) * sample;
+  }
+  if (max_ != kValueUndefined && filtered_ > max_) {
+    filtered_ = max_;
+  }
+  return filtered_;
+}
+
+void ExpFilter::UpdateBase(float alpha) {
+  alpha_ = alpha;
+}
+}  // namespace rtc