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diff --git a/media/mca/filterfw/native/core/statistics.h b/media/mca/filterfw/native/core/statistics.h
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+/*
+ * Copyright (C) 2011 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_FILTERFW_CORE_STATISTICS_H
+#define ANDROID_FILTERFW_CORE_STATISTICS_H
+
+namespace android {
+namespace filterfw {
+
+// An incrementally-constructed Normal distribution.
+class IncrementalGaussian {
+ public:
+  IncrementalGaussian();
+
+  void Add(float value);
+
+  float NumSamples() const { return n_; }
+  float Mean() const { return mean_; }
+  float Var() const { return var_; }
+  float Std() const;
+  float Pdf(float value) const;
+
+ private:
+  int n_;
+  float sum_x_;
+  float sum_x2_;
+  float mean_;
+  float var_;
+  float exp_denom_;
+  float pdf_denom_;
+};
+
+// Discrete-time implementation of a simple RC low-pass filter:
+// exponentially-weighted moving average.
+class RCFilter {
+ public:
+  explicit RCFilter(float gain)
+      : gain_(gain), n_(0), value_(0.0f) {}
+
+  void Add(float measurement) {
+    value_ = n_++ ? gain_ * measurement + (1.0f - gain_) * value_ : measurement;
+  }
+
+  void Reset() { n_ = 0; }
+
+  int NumMeasurements() const { return n_; }
+  float Output() const { return value_; }
+
+ private:
+  float gain_;
+  int n_;
+  float value_;
+};
+
+} // namespace filterfw
+} // namespace android
+
+#endif  // ANDROID_FILTERFW_CORE_STATISTICS_H