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diff --git a/media/libeffects/loudness/dsp/core/interpolator_linear.h b/media/libeffects/loudness/dsp/core/interpolator_linear.h
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+/*
+ * Copyright (C) 2013 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 LE_FX_ENGINE_DSP_CORE_INTERPOLATOR_LINEAR_H_
+#define LE_FX_ENGINE_DSP_CORE_INTERPOLATOR_LINEAR_H_
+
+#include <math.h>
+#include "dsp/core/interpolator_base.h"
+
+namespace le_fx {
+
+namespace sigmod {
+
+// Linear interpolation class.
+//
+// The main functionality of this class is provided by it's base-class, so
+// please refer to: InterpolatorBase
+//
+// Example:
+//  InterpolatorLinear<float> interp(x_data, y_data, data_length);
+//  for (int n = 0; n < data_length; n++) Y[n] = interp.Interpolate(X[n]);
+//
+template <typename T>
+class InterpolatorLinear: public InterpolatorBase<T, InterpolatorLinear<T> > {
+ public:
+  InterpolatorLinear() { }
+  ~InterpolatorLinear() { }
+
+ protected:
+  // Provides the main implementation of the linear interpolation algorithm.
+  // Assumes that: X[cached_index_] < x < X[cached_index_ + 1]
+  T MethodSpecificInterpolation(T x);
+
+  // Pre-compute internal state_ parameters.
+  bool SetInternalState();
+
+ private:
+  friend class InterpolatorBase<T, InterpolatorLinear<T> >;
+  typedef InterpolatorBase<T, InterpolatorLinear<T> > BaseClass;
+  using BaseClass::status_;
+  using BaseClass::cached_index_;
+  using BaseClass::x_data_;
+  using BaseClass::y_data_;
+  using BaseClass::data_length_;
+  using BaseClass::state_;
+
+  LE_FX_DISALLOW_COPY_AND_ASSIGN(InterpolatorLinear<T>);
+};
+
+template <typename T>
+inline T InterpolatorLinear<T>::MethodSpecificInterpolation(T x) {
+  T dX = x_data_[cached_index_ + 1] - x_data_[cached_index_];
+  T dY = y_data_[cached_index_ + 1] - y_data_[cached_index_];
+  T dx = x - x_data_[cached_index_];
+  return y_data_[cached_index_] + (dY * dx) / dX;
+}
+
+template <typename T>
+bool InterpolatorLinear<T>::SetInternalState() {
+  state_ = NULL;
+  return true;
+}
+
+}  // namespace sigmod
+
+}  // namespace le_fx
+
+#endif  // LE_FX_ENGINE_DSP_CORE_INTERPOLATOR_LINEAR_H_