| /* |
| * Copyright (C) 2010 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_SECOND_ORDER_LOW_PASS_FILTER_H |
| #define ANDROID_SECOND_ORDER_LOW_PASS_FILTER_H |
| |
| #include <stdint.h> |
| #include <sys/types.h> |
| |
| // --------------------------------------------------------------------------- |
| |
| namespace android { |
| // --------------------------------------------------------------------------- |
| |
| template<typename T> |
| class BiquadFilter; |
| |
| /* |
| * State of a 2nd order low-pass IIR filter |
| */ |
| class SecondOrderLowPassFilter { |
| template<typename T> |
| friend class BiquadFilter; |
| float iQ, fc; |
| float K, iD; |
| float a0, a1; |
| float b1, b2; |
| public: |
| SecondOrderLowPassFilter(float Q, float fc); |
| void setSamplingPeriod(float dT); |
| }; |
| |
| /* |
| * Implements a Biquad IIR filter |
| */ |
| template<typename T> |
| class BiquadFilter { |
| T x1, x2; |
| T y1, y2; |
| const SecondOrderLowPassFilter& s; |
| public: |
| BiquadFilter(const SecondOrderLowPassFilter& s); |
| T init(const T& in); |
| T operator()(const T& in); |
| }; |
| |
| /* |
| * Two cascaded biquad IIR filters |
| * (4-poles IIR) |
| */ |
| template<typename T> |
| class CascadedBiquadFilter { |
| BiquadFilter<T> mA; |
| BiquadFilter<T> mB; |
| public: |
| CascadedBiquadFilter(const SecondOrderLowPassFilter& s); |
| T init(const T& in); |
| T operator()(const T& in); |
| }; |
| |
| // --------------------------------------------------------------------------- |
| }; // namespace android |
| |
| #endif // ANDROID_SECOND_ORDER_LOW_PASS_FILTER_H |