| /* |
| * Copyright 2015 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 ANALYZER_PEAK_DETECTOR_H |
| #define ANALYZER_PEAK_DETECTOR_H |
| |
| #include <math.h> |
| |
| /** |
| * Measure a peak envelope by rising with the peaks, |
| * and decaying exponentially after each peak. |
| * The absolute value of the input signal is used. |
| */ |
| class PeakDetector { |
| public: |
| |
| void reset() { |
| mLevel = 0.0; |
| } |
| |
| double process(double input) { |
| mLevel *= mDecay; // exponential decay |
| input = fabs(input); |
| // never fall below the input signal |
| if (input > mLevel) { |
| mLevel = input; |
| } |
| return mLevel; |
| } |
| |
| double getLevel() const { |
| return mLevel; |
| } |
| |
| double getDecay() const { |
| return mDecay; |
| } |
| |
| /** |
| * Multiply the level by this amount on every iteration. |
| * This provides an exponential decay curve. |
| * A value just under 1.0 is best, for example, 0.99; |
| * @param decay scale level for each input |
| */ |
| void setDecay(double decay) { |
| mDecay = decay; |
| } |
| |
| private: |
| static constexpr double kDefaultDecay = 0.99f; |
| |
| double mLevel = 0.0; |
| double mDecay = kDefaultDecay; |
| }; |
| #endif //ANALYZER_PEAK_DETECTOR_H |