1 /* 2 * Copyright 2019 Google LLC 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * https://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 #ifndef ANDROID_FXLAB_COMBFILTER_H 17 #define ANDROID_FXLAB_COMBFILTER_H 18 19 #include "utils/DelayLine.h" 20 21 template <class iter_type> 22 class CombFilter { 23 24 public: 25 // delay > 0 in samples CombFilter(float blend,float feedForward,float feedBack,int delay)26 CombFilter(float blend, float feedForward, float feedBack, int delay) : 27 kBlend(blend), 28 kFeedForward(feedForward), 29 kFeedBack(feedBack), 30 kDelay(static_cast<size_t>(delay)) {} 31 32 operator()33 void operator () (typename std::iterator_traits<iter_type>::reference x) { 34 auto delayOutput = delayLine[kDelay]; 35 auto delayInput = x + kFeedBack * delayOutput; 36 delayLine.push(delayInput); 37 x = delayInput * kBlend + delayOutput * kFeedForward; 38 } operator()39 void operator () (iter_type begin, iter_type end) { 40 for (; begin != end; ++begin) { 41 operator()(*begin); 42 } 43 } 44 private: 45 // Weights 46 const float kBlend; 47 const float kFeedForward; 48 const float kFeedBack; 49 const size_t kDelay; 50 51 DelayLine<typename std::iterator_traits<iter_type>::value_type> delayLine {kDelay + 1}; 52 }; 53 #endif //ANDROID_FXLAB_COMBFILTER_H 54