• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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 
17 #ifndef ANDROID_FXLAB_DELAYLINEEFFECT_H
18 #define ANDROID_FXLAB_DELAYLINEEFFECT_H
19 
20 #include <functional>
21 
22 #include "utils/SineWave.h"
23 #include "utils/DelayLine.h"
24 
25 // Abstract class for implementing delay line based effects
26 // This functor retains state (it must be used sequentially)
27 // Effects are float, mono, 48000 hz
28 template <class iter_type>
29 class DelayLineEffect {
30 
31 public:
32     // delay > 0, depth in samples, mod is control signal
DelayLineEffect(float blend,float feedForward,float feedBack,int delay,int depth,std::function<float ()> && mod)33     DelayLineEffect(float blend, float feedForward, float feedBack, int delay, int depth, std::function<float()> &&mod) :
34         kBlend(blend),
35         kFeedForward(feedForward),
36         kFeedBack(feedBack),
37         kDelay(delay),
38         kDepth(depth),
39         mMod(mod) { }
40 
41 
operator()42     void operator () (typename std::iterator_traits<iter_type>::reference x) {
43         auto delayInput = x + kFeedBack * delayLine[kTap];
44         auto variableDelay = mMod() * kDepth + kTap;
45         int index = static_cast<int>(variableDelay);
46         auto fracComp = 1 - (variableDelay - index);
47         //linear
48         // auto interpolated = fracComp * delayLine[index] + (1 - fracComp) * delayLine[index + 1];
49         // all - pass
50         float interpolated = fracComp * delayLine[index] + delayLine[index + 1]
51                 - fracComp * prevInterpolated;
52 
53         prevInterpolated = interpolated;
54         delayLine.push(delayInput);
55         x = interpolated * kFeedForward + kBlend * delayInput;
56     }
operator()57     void operator () (iter_type begin, iter_type end) {
58         for (; begin != end; ++begin) {
59             operator()(*begin);
60         }
61     }
62 private:
63     // Weights
64     const float kBlend;
65     const float kFeedForward;
66     const float kFeedBack;
67     const int kDelay;
68     const int kDepth;
69     const int kTap = kDelay + kDepth;
70 
71     // Control function
72     const std::function<float()> mMod;
73 
74     // Memory
75     float prevInterpolated = 0; // for all pass interp
76     const size_t kDelayLineSize = kTap + kDepth + 1; // index one is immediate prev sample
77     DelayLine<typename std::iterator_traits<iter_type>::value_type> delayLine {kDelayLineSize};
78 };
79 #endif //ANDROID_FXLAB_DELAYLINEEFFECT_H
80