1 // Copyright 2017 Emilie Gillet.
2 //
3 // Author: Emilie Gillet (emilie.o.gillet@gmail.com)
4 //
5 // Permission is hereby granted, free of charge, to any person obtaining a copy
6 // of this software and associated documentation files (the "Software"), to deal
7 // in the Software without restriction, including without limitation the rights
8 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9 // copies of the Software, and to permit persons to whom the Software is
10 // furnished to do so, subject to the following conditions:
11 //
12 // The above copyright notice and this permission notice shall be included in
13 // all copies or substantial portions of the Software.
14 //
15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
21 // THE SOFTWARE.
22 //
23 // See http://creativecommons.org/licenses/MIT/ for more information.
24 //
25 // -----------------------------------------------------------------------------
26 //
27 // Delay line, like the one in stmlib/dsp, but for int16_t, with
28 // built-in quantization and linear interpolation guard.
29 // Too specialized to be in a library...
30 
31 #ifndef STAGES_DELAY_LINE_16_BITS_H_
32 #define STAGES_DELAY_LINE_16_BITS_H_
33 
34 #include "stmlib/stmlib.h"
35 #include "stmlib/dsp/dsp.h"
36 
37 #include <algorithm>
38 
39 namespace stages {
40 
41 template<size_t max_delay>
42 class DelayLine16Bits {
43  public:
DelayLine16Bits()44   DelayLine16Bits() { }
~DelayLine16Bits()45   ~DelayLine16Bits() { }
46 
Init()47   void Init() {
48     Reset();
49   }
50 
Reset()51   void Reset() {
52     std::fill(&line_[0], &line_[max_delay], 0);
53     write_ptr_ = 0;
54   }
55 
Write(const float sample)56   inline void Write(const float sample) {
57     int32_t word = static_cast<int32_t>(sample * 32768.0f);
58     CONSTRAIN(word, -32768, 32767);
59     line_[write_ptr_] = word;
60     if (write_ptr_ == 0) {
61       line_[max_delay] = word;
62       write_ptr_ = max_delay - 1;
63     } else {
64       --write_ptr_;
65     }
66   }
67 
Read(float delay)68   inline const float Read(float delay) const {
69     MAKE_INTEGRAL_FRACTIONAL(delay)
70     size_t read_ptr = (write_ptr_ + delay_integral) % max_delay;
71     float a = static_cast<float>(line_[read_ptr]) / 32768.0f;
72     float b = static_cast<float>(line_[read_ptr + 1]) / 32768.0f;
73     return a + (b - a) * delay_fractional;
74   }
75 
76  private:
77   size_t write_ptr_;
78   int16_t line_[max_delay + 1];
79 
80   DISALLOW_COPY_AND_ASSIGN(DelayLine16Bits);
81 };
82 
83 }  // namespace stages
84 
85 #endif  // STAGES_DELAY_LINE_16_BITS_H_
86