1 // Copyright 2015 Olivier Gillet.
2 //
3 // Author: Olivier Gillet (ol.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 // Envelope / centroid follower for FM voice.
28 
29 #ifndef RINGS_DSP_FOLLOWER_H_
30 #define RINGS_DSP_FOLLOWER_H_
31 
32 #include "stmlib/stmlib.h"
33 
34 #include <algorithm>
35 
36 #include "stmlib/dsp/dsp.h"
37 #include "stmlib/dsp/filter.h"
38 
39 namespace rings {
40 
41 using namespace stmlib;
42 
43 class Follower {
44  public:
Follower()45   Follower() { }
~Follower()46   ~Follower() { }
47 
Init(float low,float low_mid,float mid_high)48   void Init(float low, float low_mid, float mid_high) {
49     low_mid_filter_.Init();
50     mid_high_filter_.Init();
51 
52     low_mid_filter_.set_f_q<FREQUENCY_DIRTY>(low_mid, 0.5f);
53     mid_high_filter_.set_f_q<FREQUENCY_DIRTY>(mid_high, 0.5f);
54     attack_[0] = low_mid;
55     decay_[0] = Sqrt(low_mid * low);
56 
57     attack_[1] = Sqrt(low_mid * mid_high);
58     decay_[1] = low_mid;
59 
60     attack_[2] = Sqrt(mid_high * 0.5f);
61     decay_[2] = Sqrt(mid_high * low_mid);
62 
63     std::fill(&detector_[0], &detector_[3], 0.0f);
64 
65     centroid_ = 0.0f;
66   }
67 
Process(float sample,float * envelope,float * centroid)68   void Process(
69       float sample,
70       float* envelope,
71       float* centroid) {
72     float bands[3] = { 0.0f, 0.0f, 0.0f };
73 
74     bands[2] = mid_high_filter_.Process<FILTER_MODE_HIGH_PASS>(sample);
75     bands[1] = low_mid_filter_.Process<FILTER_MODE_HIGH_PASS>(
76         mid_high_filter_.lp());
77     bands[0] = low_mid_filter_.lp();
78 
79     float weighted = 0.0f;
80     float total = 0.0f;
81     float frequency = 0.0f;
82     for (int32_t i = 0; i < 3; ++i) {
83       SLOPE(detector_[i], fabs(bands[i]), attack_[i], decay_[i]);
84       weighted += detector_[i] * frequency;
85       total += detector_[i];
86       frequency += 0.5f;
87     }
88 
89     float error = weighted / (total + 0.001f) - centroid_;
90     float coefficient = error > 0.0f ? 0.05f : 0.001f;
91     centroid_ += error * coefficient;
92 
93     *envelope = total;
94     *centroid = centroid_;
95   }
96 
97  private:
98   NaiveSvf low_mid_filter_;
99   NaiveSvf mid_high_filter_;
100 
101   float attack_[3];
102   float decay_[3];
103   float detector_[3];
104 
105   float centroid_;
106 
107   DISALLOW_COPY_AND_ASSIGN(Follower);
108 };
109 
110 }  // namespace rings
111 
112 #endif  // RINGS_DSP_FOLLOWER_H_
113