|
andrewm@0
|
1 /*
|
|
andrewm@0
|
2 * FeedbackOscillator.cpp
|
|
andrewm@0
|
3 *
|
|
andrewm@0
|
4 * Recursive phase-shift oscillator implemented
|
|
andrewm@0
|
5 * on the matrix
|
|
andrewm@0
|
6 *
|
|
andrewm@0
|
7 * Andrew McPherson 2014
|
|
andrewm@0
|
8 */
|
|
andrewm@0
|
9
|
|
andrewm@0
|
10 #include "FeedbackOscillator.h"
|
|
andrewm@0
|
11 #include <cstdlib>
|
|
andrewm@0
|
12 #include <cmath>
|
|
andrewm@0
|
13
|
|
andrewm@0
|
14 #define COEFF_B0 0
|
|
andrewm@0
|
15 #define COEFF_B1 1
|
|
andrewm@0
|
16 #define COEFF_A1 2
|
|
andrewm@0
|
17
|
|
andrewm@0
|
18 FeedbackOscillator::FeedbackOscillator()
|
|
andrewm@0
|
19 : wavetable1(0), wavetable2(0)
|
|
andrewm@0
|
20 {
|
|
andrewm@0
|
21
|
|
andrewm@0
|
22 }
|
|
andrewm@0
|
23
|
|
andrewm@0
|
24 FeedbackOscillator::~FeedbackOscillator() {
|
|
andrewm@0
|
25 if(wavetable1 != 0)
|
|
andrewm@0
|
26 free(wavetable1);
|
|
andrewm@0
|
27 if(wavetable2 != 0)
|
|
andrewm@0
|
28 free(wavetable2);
|
|
andrewm@0
|
29
|
|
andrewm@0
|
30 }
|
|
andrewm@0
|
31
|
|
andrewm@0
|
32 // Initialise the settings for the feedback oscillator
|
|
andrewm@0
|
33 void FeedbackOscillator::initialise(int maxTableSize, float hpfCutoffFrequency, float matrixSampleRate) {
|
|
andrewm@0
|
34 wavetableMaxLength = maxTableSize;
|
|
andrewm@0
|
35 if(wavetable1 != 0)
|
|
andrewm@0
|
36 free(wavetable1);
|
|
andrewm@0
|
37 if(wavetable2 != 0)
|
|
andrewm@0
|
38 free(wavetable2);
|
|
andrewm@0
|
39
|
|
andrewm@0
|
40 wavetable1 = (float *)malloc(maxTableSize * sizeof(float));
|
|
andrewm@0
|
41 wavetable2 = (float *)malloc(maxTableSize * sizeof(float));
|
|
andrewm@0
|
42
|
|
andrewm@0
|
43 float omega = tan(M_PI * hpfCutoffFrequency / matrixSampleRate);
|
|
andrewm@0
|
44 float n = 1.0f / (1.0f + omega);
|
|
andrewm@0
|
45
|
|
andrewm@0
|
46 coeffs[COEFF_A1] = (omega - 1.0f) * n;
|
|
andrewm@0
|
47 coeffs[COEFF_B0] = n;
|
|
andrewm@0
|
48 coeffs[COEFF_B1] = -n;
|
|
andrewm@0
|
49
|
|
andrewm@0
|
50 for(int n = 0; n < maxTableSize; n++)
|
|
andrewm@0
|
51 wavetable1[n] = wavetable2[n] = 0;
|
|
andrewm@0
|
52
|
|
andrewm@0
|
53 wavetableRead = wavetable1;
|
|
andrewm@0
|
54 wavetableWrite = wavetable2;
|
|
andrewm@0
|
55 wavetableWritePointer = 0;
|
|
andrewm@0
|
56 sampleCount = lastTriggerCount = 0;
|
|
andrewm@0
|
57 }
|
|
andrewm@0
|
58
|
|
andrewm@0
|
59 // Process one sample and store the output value
|
|
andrewm@0
|
60 // Returns true if the wavetable needs rendering
|
|
andrewm@50
|
61 int FeedbackOscillator::process(float input, float *output) {
|
|
andrewm@50
|
62 float outFloat = coeffs[COEFF_B0] * input + coeffs[COEFF_B1] * lastInput - coeffs[COEFF_A1] * lastOutput;
|
|
andrewm@0
|
63 int requestRenderLength = 0;
|
|
andrewm@0
|
64
|
|
andrewm@50
|
65 *output = outFloat;
|
|
andrewm@0
|
66
|
|
andrewm@0
|
67 if(canTrigger && outFloat > 0 && lastOutput <= 0) {
|
|
andrewm@0
|
68 triggered = true;
|
|
andrewm@0
|
69 requestRenderLength = wavetableWritePointer; // How many samples stored thus far?
|
|
andrewm@0
|
70 if(requestRenderLength < 4)
|
|
andrewm@0
|
71 requestRenderLength = 0; // Ignore anything with fewer than 4 points
|
|
andrewm@0
|
72
|
|
andrewm@0
|
73 lastTriggerCount = sampleCount;
|
|
andrewm@0
|
74 canTrigger = false;
|
|
andrewm@0
|
75 wavetableWritePointer = 0;
|
|
andrewm@0
|
76
|
|
andrewm@0
|
77 // Swap buffers
|
|
andrewm@0
|
78 float *temp = wavetableWrite;
|
|
andrewm@0
|
79 wavetableWrite = wavetableRead;
|
|
andrewm@0
|
80 wavetableRead = temp;
|
|
andrewm@0
|
81 }
|
|
andrewm@0
|
82
|
|
andrewm@0
|
83 if(triggered) {
|
|
andrewm@0
|
84 wavetableWrite[wavetableWritePointer] = outFloat;
|
|
andrewm@0
|
85 if(++wavetableWritePointer >= wavetableMaxLength) {
|
|
andrewm@0
|
86 triggered = false;
|
|
andrewm@0
|
87 wavetableWritePointer = 0;
|
|
andrewm@0
|
88 }
|
|
andrewm@0
|
89 }
|
|
andrewm@0
|
90
|
|
andrewm@0
|
91 if(sampleCount - lastTriggerCount > 40)
|
|
andrewm@0
|
92 canTrigger = true;
|
|
andrewm@0
|
93
|
|
andrewm@0
|
94 sampleCount++;
|
|
andrewm@0
|
95
|
|
andrewm@0
|
96 lastOutput = outFloat;
|
|
andrewm@50
|
97 lastInput = input;
|
|
andrewm@0
|
98
|
|
andrewm@0
|
99 return requestRenderLength;
|
|
andrewm@0
|
100 }
|
