/[svn]/linuxsampler/trunk/src/engines/common/LFOTriangleIntMath.h
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Contents of /linuxsampler/trunk/src/engines/common/LFOTriangleIntMath.h

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Revision 720 - (show annotations) (download) (as text)
Sun Jul 24 18:22:56 2005 UTC (18 years, 8 months ago) by senkov
File MIME type: text/x-c++hdr
File size: 5784 byte(s)
Added a variation of LFOTriangleIntMath using abs()

1 /***************************************************************************
2 * *
3 * Copyright (C) 2005 Christian Schoenebeck *
4 * *
5 * This library is free software; you can redistribute it and/or modify *
6 * it under the terms of the GNU General Public License as published by *
7 * the Free Software Foundation; either version 2 of the License, or *
8 * (at your option) any later version. *
9 * *
10 * This library is distributed in the hope that it will be useful, *
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of *
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
13 * GNU General Public License for more details. *
14 * *
15 * You should have received a copy of the GNU General Public License *
16 * along with this library; if not, write to the Free Software *
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, *
18 * MA 02111-1307 USA *
19 ***************************************************************************/
20
21 #ifndef __LS_LFOTRIANGLEINTMATH_H__
22 #define __LS_LFOTRIANGLEINTMATH_H__
23
24 #include "LFOBase.h"
25
26 namespace LinuxSampler {
27
28 /** @brief Triangle LFO (int math implementation)
29 *
30 * This is a triangle Low Frequency Oscillator which uses pure integer
31 * math (without branches) to synthesize the triangular wave.
32 */
33 template<range_type_t RANGE>
34 class LFOTriangleIntMath : public LFOBase<RANGE> {
35 public:
36
37 /**
38 * Constructor
39 *
40 * @param Max - maximum value of the output levels
41 */
42 LFOTriangleIntMath(float Max) : LFOBase<RANGE>::LFOBase(Max) {
43 }
44
45 /**
46 * Calculates exactly one sample point of the LFO wave.
47 *
48 * @returns next LFO level
49 */
50 inline float render() {
51 const int signshifts = (sizeof(int) * 8) - 1;
52 iLevel += c;
53 const int iSign = (iLevel >> signshifts) | 1;
54 if (RANGE == range_unsigned)
55 return normalizer * (float) (iSign * iLevel);
56 else /* signed range */
57 return normalizer * (float) (iSign * iLevel) + offset;
58 }
59
60 /**
61 * Update LFO depth with a new external controller value.
62 *
63 * @param ExtControlValue - new external controller value
64 */
65 inline void update(const uint16_t& ExtControlValue) {
66 const unsigned int intLimit = (unsigned int) -1; // all 0xFFFF...
67 const float max = this->InternalDepth + ExtControlValue * this->ExtControlDepthCoeff;
68 if (RANGE == range_unsigned) {
69 normalizer = max / (float) intLimit;
70 } else { // signed range
71 normalizer = max / (float) intLimit * 4.0f;
72 offset = -max;
73 }
74 }
75
76 /**
77 * Will be called by the voice when the key / voice was triggered.
78 *
79 * @param Frequency - frequency of the oscillator in Hz
80 * @param StartLevel - on which level the wave should start
81 * @param InternalDepth - firm, internal oscillator amplitude
82 * @param ExtControlDepth - defines how strong the external MIDI
83 * controller has influence on the
84 * oscillator amplitude
85 * @param FlipPhase - inverts the oscillator wave against
86 * a horizontal axis
87 * @param SampleRate - current sample rate of the engines
88 * audio output signal
89 */
90 void trigger(float Frequency, start_level_t StartLevel, uint16_t InternalDepth, uint16_t ExtControlDepth, bool FlipPhase, unsigned int SampleRate) {
91 this->InternalDepth = (InternalDepth / 1200.0f) * this->Max;
92 this->ExtControlDepthCoeff = (((float) ExtControlDepth / 1200.0f) / 127.0f) * this->Max;
93 if (RANGE == range_unsigned) {
94 this->InternalDepth *= 2.0f;
95 this->ExtControlDepthCoeff *= 2.0f;
96 }
97
98 const unsigned int intLimit = (unsigned int) -1; // all 0xFFFF...
99 const float r = Frequency / (float) SampleRate; // frequency alteration quotient
100 c = (int) (intLimit * r);
101
102 switch (StartLevel) {
103 case start_level_max:
104 iLevel = (FlipPhase) ? 0 : intLimit >> 1;
105 break;
106 case start_level_mid:
107 if (FlipPhase) c = -c; // wave should go down
108 iLevel = intLimit >> 2;
109 break;
110 case start_level_min:
111 iLevel = (FlipPhase) ? intLimit >> 1 : 0;
112 break;
113 }
114 }
115
116 protected:
117 int iLevel;
118 int c;
119 float offset; ///< only needed for signed range
120 float normalizer;
121 };
122
123 } // namespace LinuxSampler
124
125 #endif // __LS_LFOTRIANGLEINTMATH_H__

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