1 /*
2 SCSP LFO handling
3
4 Part of the SCSP (YMF292-F) emulator package.
5 (not compiled directly, #included from scsp.c)
6
7 By ElSemi
8 MAME/M1 conversion and cleanup by R. Belmont
9 */
10
11 #define LFO_SHIFT 8
12
13 struct _LFO
14 {
15 unsigned short phase;
16 data32_t phase_step;
17 int *table;
18 int *scale;
19 };
20
21 #define LFIX(v) ((unsigned int) ((float) (1<<LFO_SHIFT)*(v)))
22
23 //Convert DB to multiply amplitude
24 #define DB(v) LFIX(pow(10.0,v/20.0))
25
26 //Convert cents to step increment
27 #define CENTS(v) LFIX(pow(2.0,v/1200.0))
28
29 static int PLFO_TRI[256],PLFO_SQR[256],PLFO_SAW[256],PLFO_NOI[256];
30 static int ALFO_TRI[256],ALFO_SQR[256],ALFO_SAW[256],ALFO_NOI[256];
31 static float LFOFreq[32]={0.17,0.19,0.23,0.27,0.34,0.39,0.45,0.55,0.68,0.78,0.92,1.10,1.39,1.60,1.87,2.27,
32 2.87,3.31,3.92,4.79,6.15,7.18,8.60,10.8,14.4,17.2,21.5,28.7,43.1,57.4,86.1,172.3};
33 static float ASCALE[8]={0.0,0.4,0.8,1.5,3.0,6.0,12.0,24.0};
34 static float PSCALE[8]={0.0,7.0,13.5,27.0,55.0,112.0,230.0,494};
35 static int PSCALES[8][256];
36 static int ASCALES[8][256];
37
LFO_Init(void)38 void LFO_Init(void)
39 {
40 int i,s;
41 for(i=0;i<256;++i)
42 {
43 int a,p;
44 // float TL;
45 //Saw
46 a=255-i;
47 if(i<128)
48 p=i;
49 else
50 p=255-i;
51 ALFO_SAW[i]=a;
52 PLFO_SAW[i]=p;
53
54 //Square
55 if(i<128)
56 {
57 a=255;
58 p=127;
59 }
60 else
61 {
62 a=0;
63 p=-128;
64 }
65 ALFO_SQR[i]=a;
66 PLFO_SQR[i]=p;
67
68 //Tri
69 if(i<128)
70 a=255-(i*2);
71 else
72 a=(i*2)-256;
73 if(i<64)
74 p=i*2;
75 else if(i<128)
76 p=255-i*2;
77 else if(i<192)
78 p=256-i*2;
79 else
80 p=i*2-511;
81 ALFO_TRI[i]=a;
82 PLFO_TRI[i]=p;
83
84 //noise
85 //a=lfo_noise[i];
86 a=rand()&0xff;
87 p=128-a;
88 ALFO_NOI[i]=a;
89 PLFO_NOI[i]=p;
90 }
91
92 for(s=0;s<8;++s)
93 {
94 float limit=PSCALE[s];
95 for(i=-128;i<128;++i)
96 {
97 PSCALES[s][i+128]=CENTS(((limit*(float) i)/128.0));
98 }
99 limit=-ASCALE[s];
100 for(i=0;i<256;++i)
101 {
102 ASCALES[s][i]=DB(((limit*(float) i)/256.0));
103 }
104 }
105 }
106
PLFO_Step(struct _LFO * LFO)107 static INLINE signed int PLFO_Step(struct _LFO *LFO)
108 {
109 int p;
110 LFO->phase+=LFO->phase_step;
111 #if LFO_SHIFT!=8
112 LFO->phase&=(1<<(LFO_SHIFT+8))-1;
113 #endif
114 p=LFO->table[LFO->phase>>LFO_SHIFT];
115 p=LFO->scale[p+128];
116 return p<<(SHIFT-LFO_SHIFT);
117 }
118
ALFO_Step(struct _LFO * LFO)119 static INLINE signed int ALFO_Step(struct _LFO *LFO)
120 {
121 int p;
122 LFO->phase+=LFO->phase_step;
123 #if LFO_SHIFT!=8
124 LFO->phase&=(1<<(LFO_SHIFT+8))-1;
125 #endif
126 p=LFO->table[LFO->phase>>LFO_SHIFT];
127 p=LFO->scale[p];
128 return p<<(SHIFT-LFO_SHIFT);
129 }
130
LFO_ComputeStep(struct _LFO * LFO,data32_t LFOF,data32_t LFOWS,data32_t LFOS,int ALFO)131 void LFO_ComputeStep(struct _LFO *LFO,data32_t LFOF,data32_t LFOWS,data32_t LFOS,int ALFO)
132 {
133 float step=(float) LFOFreq[LFOF]*256.0/(float)Machine->sample_rate;
134 LFO->phase_step=(unsigned int) ((float) (1<<LFO_SHIFT)*step);
135 if(ALFO)
136 {
137 switch(LFOWS)
138 {
139 case 0: LFO->table=ALFO_SAW; break;
140 case 1: LFO->table=ALFO_SQR; break;
141 case 2: LFO->table=ALFO_TRI; break;
142 case 3: LFO->table=ALFO_NOI; break;
143 }
144 LFO->scale=ASCALES[LFOS];
145 }
146 else
147 {
148 switch(LFOWS)
149 {
150 case 0: LFO->table=PLFO_SAW; break;
151 case 1: LFO->table=PLFO_SQR; break;
152 case 2: LFO->table=PLFO_TRI; break;
153 case 3: LFO->table=PLFO_NOI; break;
154 }
155 LFO->scale=PSCALES[LFOS];
156 }
157 }
158