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-rw-r--r--src/emu/sound/scsplfo.c157
1 files changed, 157 insertions, 0 deletions
diff --git a/src/emu/sound/scsplfo.c b/src/emu/sound/scsplfo.c
new file mode 100644
index 00000000000..dc9dcca674c
--- /dev/null
+++ b/src/emu/sound/scsplfo.c
@@ -0,0 +1,157 @@
+/*
+ SCSP LFO handling
+
+ Part of the SCSP (YMF292-F) emulator package.
+ (not compiled directly, #included from scsp.c)
+
+ By ElSemi
+ MAME/M1 conversion and cleanup by R. Belmont
+*/
+
+#define LFO_SHIFT 8
+
+struct _LFO
+{
+ unsigned short phase;
+ UINT32 phase_step;
+ int *table;
+ int *scale;
+};
+
+#define LFIX(v) ((unsigned int) ((float) (1<<LFO_SHIFT)*(v)))
+
+//Convert DB to multiply amplitude
+#define DB(v) LFIX(pow(10.0,v/20.0))
+
+//Convert cents to step increment
+#define CENTS(v) LFIX(pow(2.0,v/1200.0))
+
+static int PLFO_TRI[256],PLFO_SQR[256],PLFO_SAW[256],PLFO_NOI[256];
+static int ALFO_TRI[256],ALFO_SQR[256],ALFO_SAW[256],ALFO_NOI[256];
+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,
+ 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};
+static float ASCALE[8]={0.0,0.4,0.8,1.5,3.0,6.0,12.0,24.0};
+static float PSCALE[8]={0.0,7.0,13.5,27.0,55.0,112.0,230.0,494};
+static int PSCALES[8][256];
+static int ASCALES[8][256];
+
+static void LFO_Init(void)
+{
+ int i,s;
+ for(i=0;i<256;++i)
+ {
+ int a,p;
+// float TL;
+ //Saw
+ a=255-i;
+ if(i<128)
+ p=i;
+ else
+ p=255-i;
+ ALFO_SAW[i]=a;
+ PLFO_SAW[i]=p;
+
+ //Square
+ if(i<128)
+ {
+ a=255;
+ p=127;
+ }
+ else
+ {
+ a=0;
+ p=-128;
+ }
+ ALFO_SQR[i]=a;
+ PLFO_SQR[i]=p;
+
+ //Tri
+ if(i<128)
+ a=255-(i*2);
+ else
+ a=(i*2)-256;
+ if(i<64)
+ p=i*2;
+ else if(i<128)
+ p=255-i*2;
+ else if(i<192)
+ p=256-i*2;
+ else
+ p=i*2-511;
+ ALFO_TRI[i]=a;
+ PLFO_TRI[i]=p;
+
+ //noise
+ //a=lfo_noise[i];
+ a=mame_rand(Machine)&0xff;
+ p=128-a;
+ ALFO_NOI[i]=a;
+ PLFO_NOI[i]=p;
+ }
+
+ for(s=0;s<8;++s)
+ {
+ float limit=PSCALE[s];
+ for(i=-128;i<128;++i)
+ {
+ PSCALES[s][i+128]=CENTS(((limit*(float) i)/128.0));
+ }
+ limit=-ASCALE[s];
+ for(i=0;i<256;++i)
+ {
+ ASCALES[s][i]=DB(((limit*(float) i)/256.0));
+ }
+ }
+}
+
+INLINE signed int PLFO_Step(struct _LFO *LFO)
+{
+ int p;
+ LFO->phase+=LFO->phase_step;
+#if LFO_SHIFT!=8
+ LFO->phase&=(1<<(LFO_SHIFT+8))-1;
+#endif
+ p=LFO->table[LFO->phase>>LFO_SHIFT];
+ p=LFO->scale[p+128];
+ return p<<(SHIFT-LFO_SHIFT);
+}
+
+INLINE signed int ALFO_Step(struct _LFO *LFO)
+{
+ int p;
+ LFO->phase+=LFO->phase_step;
+#if LFO_SHIFT!=8
+ LFO->phase&=(1<<(LFO_SHIFT+8))-1;
+#endif
+ p=LFO->table[LFO->phase>>LFO_SHIFT];
+ p=LFO->scale[p];
+ return p<<(SHIFT-LFO_SHIFT);
+}
+
+static void LFO_ComputeStep(struct _LFO *LFO,UINT32 LFOF,UINT32 LFOWS,UINT32 LFOS,int ALFO)
+{
+ float step=(float) LFOFreq[LFOF]*256.0/(float)44100;
+ LFO->phase_step=(unsigned int) ((float) (1<<LFO_SHIFT)*step);
+ if(ALFO)
+ {
+ switch(LFOWS)
+ {
+ case 0: LFO->table=ALFO_SAW; break;
+ case 1: LFO->table=ALFO_SQR; break;
+ case 2: LFO->table=ALFO_TRI; break;
+ case 3: LFO->table=ALFO_NOI; break;
+ }
+ LFO->scale=ASCALES[LFOS];
+ }
+ else
+ {
+ switch(LFOWS)
+ {
+ case 0: LFO->table=PLFO_SAW; break;
+ case 1: LFO->table=PLFO_SQR; break;
+ case 2: LFO->table=PLFO_TRI; break;
+ case 3: LFO->table=PLFO_NOI; break;
+ }
+ LFO->scale=PSCALES[LFOS];
+ }
+}