implement #102 MSX-MUSIC YM2413 emulation using NukeYKT's OPLL

EMULib/EMULib.h

@@ -54,13 +54,10 @@
 /** Sound ****************************************************/
 // fMSX emulates:
 // - AY8910 PSG: 3 melodic + 3 noise
-// - YM2413 OPLL: 9 FM sound channels, or 6 music + 5 drums
+// - YM2413 OPLL: 9 FM sound channels (or 6 music + 5 drums, but fMSX does not emulate drums)
 // - SCC: 5 wave channels
-// fMSX does not support FM-PAC drums nor instruments (uses triangle waves), and plays either FM-PAC or SCC.
-// Thus: either 15, 12 or 11 channels active at once.
-#define SND_CHANNELS    16     /* Number of sound channels   */
-#define SND_BITS        8
-#define SND_BUFSIZE     (1<<SND_BITS)
+// Thus: max 20 channels active at once.
+#define SND_CHANNELS    20     /* Number of sound channels   */
 
 #ifdef __cplusplus
 extern "C" {

EMULib/Sound.c

@@ -11,6 +11,9 @@
 /**     changes to this file.                               **/
 /*************************************************************/
 #include "Sound.h"
+#include "MSX.h"
+
+#include "../NukeYKT/WrapNukeYKT.h"
 
 #include <string.h>
 
@@ -52,6 +55,10 @@ static struct
   { SND_MELODIC,0,0,0,0,0,0,0 },
   { SND_MELODIC,0,0,0,0,0,0,0 },
   { SND_MELODIC,0,0,0,0,0,0,0 },
+  { SND_MELODIC,0,0,0,0,0,0,0 },
+  { SND_MELODIC,0,0,0,0,0,0,0 },
+  { SND_MELODIC,0,0,0,0,0,0,0 },
+  { SND_MELODIC,0,0,0,0,0,0,0 },
   { SND_MELODIC,0,0,0,0,0,0,0 }
 };
 
@@ -63,6 +70,9 @@ static int NoiseXor   = 14;       /* NoiseGen bit used for XORing     */
 int MasterSwitch      = 0xFFFF;   /* Switches to turn channels on/off */
 int MasterVolume      = 192;      /* Master volume                    */
 
+extern YM2413_NukeYKT OPLL_NukeYKT;
+extern YM2413 OPLL;
+
 /** Sound() **************************************************/
 /** Generate sound of given frequency (Hz) and volume       **/
 /** (0..255) via given channel. Setting Freq=0 or Volume=0  **/
@@ -358,24 +368,54 @@ static unsigned int PlayAudio(int *Wave,unsigned int Samples)
 unsigned int RenderAndPlayAudio(unsigned int Samples)
 {
   int Buf[256];
-  unsigned int J,I;
+  unsigned int J,I,K,idx;
+  float ResampleRate,R,frac;
 
   /* Exit if wave sound not initialized */
   if(SndRate<8192) return(0);
 
+  /* silence fMSX FM-PAC if NukeYKT is active */
+  if(OPTION(MSX_NUKEYKT))
+  {
+    for(K=0;K<YM2413_CHANNELS;K++)
+      Sound(K+OPLL.First,0,0);
+    OPLL.Changed=0;
+  }
+
   J       = AUDIO_BUFFER_SIZE;
   Samples = Samples<J? Samples:J;
-
+  ResampleRate = (float)OPLL_NukeYKT.sample_write_index/Samples;
+
   /* Render and play sound */
-  for(I=0;I<Samples;I+=J)
+  for(I=0,R=0.0;I<Samples;I+=J)
   {
     J = Samples-I;
     J = J<sizeof(Buf)/sizeof(Buf[0])? J:sizeof(Buf)/sizeof(Buf[0]);
     memset(Buf,0,J*sizeof(Buf[0]));
     RenderAudio(Buf,J);
+
+    /*
+     * Merge in YM2413 NukeYKT using simplistic linear resampler.
+     * Max input range slightly outside [-1024,+1023], output [-32768,+32767] or 16b signed after amplification by 32.
+     * BUT matching it to PSG volume (by hand) requires a further amplification by 4.
+     * That's still a factor 4-8 less loud than fMSX's FM-PAC volume.
+     */
+    if(OPTION(MSX_NUKEYKT))
+      for(K=0;K<J;K++,R+=ResampleRate)
+      {
+        idx=(unsigned int)R;
+        frac=R-idx;
+        Buf[K]+=(int)(.5+128.0*(OPLL_NukeYKT.samples[idx]*(1.0-frac) + OPLL_NukeYKT.samples[idx+1]*frac));
+      }
+
     if(PlayAudio(Buf,J)<J) { I+=J;break; }
   }
 
+  // move last sample to beginning (for linear resampler) and signal a buffer refill
+  if (OPLL_NukeYKT.sample_write_index>0)
+    OPLL_NukeYKT.samples[0]=OPLL_NukeYKT.samples[OPLL_NukeYKT.sample_write_index-1];
+  OPLL_NukeYKT.sample_write_index=1;
+
   /* Return number of samples rendered */
   return I;
 }

Makefile

@@ -561,6 +561,7 @@ CORE_DIR	= .
 EMULIB	= $(CORE_DIR)/EMULib
 FMSXDIR = $(CORE_DIR)/fMSX
 LIBZ80	= $(CORE_DIR)/Z80
+NUKEYKT	= $(CORE_DIR)/NukeYKT
 
 include Makefile.common
 

Makefile.common

@@ -32,7 +32,9 @@ SOURCES_C := \
 	$(EMULIB)/YM2413.c \
 	$(EMULIB)/AY8910.c \
 	$(EMULIB)/SCC.c \
-	$(EMULIB)/WD1793.c
+	$(EMULIB)/WD1793.c \
+	$(NUKEYKT)/opll.c \
+	$(NUKEYKT)/WrapNukeYKT.c
 
 ifneq ($(STATIC_LINKING), 1)
 SOURCES_C += $(CORE_DIR)/libretro-common/file/retro_dirent.c \