YM2612: better DAC write scheduling

issue #1300

src/engine/platform/fmsharedbase.h

@@ -105,16 +105,17 @@ class DivPlatformFMBase: public DivDispatch {
         }
       }
     }
+    // only used by OPN2 for DAC writes
     inline void urgentWrite(unsigned short a, unsigned char v) {
       if (!skipRegisterWrites && !flushFirst) {
-        if (writes.empty()) {
+        if (!writes.empty()) {
-          writes.push_back(QueuedWrite(a,v));
+          // check for hard reset
-        } else if ((writes.size()>16 && writes.front().addr!=0xf0) || writes.front().addrOrVal) {
+          if (writes.front().addr==0xf0) {
-          // $f0 is used by OPN hard reset
+            // replace hard reset with DAC write
-          writes.push_back(QueuedWrite(a,v));
+            writes.pop_front();
-        } else {
-          writes.push_front(QueuedWrite(a,v));
           }
+        }
+        writes.push_front(QueuedWrite(a,v));
         if (dumpWrites) {
           addWrite(a,v);
         }

src/engine/platform/genesis.cpp

@@ -96,32 +96,22 @@ void DivPlatformGenesis::processDAC(int iRate) {
       //sample>>=1;
       if (sample<-128) sample=-128;
       if (sample>127) sample=127;
-      urgentWrite(0x2a,(unsigned char)sample+0x80);
+      dacWrite=(unsigned char)(sample+0x80);
     }
   } else {
-    if (!chan[5].dacReady) {
-      chan[5].dacDelay+=32000;
-      if (chan[5].dacDelay>=iRate) {
-        chan[5].dacDelay-=iRate;
-        chan[5].dacReady=true;
-      }
-    }
     if (chan[5].dacMode && chan[5].dacSample!=-1) {
       chan[5].dacPeriod+=chan[5].dacRate;
       if (chan[5].dacPeriod>=iRate) {
         DivSample* s=parent->getSample(chan[5].dacSample);
         if (s->samples>0 && chan[5].dacPos<s->samples) {
           if (!isMuted[5]) {
-            if (chan[5].dacReady && writes.size()<16) {
             int sample;
             if (parent->song.noOPN2Vol) {
               sample=s->data8[chan[5].dacDirection?(s->samples-chan[5].dacPos-1):chan[5].dacPos];
             } else {
               sample=(s->data8[chan[5].dacDirection?(s->samples-chan[5].dacPos-1):chan[5].dacPos]*dacVolTable[chan[5].outVol])>>7;
             }
-              urgentWrite(0x2a,(unsigned char)sample+0x80);
+            dacWrite=(unsigned char)(sample+0x80);
-              chan[5].dacReady=false;
-            }
           }
           chan[5].dacPos++;
           if (!chan[5].dacDirection && (s->isLoopable() && chan[5].dacPos>=(unsigned int)s->loopEnd)) {
@@ -151,24 +141,34 @@ void DivPlatformGenesis::acquire_nuked(short** buf, size_t len) {
     os[0]=0; os[1]=0;
     for (int i=0; i<6; i++) {
       if (!writes.empty()) {
-        if (--delay<0) {
-          delay=0;
         QueuedWrite& w=writes.front();
         if (w.addrOrVal) {
           //logV("%.3x = %.2x",w.addr,w.val);
           OPN2_Write(&fm,0x1+((w.addr>>8)<<1),w.val);
-            lastBusy=0;
           regPool[w.addr&0x1ff]=w.val;
           writes.pop_front();
+
+          if (dacWrite>=0) {
+            if (!canWriteDAC) {
+              canWriteDAC=true;
+            } else {
+              urgentWrite(0x2a,dacWrite);
+              dacWrite=-1;
+              canWriteDAC=writes.empty();
+            }
+          }
         } else {
-            lastBusy++;
           if (fm.write_busy==0) {
             OPN2_Write(&fm,0x0+((w.addr>>8)<<1),w.addr);
             w.addrOrVal=true;
           }
         }
-        }
       } else {
+        canWriteDAC=true;
+        if (dacWrite>=0) {
+          urgentWrite(0x2a,dacWrite);
+          dacWrite=-1;
+        }
         flushFirst=false;
       }
       
@@ -227,8 +227,22 @@ void DivPlatformGenesis::acquire_ymfm(short** buf, size_t len) {
       fm_ymfm->write(0x1+((w.addr>>8)<<1),w.val);
       regPool[w.addr&0x1ff]=w.val;
       writes.pop_front();
-      lastBusy=1;
+
+      if (dacWrite>=0) {
+        if (!canWriteDAC) {
+          canWriteDAC=true;
         } else {
+          urgentWrite(0x2a,dacWrite);
+          dacWrite=-1;
+          canWriteDAC=writes.empty();
+        }
+      }
+    } else {
+      canWriteDAC=true;
+      if (dacWrite>=0) {
+        urgentWrite(0x2a,dacWrite);
+        dacWrite=-1;
+      }
       flushFirst=false;
     }
     
@@ -1314,11 +1328,12 @@ void DivPlatformGenesis::reset() {
     pendingWrites[i]=-1;
   }
 
-  lastBusy=60;
   lfoValue=8;
   softPCMTimer=0;
   extMode=false;
   flushFirst=false;
+  dacWrite=-1;
+  canWriteDAC=true;
 
   if (softPCM) {
     chan[5].dacMode=true;
@@ -1330,8 +1345,6 @@ void DivPlatformGenesis::reset() {
 
   // LFO
   immWrite(0x22,lfoValue);
-  
-  delay=0;
 }
 
 int DivPlatformGenesis::getOutputCount() {

src/engine/platform/genesis.h

@@ -55,7 +55,6 @@ class DivPlatformGenesis: public DivPlatformOPN {
       unsigned int dacPos;
       int dacSample;
       int dacDelay;
-      bool dacReady;
       bool dacDirection;
       bool setPos;
       unsigned char sampleBank;
@@ -69,7 +68,6 @@ class DivPlatformGenesis: public DivPlatformOPN {
         dacPos(0),
         dacSample(-1),
         dacDelay(0),
-        dacReady(true),
         dacDirection(false),
         setPos(false),
         sampleBank(0),
@@ -86,8 +84,9 @@ class DivPlatformGenesis: public DivPlatformOPN {
 
     int softPCMTimer;
 
-    bool extMode, softPCM, noExtMacros, useYMFM;
+    bool extMode, softPCM, noExtMacros, useYMFM, canWriteDAC;
     unsigned char chipType;
+    short dacWrite;
   
     unsigned char dacVolTable[128];
   

src/gui/debug.cpp

@@ -62,7 +62,6 @@
 
 #define FM_CHIP_DEBUG \
   COMMON_CHIP_DEBUG; \
-  ImGui::Text("- lastBusy: %d",ch->lastBusy); \
   ImGui::Text("- delay: %d",ch->delay);
 
 #define FM_OPN_CHIP_DEBUG \
@@ -167,7 +166,6 @@
   ImGui::TextColored(ch->hardReset?colorOn:colorOff,">> hardReset"); \
   ImGui::TextColored(ch->opMaskChanged?colorOn:colorOff,">> opMaskChanged"); \
   ImGui::TextColored(ch->dacMode?colorOn:colorOff,">> DACMode"); \
-  ImGui::TextColored(ch->dacReady?colorOn:colorOff,">> DACReady"); \
   ImGui::TextColored(ch->dacDirection?colorOn:colorOff,">> DACDirection");
 
 #define GENESIS_OPCHAN_DEBUG \
@@ -381,7 +379,6 @@ void putDispatchChip(void* data, int type) {
       ImGui::Text("- pcmR: %d",ch->pcmR);
       ImGui::Text("- pcmCycles: %d",ch->pcmCycles);
       ImGui::Text("- sampleBank: %d",ch->sampleBank);
-      ImGui::Text("- lastBusy: %d",ch->lastBusy);
       COMMON_CHIP_DEBUG_BOOL;
       break;
     }
@@ -389,7 +386,6 @@ void putDispatchChip(void* data, int type) {
       DivPlatformAY8910* ch=(DivPlatformAY8910*)data;
       ImGui::Text("> AY-3-8910");
       COMMON_CHIP_DEBUG;
-      ImGui::Text("- lastBusy: %d",ch->lastBusy);
       ImGui::Text("- sampleBank: %d",ch->sampleBank);
       ImGui::Text("- stereoSep: %d",ch->stereoSep);
       ImGui::Text("- delay: %d",ch->delay);