YM2612: add reverse sample playback

src/engine/dispatch.h

@@ -59,6 +59,7 @@ enum DivDispatchCmds {
   DIV_CMD_SAMPLE_FREQ, // (frequency)
   DIV_CMD_SAMPLE_BANK, // (bank)
   DIV_CMD_SAMPLE_POS, // (pos)
+  DIV_CMD_SAMPLE_DIR, // (direction)
 
   DIV_CMD_FM_HARD_RESET, // (enabled)
   DIV_CMD_FM_LFO, // (speed)
@@ -222,6 +223,8 @@ struct DivRegWrite {
    *   - data is the sample rate
    * - 0xffffxx02: stop sample playback
    *   - xx is the instance ID
+   * - 0xffffxx03: set sample playback direction
+   *   - x is the instance ID
    * - 0xffffffff: reset
    */
   unsigned int addr;

src/engine/engine.h

@@ -375,7 +375,7 @@ class DivEngine {
   void processRow(int i, bool afterDelay);
   void nextOrder();
   void nextRow();
-  void performVGMWrite(SafeWriter* w, DivSystem sys, DivRegWrite& write, int streamOff, double* loopTimer, double* loopFreq, int* loopSample, bool isSecond);
+  void performVGMWrite(SafeWriter* w, DivSystem sys, DivRegWrite& write, int streamOff, double* loopTimer, double* loopFreq, int* loopSample, bool* sampleDir, bool isSecond);
   // returns true if end of song.
   bool nextTick(bool noAccum=false, bool inhibitLowLat=false);
   bool perSystemEffect(int ch, unsigned char effect, unsigned char effectVal);

src/engine/platform/genesis.cpp

@@ -125,6 +125,9 @@ const char* DivPlatformGenesis::getEffectName(unsigned char effect) {
     case 0x5f:
       return "5Fxx: Set decay 2 of operator 4 (0 to 1F)";
       break;
+    case 0xdf:
+      return "DFxx: Set sample playback direction (0: normal; 1: reverse)";
+      break;
   }
   return NULL;
 }
@@ -148,12 +151,12 @@ void DivPlatformGenesis::acquire_nuked(short* bufL, short* bufR, size_t start, s
         if (s->samples>0) {
           if (!isMuted[5]) {
             if (dacReady && writes.size()<16) {
-              urgentWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
+              urgentWrite(0x2a,(unsigned char)s->data8[dacDirection?(s->samples-dacPos-1):dacPos]+0x80);
               dacReady=false;
             }
           }
           if (++dacPos>=s->samples) {
-            if (s->loopStart>=0 && s->loopStart<(int)s->samples) {
+            if (s->loopStart>=0 && s->loopStart<(int)s->samples && !dacDirection) {
               dacPos=s->loopStart;
             } else {
               dacSample=-1;
@@ -228,12 +231,12 @@ void DivPlatformGenesis::acquire_ymfm(short* bufL, short* bufR, size_t start, si
         if (s->samples>0) {
           if (!isMuted[5]) {
             if (dacReady && writes.size()<16) {
-              urgentWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
+              urgentWrite(0x2a,(unsigned char)s->data8[dacDirection?(s->samples-dacPos-1):dacPos]+0x80);
               dacReady=false;
             }
           }
           if (++dacPos>=s->samples) {
-            if (s->loopStart>=0 && s->loopStart<(int)s->samples) {
+            if (s->loopStart>=0 && s->loopStart<(int)s->samples && !dacDirection) {
               dacPos=s->loopStart;
             } else {
               dacSample=-1;
@@ -770,6 +773,11 @@ int DivPlatformGenesis::dispatch(DivCommand c) {
         sampleBank=parent->song.sample.size()/12;
       }
       break;
+    case DIV_CMD_SAMPLE_DIR: {
+      dacDirection=c.value;
+      if (dumpWrites) addWrite(0xffff0003,dacDirection);
+      break;
+    }
     case DIV_CMD_LEGATO: {
       if (c.chan==5 && chan[c.chan].furnaceDac && dacMode) {
         chan[c.chan].baseFreq=parent->calcBaseFreq(1,1,c.value,false);
@@ -1062,11 +1070,14 @@ void DivPlatformGenesis::reset() {
   dacDelay=0;
   dacReady=true;
   dacSample=-1;
+  dacDirection=false;
   sampleBank=0;
   lfoValue=8;
 
   extMode=false;
 
+  if (dumpWrites) addWrite(0xffff0003,dacDirection);
+
   // LFO
   immWrite(0x22,lfoValue);
   

src/engine/platform/genesis.h

@@ -93,6 +93,7 @@ class DivPlatformGenesis: public DivDispatch {
     int dacSample;
     int dacDelay;
     bool dacReady;
+    bool dacDirection;
     unsigned char sampleBank;
     unsigned char lfoValue;
 

src/engine/playback.cpp

@@ -63,6 +63,7 @@ const char* cmdName[]={
   "SAMPLE_FREQ",
   "SAMPLE_BANK",
   "SAMPLE_POS",
+  "SAMPLE_DIR",
 
   "FM_HARD_RESET",
   "FM_LFO",
@@ -556,6 +557,9 @@ void DivEngine::processRow(int i, bool afterDelay) {
         clockDrift=0;
         subticks=0;
         break;
+      case 0xdf: // set sample direction
+        dispatchCmd(DivCommand(DIV_CMD_SAMPLE_DIR,i,effectVal));
+        break;
       case 0xe0: // arp speed
         if (effectVal>0) {
           curSubSong->arpLen=effectVal;

src/engine/vgmOps.cpp

@@ -24,7 +24,7 @@
 
 constexpr int MASTER_CLOCK_PREC=(sizeof(void*)==8)?8:0;
 
-void DivEngine::performVGMWrite(SafeWriter* w, DivSystem sys, DivRegWrite& write, int streamOff, double* loopTimer, double* loopFreq, int* loopSample, bool isSecond) {
+void DivEngine::performVGMWrite(SafeWriter* w, DivSystem sys, DivRegWrite& write, int streamOff, double* loopTimer, double* loopFreq, int* loopSample, bool* sampleDir, bool isSecond) {
   unsigned char baseAddr1=isSecond?0xa0:0x50;
   unsigned char baseAddr2=isSecond?0x80:0;
   unsigned short baseAddr2S=isSecond?0x8000:0;
@@ -502,8 +502,8 @@ void DivEngine::performVGMWrite(SafeWriter* w, DivSystem sys, DivRegWrite& write
           w->writeC(0x95);
           w->writeC(streamID);
           w->writeS(write.val); // sample number
-          w->writeC((sample->loopStart==0)); // flags
+          w->writeC((sample->loopStart==0)|(sampleDir[streamID]?0x10:0)); // flags
-          if (sample->loopStart>0) {
+          if (sample->loopStart>0 && !sampleDir[streamID]) {
             loopTimer[streamID]=sample->length8;
             loopSample[streamID]=write.val;
           }
@@ -520,6 +520,9 @@ void DivEngine::performVGMWrite(SafeWriter* w, DivSystem sys, DivRegWrite& write
         w->writeC(streamID);
         loopSample[streamID]=-1;
         break;
+      case 3: // set sample direction
+        sampleDir[streamID]=write.val;
+        break;
     }
     return;
   }
@@ -884,11 +887,13 @@ SafeWriter* DivEngine::saveVGM(bool* sysToExport, bool loop, int version) {
   double loopTimer[DIV_MAX_CHANS];
   double loopFreq[DIV_MAX_CHANS];
   int loopSample[DIV_MAX_CHANS];
+  bool sampleDir[DIV_MAX_CHANS];
 
   for (int i=0; i<DIV_MAX_CHANS; i++) {
     loopTimer[i]=0;
     loopFreq[i]=0;
     loopSample[i]=-1;
+    sampleDir[i]=false;
   }
 
   bool writeDACSamples=false;
@@ -1762,7 +1767,7 @@ SafeWriter* DivEngine::saveVGM(bool* sysToExport, bool loop, int version) {
     for (int i=0; i<song.systemLen; i++) {
       std::vector<DivRegWrite>& writes=disCont[i].dispatch->getRegisterWrites();
       for (DivRegWrite& j: writes) {
-        performVGMWrite(w,song.system[i],j,streamIDs[i],loopTimer,loopFreq,loopSample,isSecond[i]);
+        performVGMWrite(w,song.system[i],j,streamIDs[i],loopTimer,loopFreq,loopSample,sampleDir,isSecond[i]);
         writeCount++;
       }
       writes.clear();

src/gui/guiConst.cpp

@@ -394,7 +394,7 @@ const FurnaceGUIColors fxColors[256]={
   GUI_COLOR_PATTERN_EFFECT_INVALID,
   GUI_COLOR_PATTERN_EFFECT_INVALID,
   GUI_COLOR_PATTERN_EFFECT_INVALID,
-  GUI_COLOR_PATTERN_EFFECT_INVALID,
+  GUI_COLOR_PATTERN_EFFECT_MISC, // DF
 
   // E0-FF extended effects
   GUI_COLOR_PATTERN_EFFECT_MISC, // E0