add clock drift for exact tempo

src/engine/engine.cpp

@@ -836,7 +836,11 @@ bool DivEngine::init(String outName) {
         }
       }
 
-      sf_writef_short(outFile,ilBuffer,got.bufsize);
+      if (!remainingLoops) {
+        sf_writef_short(outFile,ilBuffer,totalProcessed);
+      } else {
+        sf_writef_short(outFile,ilBuffer,got.bufsize);
+      }
     }
     delete[] ilBuffer;
     sf_close(outFile);

src/engine/engine.h

@@ -66,7 +66,7 @@ class DivEngine {
   bool playing;
   bool speedAB;
   bool endOfSong;
-  int ticks, cycles, curRow, curOrder, remainingLoops, nextSpeed;
+  int ticks, cycles, curRow, curOrder, remainingLoops, nextSpeed, clockDrift;
   int changeOrd, changePos, totalTicks, totalCmds, lastCmds, cmdsPerSecond;
   DivStatusView view;
   DivChannelState chan[17];
@@ -80,6 +80,8 @@ class DivEngine {
   short* bbIn[2];
   short* bbOut[2];
 
+  size_t totalProcessed;
+
   int dispatchCmd(DivCommand c);
   void processRow(int i, bool afterDelay);
   void nextOrder();
@@ -126,6 +128,7 @@ class DivEngine {
       curOrder(0),
       remainingLoops(-1),
       nextSpeed(3),
+      clockDrift(0),
       changeOrd(-1),
       changePos(0),
       totalTicks(0),

src/engine/platform/sound/gb/apu.c

@@ -1180,11 +1180,11 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
             if ((value & 0x80)) {
                 /* DMG bug: wave RAM gets corrupted if the channel is retriggerred 1 cycle before the APU
                             reads from it. */
-                if (!CGB &&
+                /*if (!CGB &&
                     gb->apu.is_active[GB_WAVE] &&
                     gb->apu.wave_channel.sample_countdown == 0 &&
                     gb->apu.wave_channel.enable) {
-                    unsigned offset = ((gb->apu.wave_channel.current_sample_index + 1) >> 1) & 0xF;
+                    unsigned offset = ((gb->apu.wave_channel.current_sample_index + 1) >> 1) & 0xF;*/
 
                     /* This glitch varies between models and even specific instances:
                        DMG-B:     Most of them behave as emulated. A few behave differently.
@@ -1193,7 +1193,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
 
                       Additionally, I believe DMGs, including those we behave differently than emulated,
                       are all deterministic. */
-                    if (offset < 4) {
+                    /*if (offset < 4) {
                         gb->io_registers[GB_IO_WAV_START] = gb->io_registers[GB_IO_WAV_START + offset];
                         gb->apu.wave_channel.wave_form[0] = gb->apu.wave_channel.wave_form[offset / 2];
                         gb->apu.wave_channel.wave_form[1] = gb->apu.wave_channel.wave_form[offset / 2 + 1];
@@ -1206,7 +1206,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
                                gb->apu.wave_channel.wave_form + (offset & ~3) * 2,
                                8);
                     }
-                }
+                }*/
                 if (!gb->apu.is_active[GB_WAVE]) {
                     gb->apu.is_active[GB_WAVE] = true;
                     update_sample(gb, GB_WAVE,

src/engine/playback.cpp

@@ -569,15 +569,23 @@ void DivEngine::nextRow() {
 
 bool DivEngine::nextTick() {
   bool ret=false;
+  int divider=60;
   if (song.customTempo) {
-    cycles=dispatch->rate/song.hz;
+    divider=song.hz;
   } else {
     if (song.pal) {
-      cycles=dispatch->rate/60;
+      divider=60;
     } else {
-      cycles=dispatch->rate/50;
+      divider=50;
     }
   }
+  cycles=dispatch->rate/divider;
+  clockDrift+=dispatch->rate%divider;
+  if (clockDrift>=divider) {
+    clockDrift-=divider;
+    cycles++;
+  }
+
   if (--ticks<=0) {
     ret=endOfSong;
     nextRow();
@@ -691,6 +699,7 @@ void DivEngine::nextBuf(float** in, float** out, int inChans, int outChans, unsi
 
   size_t runLeft=runtotal;
   size_t runPos=0;
+  totalProcessed=0;
   while (runLeft) {
     if (!remainingLoops) {
       memset(bbIn[0]+runPos,0,runLeft*sizeof(short));
@@ -710,10 +719,12 @@ void DivEngine::nextBuf(float** in, float** out, int inChans, int outChans, unsi
       } else {
         dispatch->acquire(bbIn[0],bbIn[1],runPos,runLeft);
         cycles-=runLeft;
+        runPos=runtotal;
         break;
       }
     }
   }
+  totalProcessed=(1+runPos)*got.rate/dispatch->rate;
 
   for (size_t i=0; i<runtotal; i++) {
     temp[0]=bbIn[0][i];