From bdcbab09213818118473130600d8b47b2880c452 Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Tue, 9 May 2023 05:05:53 -0500
Subject: [PATCH] prepare to fix MIDI clock

---
 src/engine/engine.cpp        | 27 ++++++++++++++++++++++---
 src/engine/engine.h          |  8 ++++++++
 src/engine/platform/snes.cpp |  1 +
 src/engine/playback.cpp      | 39 ++++++++++++++++++++++++++++++------
 4 files changed, 66 insertions(+), 9 deletions(-)

diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index 2b5237b40..b83c68a6b 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -2034,6 +2034,10 @@ String DivEngine::getPlaybackDebugInfo() {
     "divider: %f\n"
     "cycles: %d\n"
     "clockDrift: %f\n"
+    "midiClockCycles: %d\n"
+    "midiClockDrift: %f\n"
+    "midiTimeCycles: %d\n"
+    "midiTimeDrift: %d\n"
     "changeOrd: %d\n"
     "changePos: %d\n"
     "totalSeconds: %d\n"
@@ -2048,8 +2052,9 @@ String DivEngine::getPlaybackDebugInfo() {
     "totalProcessed: %d\n"
     "bufferPos: %d\n",
     curOrder,prevOrder,curRow,prevRow,ticks,subticks,totalLoops,lastLoopPos,nextSpeed,divider,cycles,clockDrift,
-    changeOrd,changePos,totalSeconds,totalTicks,totalTicksR,totalCmds,lastCmds,cmdsPerSecond,globalPitch,
-    (int)extValue,(int)tempoAccum,(int)totalProcessed,(int)bufferPos
+    midiClockCycles,midiClockDrift,midiTimeCycles,midiTimeDrift,changeOrd,changePos,totalSeconds,totalTicks,
+    totalTicksR,totalCmds,lastCmds,cmdsPerSecond,globalPitch,(int)extValue,(int)tempoAccum,(int)totalProcessed,
+    (int)bufferPos
   );
 }
 
@@ -2165,10 +2170,16 @@ void DivEngine::playSub(bool preserveDrift, int goalRow) {
   prevOrder=0;
   prevRow=0;
   stepPlay=0;
-  int prevDrift;
+  int prevDrift, prevMidiClockDrift, prevMidiTimeDrift;
   prevDrift=clockDrift;
+  prevMidiClockDrift=midiClockDrift;
+  prevMidiTimeDrift=midiTimeDrift;
   clockDrift=0;
   cycles=0;
+  midiClockCycles=0;
+  midiClockDrift=0;
+  midiTimeCycles=0;
+  midiTimeDrift=0;
   if (!preserveDrift) {
     ticks=1;
     tempoAccum=0;
@@ -2211,9 +2222,15 @@ void DivEngine::playSub(bool preserveDrift, int goalRow) {
   repeatPattern=oldRepeatPattern;
   if (preserveDrift) {
     clockDrift=prevDrift;
+    midiClockDrift=prevMidiClockDrift;
+    midiTimeDrift=prevMidiTimeDrift;
   } else {
     clockDrift=0;
     cycles=0;
+    midiClockCycles=0;
+    midiClockDrift=0;
+    midiTimeCycles=0;
+    midiTimeDrift=0;
   }
   if (!preserveDrift) {
     ticks=1;
@@ -4367,6 +4384,10 @@ void DivEngine::quitDispatch() {
   }
   cycles=0;
   clockDrift=0;
+  midiClockCycles=0;
+  midiClockDrift=0;
+  midiTimeCycles=0;
+  midiTimeDrift=0;
   chans=0;
   playing=false;
   curSpeed=0;
diff --git a/src/engine/engine.h b/src/engine/engine.h
index 96be99551..4e7d44de5 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -378,6 +378,10 @@ class DivEngine {
   double divider;
   int cycles;
   double clockDrift;
+  int midiClockCycles;
+  double midiClockDrift;
+  int midiTimeCycles;
+  double midiTimeDrift;
   int stepPlay;
   int changeOrd, changePos, totalSeconds, totalTicks, totalTicksR, totalCmds, lastCmds, cmdsPerSecond, globalPitch;
   unsigned char extValue, pendingMetroTick;
@@ -1146,6 +1150,10 @@ class DivEngine {
       divider(60),
       cycles(0),
       clockDrift(0),
+      midiClockCycles(0),
+      midiClockDrift(0),
+      midiTimeCycles(0),
+      midiTimeDrift(0),
       stepPlay(0),
       changeOrd(-1),
       changePos(0),
diff --git a/src/engine/platform/snes.cpp b/src/engine/platform/snes.cpp
index a5684d0e8..21ae97b8d 100644
--- a/src/engine/platform/snes.cpp
+++ b/src/engine/platform/snes.cpp
@@ -202,6 +202,7 @@ void DivPlatformSNES::tick(bool sysTick) {
     }
   }
   for (int i=0; i<8; i++) {
+    // TODO: if wavetable length is higher than 32, we lose precision!
     if (chan[i].freqChanged || chan[i].keyOn || chan[i].keyOff) {
       DivSample* s=parent->getSample(chan[i].sample);
       double off=(s->centerRate>=1)?((double)s->centerRate/8363.0):1.0;
diff --git a/src/engine/playback.cpp b/src/engine/playback.cpp
index b53af4b70..93a9338a7 100644
--- a/src/engine/playback.cpp
+++ b/src/engine/playback.cpp
@@ -1317,11 +1317,6 @@ bool DivEngine::nextTick(bool noAccum, bool inhibitLowLat) {
     if (--subticks<=0) {
       subticks=tickMult;
 
-      // MIDI clock
-      if (output) if (!skipping && output->midiOut!=NULL && midiOutClock) {
-        output->midiOut->send(TAMidiMessage(TA_MIDI_CLOCK,0,0));
-      }
-
       if (stepPlay!=1) {
         tempoAccum+=curSubSong->virtualTempoN;
         while (tempoAccum>=curSubSong->virtualTempoD) {
@@ -1835,7 +1830,39 @@ void DivEngine::nextBuf(float** in, float** out, int inChans, int outChans, unsi
           pendingMetroTick=0;
         }
       } else {
-        // 3. tick the clock and fill buffers as needed
+        // 3. run MIDI clock
+        for (int i=0; i<runLeftG; i++) {
+          // TODO: TEMPO
+          if (--midiClockCycles<=0) {
+            if (output) if (!skipping && output->midiOut!=NULL && midiOutClock) {
+              output->midiOut->send(TAMidiMessage(TA_MIDI_CLOCK,0,0));
+            }
+
+            double hl=curSubSong->hilightA;
+            if (hl<=0.0) hl=4.0;
+            double timeBase=curSubSong->timeBase+1;
+            double speedSum=0;
+            double vD=curSubSong->virtualTempoD;
+            for (int i=0; i<MIN(16,speeds.len); i++) {
+              speedSum+=speeds.val[i];
+            }
+            speedSum/=MAX(1,speeds.len);
+            if (timeBase<1.0) timeBase=1.0;
+            if (speedSum<1.0) speedSum=1.0;
+            if (vD<1) vD=1;
+            double bpm=10.0*((divider)/(timeBase*hl*speedSum))*(double)curSubSong->virtualTempoN/vD;
+            logV("bpm: %f %f",bpm,divider);
+
+            midiClockCycles=got.rate*pow(2,MASTER_CLOCK_PREC)/(bpm);
+            midiClockDrift+=fmod(got.rate*pow(2,MASTER_CLOCK_PREC),(double)(bpm));
+            if (midiClockDrift>=(bpm)) {
+              midiClockDrift-=(bpm);
+              midiClockCycles++;
+            }
+          }
+        }
+
+        // 4. tick the clock and fill buffers as needed
         if (cycles<runLeftG) {
           for (int i=0; i<song.systemLen; i++) {
             int total=(cycles*disCont[i].runtotal)/(size<<MASTER_CLOCK_PREC);