Finalize and start frames right after vsync -> stabilizes algorithm.

src/emucore/tia/FrameManager.cxx

@@ -29,7 +29,7 @@ enum Metrics: uInt32 {
   overscanNTSC                  = 30,
   overscanPAL                   = 36,
   vsync                         = 3,
-  maxLinesVsync                 = 30,
+  maxLinesVsync                 = 32,
   maxLinesVsyncDuringAutodetect = 100,
   visibleOverscan               = 20,
   maxUnderscan                  = 10,
@@ -93,6 +93,8 @@ void FrameManager::reset()
   myStableVblankFrames = 0;
   myVblankViolated = false;
   myVsyncLines = 0;
+  myY = 0;
+  myFramePending = false;
 
   if (myVblankMode != VblankMode::fixed) myVblankMode = VblankMode::floating;
 }
@@ -100,13 +102,15 @@ void FrameManager::reset()
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void FrameManager::nextLine()
 {
+  State previousState = myState;
+
   myCurrentFrameTotalLines++;
   myLineInState++;
 
   switch (myState)
   {
     case State::waitForVsyncStart:
-      if (Int32(myLineInState) >= Int32(myFrameLines - myCurrentFrameFinalLines) || !myCurrentFrameFinalLines)
+      if ((myCurrentFrameTotalLines > myFrameLines - 3) || myTotalFrames == 0)
         myVsyncLines++;
 
       if (myVsyncLines > vsyncLimit(myAutodetectTvMode)) setState(State::waitForFrameStart);
@@ -125,12 +129,14 @@ void FrameManager::nextLine()
 
     case State::frame:
       if (myLineInState >= (myFixedHeight > 0 ? myFixedHeight : (myKernelLines + Metrics::visibleOverscan)))
-        finalizeFrame();
+        setState(State::waitForVsyncStart);
       break;
 
     default:
       throw runtime_error("frame manager: invalid state");
   }
+
+  if (myState == State::frame && previousState == State::frame) myY++;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
@@ -215,15 +221,11 @@ void FrameManager::setVsync(bool vsync)
       break;
 
     case State::waitForVsyncEnd:
-      if (!myVsync)
-        setState(State::waitForFrameStart);
+      if (!myVsync) setState(State::waitForFrameStart);
       break;
 
     case State::frame:
-      if (myVsync) {
-        myCurrentFrameTotalLines++;
-        finalizeFrame(State::waitForVsyncEnd);
-      }
+      if (myVsync) setState(State::waitForVsyncEnd);
       break;
 
     default:
@@ -245,13 +247,17 @@ void FrameManager::setState(FrameManager::State state)
 
   switch (myState) {
     case State::waitForFrameStart:
+      if (myFramePending) finalizeFrame();
+      if (myOnFrameStart) myOnFrameStart();
+      myFramePending = true;
+
       myVsyncLines = 0;
       myVblankViolated = false;
       break;
 
     case State::frame:
       myVsyncLines = 0;
-      if (myOnFrameStart) myOnFrameStart();
+      myY = 0;
       break;
 
     default:
@@ -260,22 +266,18 @@ void FrameManager::setState(FrameManager::State state)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void FrameManager::finalizeFrame(FrameManager::State state)
+void FrameManager::finalizeFrame()
 {
   myCurrentFrameFinalLines = myCurrentFrameTotalLines;
   myCurrentFrameTotalLines = 0;
   myTotalFrames++;
 
-  if (myOnFrameComplete) {
-    myOnFrameComplete();
-  }
+  if (myOnFrameComplete) myOnFrameComplete();
 
 #ifdef TIA_FRAMEMANAGER_DEBUG_LOG
   (cout << "frame complete @ " << myLineInState << " (" << myCurrentFrameFinalLines << " total)" << "\n").flush();
 #endif // TIA_FRAMEMANAGER_DEBUG_LOG
 
-  setState(state);
-
   if (myAutodetectTvMode) updateAutodetectedTvMode();
 
   myFrameRate = (myMode == TvMode::pal ? 15600.0 : 15720.0) /
@@ -322,6 +324,10 @@ void FrameManager::updateTvMode(TvMode mode)
 {
   if (mode == myMode) return;
 
+#ifdef TIA_FRAMEMANAGER_DEBUG_LOG
+  (cout << "TV mode switched to " << int(mode) << "\n").flush();
+#endif // TIA_FRAMEMANAGER_DEBUG_LOG
+
   myMode = mode;
 
   switch (myMode)
@@ -395,12 +401,6 @@ void FrameManager::setFixedHeight(uInt32 height)
   myFixedHeight = height;
 }
 
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-uInt32 FrameManager::currentLine() const
-{
-  return myState == State::frame ? myLineInState : 0;
-}
-
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 FrameManager::scanlines() const
 {

src/emucore/tia/FrameManager.hxx

@@ -60,7 +60,10 @@ class FrameManager : public Serializable
 
     void setFixedHeight(uInt32 height);
 
-    uInt32 currentLine() const;
+    uInt32 getY() const
+    {
+      return myY;
+    }
 
     uInt32 scanlines() const;
 
@@ -111,7 +114,7 @@ class FrameManager : public Serializable
 
     void setState(State state);
 
-    void finalizeFrame(State state = State::waitForVsyncStart);
+    void finalizeFrame();
 
     void nextLineInVsync();
 
@@ -128,6 +131,8 @@ class FrameManager : public Serializable
     uInt32 myCurrentFrameFinalLines;
     uInt32 myVsyncLines;
     float  myFrameRate;
+    uInt32 myY;
+    bool myFramePending;
 
     uInt32 myTotalFrames;
     uInt32 myFramesInMode;

src/emucore/tia/TIA.cxx

@@ -925,12 +925,12 @@ void TIA::onFrameComplete()
   mySystem->m6502().stop();
   mySystem->resetCycles();
 
-  Int32 missingScanlines = myLastFrameHeight - myFrameManager.currentLine();
+  Int32 missingScanlines = myLastFrameHeight - myFrameManager.getY();
 
   if (missingScanlines > 0)
-    memset(myCurrentFrameBuffer.get() + 160 * myFrameManager.currentLine(), 0, missingScanlines * 160);
+    memset(myCurrentFrameBuffer.get() + 160 * myFrameManager.getY(), 0, missingScanlines * 160);
 
-  myLastFrameHeight = myFrameManager.currentLine();
+  myLastFrameHeight = myFrameManager.getY();
 
   // Recalculate framerate, attempting to auto-correct for scanline 'jumps'
   if(myAutoFrameEnabled)
@@ -1003,7 +1003,7 @@ void TIA::tickHblank()
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void TIA::tickHframe()
 {
-  const uInt32 y = myFrameManager.currentLine();
+  const uInt32 y = myFrameManager.getY();
   const bool lineNotCached = myLinesSinceChange < 2 || y == 0;
   const uInt32 x = myHctr - 68 + myXDelta;
 
@@ -1027,7 +1027,7 @@ void TIA::applyRsync()
 
   if (x > 0 && myFrameManager.isRendering()) {
     myXDelta = x - 157;
-    memset(myCurrentFrameBuffer.get() + myFrameManager.currentLine() * 160 + x, 0, 160 - x);
+    memset(myCurrentFrameBuffer.get() + myFrameManager.getY() * 160 + x, 0, 160 - x);
   }
 
   myLinesSinceChange = 0;
@@ -1141,7 +1141,7 @@ void TIA::renderPixel(uInt32 x, uInt32 y, bool lineNotCached)
 void TIA::clearHmoveComb()
 {
   if (myFrameManager.isRendering() && myHstate == HState::blank)
-    memset(myCurrentFrameBuffer.get() + myFrameManager.currentLine() * 160,
+    memset(myCurrentFrameBuffer.get() + myFrameManager.getY() * 160,
            myColorHBlank, 8);
 }