Very rough and basic implementation of frameskipping.

Core/Config.cpp

@@ -68,6 +68,7 @@ void CConfig::Load(const char *iniFileName)
 	graphics->Get("LinearFiltering", &bLinearFiltering, false);
 	graphics->Get("SSAA", &SSAntiAliasing, 0);
 	graphics->Get("VBO", &bUseVBO, false);
+	graphics->Get("FrameSkip", &iFrameSkip, 0);
 #ifdef USING_GLES2
 	graphics->Get("AnisotropyLevel", &iAnisotropyLevel, 0);
 #else
@@ -131,6 +132,7 @@ void CConfig::Save()
 		graphics->Set("LinearFiltering", bLinearFiltering);
 		graphics->Set("SSAA", SSAntiAliasing);
 		graphics->Set("VBO", bUseVBO);
+		graphics->Set("FrameSkip", iFrameSkip);
 		graphics->Set("AnisotropyLevel", iAnisotropyLevel);
 		graphics->Set("DisableG3DLog", bDisableG3DLog);
 		graphics->Set("VertexCache", bVertexCache);

Core/Config.h

@@ -59,6 +59,7 @@ public:
 	bool bLinearFiltering;
 	bool bUseVBO;
 	bool bStretchToDisplay;
+	int iFrameSkip;  // 0 = off;  1 = auto;  (future:  2 = skip every 2nd frame;  3 = skip every 3rd frame etc).
 
 	int iWindowZoom;  // for Windows
 	bool SSAntiAliasing; //for Windows, too

Core/HLE/sceDisplay.cpp

@@ -89,7 +89,8 @@ static int isVblank;
 static int numSkippedFrames;
 static bool hasSetMode;
 // Don't include this in the state, time increases regardless of state.
-static double lastFrameTime;
+static double curFrameTime;
+static double nextFrameTime;
 
 std::vector<WaitVBlankInfo> vblankWaitingThreads;
 
@@ -129,7 +130,8 @@ void __DisplayInit() {
 	vCount = 0;
 	hCount = 0;
 	hCountTotal = 0;
-	lastFrameTime = 0;
+	curFrameTime = 0.0;
+	nextFrameTime = 0.0;
 
 	InitGfxState();
 }
@@ -191,7 +193,7 @@ float calculateFPS()
 	static int lastFpsFrame = 0;
 	static double lastFpsTime = 0.0;
 	static double fps = 0.0;
-        
+
 	time_update();
 	double now = time_now_d();
 
@@ -274,25 +276,56 @@ void DoFrameTiming(bool &throttle, bool &skipFrame, bool &skipFlip) {
 #endif
 	skipFlip = false;
 	skipFrame = false;
-
 	if (PSP_CoreParameter().headLess)
 		throttle = false;
 
-	if (throttle) {
-		// Best place to throttle the frame rate on non vsynced platforms is probably here. Let's try it.
-		time_update();
-		if (lastFrameTime == 0.0)
-			lastFrameTime = time_now_d();
-
-		// First, check if we are already behind.
-		// Wait until it's time.
-		while (time_now_d() < lastFrameTime + 1.0 / 60.0) {
-			Common::SleepCurrentThread(1);
-			time_update();
+	// Check if the frameskipping code should be enabled. If neither throttling or frameskipping is on,
+	// we have nothing to do here.
+	bool doFrameSkip = g_Config.iFrameSkip == 1;
+	if (!throttle && !doFrameSkip)
+		return;
+	
+	time_update();
+	
+	curFrameTime = time_now_d();
+	if (nextFrameTime == 0.0)
+		nextFrameTime = time_now_d() + 1.0 / 60.0;
+	
+	if (curFrameTime > nextFrameTime && doFrameSkip) {
+		// Argh, we are falling behind! Let's skip a frame and see if we catch up.
+		skipFrame = true;
+		skipFlip = true;
+		INFO_LOG(HLE,"FRAMESKIP %i", numSkippedFrames);
+	}
+	
+	if (curFrameTime < nextFrameTime && throttle)
+	{
+		// If time gap is huge just jump (somebody unthrottled)
+		if (nextFrameTime - curFrameTime > 1.0 / 30.0) {
+			nextFrameTime = curFrameTime + 1.0 / 60.0;
+		} else {
+			// Wait until we've catched up.
+			while (time_now_d() < nextFrameTime) {
+				Common::SleepCurrentThread(1);
+				time_update();
+			}
 		}
-		// Advance lastFrameTime by a constant amount each frame,
-		// but don't let it get too far behind.
-		lastFrameTime = std::max(lastFrameTime + 1.0 / 60.0, time_now_d() - 1.5 / 60.0);
+		curFrameTime = time_now_d();
+	}
+	// Advance lastFrameTime by a constant amount each frame,
+	// but don't let it get too far behind as things can get very jumpy.
+	const double maxFallBehindFrames = 5.5;
+
+	if (throttle || doFrameSkip) {
+		nextFrameTime = std::max(nextFrameTime + 1.0 / 60.0, time_now_d() - maxFallBehindFrames / 60.0);
+	} else {
+		nextFrameTime = nextFrameTime + 1.0 / 60.0;
+	}
+
+	// Max 6 skipped frames in a row - 10 fps is really the bare minimum for playability.
+	if (numSkippedFrames >= 4) {
+		skipFrame = false;
+		skipFlip = false;
 	}
 }
 

Windows/PPSSPP.vcxproj.filters

@@ -209,10 +209,12 @@
     <None Include="..\android\atlasscript.txt">
       <Filter>Android</Filter>
     </None>
-    <None Include="..\CMakeLists.txt" />
     <None Include="..\android\jni\Application.mk">
       <Filter>Android</Filter>
     </None>
+    <None Include="..\CMakeLists.txt">
+      <Filter>Windows</Filter>
+    </None>
   </ItemGroup>
   <ItemGroup>
     <ResourceCompile Include="ppsspp.rc">

Windows/WndMainWindow.cpp

@@ -73,8 +73,7 @@ namespace MainWindow
 
 	void Init(HINSTANCE hInstance)
 	{
-#ifdef THEMES
-		WTL::CTheme::IsThemingSupported();
+#ifdef THEMES		WTL::CTheme::IsThemingSupported();
 #endif
 		//Register classes
 		WNDCLASSEX wcex;
@@ -447,6 +446,11 @@ namespace MainWindow
 				gpu->Resized();  // easy way to force a clear...
 				break;
 
+			case ID_OPTIONS_FRAMESKIP:
+				g_Config.iFrameSkip = !g_Config.iFrameSkip;
+				UpdateMenus();
+				break;
+
 			case ID_FILE_EXIT:
 				DestroyWindow(hWnd);
 				break;
@@ -712,6 +716,7 @@ namespace MainWindow
 		CHECKITEM(ID_OPTIONS_DISABLEG3DLOG, g_Config.bDisableG3DLog);
 		CHECKITEM(ID_OPTIONS_VERTEXCACHE, g_Config.bVertexCache);
 		CHECKITEM(ID_OPTIONS_SHOWFPS, g_Config.bShowFPSCounter);
+		CHECKITEM(ID_OPTIONS_FRAMESKIP, g_Config.iFrameSkip != 0);
 
 		UINT enable = !Core_IsStepping() ? MF_GRAYED : MF_ENABLED;
 		EnableMenuItem(menu,ID_EMULATION_RUN, g_State.bEmuThreadStarted ? enable : MF_GRAYED);

Windows/resource.h

@@ -260,6 +260,7 @@
 #define ID_OPTIONS_VERTEXCACHE          40136
 #define ID_OPTIONS_SHOWFPS              40137
 #define ID_OPTIONS_STRETCHDISPLAY       40138
+#define ID_OPTIONS_FRAMESKIP            40139
 #define IDC_STATIC                      -1
 
 // Next default values for new objects
@@ -267,7 +268,7 @@
 #ifdef APSTUDIO_INVOKED
 #ifndef APSTUDIO_READONLY_SYMBOLS
 #define _APS_NEXT_RESOURCE_VALUE        233
-#define _APS_NEXT_COMMAND_VALUE         40139
+#define _APS_NEXT_COMMAND_VALUE         40140
 #define _APS_NEXT_CONTROL_VALUE         1163
 #define _APS_NEXT_SYMED_VALUE           101
 #endif

android/jni/MenuScreens.cpp

@@ -251,6 +251,9 @@ void InGameMenuScreen::render() {
 	UICheckBox(GEN_ID, x, y += 50, "Stretch to display", ALIGN_TOPLEFT, &g_Config.bStretchToDisplay);
 
 	UICheckBox(GEN_ID, x, y += 50, "Hardware Transform", ALIGN_TOPLEFT, &g_Config.bHardwareTransform);
+	bool fs = g_Config.iFrameSkip == 1;
+	UICheckBox(GEN_ID, x, y += 50, "Frameskip", ALIGN_TOPLEFT, &fs);
+	g_Config.iFrameSkip = fs ? 1 : 0;
 
 	// TODO: Add UI for more than one slot.
 	VLinear vlinear1(x, y + 80, 20);