Input optional

apps/LoopThroughWithOpenGLCompositing/LoopThroughWithOpenGLCompositing.cpp

@@ -252,6 +252,11 @@ LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
 				wglMakeCurrent( NULL, NULL );
 				if (pOpenGLComposite->Start())
 					break;						// success
+				MessageBoxA(NULL, "The OpenGL/DeckLink runtime initialized, but playout failed to start. See the previous DeckLink start message for the failing call.", "Startup failed", MB_OK | MB_ICONERROR);
+			}
+			else
+			{
+				MessageBoxA(NULL, "The OpenGL/DeckLink runtime failed to initialize. See the previous initialization message for the failing call.", "Startup failed", MB_OK | MB_ICONERROR);
 			}
 
 			// Failed to initialize - cleanup