Added an attempt at NTSC/PAL autodetection, based on number of missed vertical syncs.

Machines/Atari2600.cpp

@@ -20,7 +20,7 @@ Machine::Machine()
 	_horizontalTimer = horizontalTimerReload;
 	_lastOutputStateDuration = 0;
 	_lastOutputState = OutputState::Sync;
-	_crt = new Outputs::CRT(228, 312, 1, 4);
+	_crt = new Outputs::CRT(228, 262, 1, 4);
 	_piaTimerStatus = 0xff;
 
 	setup6502();
@@ -31,6 +31,12 @@ Machine::~Machine()
 	delete _crt;
 }
 
+void Machine::switch_region()
+{
+	_crt->set_new_timing(228, 312);
+}
+
+
 void Machine::get_output_pixel(uint8_t *pixel, int offset)
 {
 	const uint8_t palette[16][3] =

Machines/Atari2600.hpp

@@ -25,6 +25,7 @@ class Machine: public CPU6502::Processor<Machine> {
 		int perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value);
 
 		void set_rom(size_t length, const uint8_t *data);
+		void switch_region();
 
 		Outputs::CRT *get_crt() { return _crt; }
 

OSBindings/Mac/Clock Signal/CSAtari2600.mm

@@ -10,12 +10,12 @@
 #import "Atari2600.hpp"
 
 @interface CSAtari2600 (Callbacks)
-- (void)crtDidEndFrame:(CRTFrame *)frame;
+- (void)crtDidEndFrame:(CRTFrame *)frame didDetectVSync:(BOOL)didDetectVSync;
 @end
 
 struct Atari2600CRTDelegate: public Outputs::CRT::CRTDelegate {
 	__weak CSAtari2600 *atari;
-	void crt_did_end_frame(Outputs::CRT *crt, CRTFrame *frame) { [atari crtDidEndFrame:frame]; }
+	void crt_did_end_frame(Outputs::CRT *crt, CRTFrame *frame, bool did_detect_vsync) { [atari crtDidEndFrame:frame didDetectVSync:did_detect_vsync]; }
 };
 
 @implementation CSAtari2600 {
@@ -23,9 +23,25 @@ struct Atari2600CRTDelegate: public Outputs::CRT::CRTDelegate {
 	Atari2600CRTDelegate _crtDelegate;
 
 	dispatch_queue_t _serialDispatchQueue;
+
+	int _failedVSyncCount;
 }
 
-- (void)crtDidEndFrame:(CRTFrame *)frame {
+- (void)crtDidEndFrame:(CRTFrame *)frame didDetectVSync:(BOOL)didDetectVSync {
+
+	if(!didDetectVSync)
+	{
+		_failedVSyncCount++;
+
+		if(_failedVSyncCount == 60)
+		{
+			_atari2600.switch_region();
+		}
+	}
+	else
+	{
+		_failedVSyncCount = MAX(_failedVSyncCount - 2, 0);
+	}
 
 	dispatch_async(dispatch_get_main_queue(), ^{
 		BOOL hasReturn = [self.view pushFrame:frame];

OSBindings/Mac/Clock Signal/CSCathodeRayView.m

@@ -121,6 +121,7 @@ static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeSt
 
 - (BOOL)pushFrame:(CRTFrame * __nonnull)crtFrame
 {
+	BOOL hadFrame = _crtFrame ? YES : NO;
 	_crtFrame = crtFrame;
 	[self setNeedsDisplay:YES];
 
@@ -140,7 +141,7 @@ static CVReturn DisplayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeSt
 			glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, _crtFrame->size.width, _crtFrame->dirty_size.height, GL_RGBA, GL_UNSIGNED_BYTE, _crtFrame->buffers[0].data);
 	}
 
-	return YES;
+	return hadFrame;
 }
 
 #pragma mark - Frame output

Outputs/CRT.cpp

@@ -18,7 +18,7 @@ static const uint32_t kCRTFixedPointOffset	= 0x08000000;
 #define kRetraceXMask	0x01
 #define kRetraceYMask	0x02
 
-CRT::CRT(int cycles_per_line, int height_of_display, int number_of_buffers, ...)
+void CRT::set_new_timing(int cycles_per_line, int height_of_display)
 {
 	const int syncCapacityLineChargeThreshold = 5;
 	const int millisecondsHorizontalRetraceTime = 7;	// source: Dictionary of Video and Television Technology, p. 234
@@ -61,6 +61,11 @@ CRT::CRT(int cycles_per_line, int height_of_display, int number_of_buffers, ...)
 	float halfLineWidth = (float)_height_of_display * 1.6f;
 	_widths[0][0] = (sinf(angle) / halfLineWidth) * kCRTFixedPointRange;
 	_widths[0][1] = (cosf(angle) / halfLineWidth) * kCRTFixedPointRange;
+}
+
+CRT::CRT(int cycles_per_line, int height_of_display, int number_of_buffers, ...)
+{
+	set_new_timing(cycles_per_line, height_of_display);
 
 	// generate buffers for signal storage as requested — format is
 	// number of buffers, size of buffer 1, size of buffer 2...
@@ -122,6 +127,7 @@ CRT::SyncEvent CRT::next_vertical_sync_event(bool vsync_is_charging, int cycles_
 			if(proposed_sync_y > (kCRTFixedPointRange * 15) >> 4) {
 				proposedSyncTime = _sync_capacitor_charge_threshold - _sync_capacitor_charge_level;
 				proposedEvent = SyncEvent::StartVSync;
+				_did_detect_vsync = true;
 			}
 		 }
 	}
@@ -298,7 +304,7 @@ void CRT::advance_cycles(int number_of_cycles, bool hsync_requested, const bool
 					{
 						_current_frame_builder->complete();
 						_frames_with_delegate++;
-						_delegate->crt_did_end_frame(this, &_current_frame_builder->frame);
+						_delegate->crt_did_end_frame(this, &_current_frame_builder->frame, _did_detect_hsync);
 					}
 
 					if(_frames_with_delegate < kCRTNumberOfFrames)
@@ -309,6 +315,8 @@ void CRT::advance_cycles(int number_of_cycles, bool hsync_requested, const bool
 					}
 					else
 						_current_frame_builder = nullptr;
+
+					_did_detect_vsync = false;
 				break;
 
 				default: break;

Outputs/CRT.hpp

@@ -51,6 +51,8 @@ class CRT {
 		CRT(int cycles_per_line, int height_of_display, int number_of_buffers, ...);
 		~CRT();
 
+		void set_new_timing(int cycles_per_line, int height_of_display);
+
 		void output_sync(int number_of_cycles);
 		void output_blank(int number_of_cycles);
 		void output_level(int number_of_cycles, const char *type);
@@ -58,7 +60,7 @@ class CRT {
 
 		class CRTDelegate {
 			public:
-				virtual void crt_did_end_frame(CRT *crt, CRTFrame *frame) = 0;
+				virtual void crt_did_end_frame(CRT *crt, CRTFrame *frame, bool did_detect_vsync) = 0;
 		};
 		void set_delegate(CRTDelegate *delegate);
 		void return_frame();
@@ -105,6 +107,7 @@ class CRT {
 		int _expected_next_hsync;			// our current expection of when the next horizontal sync will be encountered (which implies current flywheel velocity)
 		int _horizontal_retrace_time;
 		bool _is_in_hsync;					// true for the duration of a horizontal sync — used to determine beam running direction and speed
+		bool _did_detect_vsync;				// true if vertical sync was detected in the input stream rather than forced by emergency measure
 
 		// the outer entry point for dispatching output_sync, output_blank, output_level and output_data
 		enum Type {