Finally started on generalising the C++ stuff so as to be able to be able to get a working audio binding on the OS-specific side without further repetition by factoring an appropriate protocol out from the Electron and sketching out the correct speaker class for the Atari. Added a method to ask it what a good output frequency would be.

Machines/Atari2600/Atari2600.cpp

@@ -71,6 +71,8 @@ void Machine::setup_output(float aspect_ratio)
 			"return (float(y) / 14.0) * (1.0 - amplitude) + step(1, iPhase) * amplitude * cos(phase + phaseOffset);"
 		"}");
 	_crt->set_output_device(Outputs::CRT::Television);
+
+	_speaker.set_input_rate(2 * 263 * 60);
 }
 
 void Machine::switch_region()
@@ -89,6 +91,8 @@ void Machine::switch_region()
 			"return (float(y) / 14.0) * (1.0 - amplitude) + step(4, (iPhase + 2u) & 15u) * amplitude * cos(phase + phaseOffset);"
 		"}");
 	_crt->set_new_timing(228, 312, Outputs::CRT::ColourSpace::YUV, 228, 1);
+
+	_speaker.set_input_rate(2 * 312 * 50);
 }
 
 void Machine::close_output()
@@ -445,6 +449,10 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 				returnValue &= _ram[address&0x7f];
 			} else {
 				_ram[address&0x7f] = *value;
+//				if((address&0x7f) == (0x9a&0x7f))
+//				{
+//					printf("[9a] <- %02x\n", *value);
+//				}
 			}
 		}
 
@@ -585,7 +593,10 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 						_playerGraphics[1][index^1] = _playerGraphics[0][index^1];
 					} break;
 					case 0x1d:
-					case 0x1e: _missileGraphicsEnable[decodedAddress - 0x1d] = ((*value) >> 1)&1;	break;
+					case 0x1e:
+						_missileGraphicsEnable[decodedAddress - 0x1d] = ((*value) >> 1)&1;
+//						printf("e:%02x <- %c\n", decodedAddress - 0x1d, ((*value)&1) ? 'E' : '-');
+					break;
 					case 0x1f:
 						_ballGraphicsEnable[0] = ((*value) >> 1)&1;
 					break;
@@ -623,15 +634,17 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 							_objectCounter[_objectCounterPointer][index + 2].count = (_objectCounter[_objectCounterPointer][index + 2].count + extra_offset)%160;
 						}
 						_missileGraphicsReset[index] = !!((*value) & 0x02);
+//						printf("r:%02x <- %c\n", decodedAddress - 0x28, ((*value)&2) ? 'R' : '-');
 					}
 					break;
 
-					case 0x2a:
+					case 0x2a: {
 						// justification for +5: "we need to wait at least 71 [clocks] before the HMOVE operation is complete";
 						// which will take 16*4 + 2 = 66 cycles from the first compare, implying the first compare must be
 						// in five cycles from now
+//						int start_pause = ((_horizontalTimer + 3)&3) + 4;
 						_upcomingEvents[(_upcomingEventsPointer + 5)%number_of_upcoming_events].updates |= Event::Action::HMoveSetup;
-					break;
+					} break;
 					case 0x2b:
 						_objectMotion[0] =
 						_objectMotion[1] =

Machines/Atari2600/Atari2600.hpp

@@ -10,31 +10,52 @@
 #define Atari2600_cpp
 
 #include "../../Processors/6502/CPU6502.hpp"
-#include "../../Outputs/CRT/CRT.hpp"
+#include "../CRTMachine.hpp"
 #include <stdint.h>
 #include "Atari2600Inputs.h"
 
 namespace Atari2600 {
 
-const unsigned int number_of_upcoming_events = 6;
+const unsigned int number_of_upcoming_events = 16;
 const unsigned int number_of_recorded_counters = 7;
 
-class Machine: public CPU6502::Processor<Machine> {
+class Speaker: public ::Outputs::Filter<Speaker> {
+	public:
+		void set_volume(int channel, uint8_t volume);
+		void set_divider(int channel, uint8_t divider);
+		void set_control(int channel, uint8_t control);
+
+		void get_samples(unsigned int number_of_samples, int16_t *target);
+		void skip_samples(unsigned int number_of_samples);
+
+	private:
+		uint8_t _volume[2];
+		uint8_t _divider[2];
+		uint8_t _control[2];
+		int _shift_counters[2];
+};
+
+class Machine: public CPU6502::Processor<Machine>, CRTMachine::Machine {
 
 	public:
 		Machine();
 		~Machine();
 
-		unsigned 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();
 
 		void set_digital_input(Atari2600DigitalInput input, bool state);
 
-		Outputs::CRT::CRT *get_crt() { return _crt; }
-		void setup_output(float aspect_ratio);
-		void close_output();
+		// to satisfy CPU6502::Processor
+		unsigned int perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value);
+		void synchronise() {}
+
+		// to satisfy CRTMachine::Machine
+		virtual void setup_output(float aspect_ratio);
+		virtual void close_output();
+		virtual Outputs::CRT::CRT *get_crt() { return _crt; }
+		virtual Outputs::Speaker *get_speaker() { return &_speaker; }
+		virtual void run_for_cycles(int number_of_cycles) { CPU6502::Processor<Machine>::run_for_cycles(number_of_cycles); }
 
 	private:
 		uint8_t *_rom, *_romPages[4], _ram[128];
@@ -137,7 +158,10 @@ class Machine: public CPU6502::Processor<Machine> {
 		void output_pixels(unsigned int count);
 		uint8_t get_output_pixel();
 		void update_timers(int mask);
+
+		// Outputs
 		Outputs::CRT::CRT *_crt;
+		Speaker _speaker;
 
 		// latched output state
 		unsigned int _lastOutputStateDuration;

Machines/CRTMachine.hpp

@@ -0,0 +1,30 @@
+//
+//  CRTMachine.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 31/05/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#ifndef CRTMachine_hpp
+#define CRTMachine_hpp
+
+#include "../Outputs/CRT/CRT.hpp"
+#include "../Outputs/Speaker.hpp"
+
+namespace CRTMachine {
+
+class Machine {
+	public:
+		virtual void setup_output(float aspect_ratio) = 0;
+		virtual void close_output() = 0;
+
+		virtual Outputs::CRT::CRT *get_crt() = 0;
+		virtual Outputs::Speaker *get_speaker() = 0;
+
+		virtual void run_for_cycles(int number_of_cycles) = 0;
+};
+
+}
+
+#endif /* CRTMachine_hpp */

Machines/Electron/Electron.cpp

@@ -450,7 +450,7 @@ unsigned int Machine::perform_bus_operation(CPU6502::BusOperation operation, uin
 	return cycles;
 }
 
-void Machine::update_output()
+void Machine::synchronise()
 {
 	update_display();
 	update_audio();

Machines/Electron/Electron.hpp

@@ -10,9 +10,8 @@
 #define Electron_hpp
 
 #include "../../Processors/6502/CPU6502.hpp"
-#include "../../Outputs/CRT/CRT.hpp"
-#include "../../Outputs/Speaker.hpp"
 #include "../../Storage/Tape/Tape.hpp"
+#include "../CRTMachine.hpp"
 #include <stdint.h>
 
 namespace Electron {
@@ -142,30 +141,34 @@ class Speaker: public ::Outputs::Filter<Speaker> {
 	@discussion An instance of Electron::Machine represents the current state of an
 	Acorn Electron.
 */
-class Machine: public CPU6502::Processor<Machine>, Tape::Delegate {
+class Machine: public CPU6502::Processor<Machine>, Tape::Delegate, CRTMachine::Machine {
 
 	public:
 
 		Machine();
 
-		unsigned int perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value);
-
 		void set_rom(ROMSlot slot, size_t length, const uint8_t *data);
 		void set_tape(std::shared_ptr<Storage::Tape> tape);
 
 		void set_key_state(Key key, bool isPressed);
 		void clear_all_keys();
 
-		void setup_output(float aspect_ratio);
-		void close_output();
-		Outputs::CRT::CRT *get_crt() { return _crt.get(); }
-		Outputs::Speaker *get_speaker() { return &_speaker; }
-
-		virtual void tape_did_change_interrupt_status(Tape *tape);
-
-		void update_output();
 		inline void set_use_fast_tape_hack(bool activate) { _use_fast_tape_hack = activate; }
 
+		// to satisfy CPU6502::Processor
+		unsigned int perform_bus_operation(CPU6502::BusOperation operation, uint16_t address, uint8_t *value);
+		void synchronise();
+
+		// to satisfy CRTMachine::Machine
+		virtual void setup_output(float aspect_ratio);
+		virtual void close_output();
+		virtual Outputs::CRT::CRT *get_crt() { return _crt.get(); }
+		virtual Outputs::Speaker *get_speaker() { return &_speaker; }
+		virtual void run_for_cycles(int number_of_cycles) { CPU6502::Processor<Machine>::run_for_cycles(number_of_cycles); }
+
+		// to satisfy Tape::Delegate
+		virtual void tape_did_change_interrupt_status(Tape *tape);
+
 	private:
 
 		inline void update_display();
@@ -215,12 +218,12 @@ class Machine: public CPU6502::Processor<Machine>, Tape::Delegate {
 		uint8_t *_current_output_target, *_initial_output_target;
 		unsigned int _current_output_divider;
 
-		// Tape.
+		// Tape
 		Tape _tape;
 		bool _use_fast_tape_hack;
 		bool _fast_load_is_in_data;
 
-		// Outputs.
+		// Outputs
 		std::unique_ptr<Outputs::CRT::CRT> _crt;
 		Speaker _speaker;
 };

OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj

@@ -334,6 +334,7 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		4B046DC31CFE651500E9E45E /* CRTMachine.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = CRTMachine.hpp; sourceTree = "<group>"; };
 		4B0B6E121C9DBD5D00FFB60D /* CRTConstants.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = CRTConstants.hpp; sourceTree = "<group>"; };
 		4B0CCC421C62D0B3001CAC5F /* CRT.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = CRT.cpp; sourceTree = "<group>"; };
 		4B0CCC431C62D0B3001CAC5F /* CRT.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = CRT.hpp; sourceTree = "<group>"; };
@@ -1192,6 +1193,7 @@
 			children = (
 				4B2E2D961C3A06EC00138695 /* Atari2600 */,
 				4B2E2D9E1C3A070900138695 /* Electron */,
+				4B046DC31CFE651500E9E45E /* CRTMachine.hpp */,
 			);
 			name = Machines;
 			path = ../../Machines;

OSBindings/Mac/Clock Signal/Wrappers/CSElectron.mm

@@ -19,7 +19,6 @@
 - (void)runForNumberOfCycles:(int)numberOfCycles {
 	@synchronized(self) {
 		_electron.run_for_cycles(numberOfCycles);
-		_electron.update_output();
 	}
 }
 

Outputs/Speaker.hpp

@@ -24,6 +24,18 @@ class Speaker {
 				virtual void speaker_did_complete_samples(Speaker *speaker, const int16_t *buffer, int buffer_size) = 0;
 		};
 
+		int get_ideal_clock_rate_in_range(int minimum, int maximum)
+		{
+			// return exactly the input rate if possible
+			if(_input_cycles_per_second >= minimum && _input_cycles_per_second <= maximum) return _input_cycles_per_second;
+
+			// if the input rate is lower, return the minimum
+			if(_input_cycles_per_second < minimum) return minimum;
+
+			// otherwise, return the maximum
+			return maximum;
+		}
+
 		void set_output_rate(int cycles_per_second, int buffer_size)
 		{
 			_output_cycles_per_second = cycles_per_second;

Processors/6502/CPU6502.hpp

@@ -67,9 +67,12 @@ extern const uint8_t JamOpcode;
 	@abstact An abstract base class for emulation of a 6502 processor via the curiously recurring template pattern/f-bounded polymorphism.
 
 	@discussion Subclasses should implement @c perform_bus_operation(BusOperation operation, uint16_t address, uint8_t *value) in
-	order to provde the bus on which the 6502 operates. Additional functionality can be provided by the host machine by providing
-	a jam handler and inserting jam opcodes where appropriate; that will cause call outs when the program counter reaches those
-	addresses. @c return_from_subroutine can be used to exit from a jammed state.
+	order to provide the bus on which the 6502 operates and @c synchronise(), which is called upon completion of a continuous run
+	of cycles to allow a subclass to bring any on-demand activities up to date.
+
+	Additional functionality can be provided by the host machine by providing a jam handler and inserting jam opcodes where appropriate;
+	that will cause call outs when the program counter reaches those addresses. @c return_from_subroutine can be used to exit from a
+	jammed state.
 */
 template <class T> class Processor {
 	public:
@@ -597,7 +600,7 @@ template <class T> class Processor {
 
 						case CycleFetchOperation: {
 							_lastOperationPC = _pc;
-//							printf("%04x\n", _pc.full);
+//							printf("%04x	x:%02x\n", _pc.full, _x);
 							_pc.full++;
 							read_op(_operation, _lastOperationPC.full);
 
@@ -1041,15 +1044,17 @@ template <class T> class Processor {
 						_ready_is_active = true;
 					}
 				}
-
-				_cycles_left_to_run = number_of_cycles;
-				_scheduleProgramsReadPointer = scheduleProgramsReadPointer;
-				_scheduleProgramProgramCounter = scheduleProgramProgramCounter;
-				_nextAddress = nextAddress;
-				_nextBusOperation = nextBusOperation;
-				_busAddress = busAddress;
-				_busValue = busValue;
 			}
+
+			_cycles_left_to_run = number_of_cycles;
+			_scheduleProgramsReadPointer = scheduleProgramsReadPointer;
+			_scheduleProgramProgramCounter = scheduleProgramProgramCounter;
+			_nextAddress = nextAddress;
+			_nextBusOperation = nextBusOperation;
+			_busAddress = busAddress;
+			_busValue = busValue;
+
+			static_cast<T *>(this)->synchronise();
 		}
 
 		/*!