Fix value interactions.

Components/6560/6560.cpp

@@ -12,7 +12,7 @@
 
 using namespace MOS::MOS6560;
 
-AudioGenerator::AudioGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue) :
+AudioGenerator::AudioGenerator(Outputs::Speaker::TaskQueue &audio_queue) :
 	audio_queue_(audio_queue) {}
 
 void AudioGenerator::set_volume(const uint8_t volume) {

Components/6560/6560.hpp

@@ -19,7 +19,7 @@ namespace MOS::MOS6560 {
 // audio state
 class AudioGenerator: public Outputs::Speaker::BufferSource<AudioGenerator, false> {
 public:
-	AudioGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue);
+	AudioGenerator(Outputs::Speaker::TaskQueue &audio_queue);
 
 	void set_volume(uint8_t);
 	void set_control(int channel, uint8_t value);
@@ -30,7 +30,7 @@ public:
 	void set_sample_volume_range(std::int16_t);
 
 private:
-	Concurrency::AsyncTaskQueue<false> &audio_queue_;
+	Outputs::Speaker::TaskQueue &audio_queue_;
 
 	unsigned int counters_[4] = {2, 1, 0, 0};	// create a slight phase offset for the three channels
 	unsigned int shift_registers_[4] = {0, 0, 0, 0};
@@ -64,8 +64,7 @@ public:
 	MOS6560(BusHandler &bus_handler) :
 			bus_handler_(bus_handler),
 			crt_(65*4, 1, Outputs::Display::Type::NTSC60, Outputs::Display::InputDataType::Luminance8Phase8),
-			audio_generator_(audio_queue_),
+			audio_(Cycles(4))
-			speaker_(audio_generator_)
 	{
 		// default to s-video output
 		crt_.set_display_type(Outputs::Display::DisplayType::SVideo);
@@ -75,11 +74,11 @@ public:
 	}
 
 	~MOS6560() {
-		audio_queue_.lock_flush();
+		audio_.stop();
 	}
 
 	void set_clock_rate(const double clock_rate) {
-		speaker_.set_input_rate(float(clock_rate / 4.0));
+		audio_.speaker().set_input_rate(float(clock_rate / 4.0));
 	}
 
 	void set_scan_target(Outputs::Display::ScanTarget *const scan_target) {
@@ -95,11 +94,11 @@ public:
 		return crt_.get_display_type();
 	}
 	Outputs::Speaker::Speaker *get_speaker() {
-		return &speaker_;
+		return &audio_.speaker();
 	}
 
 	void set_high_frequency_cutoff(const float cutoff) {
-		speaker_.set_high_frequency_cutoff(cutoff);
+		audio_.speaker().set_high_frequency_cutoff(cutoff);
 	}
 
 	/*!
@@ -180,7 +179,7 @@ public:
 	*/
 	inline void run_for(const Cycles cycles) {
 		// keep track of the amount of time since the speaker was updated; lazy updates are applied
-		cycles_since_speaker_update_ += cycles;
+		audio_ += cycles;
 
 		auto number_of_cycles = cycles.as_integral();
 		while(number_of_cycles--) {
@@ -377,8 +376,7 @@ public:
 		Causes the 6560 to flush as much pending CRT and speaker communications as possible.
 	*/
 	inline void flush() {
-		update_audio();
+		audio_.perform();
-		audio_queue_.perform();
 	}
 
 	/*!
@@ -420,14 +418,12 @@ public:
 			case 0xb:
 			case 0xc:
 			case 0xd:
-				update_audio();
+				audio_->set_control(address - 0xa, value);
-				audio_generator_.set_control(address - 0xa, value);
 			break;
 
 			case 0xe:
-				update_audio();
 				registers_.auxiliary_colour = colours_[value >> 4];
-				audio_generator_.set_volume(value & 0xf);
+				audio_->set_volume(value & 0xf);
 			break;
 
 			case 0xf: {
@@ -467,14 +463,7 @@ private:
 	BusHandler &bus_handler_;
 	Outputs::CRT::CRT crt_;
 
-	Concurrency::AsyncTaskQueue<false> audio_queue_;
+	Outputs::Speaker::PullLowpassSpeakerQueue<Cycles, AudioGenerator> audio_;
-	AudioGenerator audio_generator_;
-	Outputs::Speaker::PullLowpass<AudioGenerator> speaker_;
-
-	Cycles cycles_since_speaker_update_;
-	void update_audio() {
-		speaker_.run_for(audio_queue_, Cycles(cycles_since_speaker_update_.divide(Cycles(4))));
-	}
 
 	// register state
 	struct {

Concurrency/AsyncTaskQueue.hpp

@@ -40,9 +40,12 @@ private:
 /// An implementation detail; provides a no-op implementation of time advances for TaskQueues without a Performer.
 template <> struct TaskQueueStorage<void> {
 	TaskQueueStorage() {}
+protected:
+	void update() {}
+};
 
-	protected:
+struct EnqueueDelegate {
-		void update() {}
+	virtual std::function<void(void)> prepare_enqueue() = 0;
 };
 
 /*!
@@ -67,10 +70,15 @@ template <> struct TaskQueueStorage<void> {
 template <
 	bool perform_automatically,
 	bool start_immediately = true,
+	bool use_enqueue_delegate = false,
 	typename Performer = void
 >
 class AsyncTaskQueue: public TaskQueueStorage<Performer> {
 public:
+	void set_enqueue_delegate(EnqueueDelegate *const delegate) {
+		enqueue_delegate_ = delegate;
+	}
+
 	template <typename... Args> AsyncTaskQueue(Args&&... args) :
 		TaskQueueStorage<Performer>(std::forward<Args>(args)...) {
 		if constexpr (start_immediately) {
@@ -90,6 +98,9 @@ public:
 	/// to 'now'.
 	void enqueue(const std::function<void(void)> &post_action) {
 		const std::lock_guard guard(condition_mutex_);
+		if constexpr (use_enqueue_delegate) {
+			actions_.push_back(enqueue_delegate_->prepare_enqueue());
+		}
 		actions_.push_back(post_action);
 
 		if constexpr (perform_automatically) {
@@ -206,6 +217,8 @@ private:
 		};
 	}
 
+	EnqueueDelegate *enqueue_delegate_ = nullptr;
+
 	// The list of actions waiting be performed. These will be elided,
 	// increasing their latency, if the emulation thread falls behind.
 	using ActionVector = std::vector<std::function<void(void)>>;

Machines/Acorn/Electron/Electron.cpp

@@ -15,7 +15,6 @@
 #include "ClockReceiver/ClockReceiver.hpp"
 #include "ClockReceiver/ForceInline.hpp"
 #include "Configurable/StandardOptions.hpp"
-#include "Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
 #include "Processors/6502/6502.hpp"
 
 #include "Storage/MassStorage/SCSI/SCSI.hpp"
@@ -27,6 +26,8 @@
 
 #include "ClockReceiver/JustInTime.hpp"
 
+#include "Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
+
 #include "Interrupts.hpp"
 #include "Keyboard.hpp"
 #include "Plus3.hpp"
@@ -58,8 +59,11 @@ public:
 			hard_drive_(scsi_bus_, 0),
 			scsi_device_(scsi_bus_.add_device()),
 			video_(ram_),
-			sound_generator_(audio_queue_),
+			audio_(
-			speaker_(sound_generator_) {
+				2000000.0 / SoundGenerator::clock_rate_divider,
+				SoundGenerator::clock_rate_divider,
+				6000.0f
+			) {
 		memset(key_states_, 0, sizeof(key_states_));
 		for(int c = 0; c < 16; c++)
 			memset(roms_[c], 0xff, 16384);
@@ -67,9 +71,6 @@ public:
 		tape_.set_delegate(this);
 		set_clock_rate(2000000);
 
-		speaker_.set_input_rate(2000000 / SoundGenerator::clock_rate_divider);
-		speaker_.set_high_frequency_cutoff(6000);
-
 		::ROM::Request request = ::ROM::Request(::ROM::Name::AcornBASICII) && ::ROM::Request(::ROM::Name::AcornElectronMOS100);
 		if(target.has_pres_adfs) {
 			request = request && ::ROM::Request(::ROM::Name::PRESADFSSlot1) && ::ROM::Request(::ROM::Name::PRESADFSSlot2);
@@ -143,7 +144,7 @@ public:
 	}
 
 	~ConcreteMachine() {
-		audio_queue_.lock_flush();
+		audio_.stop();
 	}
 
 	void set_key_state(uint16_t key, bool isPressed) final {
@@ -234,8 +235,7 @@ public:
 		const auto [cycles, video_interrupts] = run_for_access(address);
 		signal_interrupt(video_interrupts);
 
-		cycles_since_audio_update_ += cycles;
+		audio_ += cycles;
-		if(cycles_since_audio_update_ > Cycles(16384)) update_audio();
 		tape_.run_for(cycles);
 
 		if(typer_) typer_->run_for(cycles);
@@ -278,8 +278,7 @@ public:
 						// update speaker mode
 						bool new_speaker_is_enabled = (*value & 6) == 2;
 						if(new_speaker_is_enabled != speaker_is_enabled_) {
-							update_audio();
+							audio_->set_is_enabled(new_speaker_is_enabled);
-							sound_generator_.set_is_enabled(new_speaker_is_enabled);
 							speaker_is_enabled_ = new_speaker_is_enabled;
 						}
 
@@ -340,8 +339,7 @@ public:
 				break;
 				case 0xfe06:
 					if(!is_read(operation)) {
-						update_audio();
+						audio_->set_divider(*value);
-						sound_generator_.set_divider(*value);
 						tape_.set_counter(*value);
 					}
 				break;
@@ -510,8 +508,7 @@ public:
 
 	void flush_output(int outputs) final {
 		if(outputs & Output::Audio) {
-			update_audio();
+			audio_.perform();
-			audio_queue_.perform();
 		}
 	}
 
@@ -532,7 +529,7 @@ public:
 	}
 
 	Outputs::Speaker::Speaker *get_speaker() final {
-		return &speaker_;
+		return &audio_.speaker();
 	}
 
 	void run_for(const Cycles cycles) final {
@@ -682,10 +679,6 @@ private:
 	}
 
 	// MARK: - Work deferral updates.
-	inline void update_audio() {
-		speaker_.run_for(audio_queue_, cycles_since_audio_update_.divide(Cycles(SoundGenerator::clock_rate_divider)));
-	}
-
 	inline void signal_interrupt(uint8_t interrupt) {
 		if(!interrupt) {
 			return;
@@ -732,9 +725,6 @@ private:
 	uint8_t key_states_[14];
 	Electron::KeyboardMapper keyboard_mapper_;
 
-	// Counters related to simultaneous subsystems
-	Cycles cycles_since_audio_update_ = 0;
-
 	// Tape
 	Tape tape_;
 	bool use_fast_tape_hack_ = false;
@@ -770,10 +760,7 @@ private:
 
 	// Outputs
 	VideoOutput video_;
-
+	Outputs::Speaker::PullLowpassSpeakerQueue<Cycles, SoundGenerator> audio_;
-	Concurrency::AsyncTaskQueue<false> audio_queue_;
-	SoundGenerator sound_generator_;
-	Outputs::Speaker::PullLowpass<SoundGenerator> speaker_;
 
 	bool speaker_is_enabled_ = false;
 

Machines/Acorn/Electron/SoundGenerator.cpp

@@ -12,7 +12,7 @@
 
 using namespace Electron;
 
-SoundGenerator::SoundGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue) :
+SoundGenerator::SoundGenerator(Outputs::Speaker::TaskQueue &audio_queue) :
 	audio_queue_(audio_queue) {}
 
 void SoundGenerator::set_sample_volume_range(std::int16_t range) {
@@ -40,13 +40,13 @@ template void SoundGenerator::apply_samples<Outputs::Speaker::Action::Mix>(std::
 template void SoundGenerator::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, Outputs::Speaker::MonoSample *);
 template void SoundGenerator::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, Outputs::Speaker::MonoSample *);
 
-void SoundGenerator::set_divider(uint8_t divider) {
+void SoundGenerator::set_divider(const uint8_t divider) {
 	audio_queue_.enqueue([this, divider]() {
 		divider_ = divider * 32 / clock_rate_divider;
 	});
 }
 
-void SoundGenerator::set_is_enabled(bool is_enabled) {
+void SoundGenerator::set_is_enabled(const bool is_enabled) {
 	audio_queue_.enqueue([this, is_enabled]() {
 		is_enabled_ = is_enabled;
 		counter_ = 0;

Machines/Acorn/Electron/SoundGenerator.hpp

@@ -9,13 +9,13 @@
 #pragma once
 
 #include "Outputs/Speaker/Implementation/BufferSource.hpp"
-#include "Concurrency/AsyncTaskQueue.hpp"
+#include "Outputs/Speaker/SpeakerQueue.hpp"
 
 namespace Electron {
 
 class SoundGenerator: public ::Outputs::Speaker::BufferSource<SoundGenerator, false> {
 public:
-	SoundGenerator(Concurrency::AsyncTaskQueue<false> &);
+	SoundGenerator(Outputs::Speaker::TaskQueue &);
 
 	void set_divider(uint8_t);
 	void set_is_enabled(bool);
@@ -28,7 +28,7 @@ public:
 	void set_sample_volume_range(std::int16_t range);
 
 private:
-	Concurrency::AsyncTaskQueue<false> &audio_queue_;
+	Outputs::Speaker::TaskQueue &audio_queue_;
 	unsigned int counter_ = 0;
 	unsigned int divider_ = 0;
 	bool is_enabled_ = false;

Machines/Atari/2600/Atari2600.cpp

@@ -159,7 +159,7 @@ public:
 
 	// to satisfy CRTMachine::Machine
 	void set_scan_target(Outputs::Display::ScanTarget *scan_target) final {
-		bus_->speaker_.set_input_rate(float(get_clock_rate() / double(CPUTicksPerAudioTick)));
+		bus_->audio_.speaker().set_input_rate(float(get_clock_rate() / double(CPUTicksPerAudioTick)));
 		bus_->tia_.set_crt_delegate(&frequency_mismatch_warner_);
 		bus_->tia_.set_scan_target(scan_target);
 	}
@@ -169,7 +169,7 @@ public:
 	}
 
 	Outputs::Speaker::Speaker *get_speaker() final {
-		return &bus_->speaker_;
+		return &bus_->audio_.speaker();
 	}
 
 	void run_for(const Cycles cycles) final {
@@ -206,11 +206,11 @@ private:
 	// a confidence counter
 	Analyser::Dynamic::ConfidenceCounter confidence_counter_;
 
-	void set_is_ntsc(bool is_ntsc) {
+	void set_is_ntsc(const bool is_ntsc) {
 		bus_->tia_.set_output_mode(is_ntsc ? TIA::OutputMode::NTSC : TIA::OutputMode::PAL);
 		const double clock_rate = is_ntsc ? NTSC_clock_rate : PAL_clock_rate;
-		bus_->speaker_.set_input_rate(float(clock_rate) / float(CPUTicksPerAudioTick));
+		bus_->audio_.speaker().set_input_rate(float(clock_rate) / float(CPUTicksPerAudioTick));
-		bus_->speaker_.set_high_frequency_cutoff(float(clock_rate) / float(CPUTicksPerAudioTick * 2));
+		bus_->audio_.speaker().set_high_frequency_cutoff(float(clock_rate) / float(CPUTicksPerAudioTick * 2));
 		set_clock_rate(clock_rate);
 	}
 };

Machines/Atari/2600/Bus.hpp

@@ -21,12 +21,10 @@ namespace Atari2600 {
 
 class Bus {
 public:
-	Bus() :
+	Bus() : audio_(Cycles(CPUTicksPerAudioTick * 3)) {}
-		tia_sound_(audio_queue_),
-		speaker_(tia_sound_) {}
 
 	virtual ~Bus() {
-		audio_queue_.lock_flush();
+		audio_.stop();
 	}
 
 	virtual void run_for(const Cycles cycles) = 0;
@@ -34,31 +32,22 @@ public:
 	virtual void set_reset_line(bool state) = 0;
 	virtual void flush() = 0;
 
-	// the RIOT, TIA and speaker
+	// The RIOT, TIA and speaker.
 	PIA mos6532_;
 	TIA tia_;
+	Outputs::Speaker::PullLowpassSpeakerQueue<Cycles, TIASound> audio_;
 
-	Concurrency::AsyncTaskQueue<false> audio_queue_;
+	// Joystick state.
-	TIASound tia_sound_;
-	Outputs::Speaker::PullLowpass<TIASound> speaker_;
-
-	// joystick state
 	uint8_t tia_input_value_[2] = {0xff, 0xff};
 
 protected:
-	// speaker backlog accumlation counter
+	// Video backlog accumulation counter.
-	Cycles cycles_since_speaker_update_;
-	inline void update_audio() {
-		speaker_.run_for(audio_queue_, cycles_since_speaker_update_.divide(Cycles(CPUTicksPerAudioTick * 3)));
-	}
-
-	// video backlog accumulation counter
 	Cycles cycles_since_video_update_;
 	inline void update_video() {
 		tia_.run_for(cycles_since_video_update_.flush<Cycles>());
 	}
 
-	// RIOT backlog accumulation counter
+	// RIOT backlog accumulation counter.
 	Cycles cycles_since_6532_update_;
 	inline void update_6532() {
 		mos6532_.run_for(cycles_since_6532_update_.flush<Cycles>());

Machines/Atari/2600/Cartridges/Cartridge.hpp

@@ -70,10 +70,11 @@ public:
 		// leap to the end of ready only once ready is signalled because on a 6502 ready doesn't take
 		// effect until the next read; therefore it isn't safe to assume that signalling ready immediately
 		// skips to the end of the line.
-		if(operation == CPU::MOS6502::BusOperation::Ready)
+		if(operation == CPU::MOS6502::BusOperation::Ready) {
 			cycles_run_for = tia_.get_cycles_until_horizontal_blank(cycles_since_video_update_);
+		}
 
-		cycles_since_speaker_update_ += Cycles(cycles_run_for);
+		audio_ += Cycles(cycles_run_for);
 		cycles_since_video_update_ += Cycles(cycles_run_for);
 		cycles_since_6532_update_ += Cycles(cycles_run_for / 3);
 		bus_extender_.advance_cycles(cycles_run_for / 3);
@@ -171,11 +172,11 @@ public:
 						case 0x2c:	update_video(); tia_.clear_collision_flags();										break;
 
 						case 0x15:
-						case 0x16:	update_audio(); tia_sound_.set_control(decodedAddress - 0x15, *value);				break;
+						case 0x16:	audio_->set_control(decodedAddress - 0x15, *value);			break;
 						case 0x17:
-						case 0x18:	update_audio(); tia_sound_.set_divider(decodedAddress - 0x17, *value);				break;
+						case 0x18:	audio_->set_divider(decodedAddress - 0x17, *value);			break;
 						case 0x19:
-						case 0x1a:	update_audio(); tia_sound_.set_volume(decodedAddress - 0x19, *value);				break;
+						case 0x1a:	audio_->set_volume(decodedAddress - 0x19, *value);				break;
 					}
 				}
 			}
@@ -201,9 +202,8 @@ public:
 	}
 
 	void flush() override {
-		update_audio();
 		update_video();
-		audio_queue_.perform();
+		audio_.perform();
 	}
 
 protected:

Machines/Atari/2600/TIASound.cpp

@@ -10,7 +10,7 @@
 
 using namespace Atari2600;
 
-Atari2600::TIASound::TIASound(Concurrency::AsyncTaskQueue<false> &audio_queue) :
+Atari2600::TIASound::TIASound(Outputs::Speaker::TaskQueue &audio_queue) :
 	audio_queue_(audio_queue)
 {}
 

Machines/Atari/2600/TIASound.hpp

@@ -9,7 +9,7 @@
 #pragma once
 
 #include "Outputs/Speaker/Implementation/BufferSource.hpp"
-#include "Concurrency/AsyncTaskQueue.hpp"
+#include "Outputs/Speaker/SpeakerQueue.hpp"
 
 namespace Atari2600 {
 
@@ -19,7 +19,7 @@ constexpr int CPUTicksPerAudioTick = 2;
 
 class TIASound: public Outputs::Speaker::BufferSource<TIASound, false> {
 public:
-	TIASound(Concurrency::AsyncTaskQueue<false> &);
+	TIASound(Outputs::Speaker::TaskQueue &);
 
 	void set_volume(int channel, uint8_t volume);
 	void set_divider(int channel, uint8_t divider);
@@ -30,7 +30,7 @@ public:
 	void set_sample_volume_range(std::int16_t);
 
 private:
-	Concurrency::AsyncTaskQueue<false> &audio_queue_;
+	Outputs::Speaker::TaskQueue &audio_queue_;
 
 	uint8_t volume_[2];
 	uint8_t divider_[2];

Machines/Commodore/Plus4/Audio.hpp

@@ -9,13 +9,13 @@
 #pragma once
 
 #include "Outputs/Speaker/Implementation/BufferSource.hpp"
-#include "Concurrency/AsyncTaskQueue.hpp"
+#include "Outputs/Speaker/SpeakerQueue.hpp"
 
 namespace Commodore::Plus4 {
 
 class Audio: public Outputs::Speaker::BufferSource<Audio, false> {
 public:
-	Audio(Concurrency::AsyncTaskQueue<false> &audio_queue) :
+	Audio(Outputs::Speaker::TaskQueue &audio_queue) :
 		audio_queue_(audio_queue) {}
 
 	template <Outputs::Speaker::Action action>
@@ -122,7 +122,7 @@ public:
 
 private:
 	// Calling-thread state.
-	Concurrency::AsyncTaskQueue<false> &audio_queue_;
+	Outputs::Speaker::TaskQueue &audio_queue_;
 
 	// Audio-thread state.
 	int16_t external_volume_ = 0;

Machines/Commodore/Plus4/Plus4.cpp

@@ -186,13 +186,11 @@ public:
 		interrupts_(*this),
 		timers_(interrupts_),
 		video_(video_map_, interrupts_),
-		audio_(audio_queue_),
+		audio_(clock_rate(false), Cycles(1))
-		speaker_(audio_)
 	{
 		const auto clock = clock_rate(false);
 		media_divider_ = Cycles(clock);
 		set_clock_rate(clock);
-		speaker_.set_input_rate(float(clock));
 
 		const auto kernel = ROM::Name::Plus4KernelPALv5;
 		const auto basic = ROM::Name::Plus4BASIC;
@@ -236,7 +234,7 @@ public:
 	}
 
 	~ConcreteMachine() {
-		audio_queue_.lock_flush();
+		audio_.stop();
 	}
 
 	// HACK. NOCOMMIT.
@@ -258,8 +256,7 @@ public:
 				c1541_->run_for(c1541_cycles_.divide(media_divider_));
 			}
 
-
+			audio_ += length;
-			time_since_audio_update_ += length;
 		}
 
 		if(operation == CPU::MOS6502Mk2::BusOperation::Ready) {
@@ -532,8 +529,7 @@ public:
 					case 0xff06:	video_.write<0xff06>(value);	break;
 					case 0xff07:
 						video_.write<0xff07>(value);
-						update_audio();
+						audio_->set_divider(value);
-						audio_.set_divider(value);
 					break;
 					case 0xff08:
 						// Observation here: the kernel posts a 0 to this
@@ -560,23 +556,19 @@ public:
 					case 0xff0d:	video_.write<0xff0d>(value);	break;
 					case 0xff0e:
 						ff0e_ = value;
-						update_audio();
+						audio_->set_frequency_low<0>(value);
-						audio_.set_frequency_low<0>(value);
 					break;
 					case 0xff0f:
 						ff0f_ = value;
-						update_audio();
+						audio_->set_frequency_low<1>(value);
-						audio_.set_frequency_low<1>(value);
 					break;
 					case 0xff10:
 						ff10_ = value;
-						update_audio();
+						audio_->set_frequency_high<1>(value);
-						audio_.set_frequency_high<1>(value);
 					break;
 					case 0xff11:
 						ff11_ = value;
-						update_audio();
+						audio_->set_control(value);
-						audio_.set_control(value);
 					break;
 					case 0xff12:
 						ff12_ = value & 0x3f;
@@ -588,8 +580,7 @@ public:
 							page_video_ram();
 						}
 
-						update_audio();
+						audio_->set_frequency_high<0>(value);
-						audio_.set_frequency_high<0>(value);
 					break;
 					case 0xff13:
 						ff13_ = value & 0xfe;
@@ -633,7 +624,7 @@ private:
 	CPU::MOS6502Mk2::Processor<CPU::MOS6502Mk2::Model::M6502, M6502Traits> m6502_;
 
 	Outputs::Speaker::Speaker *get_speaker() override {
-		return &speaker_;
+		return &audio_.speaker();
 	}
 
 	void set_activity_observer(Activity::Observer *const observer) final {
@@ -687,16 +678,12 @@ private:
 
 	void run_for(const Cycles cycles) final {
 		m6502_.run_for(cycles);
-
+		audio_.perform();
-		// I don't know why.
-		update_audio();
-		audio_queue_.perform();
 	}
 
 	void flush_output(int outputs) override {
 		if(outputs & Output::Audio) {
-			update_audio();
+			audio_.perform();
-			audio_queue_.perform();
 		}
 	}
 
@@ -723,14 +710,7 @@ private:
 	Cycles timers_subcycles_;
 	Timers timers_;
 	Video video_;
-
+	Outputs::Speaker::PullLowpassSpeakerQueue<Cycles, Audio> audio_;
-	Concurrency::AsyncTaskQueue<false> audio_queue_;
-	Audio audio_;
-	Cycles time_since_audio_update_;
-	Outputs::Speaker::PullLowpass<Audio> speaker_;
-	void update_audio() {
-		speaker_.run_for(audio_queue_, time_since_audio_update_.flush<Cycles>());
-	}
 
 	// MARK: - MappedKeyboardMachine.
 	MappedKeyboardMachine::KeyboardMapper *get_keyboard_mapper() override {

Machines/Enterprise/Dave.cpp

@@ -12,7 +12,7 @@ using namespace Enterprise::Dave;
 
 // MARK: - Audio generator
 
-Audio::Audio(Concurrency::AsyncTaskQueue<false> &audio_queue) :
+Audio::Audio(Outputs::Speaker::TaskQueue &audio_queue) :
 	audio_queue_(audio_queue) {}
 
 void Audio::write(uint16_t address, const uint8_t value) {

Machines/Enterprise/Dave.hpp

@@ -11,7 +11,7 @@
 #include <cstdint>
 
 #include "ClockReceiver/ClockReceiver.hpp"
-#include "Concurrency/AsyncTaskQueue.hpp"
+#include "Outputs/Speaker/SpeakerQueue.hpp"
 #include "Numeric/LFSR.hpp"
 #include "Outputs/Speaker/Implementation/BufferSource.hpp"
 
@@ -28,7 +28,7 @@ enum class Interrupt: uint8_t {
 */
 class Audio: public Outputs::Speaker::BufferSource<Audio, true> {
 public:
-	Audio(Concurrency::AsyncTaskQueue<false> &audio_queue);
+	Audio(Outputs::Speaker::TaskQueue &);
 
 	/// Modifies an register in the audio range; only the low 4 bits are
 	/// used for register decoding so it's assumed that the caller has
@@ -41,7 +41,7 @@ public:
 	void apply_samples(std::size_t number_of_samples, Outputs::Speaker::StereoSample *target);
 
 private:
-	Concurrency::AsyncTaskQueue<false> &audio_queue_;
+	Outputs::Speaker::TaskQueue &audio_queue_;
 
 	// Global divider (i.e. 8MHz/12Mhz switch).
 	uint8_t global_divider_;

Machines/Enterprise/Enterprise.cpp

@@ -103,12 +103,10 @@ public:
 		min_ram_slot_(min_ram_slot(target)),
 		z80_(*this),
 		nick_(ram_.end() - 65536),
-		dave_audio_(audio_queue_),
+		audio_(float(clock_rate) / float(DaveDivider), DaveDivider) {
-		speaker_(dave_audio_) {
 
 		// Request a clock of 4Mhz; this'll be mapped upwards for Nick and downwards for Dave elsewhere.
 		set_clock_rate(clock_rate);
-		speaker_.set_input_rate(float(clock_rate) / float(dave_divider));
 
 		ROM::Request request;
 		using Target = Analyser::Static::Enterprise::Target;
@@ -257,7 +255,7 @@ public:
 	}
 
 	~ConcreteMachine() {
-		audio_queue_.lock_flush();
+		audio_.stop();
 	}
 
 	// MARK: - Z80::BusHandler.
@@ -344,7 +342,7 @@ public:
 		}
 
 		const HalfCycles full_length = cycle.length + penalty;
-		time_since_audio_update_ += full_length;
+		audio_ += full_length;
 		advance_nick(full_length);
 		if(dave_timer_ += full_length) {
 			set_interrupts(dave_timer_.last_valid()->get_new_interrupts(), dave_timer_.last_sequence_point_overrun());
@@ -475,8 +473,7 @@ public:
 					case 0xa4:	case 0xa5:	case 0xa6:	case 0xa7:
 					case 0xa8:	case 0xa9:	case 0xaa:	case 0xab:
 					case 0xac:	case 0xad:	case 0xae:	case 0xaf:
-						update_audio();
+						audio_->write(address, *cycle.value);
-						dave_audio_.write(address, *cycle.value);
 						dave_timer_->write(address, *cycle.value);
 					break;
 
@@ -563,8 +560,7 @@ public:
 			nick_.flush();
 		}
 		if(outputs & Output::Audio) {
-			update_audio();
+			audio_.perform();
-			audio_queue_.perform();
 		}
 	}
 
@@ -650,7 +646,7 @@ private:
 	// MARK: - AudioProducer
 
 	Outputs::Speaker::Speaker *get_speaker() final {
-		return &speaker_;
+		return &audio_.speaker();
 	}
 
 	// MARK: - TimedMachine
@@ -726,20 +722,13 @@ private:
 	bool previous_nick_interrupt_line_ = false;
 	// Cf. timing guesses above.
 
-	Concurrency::AsyncTaskQueue<false> audio_queue_;
+	Outputs::Speaker::PullLowpassSpeakerQueue<HalfCycles, Dave::Audio> audio_;
-	Dave::Audio dave_audio_;
-	Outputs::Speaker::PullLowpass<Dave::Audio> speaker_;
-	HalfCycles time_since_audio_update_;
-
 	HalfCycles dave_delay_ = HalfCycles(2);
 
 	// The divider supplied to the JustInTimeActor and the manual divider used in
-	// update_audio() should match.
+	// the spekaer queue should match.
-	static constexpr int dave_divider = 8;
+	static constexpr int DaveDivider = 8;
-	JustInTimeActor<Dave::TimedInterruptSource, HalfCycles, 1, dave_divider> dave_timer_;
+	JustInTimeActor<Dave::TimedInterruptSource, HalfCycles, 1, DaveDivider> dave_timer_;
-	inline void update_audio() {
-		speaker_.run_for(audio_queue_, time_since_audio_update_.divide_cycles(Cycles(dave_divider)));
-	}
 
 	// MARK: - EXDos card.
 	EXDos exdos_;

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

@@ -2523,6 +2523,7 @@
 		4BEF6AA81D35CE9E00E73575 /* DigitalPhaseLockedLoopBridge.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = DigitalPhaseLockedLoopBridge.h; sourceTree = "<group>"; };
 		4BEF6AA91D35CE9E00E73575 /* DigitalPhaseLockedLoopBridge.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = DigitalPhaseLockedLoopBridge.mm; sourceTree = "<group>"; };
 		4BEF6AAB1D35D1C400E73575 /* DPLLTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DPLLTests.swift; sourceTree = "<group>"; };
+		4BEF9CA92EC8294E00DDD0F6 /* SpeakerQueue.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = SpeakerQueue.hpp; sourceTree = "<group>"; };
 		4BF0BC67297108D100CCA2B5 /* MemorySlotHandler.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = MemorySlotHandler.cpp; sourceTree = "<group>"; };
 		4BF0BC6F2973318E00CCA2B5 /* RP5C01.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = RP5C01.cpp; sourceTree = "<group>"; };
 		4BF0BC702973318E00CCA2B5 /* RP5C01.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = RP5C01.hpp; sourceTree = "<group>"; };
@@ -5312,6 +5313,7 @@
 		4BD060A41FE49D3C006E14BE /* Speaker */ = {
 			isa = PBXGroup;
 			children = (
+				4BEF9CA92EC8294E00DDD0F6 /* SpeakerQueue.hpp */,
 				4BD060A51FE49D3C006E14BE /* Speaker.hpp */,
 				4B8EF6051FE5AF830076CCDD /* Implementation */,
 			);

OSBindings/Mac/Clock Signal/Machine/CSMachine.mm

@@ -39,7 +39,7 @@
 namespace {
 
 struct MachineUpdater {
-	void perform(Time::Nanos duration) {
+	void perform(const Time::Nanos duration) {
 		// Top out at 1/20th of a second; this is a safeguard against a negative
 		// feedback loop if emulation starts running slowly.
 		const auto seconds = std::min(Time::seconds(duration), 0.05);
@@ -51,7 +51,7 @@ struct MachineUpdater {
 	MachineTypes::TimedMachine *timed_machine = nullptr;
 };
 
-using Updater = Concurrency::AsyncTaskQueue<true, false, MachineUpdater>;
+using Updater = Concurrency::AsyncTaskQueue<true, false, false, MachineUpdater>;
 
 }
 

OSBindings/Mac/Clock SignalTests/SIDTests.mm

@@ -0,0 +1,83 @@
+//
+//  SIDTests.mm
+//  Clock SignalTests
+//
+//  Created by Thomas Harte on 11/11/2025.
+//  Copyright © 2025 Thomas Harte. All rights reserved.
+//
+
+#import <XCTest/XCTest.h>
+
+#include "Components/SID/SID.hpp"
+
+@interface SIDTests : XCTestCase
+@end
+
+@implementation SIDTests
+
+- (void)testOscillator {
+	MOS::SID::Voice prior;
+	MOS::SID::Voice voice;
+	const uint32_t pulse_width = 0x02'3;
+
+	voice.oscillator.pitch = 0x00'1000'00;
+	voice.oscillator.pulse_width = pulse_width << 20;
+	voice.oscillator.reset_phase();
+
+	int c = 0;
+
+	// Run for first half of a cycle.
+	while(!voice.oscillator.did_raise_b23()) {
+		// Force envelope.
+		voice.adsr.envelope = 255;
+
+		// Test sawtooth.
+		voice.set_control(0x20);
+		XCTAssertEqual(voice.output(prior), c);
+
+		// Test triangle.
+		voice.set_control(0x10);
+		XCTAssertEqual(voice.output(prior), c << 1);
+
+		// Test pulse.
+		voice.set_control(0x40);
+		XCTAssertEqual(voice.output(prior), (c < pulse_width) ? 0 : 4095);
+
+		// Advance.
+		voice.update();
+		++c;
+	}
+
+	// B23 should go up halfway through the 12-bit range.
+	XCTAssertEqual(c, 2048);
+
+	// Run for second half of a cycle.
+	while(c < 4096) {
+		// Force envelope.
+		voice.adsr.envelope = 255;
+
+		// Test sawtooth.
+		voice.set_control(0x20);
+		XCTAssertEqual(voice.output(prior), c);
+
+		// Test triangle.
+		voice.set_control(0x10);
+		XCTAssertEqual(voice.output(prior), 4095 - ((c << 1) & 4095));
+
+		// Test pulse.
+		voice.set_control(0x40);
+		XCTAssertEqual(voice.output(prior), (c <= pulse_width) ? 0 : 4095);
+
+		// Advance.
+		voice.update();
+		++c;
+
+		XCTAssert(!voice.oscillator.did_raise_b23());
+	}
+
+	// Check that B23 doesn't false rise again.
+	voice.update();
+	XCTAssert(!voice.oscillator.did_raise_b23());
+}
+
+@end

Outputs/Speaker/Implementation/BufferSource.hpp

@@ -9,6 +9,7 @@
 #pragma once
 
 #include "Outputs/Speaker/Speaker.hpp"
+#include "Concurrency/AsyncTaskQueue.hpp"
 
 #include <algorithm>
 #include <array>
@@ -26,7 +27,7 @@ enum class Action {
 	Ignore,
 };
 
-template <Action action, typename SampleT> void apply(SampleT &lhs, SampleT rhs) {
+template <Action action, typename SampleT> void apply(SampleT &lhs, const SampleT rhs) {
 	switch(action) {
 		case Action::Mix:	lhs += rhs;	break;
 		case Action::Store:	lhs = rhs;	break;
@@ -34,7 +35,8 @@ template <Action action, typename SampleT> void apply(SampleT &lhs, SampleT rhs)
 	}
 }
 
-template <Action action, typename IteratorT, typename SampleT> void fill(IteratorT begin, IteratorT end, SampleT value) {
+template <Action action, typename IteratorT, typename SampleT>
+void fill(IteratorT begin, const IteratorT end, const SampleT value) {
 	switch(action) {
 		case Action::Mix:
 			while(begin != end) {
@@ -56,45 +58,45 @@ template <Action action, typename IteratorT, typename SampleT> void fill(Iterato
 */
 template <typename SourceT, bool stereo>
 class BufferSource {
-	public:
+public:
-		/*!
+	/*!
-			Indicates whether this component will write stereo samples.
+		Indicates whether this component will write stereo samples.
-		*/
+	*/
-		static constexpr bool is_stereo = stereo;
+	static constexpr bool is_stereo = stereo;
 
-		/*!
+	/*!
-			Should 'apply' the next @c number_of_samples to @c target ; application means applying @c action which can be achieved either via the
+		Should 'apply' the next @c number_of_samples to @c target ; application means applying @c action which can be achieved either via the
-			helper functions above — @c apply and @c fill — or by semantic inspection (primarily, if an obvious quick route for @c Action::Ignore is available).
+		helper functions above — @c apply and @c fill — or by semantic inspection (primarily, if an obvious quick route for @c Action::Ignore is available).
 
-			No default implementation is provided.
+		No default implementation is provided.
-		*/
+	*/
-		template <Action action>
+	template <Action action>
-		void apply_samples(std::size_t number_of_samples, typename SampleT<stereo>::type *target);
+	void apply_samples(std::size_t number_of_samples, typename SampleT<stereo>::type *);
 
-		/*!
+	/*!
-			@returns @c true if it is trivially true that a call to get_samples would just
+		@returns @c true if it is trivially true that a call to get_samples would just
-				fill the target with zeroes; @c false if a call might return all zeroes or
+			fill the target with zeroes; @c false if a call might return all zeroes or
-				might not.
+			might not.
-		*/
+	*/
-//		bool is_zero_level() const						{	return false;	}
+//	bool is_zero_level() const						{	return false;	}
 
-		/*!
+	/*!
-			Sets the proper output range for this sample source; it should write values
+		Sets the proper output range for this sample source; it should write values
-			between 0 and volume.
+		between 0 and volume.
-		*/
+	*/
-//		void set_sample_volume_range(std::int16_t volume);
+//	void set_sample_volume_range(std::int16_t volume);
 
-		/*!
+	/*!
-			Permits a sample source to declare that, averaged over time, it will use only
+		Permits a sample source to declare that, averaged over time, it will use only
-			a certain proportion of the allocated volume range. This commonly happens
+		a certain proportion of the allocated volume range. This commonly happens
-			in sample sources that use a time-multiplexed sound output — for example, if
+		in sample sources that use a time-multiplexed sound output — for example, if
-			one were to output only every other sample then it would return 0.5.
+		one were to output only every other sample then it would return 0.5.
 
-			This is permitted to vary over time but there is no contract as to when it will be
+		This is permitted to vary over time but there is no contract as to when it will be
-			used by a speaker. If it varies, it should do so very infrequently and only to
+		used by a speaker. If it varies, it should do so very infrequently and only to
-			represent changes in hardware configuration.
+		represent changes in hardware configuration.
-		*/
+	*/
-		double average_output_peak() const { return 1.0; }
+	double average_output_peak() const { return 1.0; }
 };
 
 ///
@@ -140,7 +142,7 @@ public:
 
 	// TODO: use a concept here, when C++20 filters through.
 	//
-	// Until then: sample sources should implement this.
+	// Until then: sample sources can implement this rather than apply_samples.
 //	typename SampleT<stereo>::type level() const;
 //	void advance();
 

Outputs/Speaker/Implementation/LowpassSpeaker.hpp

@@ -10,6 +10,7 @@
 
 #include "BufferSource.hpp"
 #include "Outputs/Speaker/Speaker.hpp"
+#include "Outputs/Speaker/SpeakerQueue.hpp"
 #include "SignalProcessing/FIRFilter.hpp"
 #include "ClockReceiver/ClockReceiver.hpp"
 #include "Concurrency/AsyncTaskQueue.hpp"
@@ -375,10 +376,13 @@ public:
 		if(cycles == Cycles(0)) {
 			return;
 		}
+		queue.enqueue(update_for(cycles));
+	}
 
-		queue.enqueue([this, cycles] {
+	std::function<void(void)> update_for(const Cycles cycles) {
+		return [this, cycles] {
 			run_for(cycles);
-		});
+		};
 	}
 
 private:
@@ -414,4 +418,7 @@ private:
 	}
 };
 
+template <typename CyclesT, typename GeneratorT>
+using PullLowpassSpeakerQueue = SpeakerQueue<CyclesT, Outputs::Speaker::PullLowpass<GeneratorT>, GeneratorT>;
+
 }

Outputs/Speaker/SpeakerQueue.hpp

@@ -0,0 +1,68 @@
+//
+//  SpeakerQueue.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 14/11/2025.
+//  Copyright © 2025 Thomas Harte. All rights reserved.
+//
+
+#pragma once
+
+#include "Concurrency/AsyncTaskQueue.hpp"
+#include "ClockReceiver/ClockReceiver.hpp"
+
+namespace Outputs::Speaker {
+using TaskQueue = Concurrency::AsyncTaskQueue<false, true, true>;
+
+template <typename CyclesT, typename SpeakerT, typename GeneratorT>
+struct SpeakerQueue: private Concurrency::EnqueueDelegate {
+	constexpr SpeakerQueue(const CyclesT divider) noexcept :
+		generator_(queue_), speaker_(generator_), divider_(divider)
+	{
+		queue_.set_enqueue_delegate(this);
+	}
+
+	constexpr SpeakerQueue(const float input_rate, const CyclesT divider, const float high_cutoff = -1.0f) noexcept :
+		SpeakerQueue(divider)
+	{
+		speaker_.set_input_rate(input_rate);
+		if(high_cutoff >= 0.0) {
+			speaker_.set_high_frequency_cutoff(high_cutoff);
+		}
+	}
+
+	void operator += (const CyclesT &duration) {
+		time_since_update_ += duration;
+	}
+
+	void stop() {
+		queue_.stop();
+	}
+
+	void perform() {
+		// TODO: is there a way to avoid the empty lambda?
+		queue_.enqueue([]() {});
+		queue_.perform();
+	}
+
+	SpeakerT &speaker() {
+		return speaker_;
+	}
+
+	GeneratorT *operator ->() {
+		return &generator_;
+	}
+
+private:
+	TaskQueue queue_;
+	GeneratorT generator_;
+	SpeakerT speaker_;
+	CyclesT divider_;
+	CyclesT time_since_update_;
+
+	std::function<void(void)> prepare_enqueue() final {
+		return speaker_.update_for(time_since_update_.template divide<Cycles>(divider_));
+	}
+};
+
+}