Made an attempt also to trigger updates upon audio packets being returned, and significantly to reduce the size and quantity of those. This should get down to 11ms latency if the output wave is 44100; I might need to scale up the buffer size as the sampling rate increases or this is going to get crazy at 192Khz.

OSBindings/Mac/Clock Signal/Audio/CSAudioQueue.h

@@ -10,7 +10,7 @@
 
 @class CSAudioQueue;
 
-@protocol AudioQueueDelegate
+@protocol CSAudioQueueDelegate
 - (void)audioQueueDidCompleteBuffer:(nonnull CSAudioQueue *)audioQueue;
 @end
 
@@ -20,8 +20,9 @@
 - (void)enqueueAudioBuffer:(nonnull const int16_t *)buffer numberOfSamples:(size_t)lengthInSamples;
 
 @property (nonatomic, readonly) Float64 samplingRate;
-@property (nonatomic, weak) id<AudioQueueDelegate> delegate;
+@property (nonatomic, weak) id<CSAudioQueueDelegate> delegate;
 
 + (Float64)preferredSamplingRate;
++ (NSUInteger)bufferSize;
 
 @end

OSBindings/Mac/Clock Signal/Audio/CSAudioQueue.m

@@ -9,9 +9,9 @@
 #import "CSAudioQueue.h"
 @import AudioToolbox;
 
-#define AudioQueueNumAudioBuffers	4
-#define AudioQueueStreamLength		4096
-#define AudioQueueBufferLength		512
+#define AudioQueueStreamLength		768
+#define AudioQueueBufferLength		256
+#define AudioQueueNumAudioBuffers	(AudioQueueStreamLength/AudioQueueBufferLength)
 
 enum {
 	AudioQueueCanProceed,
@@ -30,7 +30,6 @@ enum {
 	int _dequeuedCount;
 }
 
-
 #pragma mark -
 #pragma mark AudioQueue callbacks and setup; for pushing audio out
 
@@ -224,4 +223,9 @@ static void audioOutputCallback(
 	return AudioObjectGetPropertyData([self defaultOutputDevice], &address, sizeof(AudioObjectPropertyAddress), NULL, &size, &samplingRate) ? 0.0 : samplingRate;
 }
 
++ (NSUInteger)bufferSize
+{
+	return AudioQueueBufferLength;
+}
+
 @end

OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift

@@ -9,8 +9,14 @@
 import Cocoa
 import AudioToolbox
 
-class MachineDocument: NSDocument, CSOpenGLViewDelegate, CSOpenGLViewResponderDelegate, CSBestEffortUpdaterDelegate, NSWindowDelegate {
-
+class MachineDocument:
+	NSDocument,
+	NSWindowDelegate,
+	CSOpenGLViewDelegate,
+	CSOpenGLViewResponderDelegate,
+	CSBestEffortUpdaterDelegate,
+	CSAudioQueueDelegate
+{
 	lazy var actionLock = NSLock()
 	lazy var drawLock = NSLock()
 	func machine() -> CSMachine! {
@@ -55,8 +61,9 @@ class MachineDocument: NSDocument, CSOpenGLViewDelegate, CSOpenGLViewResponderDe
 		let selectedSamplingRate = self.machine().idealSamplingRateFromRange(NSRange(location: 0, length: NSInteger(maximumSamplingRate)))
 		if selectedSamplingRate > 0 {
 			audioQueue = CSAudioQueue(samplingRate: Float64(selectedSamplingRate))
+			audioQueue.delegate = self
 			self.machine().audioQueue = self.audioQueue
-			self.machine().setAudioSamplingRate(selectedSamplingRate)
+			self.machine().setAudioSamplingRate(selectedSamplingRate, bufferSize:CSAudioQueue.bufferSize() / 2)
 		}
 
 		self.bestEffortUpdater.clockRate = self.machine().clockRate
@@ -73,10 +80,18 @@ class MachineDocument: NSDocument, CSOpenGLViewDelegate, CSOpenGLViewResponderDe
 		super.close()
 	}
 
+	// MARK: CSBestEffortUpdaterDelegate
 	final func bestEffortUpdater(bestEffortUpdater: CSBestEffortUpdater!, runForCycles cycles: UInt, didSkipPreviousUpdate: Bool) {
 		runForNumberOfCycles(Int32(cycles))
 	}
 
+	func runForNumberOfCycles(numberOfCycles: Int32) {
+		if actionLock.tryLock() {
+			self.machine().runForNumberOfCycles(numberOfCycles)
+			actionLock.unlock()
+		}
+	}
+
 	// MARK: Utilities for children
 	func dataForResource(name : String, ofType type: String, inDirectory directory: String) -> NSData? {
 		if let path = NSBundle.mainBundle().pathForResource(name, ofType: type, inDirectory: directory) {
@@ -86,15 +101,13 @@ class MachineDocument: NSDocument, CSOpenGLViewDelegate, CSOpenGLViewResponderDe
 		return nil
 	}
 
-	// MARK: CSOpenGLViewDelegate
-	func runForNumberOfCycles(numberOfCycles: Int32) {
-		if actionLock.tryLock() {
-			self.machine().runForNumberOfCycles(numberOfCycles)
-			actionLock.unlock()
-		}
+	// MARK: CSAudioQueueDelegate
+	final func audioQueueDidCompleteBuffer(audioQueue: CSAudioQueue) {
+		bestEffortUpdater.update()
 	}
 
-	func openGLView(view: CSOpenGLView, drawViewOnlyIfDirty onlyIfDirty: Bool) {
+	// MARK: CSOpenGLViewDelegate
+	final func openGLView(view: CSOpenGLView, drawViewOnlyIfDirty onlyIfDirty: Bool) {
 		bestEffortUpdater.update()
 		if drawLock.tryLock() {
 			self.machine().drawViewForPixelSize(view.backingSize, onlyIfDirty: onlyIfDirty)

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

@@ -20,7 +20,7 @@
 - (void)runForNumberOfCycles:(int)numberOfCycles;
 
 - (float)idealSamplingRateFromRange:(NSRange)range;
-- (void)setAudioSamplingRate:(float)samplingRate;
+- (void)setAudioSamplingRate:(float)samplingRate bufferSize:(NSUInteger)bufferSize;
 
 - (void)setView:(CSOpenGLView *)view aspectRatio:(float)aspectRatio;
 - (void)drawViewForPixelSize:(CGSize)pixelSize onlyIfDirty:(BOOL)onlyIfDirty;

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

@@ -47,19 +47,19 @@ struct SpeakerDelegate: public Outputs::Speaker::Delegate {
 	}
 }
 
-- (void)setAudioSamplingRate:(float)samplingRate {
+- (void)setAudioSamplingRate:(float)samplingRate bufferSize:(NSUInteger)bufferSize {
 	@synchronized(self) {
 		_speakerDelegate.machine = self;
-		[self setSpeakerDelegate:&_speakerDelegate sampleRate:samplingRate];
+		[self setSpeakerDelegate:&_speakerDelegate sampleRate:samplingRate bufferSize:bufferSize];
 	}
 }
 
-- (BOOL)setSpeakerDelegate:(Outputs::Speaker::Delegate *)delegate sampleRate:(float)sampleRate {
+- (BOOL)setSpeakerDelegate:(Outputs::Speaker::Delegate *)delegate sampleRate:(float)sampleRate bufferSize:(NSUInteger)bufferSize {
 	@synchronized(self) {
 		Outputs::Speaker *speaker = self.machine->get_speaker();
 		if(speaker)
 		{
-			speaker->set_output_rate(sampleRate, 512);
+			speaker->set_output_rate(sampleRate, (int)bufferSize);
 			speaker->set_delegate(delegate);
 			return YES;
 		}