Added lots of debugging output while I attempt to locate the source of audio scratchiness, also simplified manner of dealing with wraparound within the AudioQueue wrapper.

OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.h

@@ -10,6 +10,6 @@
 
 @interface AudioQueue : NSObject
 
-- (void)enqueueAudioBuffer:(const int16_t *)buffer numberOfSamples:(unsigned int)lengthInSamples;
+- (void)enqueueAudioBuffer:(const int16_t *)buffer numberOfSamples:(size_t)lengthInSamples;
 
 @end

OSBindings/Mac/Clock Signal/Wrappers/AudioQueue.m

@@ -17,9 +17,8 @@
 {
 	AudioQueueRef _audioQueue;
 	AudioQueueBufferRef _audioBuffers[AudioQueueNumAudioBuffers];
-	unsigned int _audioStreamReadPosition, _audioStreamWritePosition, _queuedAudioStreamSegments;
+	unsigned int _audioStreamReadPosition, _audioStreamWritePosition;
 	int16_t _audioStream[AudioQueueStreamLength];
-	BOOL _isOutputtingAudio;
 }
 
 
@@ -30,18 +29,26 @@
 {
 	@synchronized(self)
 	{
-		if(_queuedAudioStreamSegments > AudioQueueNumAudioBuffers-1) _isOutputtingAudio = YES;
+		const unsigned int writeLead = _audioStreamWritePosition - _audioStreamReadPosition;
-
+		const size_t audioDataSampleSize = buffer->mAudioDataByteSize / sizeof(int16_t);
-		if(_isOutputtingAudio && _queuedAudioStreamSegments)
+		if(writeLead >= audioDataSampleSize)
 		{
-			_queuedAudioStreamSegments--;
+			size_t samplesBeforeOverflow = AudioQueueStreamLength - (_audioStreamReadPosition % AudioQueueStreamLength);
-			memcpy(buffer->mAudioData, &_audioStream[_audioStreamReadPosition], buffer->mAudioDataByteSize);
+			if(audioDataSampleSize <= samplesBeforeOverflow)
-			_audioStreamReadPosition = (_audioStreamReadPosition + AudioQueueBufferLength)%AudioQueueStreamLength;
+			{
+				memcpy(buffer->mAudioData, &_audioStream[_audioStreamReadPosition % AudioQueueStreamLength], buffer->mAudioDataByteSize);
+			}
+			else
+			{
+				const size_t bytesRemaining = samplesBeforeOverflow * sizeof(int16_t);
+				memcpy(buffer->mAudioData, &_audioStream[_audioStreamReadPosition % AudioQueueStreamLength], bytesRemaining);
+				memcpy(buffer->mAudioData, &_audioStream[0], buffer->mAudioDataByteSize - bytesRemaining);
+			}
+			_audioStreamReadPosition += audioDataSampleSize;
 		}
 		else
 		{
 			memset(buffer->mAudioData, 0, buffer->mAudioDataByteSize);
-			_isOutputtingAudio = NO;
 		}
 		AudioQueueEnqueueBuffer(theAudioQueue, buffer, 0, NULL);
 	}
@@ -91,7 +98,6 @@ static void audioOutputCallback(
 			0,
 			&_audioQueue))
 		{
-			_audioStreamWritePosition = AudioQueueBufferLength;
 			UInt32 bufferBytes = AudioQueueBufferLength * sizeof(int16_t);
 
 			int c = AudioQueueNumAudioBuffers;
@@ -115,21 +121,23 @@ static void audioOutputCallback(
 	if(_audioQueue) AudioQueueDispose(_audioQueue, NO);
 }
 
-- (void)enqueueAudioBuffer:(const int16_t *)buffer numberOfSamples:(unsigned int)lengthInSamples
+- (void)enqueueAudioBuffer:(const int16_t *)buffer numberOfSamples:(size_t)lengthInSamples
 {
 	@synchronized(self)
 	{
-		memcpy(&_audioStream[_audioStreamWritePosition], buffer, lengthInSamples * sizeof(int16_t));
+		size_t samplesBeforeOverflow = AudioQueueStreamLength - (_audioStreamWritePosition % AudioQueueStreamLength);
-		_audioStreamWritePosition = (_audioStreamWritePosition + lengthInSamples)%AudioQueueStreamLength;
 
-		if(_queuedAudioStreamSegments == (AudioQueueStreamLength/AudioQueueBufferLength))
+		if(samplesBeforeOverflow < lengthInSamples)
 		{
-			_audioStreamReadPosition = (_audioStreamReadPosition + lengthInSamples)%AudioQueueStreamLength;
+			memcpy(&_audioStream[_audioStreamWritePosition % AudioQueueStreamLength], buffer, samplesBeforeOverflow * sizeof(int16_t));
+			memcpy(&_audioStream[0], &buffer[samplesBeforeOverflow], (lengthInSamples - samplesBeforeOverflow) * sizeof(int16_t));
 		}
 		else
 		{
-			_queuedAudioStreamSegments++;
+			memcpy(&_audioStream[_audioStreamWritePosition % AudioQueueStreamLength], buffer, lengthInSamples * sizeof(int16_t));
 		}
+
+		_audioStreamWritePosition += lengthInSamples;
 	}
 }
 

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

@@ -13,9 +13,21 @@
 
 @implementation CSElectron {
 	Electron::Machine _electron;
+
+	NSTimeInterval _periodicStart;
+	int _numberOfCycles;
 }
 
 - (void)doRunForNumberOfCycles:(int)numberOfCycles {
+	_numberOfCycles += numberOfCycles;
+	NSTimeInterval timeNow = [NSDate timeIntervalSinceReferenceDate];
+	NSTimeInterval difference = timeNow - _periodicStart;
+	if(difference > 1.0)
+	{
+		NSLog(@"cycles: %0.0f", (double)_numberOfCycles / difference);
+		_periodicStart = timeNow;
+		_numberOfCycles = 0;
+	}
 	_electron.run_for_cycles(numberOfCycles);
 }
 

Outputs/Speaker.hpp

@@ -11,6 +11,7 @@
 
 #include <stdint.h>
 #include <stdio.h>
+#include <time.h>
 #include "../SignalProcessing/Stepper.hpp"
 
 namespace Outputs {
@@ -76,6 +77,17 @@ template <class T> class Filter: public Speaker {
 		{
 			if(_coefficients_are_dirty) update_filter_coefficients();
 
+			_periodic_cycles += input_cycles;
+			time_t time_now = time(nullptr);
+			if(time_now > _periodic_start)
+			{
+				printf("input audio samples: %d\n", _periodic_cycles);
+				printf("output audio samples: %d\n", _periodic_output);
+				_periodic_cycles = 0;
+				_periodic_output = 0;
+				_periodic_start = time_now;
+			}
+
 			// point sample for now, as a temporary measure
 			input_cycles += _input_cycles_carry;
 			while(input_cycles > 0)
@@ -99,11 +111,17 @@ template <class T> class Filter: public Speaker {
 				if(steps > 1)
 					static_cast<T *>(this)->skip_samples((unsigned int)(steps-1));
 				input_cycles -= steps;
+				_periodic_output ++;
 			}
 			_input_cycles_carry = input_cycles;
 		}
 
+		Filter() : _periodic_cycles(0), _periodic_start(0) {}
+
 	private:
+				time_t _periodic_start;
+				int _periodic_cycles;
+				int _periodic_output;
 		SignalProcessing::Stepper *_stepper;
 		int _input_cycles_carry;