lewislepton/BufferedAudioBus.hpp

## BufferedAudioBus.hpp
/*
	<samplecode>
 <abstract>
 Utility classes to manage audio formats and buffers for an audio unit implementation's input and output audio busses.
 </abstract>
	</samplecode>
 */

#import <AudioToolbox/AudioToolbox.h>
#import <AudioUnit/AudioUnit.h>
#import <AVFoundation/AVFoundation.h>

#pragma mark BufferedAudioBus Utility Class
// Utility classes to manage audio formats and buffers for an audio unit implementation's input and output audio busses.

// Reusable non-ObjC class, accessible from render thread.
struct BufferedAudioBus {
    AUAudioUnitBus* bus = nullptr;
    AUAudioFrameCount maxFrames = 0;

    AVAudioPCMBuffer* pcmBuffer = nullptr;

    AudioBufferList const* originalAudioBufferList = nullptr;
    AudioBufferList* mutableAudioBufferList = nullptr;

    void init(AVAudioFormat* defaultFormat, AVAudioChannelCount maxChannels) {
        maxFrames = 0;
        pcmBuffer = nullptr;
        originalAudioBufferList = nullptr;
        mutableAudioBufferList = nullptr;

        bus = [[AUAudioUnitBus alloc] initWithFormat:defaultFormat error:nil];

        bus.maximumChannelCount = maxChannels;
    }

    void allocateRenderResources(AUAudioFrameCount inMaxFrames) {
        maxFrames = inMaxFrames;

        pcmBuffer = [[AVAudioPCMBuffer alloc] initWithPCMFormat:bus.format frameCapacity: maxFrames];

        originalAudioBufferList = pcmBuffer.audioBufferList;
        mutableAudioBufferList = pcmBuffer.mutableAudioBufferList;
    }

    void deallocateRenderResources() {
        pcmBuffer = nullptr;
        originalAudioBufferList = nullptr;
        mutableAudioBufferList = nullptr;
    }
};

#pragma mark - BufferedOutputBus: BufferedAudioBus
#pragma mark prepareOutputBufferList()
/*
 BufferedOutputBus

	This class provides a prepareOutputBufferList method to copy the internal buffer pointers
	to the output buffer list in case the client passed in null buffer pointers.
 */
struct BufferedOutputBus: BufferedAudioBus {
    void prepareOutputBufferList(AudioBufferList* outBufferList, AVAudioFrameCount frameCount, bool zeroFill) {
        UInt32 byteSize = frameCount * sizeof(float);
        for (UInt32 i = 0; i < outBufferList->mNumberBuffers; ++i) {
            outBufferList->mBuffers[i].mNumberChannels = originalAudioBufferList->mBuffers[i].mNumberChannels;
            outBufferList->mBuffers[i].mDataByteSize = byteSize;
            if (outBufferList->mBuffers[i].mData == nullptr) {
                outBufferList->mBuffers[i].mData = originalAudioBufferList->mBuffers[i].mData;
            }
            if (zeroFill) {
                memset(outBufferList->mBuffers[i].mData, 0, byteSize);
            }
        }
    }
};

#pragma mark - BufferedInputBus: BufferedAudioBus
#pragma mark pullInput()
#pragma mark prepareInputBufferList()
/*
	BufferedInputBus

	This class manages a buffer into which an audio unit with input busses can
 pull its input data.
 */
struct BufferedInputBus : BufferedAudioBus {
    /*
     Gets input data for this input by preparing the input buffer list and pulling
     the pullInputBlock.
     */
    AUAudioUnitStatus pullInput(AudioUnitRenderActionFlags *actionFlags,
                                AudioTimeStamp const* timestamp,
                                AVAudioFrameCount frameCount,
                                NSInteger inputBusNumber,
                                AURenderPullInputBlock pullInputBlock) {
        if (pullInputBlock == nullptr) {
            return kAudioUnitErr_NoConnection;
        }

        prepareInputBufferList();

        return pullInputBlock(actionFlags, timestamp, frameCount, inputBusNumber, mutableAudioBufferList);
    }

    /*
     prepareInputBufferList populates the mutableAudioBufferList with the data
     pointers from the originalAudioBufferList.

     The upstream audio unit may overwrite these with its own pointers, so each
     render cycle this function needs to be called to reset them.
     */
    void prepareInputBufferList() {
        UInt32 byteSize = maxFrames * sizeof(float);

        mutableAudioBufferList->mNumberBuffers = originalAudioBufferList->mNumberBuffers;

        for (UInt32 i = 0; i < originalAudioBufferList->mNumberBuffers; ++i) {
            mutableAudioBufferList->mBuffers[i].mNumberChannels = originalAudioBufferList->mBuffers[i].mNumberChannels;
            mutableAudioBufferList->mBuffers[i].mData = originalAudioBufferList->mBuffers[i].mData;
            mutableAudioBufferList->mBuffers[i].mDataByteSize = byteSize;
        }
    }
};

## IAYBridge.swift
//
//  IAYBridge.swift
//  Elliott
//
//  Created by yellow on 06/10/2016.
//  Copyright © 2016 iamyellow.net. All rights reserved.
//

import AVFoundation
import AudioKit

open class IAYBridge: AKNode {

    internal var internalAU: IAYBridgeAudioUnit?

    var ringBuffer: UnsafeMutableRawPointer? {
        return internalAU?.ringBuffer()
    }

    public init(_ input: AKNode) {
        var description = AudioComponentDescription()
        description.componentType         = kAudioUnitType_Effect
        description.componentSubType      = fourCC("brdg")
        description.componentManufacturer = fourCC("IAYe")
        description.componentFlags        = 0
        description.componentFlagsMask    = 0

        AUAudioUnit.registerSubclass(
            IAYBridgeAudioUnit.self,
            as: description,
            name: "Elliott Bridge",
            version: UInt32.max)

        super.init()

        AVAudioUnit.instantiate(with: description, options: []) {
            avAudioUnit, error in

            guard let avAudioUnitEffect = avAudioUnit else { return }

            self.avAudioNode = avAudioUnitEffect
            self.internalAU = avAudioUnitEffect.auAudioUnit as? IAYBridgeAudioUnit

            AudioKit.engine.attach(self.avAudioNode)
            input.addConnectionPoint(self)
        }
    }

}

## IAYBridgeAudioUnit.h
//
//  IAYBridgeAudioUnit.h
//  Elliott
//
//  Created by yellow on 06/10/2016.
//  Copyright © 2016 iamyellow.net. All rights reserved.
//

#ifndef IAYBridgeAudioUnit_h
#define IAYBridgeAudioUnit_h

#import <AudioToolbox/AudioToolbox.h>

@interface IAYBridgeAudioUnit : AUAudioUnit

-(nullable void*)ringBuffer;

@end

#endif /* IAYBridgeAudioUnit_h */

## IAYBridgeAudioUnit.mm
//
//  IAYBridgeAudioUnit.m
//  Elliott
//
//  Created by yellow on 06/10/2016.
//  Copyright © 2016 iamyellow.net. All rights reserved.
//

#import "IAYBridgeAudioUnit.h"

#import <AVFoundation/AVFoundation.h>

#import <AudioKit/AudioKit-Swift.h>

#import <AudioKit/TPCircularBuffer.h>

#import "BufferedAudioBus.hpp"

@interface IAYBridgeAudioUnit()

@property AUAudioUnitBus* outputBus;
@property AUAudioUnitBusArray* inputBusArray;
@property AUAudioUnitBusArray* outputBusArray;

@property (nonatomic, readwrite) AUParameterTree* parameterTree;

@end

@implementation IAYBridgeAudioUnit {
    BufferedInputBus _inputBus;
    TPCircularBuffer _ringBuffer;

    UInt32 _frames, _numberOfBuffers, _bytesPerBuffer;
}

@synthesize parameterTree = _parameterTree;

-(instancetype)initWithComponentDescription:(AudioComponentDescription)cd
                                    options:(AudioComponentInstantiationOptions)options
                                      error:(NSError**)outError
{

    self = [super initWithComponentDescription:cd options:options error:outError];

    if (!self) {
        return nil;
    }

    AVAudioFormat* defaultFormat = [[AVAudioFormat alloc] initStandardFormatWithSampleRate:AKSettings.sampleRate
                                                                                  channels:AKSettings.numberOfChannels];

    _parameterTree = [AUParameterTree createTreeWithChildren:@[]];

    _inputBus.init(defaultFormat, 8);
    _inputBusArray  = [[AUAudioUnitBusArray alloc] initWithAudioUnit:self
                                                             busType:AUAudioUnitBusTypeInput
                                                              busses: @[_inputBus.bus]];

    _outputBus = [[AUAudioUnitBus alloc] initWithFormat:defaultFormat
                                                  error:nil];
    _outputBusArray = [[AUAudioUnitBusArray alloc] initWithAudioUnit:self
                                                             busType:AUAudioUnitBusTypeOutput
                                                              busses: @[_outputBus]];

    self.maximumFramesToRender = 1024;

    return self;
}

-(nullable void*)ringBuffer
{
    return &_ringBuffer;
}

#pragma mark - AUAudioUnit Overrides

-(AUAudioUnitBusArray*)inputBusses
{
    return _inputBusArray;
}

-(AUAudioUnitBusArray*)outputBusses
{
    return _outputBusArray;
}

-(BOOL)allocateRenderResourcesAndReturnError:(NSError**)outError
{
    if (![super allocateRenderResourcesAndReturnError:outError]) {
        return NO;
    }

    if (self.outputBus.format.channelCount != _inputBus.bus.format.channelCount) {
        if (outError) {
            *outError = [NSError errorWithDomain:NSOSStatusErrorDomain
                                            code:kAudioUnitErr_FailedInitialization
                                        userInfo:nil];
        }
        self.renderResourcesAllocated = NO;

        return NO;
    }

    _frames = ceil([AKSettings sampleRate] * [AVAudioSession sharedInstance].IOBufferDuration);

    const AudioStreamBasicDescription* asbd = [AKSettings audioFormat].streamDescription;
    _numberOfBuffers = (asbd->mFormatFlags & kAudioFormatFlagIsNonInterleaved) == kAudioFormatFlagIsNonInterleaved ? asbd->mChannelsPerFrame : 1;
    _bytesPerBuffer = asbd->mBytesPerFrame * _frames;
    TPCircularBufferInit(&_ringBuffer, 3 * _numberOfBuffers * _bytesPerBuffer);

    _inputBus.allocateRenderResources(_frames);

    return YES;
}

-(void)deallocateRenderResources
{
    [super deallocateRenderResources];

    TPCircularBufferCleanup(&_ringBuffer);

    _inputBus.deallocateRenderResources();
}

-(AUInternalRenderBlock)internalRenderBlock
{
    __block BufferedInputBus* input = &_inputBus;
    __block TPCircularBuffer* ringBuffer = &_ringBuffer;

    return ^AUAudioUnitStatus(AudioUnitRenderActionFlags* actionFlags,
                              const AudioTimeStamp* timestamp,
                              AVAudioFrameCount frameCount,
                              NSInteger outputBusNumber,
                              AudioBufferList* outputData,
                              const AURenderEvent* realtimeEventListHead,
                              AURenderPullInputBlock pullInputBlock) {

        AudioUnitRenderActionFlags pullFlags = 0;
        AUAudioUnitStatus err = input->pullInput(&pullFlags, timestamp, frameCount, 0, pullInputBlock);

        if (err != noErr) {
            return err;
        }

        AudioBufferList* inAudioBufferList = input->mutableAudioBufferList;

        UInt32 neededBytes = _numberOfBuffers * _bytesPerBuffer;
        int32_t availableBytes;
        void* dstBuffer = TPCircularBufferHead(ringBuffer, &availableBytes);

        if (availableBytes >= neededBytes) {
            void* srcBuffer = (void*)inAudioBufferList->mBuffers[0].mData;
            memcpy(dstBuffer, srcBuffer, _bytesPerBuffer);
            if (_numberOfBuffers > 1) {
                memcpy((char*)dstBuffer + _bytesPerBuffer, srcBuffer, _bytesPerBuffer);
            }
            TPCircularBufferProduce(ringBuffer, neededBytes);
        }

        return -1;
    };
}

@end

## MyAudioUnit.h
//
//  MyAudioUnit.h
//  ElliottAUExtension
//
//  Created by yellow on 18/06/16.
//  Copyright © 2016 iamyellow.net. All rights reserved.
//

#import <AudioToolbox/AudioToolbox.h>

@interface MyAudioUnit : AUAudioUnit

@end

## MyAudioUnit.mm
//
//  MyAudioUnit.m
//  ElliottAUExtension
//
//  Created by yellow on 18/06/16.
//  Copyright © 2016 iamyellow.net. All rights reserved.
//

#import "MyAudioUnit.h"

#import <AVFoundation/AVFoundation.h>
#import <AudioUnit/AudioUnit.h>

#import <ElliottKit/ElliottKit-Swift.h>

#import <AudioKit/AudioKit-Swift.h>
#import <AudioKit/TPCircularBuffer.h>

@interface MyAudioUnit ()

@property AUAudioUnitBusArray* inputBusArray;
@property AUAudioUnitBus* outputBus;
@property AUAudioUnitBusArray* outputBusArray;

@property (nonatomic, readwrite) AUParameterTree* parameterTree;

@property (nonatomic, strong) IAYInstrument* instrument;

@end

@implementation MyAudioUnit

@synthesize parameterTree = _parameterTree;

-(instancetype)initWithComponentDescription:(AudioComponentDescription)componentDescription
                                     options:(AudioComponentInstantiationOptions)options
                                       error:(NSError**)outError
{

    self = [super initWithComponentDescription:componentDescription options:options error:outError];

    if (self == nil) {
        return nil;
    }

    self.instrument = [[IAYInstrument alloc] init:YES];

    _parameterTree = [AUParameterTree createTreeWithChildren:@[]];

    AVAudioFormat* defaultFormat = [[AVAudioFormat alloc] initStandardFormatWithSampleRate:[AKSettings sampleRate]
                                                                                  channels:[AKSettings numberOfChannels]];
    self.outputBus = [[AUAudioUnitBus alloc] initWithFormat:defaultFormat
                                                      error:nil];
    self.outputBusArray = [[AUAudioUnitBusArray alloc] initWithAudioUnit:self
                                                                 busType:AUAudioUnitBusTypeOutput
                                                                  busses:@[self.outputBus]];

    self.maximumFramesToRender = 1024;

    return self;
}

#pragma mark - AUAudioUnit Overrides

-(AUAudioUnitBusArray*)outputBusses
{
    return self.outputBusArray;
}

-(BOOL)allocateRenderResourcesAndReturnError:(NSError**)outError
{
    if (![super allocateRenderResourcesAndReturnError:outError]) {
        return NO;
    }

    NSArray<NSURL*>* exsFilePaths = [FileUtil getExs24Instruments:[FileUtil sharedFolderURL]];
    if (exsFilePaths.count == 0) {
        NSLog(@">> no EXS24");
        return YES;
    }

    if (![self.instrument loadExs24At:exsFilePaths[0]]) {
        NSLog(@">> error loading %@", exsFilePaths[0]);
    }

    return YES;
}

-(void)deallocateRenderResources
{
    [super deallocateRenderResources];
}

#pragma mark - Render

-(AUInternalRenderBlock)internalRenderBlock
{
    // http://rypress.com/tutorials/objective-c/blocks

    __block AVAudioUnitSampler* sampler = self.instrument.avAudioUnitSampler;
    __block TPCircularBuffer* ringBuffer = (TPCircularBuffer*)self.instrument.ringBuffer;

    return ^AUAudioUnitStatus(AudioUnitRenderActionFlags* actionFlags,
                              const AudioTimeStamp* timestamp,
                              AVAudioFrameCount frameCount,
                              NSInteger outputBusNumber,
                              AudioBufferList* data,
                              const AURenderEvent* realtimeEventListHead,
                              AURenderPullInputBlock pullInputBlock) {

        // midi events

        AURenderEvent const* event = realtimeEventListHead;
        while (event != NULL) {
            if (event->head.eventType == AURenderEventMIDI) {
                [sampler sendMIDIEvent:event->MIDI.data[0]
                                 data1:event->MIDI.data[1]
                                 data2:event->MIDI.data[2]];
            }

            event = event->head.next;
        }

        // render

        if (ringBuffer) {
            UInt32 neededBytes = data->mBuffers[0].mDataByteSize;
            if (data->mNumberBuffers > 1) {
                neededBytes += data->mBuffers[1].mDataByteSize;
            }

            int32_t availableBytes;
            void* srcBuffer = TPCircularBufferTail(ringBuffer, &availableBytes);
            if (availableBytes >= neededBytes) {
                void* dstBuffer = data->mBuffers[0].mData;
                UInt32 offset = data->mBuffers[0].mDataByteSize;
                memcpy(dstBuffer, srcBuffer, offset);
                if (data->mNumberBuffers > 1) {
                    dstBuffer = data->mBuffers[1].mData;
                    memcpy(dstBuffer, (char*)srcBuffer + offset, data->mBuffers[1].mDataByteSize);
                }
                TPCircularBufferConsume(ringBuffer, neededBytes);
            }
        }

        return noErr;
    };
}

@end
	/*
	<samplecode>
	<abstract>
	Utility classes to manage audio formats and buffers for an audio unit implementation's input and output audio busses.
	</abstract>
	</samplecode>
	*/

	#import <AudioToolbox/AudioToolbox.h>
	#import <AudioUnit/AudioUnit.h>
	#import <AVFoundation/AVFoundation.h>

	#pragma mark BufferedAudioBus Utility Class
	// Utility classes to manage audio formats and buffers for an audio unit implementation's input and output audio busses.

	// Reusable non-ObjC class, accessible from render thread.
	struct BufferedAudioBus {
	AUAudioUnitBus* bus = nullptr;
	AUAudioFrameCount maxFrames = 0;

	AVAudioPCMBuffer* pcmBuffer = nullptr;

	AudioBufferList const* originalAudioBufferList = nullptr;
	AudioBufferList* mutableAudioBufferList = nullptr;

	void init(AVAudioFormat* defaultFormat, AVAudioChannelCount maxChannels) {
	maxFrames = 0;
	pcmBuffer = nullptr;
	originalAudioBufferList = nullptr;
	mutableAudioBufferList = nullptr;

	bus = [[AUAudioUnitBus alloc] initWithFormat:defaultFormat error:nil];

	bus.maximumChannelCount = maxChannels;
	}

	void allocateRenderResources(AUAudioFrameCount inMaxFrames) {
	maxFrames = inMaxFrames;

	pcmBuffer = [[AVAudioPCMBuffer alloc] initWithPCMFormat:bus.format frameCapacity: maxFrames];

	originalAudioBufferList = pcmBuffer.audioBufferList;
	mutableAudioBufferList = pcmBuffer.mutableAudioBufferList;
	}

	void deallocateRenderResources() {
	pcmBuffer = nullptr;
	originalAudioBufferList = nullptr;
	mutableAudioBufferList = nullptr;
	}
	};

	#pragma mark - BufferedOutputBus: BufferedAudioBus
	#pragma mark prepareOutputBufferList()
	/*
	BufferedOutputBus

	This class provides a prepareOutputBufferList method to copy the internal buffer pointers
	to the output buffer list in case the client passed in null buffer pointers.
	*/
	struct BufferedOutputBus: BufferedAudioBus {
	void prepareOutputBufferList(AudioBufferList* outBufferList, AVAudioFrameCount frameCount, bool zeroFill) {
	UInt32 byteSize = frameCount * sizeof(float);
	for (UInt32 i = 0; i < outBufferList->mNumberBuffers; ++i) {
	outBufferList->mBuffers[i].mNumberChannels = originalAudioBufferList->mBuffers[i].mNumberChannels;
	outBufferList->mBuffers[i].mDataByteSize = byteSize;
	if (outBufferList->mBuffers[i].mData == nullptr) {
	outBufferList->mBuffers[i].mData = originalAudioBufferList->mBuffers[i].mData;
	}
	if (zeroFill) {
	memset(outBufferList->mBuffers[i].mData, 0, byteSize);
	}
	}
	}
	};

	#pragma mark - BufferedInputBus: BufferedAudioBus
	#pragma mark pullInput()
	#pragma mark prepareInputBufferList()
	/*
	BufferedInputBus

	This class manages a buffer into which an audio unit with input busses can
	pull its input data.
	*/
	struct BufferedInputBus : BufferedAudioBus {
	/*
	Gets input data for this input by preparing the input buffer list and pulling
	the pullInputBlock.
	*/
	AUAudioUnitStatus pullInput(AudioUnitRenderActionFlags *actionFlags,
	AudioTimeStamp const* timestamp,
	AVAudioFrameCount frameCount,
	NSInteger inputBusNumber,
	AURenderPullInputBlock pullInputBlock) {
	if (pullInputBlock == nullptr) {
	return kAudioUnitErr_NoConnection;
	}

	prepareInputBufferList();

	return pullInputBlock(actionFlags, timestamp, frameCount, inputBusNumber, mutableAudioBufferList);
	}

	/*
	prepareInputBufferList populates the mutableAudioBufferList with the data
	pointers from the originalAudioBufferList.

	The upstream audio unit may overwrite these with its own pointers, so each
	render cycle this function needs to be called to reset them.
	*/
	void prepareInputBufferList() {
	UInt32 byteSize = maxFrames * sizeof(float);

	mutableAudioBufferList->mNumberBuffers = originalAudioBufferList->mNumberBuffers;

	for (UInt32 i = 0; i < originalAudioBufferList->mNumberBuffers; ++i) {
	mutableAudioBufferList->mBuffers[i].mNumberChannels = originalAudioBufferList->mBuffers[i].mNumberChannels;
	mutableAudioBufferList->mBuffers[i].mData = originalAudioBufferList->mBuffers[i].mData;
	mutableAudioBufferList->mBuffers[i].mDataByteSize = byteSize;
	}
	}
	};
	//
	// IAYBridge.swift
	// Elliott
	//
	// Created by yellow on 06/10/2016.
	// Copyright © 2016 iamyellow.net. All rights reserved.
	//

	import AVFoundation
	import AudioKit

	open class IAYBridge: AKNode {

	internal var internalAU: IAYBridgeAudioUnit?

	var ringBuffer: UnsafeMutableRawPointer? {
	return internalAU?.ringBuffer()
	}

	public init(_ input: AKNode) {
	var description = AudioComponentDescription()
	description.componentType = kAudioUnitType_Effect
	description.componentSubType = fourCC("brdg")
	description.componentManufacturer = fourCC("IAYe")
	description.componentFlags = 0
	description.componentFlagsMask = 0

	AUAudioUnit.registerSubclass(
	IAYBridgeAudioUnit.self,
	as: description,
	name: "Elliott Bridge",
	version: UInt32.max)

	super.init()

	AVAudioUnit.instantiate(with: description, options: []) {
	avAudioUnit, error in

	guard let avAudioUnitEffect = avAudioUnit else { return }

	self.avAudioNode = avAudioUnitEffect
	self.internalAU = avAudioUnitEffect.auAudioUnit as? IAYBridgeAudioUnit

	AudioKit.engine.attach(self.avAudioNode)
	input.addConnectionPoint(self)
	}
	}

	}
	//
	// IAYBridgeAudioUnit.h
	// Elliott
	//
	// Created by yellow on 06/10/2016.
	// Copyright © 2016 iamyellow.net. All rights reserved.
	//

	#ifndef IAYBridgeAudioUnit_h
	#define IAYBridgeAudioUnit_h

	#import <AudioToolbox/AudioToolbox.h>

	@interface IAYBridgeAudioUnit : AUAudioUnit

	-(nullable void*)ringBuffer;

	@end

	#endif /* IAYBridgeAudioUnit_h */
	//
	// IAYBridgeAudioUnit.m
	// Elliott
	//
	// Created by yellow on 06/10/2016.
	// Copyright © 2016 iamyellow.net. All rights reserved.
	//

	#import "IAYBridgeAudioUnit.h"

	#import <AVFoundation/AVFoundation.h>

	#import <AudioKit/AudioKit-Swift.h>

	#import <AudioKit/TPCircularBuffer.h>

	#import "BufferedAudioBus.hpp"

	@interface IAYBridgeAudioUnit()

	@property AUAudioUnitBus* outputBus;
	@property AUAudioUnitBusArray* inputBusArray;
	@property AUAudioUnitBusArray* outputBusArray;

	@property (nonatomic, readwrite) AUParameterTree* parameterTree;

	@end

	@implementation IAYBridgeAudioUnit {
	BufferedInputBus _inputBus;
	TPCircularBuffer _ringBuffer;

	UInt32 _frames, _numberOfBuffers, _bytesPerBuffer;
	}

	@synthesize parameterTree = _parameterTree;

	-(instancetype)initWithComponentDescription:(AudioComponentDescription)cd
	options:(AudioComponentInstantiationOptions)options
	error:(NSError**)outError
	{

	self = [super initWithComponentDescription:cd options:options error:outError];

	if (!self) {
	return nil;
	}

	AVAudioFormat* defaultFormat = [[AVAudioFormat alloc] initStandardFormatWithSampleRate:AKSettings.sampleRate
	channels:AKSettings.numberOfChannels];

	_parameterTree = [AUParameterTree createTreeWithChildren:@[]];

	_inputBus.init(defaultFormat, 8);
	_inputBusArray = [[AUAudioUnitBusArray alloc] initWithAudioUnit:self
	busType:AUAudioUnitBusTypeInput
	busses: @[_inputBus.bus]];

	_outputBus = [[AUAudioUnitBus alloc] initWithFormat:defaultFormat
	error:nil];
	_outputBusArray = [[AUAudioUnitBusArray alloc] initWithAudioUnit:self
	busType:AUAudioUnitBusTypeOutput
	busses: @[_outputBus]];

	self.maximumFramesToRender = 1024;

	return self;
	}

	-(nullable void*)ringBuffer
	{
	return &_ringBuffer;
	}

	#pragma mark - AUAudioUnit Overrides

	-(AUAudioUnitBusArray*)inputBusses
	{
	return _inputBusArray;
	}

	-(AUAudioUnitBusArray*)outputBusses
	{
	return _outputBusArray;
	}

	-(BOOL)allocateRenderResourcesAndReturnError:(NSError**)outError
	{
	if (![super allocateRenderResourcesAndReturnError:outError]) {
	return NO;
	}

	if (self.outputBus.format.channelCount != _inputBus.bus.format.channelCount) {
	if (outError) {
	*outError = [NSError errorWithDomain:NSOSStatusErrorDomain
	code:kAudioUnitErr_FailedInitialization
	userInfo:nil];
	}
	self.renderResourcesAllocated = NO;

	return NO;
	}

	_frames = ceil([AKSettings sampleRate] * [AVAudioSession sharedInstance].IOBufferDuration);

	const AudioStreamBasicDescription* asbd = [AKSettings audioFormat].streamDescription;
	_numberOfBuffers = (asbd->mFormatFlags & kAudioFormatFlagIsNonInterleaved) == kAudioFormatFlagIsNonInterleaved ? asbd->mChannelsPerFrame : 1;
	_bytesPerBuffer = asbd->mBytesPerFrame * _frames;
	TPCircularBufferInit(&_ringBuffer, 3 * _numberOfBuffers * _bytesPerBuffer);

	_inputBus.allocateRenderResources(_frames);

	return YES;
	}

	-(void)deallocateRenderResources
	{
	[super deallocateRenderResources];

	TPCircularBufferCleanup(&_ringBuffer);

	_inputBus.deallocateRenderResources();
	}

	-(AUInternalRenderBlock)internalRenderBlock
	{
	__block BufferedInputBus* input = &_inputBus;
	__block TPCircularBuffer* ringBuffer = &_ringBuffer;

	return ^AUAudioUnitStatus(AudioUnitRenderActionFlags* actionFlags,
	const AudioTimeStamp* timestamp,
	AVAudioFrameCount frameCount,
	NSInteger outputBusNumber,
	AudioBufferList* outputData,
	const AURenderEvent* realtimeEventListHead,
	AURenderPullInputBlock pullInputBlock) {

	AudioUnitRenderActionFlags pullFlags = 0;
	AUAudioUnitStatus err = input->pullInput(&pullFlags, timestamp, frameCount, 0, pullInputBlock);

	if (err != noErr) {
	return err;
	}

	AudioBufferList* inAudioBufferList = input->mutableAudioBufferList;

	UInt32 neededBytes = _numberOfBuffers * _bytesPerBuffer;
	int32_t availableBytes;
	void* dstBuffer = TPCircularBufferHead(ringBuffer, &availableBytes);

	if (availableBytes >= neededBytes) {
	void* srcBuffer = (void*)inAudioBufferList->mBuffers[0].mData;
	memcpy(dstBuffer, srcBuffer, _bytesPerBuffer);
	if (_numberOfBuffers > 1) {
	memcpy((char*)dstBuffer + _bytesPerBuffer, srcBuffer, _bytesPerBuffer);
	}
	TPCircularBufferProduce(ringBuffer, neededBytes);
	}

	return -1;
	};
	}

	@end
	//
	// MyAudioUnit.h
	// ElliottAUExtension
	//
	// Created by yellow on 18/06/16.
	// Copyright © 2016 iamyellow.net. All rights reserved.
	//

	#import <AudioToolbox/AudioToolbox.h>

	@interface MyAudioUnit : AUAudioUnit

	@end
	//
	// MyAudioUnit.m
	// ElliottAUExtension
	//
	// Created by yellow on 18/06/16.
	// Copyright © 2016 iamyellow.net. All rights reserved.
	//

	#import "MyAudioUnit.h"

	#import <AVFoundation/AVFoundation.h>
	#import <AudioUnit/AudioUnit.h>

	#import <ElliottKit/ElliottKit-Swift.h>

	#import <AudioKit/AudioKit-Swift.h>
	#import <AudioKit/TPCircularBuffer.h>

	@interface MyAudioUnit ()

	@property AUAudioUnitBusArray* inputBusArray;
	@property AUAudioUnitBus* outputBus;
	@property AUAudioUnitBusArray* outputBusArray;

	@property (nonatomic, readwrite) AUParameterTree* parameterTree;

	@property (nonatomic, strong) IAYInstrument* instrument;

	@end

	@implementation MyAudioUnit

	@synthesize parameterTree = _parameterTree;

	-(instancetype)initWithComponentDescription:(AudioComponentDescription)componentDescription
	options:(AudioComponentInstantiationOptions)options
	error:(NSError**)outError
	{

	self = [super initWithComponentDescription:componentDescription options:options error:outError];

	if (self == nil) {
	return nil;
	}

	self.instrument = [[IAYInstrument alloc] init:YES];

	_parameterTree = [AUParameterTree createTreeWithChildren:@[]];

	AVAudioFormat* defaultFormat = [[AVAudioFormat alloc] initStandardFormatWithSampleRate:[AKSettings sampleRate]
	channels:[AKSettings numberOfChannels]];
	self.outputBus = [[AUAudioUnitBus alloc] initWithFormat:defaultFormat
	error:nil];
	self.outputBusArray = [[AUAudioUnitBusArray alloc] initWithAudioUnit:self
	busType:AUAudioUnitBusTypeOutput
	busses:@[self.outputBus]];

	self.maximumFramesToRender = 1024;

	return self;
	}

	#pragma mark - AUAudioUnit Overrides

	-(AUAudioUnitBusArray*)outputBusses
	{
	return self.outputBusArray;
	}

	-(BOOL)allocateRenderResourcesAndReturnError:(NSError**)outError
	{
	if (![super allocateRenderResourcesAndReturnError:outError]) {
	return NO;
	}

	NSArray<NSURL> exsFilePaths = [FileUtil getExs24Instruments:[FileUtil sharedFolderURL]];
	if (exsFilePaths.count == 0) {
	NSLog(@">> no EXS24");
	return YES;
	}

	if (![self.instrument loadExs24At:exsFilePaths[0]]) {
	NSLog(@">> error loading %@", exsFilePaths[0]);
	}

	return YES;
	}

	-(void)deallocateRenderResources
	{
	[super deallocateRenderResources];
	}

	#pragma mark - Render

	-(AUInternalRenderBlock)internalRenderBlock
	{
	// http://rypress.com/tutorials/objective-c/blocks

	__block AVAudioUnitSampler* sampler = self.instrument.avAudioUnitSampler;
	__block TPCircularBuffer* ringBuffer = (TPCircularBuffer*)self.instrument.ringBuffer;

	return ^AUAudioUnitStatus(AudioUnitRenderActionFlags* actionFlags,
	const AudioTimeStamp* timestamp,
	AVAudioFrameCount frameCount,
	NSInteger outputBusNumber,
	AudioBufferList* data,
	const AURenderEvent* realtimeEventListHead,
	AURenderPullInputBlock pullInputBlock) {

	// midi events

	AURenderEvent const* event = realtimeEventListHead;
	while (event != NULL) {
	if (event->head.eventType == AURenderEventMIDI) {
	[sampler sendMIDIEvent:event->MIDI.data[0]
	data1:event->MIDI.data[1]
	data2:event->MIDI.data[2]];
	}

	event = event->head.next;
	}

	// render

	if (ringBuffer) {
	UInt32 neededBytes = data->mBuffers[0].mDataByteSize;
	if (data->mNumberBuffers > 1) {
	neededBytes += data->mBuffers[1].mDataByteSize;
	}

	int32_t availableBytes;
	void* srcBuffer = TPCircularBufferTail(ringBuffer, &availableBytes);
	if (availableBytes >= neededBytes) {
	void* dstBuffer = data->mBuffers[0].mData;
	UInt32 offset = data->mBuffers[0].mDataByteSize;
	memcpy(dstBuffer, srcBuffer, offset);
	if (data->mNumberBuffers > 1) {
	dstBuffer = data->mBuffers[1].mData;
	memcpy(dstBuffer, (char*)srcBuffer + offset, data->mBuffers[1].mDataByteSize);
	}
	TPCircularBufferConsume(ringBuffer, neededBytes);
	}
	}

	return noErr;
	};
	}

	@end