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Retired Document

Important: This sample code may not represent best practices for current development. The project may use deprecated symbols and illustrate technologies and techniques that are no longer recommended.

Relevant replacement documents include:

http://developer.apple.com/library/mac/#samplecode/AVRecorder/Introduction/Intro.html

Sources/Classes/SeqGrab/SGAudio.mm

/*  Copyright:  © Copyright 2005 Apple Computer, Inc. All rights reserved.

    Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple Computer, Inc.

            ("Apple") in consideration of your agreement to the following terms, and your

            use, installation, modification or redistribution of this Apple software

            constitutes acceptance of these terms.  If you do not agree with these terms,

            please do not use, install, modify or redistribute this Apple software.

            In consideration of your agreement to abide by the following terms, and subject

            to these terms, Apple grants you a personal, non-exclusive license, under AppleÕs

            copyrights in this original Apple software (the "Apple Software"), to use,

            reproduce, modify and redistribute the Apple Software, with or without

            modifications, in source and/or binary forms; provided that if you redistribute

            the Apple Software in its entirety and without modifications, you must retain

            this notice and the following text and disclaimers in all such redistributions of

            the Apple Software.  Neither the name, trademarks, service marks or logos of

            Apple Computer, Inc. may be used to endorse or promote products derived from the

            Apple Software without specific prior written permission from Apple.  Except as

            expressly stated in this notice, no other rights or licenses, express or implied,

            are granted by Apple herein, including but not limited to any patent rights that

            may be infringed by your derivative works or by other works in which the Apple

            Software may be incorporated.

            The Apple Software is provided by Apple on an "AS IS" basis.  APPLE MAKES NO

            WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE IMPLIED

            WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR

            PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND OPERATION ALONE OR IN

            COMBINATION WITH YOUR PRODUCTS.

            IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL OR

            CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE

            GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

            ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION, MODIFICATION AND/OR DISTRIBUTION

            OF THE APPLE SOFTWARE, HOWEVER CAUSED AND WHETHER UNDER THEORY OF CONTRACT, TORT

            (INCLUDING NEGLIGENCE), STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN

            ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

#import "SGAudio.h"

#import "WhackedDebugMacros.h"

#import <CoreAudioKit/CoreAudioKit.h>

#import "SGAudioSettings.h"

NSString * SGAudioDeviceListChangedNotification                     = @"SGAudioDeviceListChangedNotification";

NSString * SGAudioRecordDeviceDiedNotification                      = @"SGAudioRecordDeviceDiedNotification";

NSString * SGAudioRecordDeviceHoggedChangedNotification             = @"SGAudioRecordDeviceHoggedChangedNotification";

NSString * SGAudioRecordDeviceInUseChangedNotification              = @"SGAudioRecordDeviceInUseChangedNotification";

NSString * SGAudioRecordDeviceStreamFormatChangedNotification       = @"SGAudioRecordDeviceStreamFormatChangedNotification";

NSString * SGAudioRecordDeviceStreamFormatListChangedNotification   = @"SGAudioRecordDeviceStreamFormatListChangedNotification";

NSString * SGAudioRecordDeviceInputSelectionNotification            = @"SGAudioRecordDeviceInputSelectionNotification";

NSString * SGAudioRecordDeviceInputListChangedNotification          = @"SGAudioRecordDeviceInputListChangedNotification";

NSString * SGAudioPreviewDeviceDiedNotification                     = @"SGAudioPreviewDeviceDiedNotification";

NSString * SGAudioPreviewDeviceHoggedChangedNotification            = @"SGAudioPreviewDeviceHoggedChangedNotification";

NSString * SGAudioPreviewDeviceInUseChangedNotification             = @"SGAudioPreviewDeviceInUseChangedNotification";

NSString * SGAudioPreviewDeviceStreamFormatChangedNotification      = @"SGAudioPreviewDeviceStreamFormatChangedNotification";

NSString * SGAudioPreviewDeviceStreamFormatListChangedNotification  = @"SGAudioPreviewDeviceStreamFormatListChangedNotification";

NSString * SGAudioPreviewDeviceOutputSelectionChangedNotification   = @"SGAudioPreviewDeviceOutputSelectionChangedNotification";

NSString * SGAudioPreviewDeviceOutputListChangedNotification        = @"SGAudioPreviewDeviceOutputListChangedNotification";

NSString * SGAudioOutputStreamFormatChangedNotification             = @"SGAudioOutputStreamFormatChangedNotification";

static OSStatus myPreMixSGAudioCallback(

    SGChannel                           c,

    void *                              inRefCon,

    SGAudioCallbackFlags *              ioFlags,

    const AudioTimeStamp *              inTimeStamp,

    const UInt32 *                      inNumberPackets,

    const AudioBufferList *             inData,

    const AudioStreamPacketDescription* inPacketDescriptions);

static OSStatus

fxUnitInputProc(void *inRefCon,

                AudioUnitRenderActionFlags *ioActionFlags,

                const AudioTimeStamp *inTimeStamp,

                UInt32 inBusNumber,

                UInt32 inNumberFrames,

                AudioBufferList *ioData);

static void

sgAudioPropListenerCallback(ComponentInstance inComponent,

                            ComponentPropertyClass inPropClass,

                            ComponentPropertyID inPropID,

                            void *inUserData);

@implementation SGAudio

/*___________________________________________________________________________________________

*/

- (id)initWithSeqGrab:(SeqGrab*)sg

    OSStatus err = noErr;

    NSData * data = nil;

    ComponentPropertyInfo * cpi = NULL;

    Boolean audiComponentAlreadyOpened = (mChan != NULL);

    self = [super initWithSeqGrab:sg];

    if (false == audiComponentAlreadyOpened)

        BAILSETERR( SGNewChannel([sg seqGrabComponent], SGAudioMediaType, &mChan) );

    BAILSETERR( SGSetChannelRefCon(mChan, (long)self) );

    [mSG addChannel:self];

    [self setUsage:seqGrabPreview + seqGrabRecord];

        // register self as a listener of all the SGAudio Listenable properties.

        // we will create notifications for all the listenable properties we recognize

    [self getPropertyWithClass:kComponentPropertyClassPropertyInfo

                                    id:kComponentPropertyInfoList

                                    size:sizeof(data)

                                    address:&data

                                    sizeUsed:NULL];

    cpi = (ComponentPropertyInfo*)[data bytes];

    if (cpi)

        for (int i = 0; i < [data length]/sizeof(ComponentPropertyInfo); i++)

            if (cpi[i].propFlags & kComponentPropertyFlagWillNotifyListeners)

                QTAddComponentPropertyListener(mChan,

                    cpi[i].propClass, cpi[i].propID,

                    (QTComponentPropertyListenerUPP)sgAudioPropListenerCallback,

                    self);

    // set the channel map on the record device to expressly indicate our desire to

    // receive all channels from the record device (a reasonable default)

    if (false == audiComponentAlreadyOpened)

        AudioStreamBasicDescription devFormat;

        if (noErr == [self getPropertyWithClass: kQTPropertyClass_SGAudioRecordDevice

                        id: kQTSGAudioPropertyID_StreamFormat

                        size:sizeof(devFormat)

                        address:&devFormat

                        sizeUsed:NULL])

            SInt32 * map = (SInt32*)malloc(devFormat.mChannelsPerFrame * sizeof(SInt32));

            for (int i = 0; i < devFormat.mChannelsPerFrame; i++)

                map[i] = i;

            [self setPropertyWithClass: kQTPropertyClass_SGAudioRecordDevice

                    id: kQTSGAudioPropertyID_ChannelMap

                    size: devFormat.mChannelsPerFrame * sizeof(SInt32)

                    address: map];

            free(map);

    mDoInitFXUnits = YES;

bail:

    [data release];

    if (err)

        [self release];

        return nil;

    return self;

/*___________________________________________________________________________________________

*/

- (void)dealloc

    //NSLog(@"[SGAudio dealloc] %p", self);

    while (mFXUnitsCount--)

        CloseComponent(mFXUnits[mFXUnitsCount]);

    [super dealloc];

/*___________________________________________________________________________________________

*/

- (OSType)channelType

    return SGAudioMediaType;

};

/*___________________________________________________________________________________________

*/

- (OSStatus)getPropertyInfoWithClass:(ComponentPropertyClass)theClass

                                    id:(ComponentPropertyID)theID

                                    type:(ComponentValueType*)type

                                    size:(ByteCount*)sz

                                    flags:(UInt32*)flags

    return QTGetComponentPropertyInfo(mChan, theClass, theID, type, sz, flags);

/*___________________________________________________________________________________________

*/

- (OSStatus)getPropertyWithClass:(ComponentPropertyClass)theClass

                                    id:(ComponentPropertyID)theID

                                    size:(ByteCount)sz

                                    address:(ComponentValuePtr)addr

                                    sizeUsed:(ByteCount*)szUsed

    return QTGetComponentProperty(mChan, theClass, theID, sz, addr, szUsed);

/*___________________________________________________________________________________________

*/

- (OSStatus)setPropertyWithClass:(ComponentPropertyClass)theClass

                                id:(ComponentPropertyID)theID

                                size:(ByteCount)sz

                                address:(ConstComponentValuePtr)addr

    return QTSetComponentProperty(mChan, theClass, theID, sz, addr);

/*___________________________________________________________________________________________

*/

// The following three functions are for convenience in getting common properties

- (NSArray*)deviceList

    NSArray * devList = nil;

    [self getPropertyWithClass: kQTPropertyClass_SGAudio

                             id: kQTSGAudioPropertyID_DeviceListWithAttributes

                           size: sizeof(NSArray*)

                        address: &devList

                       sizeUsed: NULL];

    return [devList autorelease];

/*___________________________________________________________________________________________

*/

- (NSArray*)recordCapableDeviceList

    NSArray * devList = [self deviceList];

    NSMutableArray * myList = nil;

    if (devList)

        myList = [NSMutableArray array];

        for (int i = 0; i < [devList count]; i++)

            NSDictionary * devDict = [devList objectAtIndex:i];

            UInt32 key = kQTAudioDeviceAttribute_DeviceCanRecordKey;

            if (YES == [(NSNumber*)[devDict objectForKey:(id)key] boolValue])

                [myList addObject:devDict];

    return myList;

/*___________________________________________________________________________________________

*/

- (NSArray*)previewCapableDeviceList

    NSArray * devList = [self deviceList];

    NSMutableArray * myList = nil;

    if (devList)

        myList = [NSMutableArray array];

        for (int i = 0; i < [devList count]; i++)

            NSDictionary * devDict = [devList objectAtIndex:i];

            UInt32 key = kQTAudioDeviceAttribute_DeviceCanPreviewKey;

            if (YES == [(NSNumber*)[devDict objectForKey:(id)key] boolValue])

                [myList addObject:devDict];

    return myList;

/*________________________________________________________________________________________

*/

- (NSString*)summaryString

    NSString * device = nil;

    NSDictionary * attribs = nil;

    NSString * retval = nil;

    [self getPropertyWithClass: kQTPropertyClass_SGAudioRecordDevice

                             id: kQTSGAudioPropertyID_DeviceAttributes

                           size: sizeof(attribs)

                        address: &attribs

                       sizeUsed: NULL];

    device = [attribs objectForKey:(id)kQTAudioDeviceAttribute_DeviceNameKey];

    retval = [NSString stringWithFormat:@"[%p] SGAudio: %@", self, device];

    [attribs release];

    return retval;

/*________________________________________________________________________________________

*/

- (BOOL)isVideoChannel

    return NO;

/*________________________________________________________________________________________

*/

- (BOOL)isAudioChannel

    return YES;

/*________________________________________________________________________________________

*/

// we override the SGChan base class's showSettingsDialog implementation, as the

// SGAudioMediaType channel that shipped in QT 7 does not implement SGSettingsDialog(),

// but our Cocoa wrapper does.

- (OSStatus)showSettingsDialog

    SGAudioSettings * settings = [[SGAudioSettings alloc] initWithSGChan:self];

    [settings showPanel:self];

    [settings release];

    return noErr;

/*________________________________________________________________________________________

*/

- (void)notifyOfChangeInPropClass:(ComponentPropertyClass)theClass

            id:(ComponentPropertyID)theID

    NSString * notif = nil;

    switch (theClass) {

        case kQTPropertyClass_SGAudio:

            switch (theID) {

                case kQTSGAudioPropertyID_DeviceListWithAttributes:

                    notif = SGAudioDeviceListChangedNotification;

                    break;

                case kQTSGAudioPropertyID_StreamFormat:

                    notif = SGAudioOutputStreamFormatChangedNotification;

                    break;

                default:

                    NSLog(@"Unknown SGAudio property (%.4s)", (char*)&theID);

                    break;

};

            break;

        case kQTPropertyClass_SGAudioRecordDevice:

            switch (theID) {

                case kQTSGAudioPropertyID_DeviceAlive:

                    notif = SGAudioRecordDeviceDiedNotification;

                    mDoInitFXUnits = YES;

                    break;

                case kQTSGAudioPropertyID_DeviceHogged:

                    notif = SGAudioRecordDeviceHoggedChangedNotification;

                    break;

                case kQTSGAudioPropertyID_DeviceInUse:

                    notif = SGAudioRecordDeviceInUseChangedNotification;

                    break;

                case kQTSGAudioPropertyID_StreamFormat:

                    notif = SGAudioRecordDeviceStreamFormatChangedNotification;

                    mDoInitFXUnits = YES;

                    break;

                case kQTSGAudioPropertyID_StreamFormatList:

                    notif = SGAudioRecordDeviceStreamFormatListChangedNotification;

                    break;

                case kQTSGAudioPropertyID_InputSelection:

                    notif = SGAudioRecordDeviceInputSelectionNotification;

                    break;

                case kQTSGAudioPropertyID_InputListWithAttributes:

                    notif = SGAudioRecordDeviceInputListChangedNotification;

                    break;

                default:

                    NSLog(@"Unknown SGAudioRecordDevice property (%.4s)", (char*)&theID);

                    break;

};

            break;

        case kQTPropertyClass_SGAudioPreviewDevice:

            switch (theID) {

                case kQTSGAudioPropertyID_DeviceAlive:

                    notif = SGAudioPreviewDeviceDiedNotification;

                    break;

                case kQTSGAudioPropertyID_DeviceHogged:

                    notif = SGAudioPreviewDeviceHoggedChangedNotification;

                    break;

                case kQTSGAudioPropertyID_DeviceInUse:

                    notif = SGAudioPreviewDeviceInUseChangedNotification;

                    break;

                case kQTSGAudioPropertyID_StreamFormat:

                    notif = SGAudioPreviewDeviceStreamFormatChangedNotification;

                    break;

                case kQTSGAudioPropertyID_StreamFormatList:

                    notif = SGAudioPreviewDeviceStreamFormatListChangedNotification;

                    break;

                case kQTSGAudioPropertyID_OutputSelection:

                    notif = SGAudioPreviewDeviceOutputSelectionChangedNotification;

                    break;

                case kQTSGAudioPropertyID_OutputListWithAttributes:

                    notif = SGAudioPreviewDeviceOutputListChangedNotification;

                    break;

                default:

                    NSLog(@"Unknown SGAudioPreviewDevice property (%.4s)", (char*)&theID);

                    break;

};

            break;

        default:

            NSLog(@"[SGAudio] Unknown property class (%.4s), id (%.4s)", (char*)&theClass, (char*)&theID);

            break;

};

    if (notif)

        [[NSNotificationCenter defaultCenter] postNotificationName:notif object:self];

/*________________________________________________________________________________________

*/

- (AudioUnit *)fxUnits

    return mFXUnits;

/*________________________________________________________________________________________

*/

- (UInt32)fxUnitsCount

    return mFXUnitsCount;

/*________________________________________________________________________________________

*/

// The SGAudioMediaType channel that shipped in QT 7 has no built in support for

// AudioUnit fx, but our Cocoa wrapper does, using the SGAudioMediaType SGChannel's

// SGAudioCallback mechanism.

- (AudioUnit)insertAUFXUnit:(ComponentDescription *)fxUnitDesc;

    Component c;

    AudioUnit au;

    SGAudioCallbackStruct cbStruct;

    if (mFXUnitsCount == kMaxFXUnits)

        return NULL;

    if (fxUnitDesc->componentType != 'aufx')

        return NULL;

    c = FindNextComponent(NULL, fxUnitDesc);

    if (!c)

        return NULL;

    au = OpenComponent(c);

    if (!au)

        return NULL;

    // register our callback proc

    cbStruct.inputProc = myPreMixSGAudioCallback;

    cbStruct.inputProcRefCon = self;

    [self setPropertyWithClass:kQTPropertyClass_SGAudio

                            id:kQTSGAudioPropertyID_PreMixCallback

                            size:sizeof(cbStruct)

                            address:&cbStruct];

    mFXUnits[mFXUnitsCount++] = au;

    mDoInitFXUnits = YES;

    return au;

/*________________________________________________________________________________________

*/

- (BOOL)removeAUFXUnit:(AudioUnit)doomedFXUnit

    for (int i = 0; i < mFXUnitsCount; i++)

        if (mFXUnits[i] == doomedFXUnit)

            CloseComponent(doomedFXUnit);

            memcpy(&mFXUnits[i], &mFXUnits[i+1], (--mFXUnitsCount - i) * sizeof(AudioUnit));

                // when we go down to zero, we should remove the callback from firing

            if (mFXUnitsCount == 0)

                SGAudioCallbackStruct cbStruct;

                cbStruct.inputProc = NULL;

                cbStruct.inputProcRefCon = 0;

                [self setPropertyWithClass:kQTPropertyClass_SGAudio

                            id:kQTSGAudioPropertyID_PreMixCallback

                            size:sizeof(cbStruct)

                            address:&cbStruct];

            return YES;

    return NO;

/*________________________________________________________________________________________

*/

- (OSStatus)sgAudioCallbackRender:

                (SGAudioCallbackFlags *)ioFlags

                timestamp:(const AudioTimeStamp *)inTimeStamp

                numPackets:(const UInt32 *)inNumberPackets

                buffer:(const AudioBufferList *)inData

                packetDescs:(const AudioStreamPacketDescription*)inPacketDescriptions

#pragma unused (ioFlags)

#pragma unused (inPacketDescriptions)

        // sgAudioCallbackRender gets called when pre-mixed data is available.

    OSStatus err = noErr;

    UInt32      numFrames = *inNumberPackets;

        // we lazily initialize the units, so this code will execute the first time we

        // get a render callback

    if (mDoInitFXUnits)

        AudioStreamBasicDescription asbd;

        UInt32 maxFrames = numFrames + 512; // extra 512 for safety

            // get the pre-mix callback format

        [self getPropertyWithClass:kQTPropertyClass_SGAudio

                                id:kQTSGAudioPropertyID_PreMixCallbackFormat

                                size:sizeof(asbd)

                                address:&asbd

                                sizeUsed:NULL];

        for (int i = 0; i < mFXUnitsCount; i++)

                // set up fx units

            UInt32                  inPlace, size;

            Boolean                 writable;

            OSStatus                caErr = noErr, inPlaceErr = noErr;

            if (mFXUnits[i])

                AudioUnitUninitialize(mFXUnits[i]);

                caErr = AudioUnitSetProperty(

                            mFXUnits[i],

                            kAudioUnitProperty_StreamFormat,

                            kAudioUnitScope_Input,

                            0, &asbd, sizeof(asbd));

                if (caErr == noErr)

                    caErr = AudioUnitSetProperty(mFXUnits[i],

                                                kAudioUnitProperty_StreamFormat,

                                                kAudioUnitScope_Output,

                                                0, &asbd, sizeof(asbd));

                if (caErr == noErr)

                    caErr = AudioUnitSetProperty(

                                mFXUnits[i],

                                kAudioUnitProperty_MaximumFramesPerSlice,

                                kAudioUnitScope_Global,

                                0, &maxFrames, sizeof(maxFrames));

                    // prefer in place processing, if the fx unit can do it

                if (caErr == noErr)

                    inPlaceErr = AudioUnitGetPropertyInfo(

                                    mFXUnits[i],

                                    kAudioUnitProperty_InPlaceProcessing,

                                    kAudioUnitScope_Global,

                                    0, &size, &writable);

                if (caErr == noErr && inPlaceErr == noErr)

                    caErr = AudioUnitGetProperty(

                                mFXUnits[i],

                                kAudioUnitProperty_InPlaceProcessing,

                                kAudioUnitScope_Global,

                                0, &inPlace, &size);

                    if (caErr == noErr && writable)

                        inPlace = 1;

                        caErr = AudioUnitSetProperty(

                                    mFXUnits[i],

                                    kAudioUnitProperty_InPlaceProcessing,

                                    kAudioUnitScope_Global,

                                    0, &inPlace, sizeof(inPlace));

                AURenderCallbackStruct cb;

                cb.inputProc = fxUnitInputProc;

                cb.inputProcRefCon = self;

                if (caErr == noErr)

                    caErr = AudioUnitSetProperty(

                                mFXUnits[i],

                                kAudioUnitProperty_SetRenderCallback,

                                kAudioUnitScope_Global, 0,

                                &cb, sizeof(cb) );

                if (caErr == noErr)

                    caErr = AudioUnitInitialize(mFXUnits[i]);

                if (caErr != noErr)

                    [self removeAUFXUnit:mFXUnits[i]];

                    i = 0; // start over

        mDoInitFXUnits = NO;

        // Here, we stow away the buffer, and begin

        // the pull on our Audio Unit chain

        // we are treating the passed buffer list as

        // read/write, so we explicitly cast away the const

    mPullBuffer = (AudioBufferList*)inData;

    if (mFXUnitsCount)

        mPullUnitIndex = mFXUnitsCount - 1;

        BAILSETERR( AudioUnitRender(  mFXUnits[mPullUnitIndex],

                                NULL,

                                inTimeStamp, 0, numFrames, mPullBuffer) );

bail:

    return err;

/*________________________________________________________________________________________

*/

- (OSStatus)fxUnitRender:(AudioUnitRenderActionFlags *)ioActionFlags

                            timestamp:(const AudioTimeStamp *)inTimeStamp

                            bus:(UInt32)inBusNumber

                            numFrames:(UInt32)inNumberFrames

                            buffer:(AudioBufferList *)ioData

#pragma unused (ioActionFlags)

#pragma unused (inBusNumber)

        // fxUnitRender gets called to feed data to the AudioUnit

        // at location mFXUnits[mPullUnitIndex].  If mPullUnitIndex

        // is zero, it's already been pulled, and we need to

        // feed the buffer passed in the SGAudioCallbackProc

    OSStatus    err = noErr;

    if (mPullUnitIndex > 0)

        BAILSETERR( AudioUnitRender(  mFXUnits[--mPullUnitIndex],

                                NULL,

                                inTimeStamp, 0, inNumberFrames, ioData) );

    else {

        // we've pulled through every audio unit, now we need to feed

        // the SGAudioCallback stashed buffer

        if (mPullBuffer && (mPullBuffer->mNumberBuffers == ioData->mNumberBuffers))

            for (int i = 0; i < ioData->mNumberBuffers; i++)

                ioData->mBuffers[i].mData = mPullBuffer->mBuffers[i].mData;

                ioData->mBuffers[i].mDataByteSize = mPullBuffer->mBuffers[i].mDataByteSize;

bail:

    return err;

/*________________________________________________________________________________________

*/

@end

/*________________________________________________________________________________________

*/

static OSStatus

fxUnitInputProc(void *inRefCon,

                AudioUnitRenderActionFlags *ioActionFlags,

                const AudioTimeStamp *inTimeStamp,

                UInt32 inBusNumber,

                UInt32 inNumberFrames,

                AudioBufferList *ioData)

    SGAudio * myself = (SGAudio*)inRefCon;

    return ([myself fxUnitRender:ioActionFlags

                    timestamp:inTimeStamp

                    bus:inBusNumber

                    numFrames:inNumberFrames

                    buffer:ioData]);

/*________________________________________________________________________________________

*/

static OSStatus myPreMixSGAudioCallback(

    SGChannel                           c,

    void *                              inRefCon,

    SGAudioCallbackFlags *              ioFlags,

    const AudioTimeStamp *              inTimeStamp,

    const UInt32 *                      inNumberPackets,

    const AudioBufferList *             inData,

    const AudioStreamPacketDescription* inPacketDescriptions)

#pragma unused (c)

    SGAudio * myself = (SGAudio*)inRefCon;

    return ([myself sgAudioCallbackRender:ioFlags

                    timestamp:inTimeStamp

                    numPackets:inNumberPackets

                    buffer:inData

                    packetDescs:inPacketDescriptions]);

/*________________________________________________________________________________________

*/

static void

sgAudioPropListenerCallback(ComponentInstance inComponent,

                            ComponentPropertyClass inPropClass,

                            ComponentPropertyID inPropID,

                            void *inUserData)

#pragma unused (inComponent)

    // this callback will be called from a non cocoa thread.  We'll need our own autorelease pool.

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    SGAudio * myself = (SGAudio*)inUserData;

    [myself notifyOfChangeInPropClass:inPropClass id:inPropID];

    [pool release];

/*________________________________________________________________________________________

*/

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