I am trying to include a VU meter in my application to display the
level of the audio coming in through the mic.
I went through wakedTV sample code and pulled what i think i need
to get it to work (see end of message) but when it is time to ask
for kQTSGAudioPropertyID_AveragePowerLevels i always get the error
kQTPropertyAskLaterErr. no matter how long i wait this is what i get.
Obviously, when i run wackedTV everything works fine:-)
Anybody has any idea of what is wrong or a sample code of how to do
this?
Thanks
Olivier Destrebecq
http://otusweb.spymac.com/portfolio/
I left all the code related to the audio and stripped the rest, so
if i don't do something here, that means i'm not doing it:-)
@implementation recorderWindowController
- (id) init
{
...
mMutex = QTMLCreateMutex();
[self setSequenceGrabberAudio: [[[SGAudio alloc]
initWithSeqGrab: [[[SeqGrab alloc] init] autorelease]] autorelease]];
[[self sequenceGrabberAudio] setUsage: seqGrabPreview +
seqGrabRecord + seqGrabPlayDuringRecord];
if ( [[[[self sequenceGrabberAudio] grabber] channels] count] > 0)
{
[[[self sequenceGrabberAudio] grabber] preview];
}
}
return self;
}
//===========================================================
// updateAudioLevelTimer
//===========================================================
- (NSTimer *)updateAudioLevelTimer
{
//NSLog(@"in -updateAudioLevelTimer, returned
updateAudioLevelTimer = %@", updateAudioLevelTimer);
return [[updateAudioLevelTimer retain] autorelease];
}
- (void)setUpdateAudioLevelTimer:(NSTimer *)anUpdateAudioLevelTimer
{
//NSLog(@"in -setUpdateAudioLevelTimer:, old value of
updateAudioLevelTimer: %@, changed to: %@", updateAudioLevelTimer,
anUpdateAudioLevelTimer);
if (updateAudioLevelTimer != anUpdateAudioLevelTimer) {
[updateAudioLevelTimer invalidate];
updateAudioLevelTimer = [anUpdateAudioLevelTimer retain];
}
}
//===========================================================
// volumeLevelValue
//===========================================================
- (float)volumeLevelValue
{
//NSLog(@"in -volumeLevelValue, returned volumeLevelValue = %i",
volumeLevelValue);
return volumeLevelValue;
}
- (void)setVolumeLevelValue:(float)aVolumeLevelValue
{
//NSLog(@"in -setVolumeLevelValue, old value of volumeLevelValue:
%i, changed to: %i", volumeLevelValue, aVolumeLevelValue);
volumeLevelValue = aVolumeLevelValue;
}
//===========================================================
// sequenceGrabberAudio
//===========================================================
- (SGAudio *)sequenceGrabberAudio
{
//NSLog(@"in -sequenceGrabberAudio, returned sequenceGrabberAudio
= %@", sequenceGrabberAudio);
return [[sequenceGrabberAudio retain] autorelease];
}
- (void)setSequenceGrabberAudio:(SGAudio *)aSequenceGrabberAudio
{
//NSLog(@"in -setSequenceGrabberAudio:, old value of
sequenceGrabberAudio: %@, changed to: %@", sequenceGrabberAudio,
aSequenceGrabberAudio);
if (sequenceGrabberAudio != aSequenceGrabberAudio) {
[sequenceGrabberAudio release];
sequenceGrabberAudio = [aSequenceGrabberAudio retain];
}
}
@end
@implementation recorderWindowController (privateInterface)
- (void)invalidateChannelMap
{
QTMLGrabMutex(mMutex);
if (mLevelsArray)
free(mLevelsArray);
mLevelsArray = NULL;
QTMLReturnMutex(mMutex);
}
- (void) updateLevelIndicator: (NSTimer *) inTimer
{
#pragma unused(inTimer)
Float32 amps = -FLT_MAX;
QTMLGrabMutex(mMutex);
SGAudio * myAudi = [self sequenceGrabberAudio];
if (mLevelsArray == NULL)
{
UInt32 size;
[myAudi
getPropertyInfoWithClass:kQTPropertyClass_SGAudioRecordDevice
id:kQTSGAudioPropertyID_ChannelMap
type:NULL size:&size flags:NULL];
if (size > 0)
{
SInt32 * map = (SInt32 *)malloc(size);
[myAudi
getPropertyWithClass:kQTPropertyClass_SGAudioRecordDevice
id:kQTSGAudioPropertyID_ChannelMap
size:size
address:map sizeUsed:&size];
for (int i = 0; i < size/sizeof(SInt32); i++)
{
if (mChannelNumber == map[i])
{
mMyIndex = i;
mLevelsArraySize = size; // SInt32 and Float32 are the
same size
mLevelsArray = (Float32*)malloc(mLevelsArraySize);
break;
}
}
free(map);
}
}
if (mLevelsArray) // paranoia
{
// get the avg power level
OSStatus error= [myAudi
getPropertyWithClass:kQTPropertyClass_SGAudioRecordDevice
id:kQTSGAudioPropertyID_AveragePowerLevels
size:mLevelsArraySize
address:mLevelsArray
sizeUsed:NULL];
if (noErr == error)
{
amps = mLevelsArray[mMyIndex];
}
}
QTMLReturnMutex(mMutex);
[self setVolumeLevelValue: dbamp(amps)];
}
double dbamp(double db)
{
return pow(10., 0.05 * db);
}
double ampdb(double amp)
{
return 20. * log10(amp);
}
@end
@implementation recorderWindowController
(MTCoreAudioHardwarePropertyNotifications)
- (void) audioHardwareDeviceListDidChange
{
...
if ([devices count] 0)
{
//start the time to update the mic level indicator
//
[self setUpdateAudioLevelTimer: [NSTimer
scheduledTimerWithTimeInterval: 1./20
target: self
s
elector: @selector(updateLevelIndicator:)
u
serInfo: nil
repeats: YES]];
}
}
@end
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