Question

I am developing an application where the user can tap multiple hit areas which produces sounds.
But the result is a little laggy, when multiple sounds start at the same time, the sounds are played with an ugly delay.

I am using AVAudioPlayer instances for each sound.
Is there a better way to play sounds and prevent this lag?

Here’s the code:

#import "MBImageView.h"
#import <AVFoundation/AVFoundation.h>

@implementation MBImageView

-(void)awakeFromNib
{
NSURL* audioFile = [NSURL fileURLWithPath[[NSBundlemainBundle] pathForResource:@"shaker" 
                                               ofType:@"caf"]]; 
    AudioServicesCreateSystemSoundID((CFURLRef)audioFile, &shortSound); 

}

- (id)initWithImage:(UIImage *)image{ 
    return self; 
}

- (void) touchesBegan:(NSSet*)touches withEvent:(UIEvent*)event
{
    AudioServicesPlaySystemSound(shortSound);
}


@end

Regards.

Answer 1

Most of these sounds (AVAudioPlayer and AudioServices) are playing after your runloop ends. That is, you say play and they get queued for playing, and they don’t start playing immediately.

If you want lag free sound, you use Audio Unit:

To provide lowest latency audio,
especially when doing simultaneous
input and output (such as for a VoIP
application), use the I/O unit or the
Voice Processing I/O unit. See “Audio
Unit Support in iPhone OS.”

You may also want to look at Audio Toolbox:

Use the Audio Toolbox framework to
play audio with synchronization
capabilities, access packets of
incoming audio, parse audio streams,
convert audio formats, and record
audio with access to individual
packets. For details, see Audio
Toolbox Framework Reference and the
SpeakHere sample code project.