More Efficient Code? (AVAudioPlayer) - iphone

Question

In the phone below I am readying an AVAudioPlayer for four different sounds in my app. If I do not do this, it causes the app to delay about 1.5 seconds is I just do it where I need to hear it. So is there any way to make this code look better or work more efficiently because now I am readying these sounds in my App-Delegate and it slows down the launch a little bit. So here is the code and let me know if there is any way to make this code below better:
- (void)readySounds {
NSString *path = [[NSBundle mainBundle] pathForResource:#"TrackUno" ofType:#"mp3"];
NSURL *file = [[NSURL alloc] initFileURLWithPath:path];
AVAudioPlayer *one = [[AVAudioPlayer alloc] initWithContentsOfURL:file error:nil];
[file release];
self.tr1 = one;
[one release];
[tr1 prepareToPlay];
[tr1 setDelegate:self];
NSString *path2 = [[NSBundle mainBundle] pathForResource:#"TrackDos" ofType:#"mp3"];
NSURL *file2 = [[NSURL alloc] initFileURLWithPath:path2];
AVAudioPlayer *two = [[AVAudioPlayer alloc] initWithContentsOfURL:file2 error:nil];
[file2 release];
self.tr2 = two;
[two release];
[tr2 prepareToPlay];
[tr2 setDelegate:self];
NSString *path3 = [[NSBundle mainBundle] pathForResource:#"Click" ofType:#"mp3"];
NSURL *file3 = [[NSURL alloc] initFileURLWithPath:path3];
AVAudioPlayer *three = [[AVAudioPlayer alloc] initWithContentsOfURL:file3 error:nil];
[file3 release];
self.clk = three;
[three release];
[clk prepareToPlay];
[clk setDelegate:self];
NSString *path4 = [[NSBundle mainBundle] pathForResource:#"HSSound" ofType:#"mp3"];
NSURL *file4 = [[NSURL alloc] initFileURLWithPath:path4];
AVAudioPlayer *four = [[AVAudioPlayer alloc] initWithContentsOfURL:file4 error:nil];
[file4 release];
self.hs = four;
[four release];
[hs prepareToPlay];
[hs setDelegate:self];
}

Answer 1

If initialization times are your sole concern, then you could possibly* create this on a secondary thread and improve the perceived launch times. It would then init the streams and decoders, and open the audio files from disk from a secondary thread.
If playback, stream count, memory usage, CPU, load times, decoding, filtering, resampling, etc. are still factors: You are using the highest level APIs, you can drop down a few levels and have all the control you want over each and every one of these aspects.
You can make it look better by refactoring it -- the method does a similar sequence four times.
*'possibly' because I have only used the lower level APIs, I don't know if AVAudioPlayer has threading constraints.
Example refactoring with added error checking:
Not compiled, but you get the idea:
- (AVAudioPlayer *)newAudioPlayerForFile:(NSString *)fileName extension:(NSString *)extension inBundle:(NSBundle *)bundle
{
assert(fileName && extension && bundle);
NSURL * url = [bundle URLForResource:fileName ofType:extension];
if (nil == url) {
assert(0 && "could not locate resource");
return nil;
}
NSError * error = 0;
AVAudioPlayer * spieler = [[AVAudioPlayer alloc] initWithContentsOfURL:url error:&error];
assert(spieler);
if (nil != error) {
NSLog(#"Error encountered creating audio player for file (%#): %#", fileName, error);
[spieler release], spieler = nil;
return nil;
}
[spieler prepareToPlay];
[spieler setDelegate:self];
return spieler;
}
- (void)readySounds
{
NSAutoreleasePool * pool = [NSAutoreleasePool new];
NSBundle * mainBundle = [NSBundle mainBundle];
self.tr1 = [[self newAudioPlayerForFile:#"TrackUno" extension:#"mp3" inBundle:mainBundle] autorelease];
self.tr2 = [[self newAudioPlayerForFile:#"TrackDos" extension:#"mp3" inBundle:mainBundle] autorelease];
self.clk = [[self newAudioPlayerForFile:#"Click" extension:#"mp3" inBundle:mainBundle] autorelease];
self.hs = [[self newAudioPlayerForFile:#"HSSound" extension:#"mp3" inBundle:mainBundle] autorelease];
[pool release], pool = nil;
}

Answer 2

I found that the solution to load in the background was a problem... it worked and then the 30th time I used the sound from the main thread all sound stopped working. There are a couple of things that could have happened - I had to create my own autorelease pool and the background thread could have gone away junking the object.
Thinking about it I only have short sound effects - creating the first AVAudioPlayer was slow but the subsequent ones were fine. So to solve it I created a tiny silent wav file and used that as the first one to load. I used audacity to create the file and did Tracks > Add New > Audio Track, then I did Generate > Silence, picked a very small interval like .01s, then I File > Export'ed the sound and added the file to XCode.
I force the small, silent wav file to load in viewDidLoad and that shortened the lag for me.
Hope this is helpful to someone with a similar problem.