iPhone AVAudioPlayer app freeze on first play

Question

I'm using AVAudioPlayer from iOS SDK for playing short sounds on each click in tableView rows. I have manually made @selector on button in each row that fires up method playSound:(id)receiver {}. From receiver I get sound url so I can play it up.

This method looks like that:

- (void)playSound:(id)sender {
    [audioPlayer prepareToPlay];
    UIButton *audioButton = (UIButton *)sender;
    [audioButton setImage:[UIImage imageNamed:@"sound_preview.png"] forState:UIControlStateNormal];
    NSString *soundUrl = [[listOfItems objectForKey:[NSString stringWithFormat:@"%i",currentPlayingIndex]] objectForKey:@"sound_url"];

    //here I get mp3 file from http url via NSRequest in NSData
    NSData *soundData = [sharedAppSettingsController getSoundUrl:defaultDictionaryID uri:soundUrl];
    NSError *error;
    audioPlayer = [[AVAudioPlayer alloc] initWithData:soundData error:&error];
    audioPlayer.numberOfLoops = 0;
    if (error) {
        NSLog(@"Error: %@",[error description]);
    }
    else {
        audioPlayer.delegate = self;
        [audioPlayer play];
    }
}

Everything works fine except for the first play of some sound. The application freezes for about 2 seconds and than sound is played. Second and every other sound play works just right after click on sound button.

I wonder why there is that about 2 seconds freeze on first play when application starts?

Answer 1

From your code snippet, audioPlayer must be an ivar, right?

At the top of the method, you invoke -prepareToPlay on the existing audioPlayer instance (which could be nil, at least on the first pass).

Later in the method, you replace this existing audio player with a brand new AVAudioPlayer instance. The previous -prepareToPlay is wasted. And you're leaking memory with each new AVAudioPlayer.

Instead of caching sound data or URLs, I would try creating a cache of AVAudioPlayer objects, one for each sound. In your -playSound: method, get a reference to the appropriate audio player for the table row, and -play.

You can use -tableView:cellForRowAtIndexPath: as the appropriate point to get the AVAudioPlayer instance for that row, maybe lazily creating the instance and caching it there as well.

You can try -tableView:willDisplayCell:forRowAtIndexPath: as the point where you would invoke -prepareToPlay on the row's AVAudioPlayer instance.

Or you could just do the prepare in -tableView:cellForRowAtIndexPath:. Experiment and see which works best.