Slow start for AVAudioPlayer the first time a sound is played

Question

I\'m trying to eliminate startup lag when playing a (very short -- less than 2 seconds) audio file via AVAudioPlayer on the iPhone.

First, the code:

Answer 1

Here's a simple Swift extension to AVAudioPlayer that uses the play-and-stop at 0 volume idea presented in previous answers. PrepareToPlay() unfortunately at least for me did not do the trick.

extension AVAudioPlayer {
    private func initDelaylessPlayback() {
        volume = 0
        play()
        stop()
        volume = 1
    }

    convenience init(contentsOfWithoutDelay : URL) throws {
        try self.init(contentsOf: contentsOfWithoutDelay, fileTypeHint: nil)
        initDelaylessPlayback()
    }
}

Answer 2

Here's what I've done (in a separate thread):

[audioplayer start]
[audioplayer stop]
self.audioplayer = audioplayer

[audioplayer prepareToPlay] seems to be an asynchronous method, so you can't be sure when it returns if the audio is in fact ready to play.

In my case I call start to actually start playing - this appears to be synchronous. Then I stop it immediately. In the simulator anyway I don't hear any sound coming out from this activity. Now that the sound is "really" ready to play, I assign the local variable to a member variable so code outside the thread has access to it.

I must say I find it somewhat surprising that even on iOS 4 it takes some 2 seconds just to load an audio file that is only 4 seconds in length....

Answer 3

I've taken an alternative approach that works for me. I've seen this technique mentioned elsewhere (tho I don't recall at the moment where that was).

In short, preflight the sound system by loading and playing a short, "blank" sound before you do anything else. The code looks like this for a short mp3 file I preload in my view controller'sviewDidLoad method that's of .1 second duration:

   NSError* error = nil;
   NSString* soundfilePath = [[NSBundle mainBundle] pathForResource:@"point1sec" ofType:@"mp3"];
   NSURL* soundfileURL = [NSURL fileURLWithPath:soundfilePath];
   AVAudioPlayer* player = [[[AVAudioPlayer alloc] initWithContentsOfURL:soundfileURL error:&error] autorelease];
   [player play];  

You can create your own blank mp3 if you want, or do a google search on "blank mp3s" to find and download one already constructed by somebody else.