Playing sounds in iPhone games - slowdowns

Question

I'm using the AVAudioPlayer to play sound FX on a separate thread in my app. Right now my app is fairly simple, I have a UIScrollView for a scrolling background, and a couple of CALayers that represent a player and an enemy in a simple side-scroller type game (think Mario or Kung Fu or whatnot)...I can move the player left and right, with the view scrolling appropriately with no problems. I have an "attack" button that's playing a sound effect...and many times when I play the sound effect, I get a little bit of a hitch, graphically. Is this just par for the course on the iPhone using Quartz? Is there some way to have this perform a little more smoothly without starting to investigate OpenGL?

Answer 1

How are you playing the sound? If I was to make a guess it would be that each time the sound is played the OS is actually loading it from disk as well as playing it.

Update:

Ok, you really don't need to be creating a new thread to play a sound. This alone could cause a stutter in a game and is also redundant - The AVAudioPlayer play method is asynchronous - it returns immediately and not when the sound ends.

Answer 2

(Using an answer rather than a comment for length and so I can show code):

My sound playing method is as follows:

- (void)playSoundThreaded:(id)soundPlayer
{
  if(soundPlayer == nil)
    return;

  NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
  [(AVAudioPlayer*)soundPlayer play];
  [pool release];
}

- (void)playSound:(AVAudioPlayer*)player
{
  if(player == nil)
    return;

  [NSThread detachNewThreadSelector:@selector(playSoundThreaded:)
    toTarget:self withObject:(id)player];
}

And the sound is loaded up as follows:

fxPlayer = [[AVAudioPlayer alloc] initWithData:
  [NSData dataWithContentsOfFile:
    [[NSBundle mainBundle] pathForResource:@"voicehiya" ofType:@"caf"]] error:NULL];

We've had some inkling that the sound is being reloaded from disk every time...but have no idea as to why that is or how to prevent it.

Answer 3

Use NSData dataWithContentsOfMappedFile instead of dataWithContentsOfFile.

Also AVAudioPlayer handles it's own threading, you don't need to create one. [AVAudioPlayer play] returns after it started playing, not after it is done playing.

And don't forget to release your AVAudioPlayer when you no longer need it, for example if you only want to play a sound onces, implemement the audioPlayerDidFinishPlaying:successfully: delegate and release it in there.

Answer 4

I think the thread is over complicating your player. Try this for a go:

/* setup the sound player */
AVAudioPlayer *player1=[[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL     fileURLWithPath:audioFilePath] error:NULL];
player1.numberOfLoops = 0;
player1.volume=1.0f;
[player1 prepareToPlay];

and then playSound becomes

[player play];

And don't forget to have the AudioSession category set correctly too.

Answer 5

I had the same problem with slowdown. To solve it, I first play and pause the sound when it first loads at volume 0 - this works better than prepareToPlay which still seems to result in slowdown:

player.volume = 0.0;
[player play];
[player pause];
player.volume = 1.0;

When it comes time to play a sound I just [player play];. Then every update cycle I loop through all my active sounds and catch ones that are about to end and rewind them instead of letting them expire - this avoids the overhead and slowdown of starting up the sound from scratch. The example here stops the sounds 1/15th of a second from the end of the sound:

for ({each player in active sounds})
{
  if ((player.duration - player.currentTime) <= (1.0/15.0))
  {
    [player pause];
    player.currentTime = 0.0;
  }
}

Now it's ready to go for the next play. Seems to work fine!

Update: Turns out I was still getting some pauses the very first time the sound was played. I think playing it at zero volume wasn't actually doing anything, but I changed it to play at 0.0001 volume and then pause - it's inaudible but seems to do the job of prepping the sound.

Answer 6

Why not just use AudioServicesPlaySystemSound? This is well suited to sound effects.

I use it in my game (vConqr) which is also based on a UIScrollView, with numerous other views (so all having their own CALayer), and it doesn't significantly impact performance.