Finch is a simple OpenAL-based sound effect player for iOS. The reasons for
writing Finch instead of sticking with Apple’s AVAudioPlayer are described in
my question on Stack Overflow. The goals are simple: (1) Play sound
effects without much fuss, and (2) do not lag in the play method as
AVAudioPlayer does. Finch is not meant to play background music. If you want
to play background music, you can go with AVAudioPlayer. Finch will play the
sound effects over the background music just fine.
The code is fairly tested. The interface changes from time to time as I don’t bother with backward compatibility, but it should be fairly easy to keep up with the changes. Basic use case:
#import "Finch.h"
#import "Sound.h"
#import "RevolverSound.h"
// Initializes OpenAL
Finch *soundEngine = [[Finch alloc] init];
NSBundle *bundle = [NSBundle mainBundle];
// Simple sound, only one instance can play at a time.
// If you call ‘play’ and the sound is still playing,
// it will start from the beginning.
Sound *click = [[Sound alloc] initWithFile:
[bundle URLForResource:@"click" withExtension:@"wav"]];
[click play];
// For playing multiple instances of the same sample at once
RevolverSound *gun = [[RevolverSound alloc] initWithFile:
[bundle URLForResource:@"gunshot" withExtension:@"wav"] rounds:10];
// Now I have a machinegun, ho-ho-ho
for (int i=1; i<=10; i++)
[gun play];
Don’t forget to link the application with AudioToolbox and OpenAL
frameworks. And please note that Finch does not yet support compressed
audio. You should be safe with mono or stereo WAV files sampled at 44.100 Hz.
Download the demo project to see more.
Before your application can play any sound whatsoever, you should set up the audio session so that the system knows how to work with your sounds – if they should be muted by the hardware Mute switch, for example, or if the iPod music should play behind your sounds.
Finch used to set up the audio session for you, but that’s not the right way to
do it™, so that in recent versions you have to set the audio session yourself.
Yes, that’s considered progress :-) The good news is that there is a nice class
called AVAudioSession shipped by Apple that lets you configure the
session in no time. The basic code looks like this:
NSError *error = nil;
AVAudioSession *session = [AVAudioSession sharedInstance];
[session setCategory:AVAudioSessionCategoryPlayback error:&error];
NSAssert(error == nil, @"Failed to set audio session category.");
[session setActive:YES error:&error];
NSAssert(error == nil, @"Failed to activate audio session.");
The main point is the AVAudioSessionCategoryPlayback constant. See the
AVAudioSession documentation for a list of the possible categories and their
meaning. This matters, you should know which category you are choosing.
Finch has been designed so that its components can be used separately. If you
want to, you can initialize the OpenAL yourself and only use the Sound class.
And if you want to, you can use just the Decoder to get raw PCM data from WAV
and CAF files without having to import the Finch and Sound classes. You can
also come up with the PCM data yourself and pass it to OpenAL using the designated
initializer of the Sound class:
- (id) initWithData: (const ALvoid*) data size: (ALsizei) size
format: (ALenum) format sampleRate: (ALsizei) frequency
duration: (float) seconds;
Many people are having problems with OpenAL sound in the simulator. I have not found a definitive answer from Apple, but it seems that OpenAL quite often does not work in the simulator.
Licensed under the MIT License. Essentially you can do with this software whatever you like, provided that you keep the copyright notice and the license text along.
Some links you might find useful:
Tomáš Znamenáček, [email protected]. Suggestions welcomed.
If you have a question that could possibly be of interest to other people, you can ask it on Stack Overflow and send me a link to your question. It’s better than discussing it in private, because you can get answers from other people and once the question has been answered, other people can benefit from the answer, too.