Programming iOS 6, 3rd Edition

Audio Player

An audio player is an instance of the AVAudioPlayer class. This is the easiest way to play sounds with any degree of sophistication. A wide range of sound types is acceptable, including MP3, AAC, and ALAC, as well as AIFF and WAV. You can set a sound’s volume and stereo pan features, loop a sound, synchronize the playing of multiple sounds simultaneously, change the playing rate, and set playback to begin somewhere in the middle of a sound. New in iOS 6, you can even tell the audio player what output channels of the device to use in producing its sound.

To use an audio player, you’ll need to link to AVFoundation.framework and import <AVFoundation/AVFoundation.h>. An audio player should always be used in conjunction with an audio session; see the previous section.

Warning

Not every device type can play a compressed sound format in every degree of compression, and the limits can be difficult or impossible to learn except by experimentation. I encountered this issue when an app of mine worked correctly on an iPod touch 32GB but failed to play its sounds on an iPod touch 8GB (even though the latter was newer). Even more frustrating, the files played just fine in the Music app on both devices. The problem appears to be that the compression bit rate of my sound files was too low for AVAudioPlayer on the 8GB device, but not on the 32GB device. But there is no documentation of the limits involved.

An audio player can possess and play only one sound, but it can play that sound repeatedly, ...