ios audio playback technologies

Table 3-2Audio interruption handling techniques according to audio technology

Audio technology

How interruptions work

AVFoundationframework	TheAVAudioPlayerandAVAudioRecorderclasses provide delegate methods for interruption start and end. Implement these methods to update your user interface and optionally, after interruption ends, to resume paused playback. The system automatically pauses playback or recording upon interruption, and reactivates your audio session when you resume playback or recording. If you want to save and restore playback position between application launches, save playback position on interruption as well as on application quit.
Audio Queue Services, I/O audio unit	These technologies put your application in control of handling interruptions. You are responsible for saving playback or recording position and reactivating your audio session after interruption ends. As explained in“Responding to Audio Session Interruptions,”implement theAVAudioSessioninterruption delegate methods or write an interruption listener callback function. If using these technologies for hardware-assisted encoding to AAC, refer to“Hardware-Assisted Codecs and Audio Interruptions.”
OpenAL	When using OpenAL for playback, implement theAVAudioSessioninterruption delegate methods or write an interruption listener callback function—as when using Audio Queue Services. However, the delegate or callback must additionally manage the OpenAL context. See“OpenAL and Audio Interruptions.”
System Sound Services	Sounds played using System Sound Services go silent when an interruption starts. They can automatically be used again if the interruption ends. Applications cannot influence the interruption behavior for sounds that use this playback technology.