4. Recording

The first three chapters explored the nature of digital audio and how it is represented by Core Audio. The next step is processing—actually doing something with the audio. In the next two chapters, we’ll start moving samples through Core Audio’s recording and playback engines.

To do this, you’ll use Audio Queue Services, the highest-level playback and recording API in Core Audio. By the end of the chapter, you may think we’re nuts to call a C-based, callback-driven API “high level,” but audio queues provide some conveniences that the lower-level APIs don’t:

• Unlike with OpenAL and Audio Units, you can use encoded formats such as AAC and MP3 with audio queues.

• By default, Audio Queues call you back on their own thread, which isolates ...

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