Chapter 2, “The Story of Sound,” discussed the difference between audio file formats (
.caf, and so on) and stream formats (LPCM, AAC, and so on). The last few chapters focused on the stream formats of the audio that you either recorded or played back. Audio Queue was a big help here because it handled the conversion from LPCM to and from encodings such as AAC.
But what happens when you’re interested only in that conversion? If you wanted to compress some LPCM data to AAC, you wouldn’t want to have to play it through an audio queue. You should rightly expect that there are APIs for doing these kinds of conversions directly.
Core Audio provides several approaches for converting between formats. This chapter starts by looking ...