Programming iOS 6, 3rd Edition

Further Topics in Sound

iOS is a powerful milieu for production and processing of sound; its sound-related technologies are extensive. This is a big topic, and an entire book could be written about it (in fact, such books do exist). I’ll talk in Chapter 29 about accessing sound files in the user’s music library. But here are some further topics that there is no room to discuss here:

Other audio session policies

If your app accepts sound input or does audio processing, you’ll want to look into additional audio session policies I didn’t talk about earlier — Record, Play and Record, and Audio Processing. In addition, if you’re using Record or Play and Record, there are modes — voice chat, video recording, and measurement (of the sound being input) — that optimize how sound is routed (for example, what microphone is used) and how it is modified.

Recording sound

To record sound simply, use AVAudioRecorder. Your audio session policy will need to adopt a Record policy before recording begins.

Audio queues

Audio queues implement sound playing and recording through a C API with more granularity than the Objective-C AVAudioPlayer and AVAudioRecorder (though it is still regarded as a high-level API), giving you access to the buffers used to move chunks of sound data between a storage format (a sound file) and sound hardware.

Extended Audio File Services

A C API for reading and writing sound files in chunks. It is useful in connection with technologies such as audio queues.

Audio Converter ...