Programming iOS 4

Further Topics in Sound

iOS is a powerful milieu for production and processing of sound; its sound-related technologies are extensive. Here are some further topics, beyond the scope of this book:

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 stored sound data 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 Services

A C API for converting sound files between formats.

Streaming audio

Audio streamed in real time over the network, such as an Internet radio station, can be played with Audio File Stream Services, in connection with audio queues.

OpenAL

An advanced technology for playing sound with fine control over its stereo stage and directionality.

Audio units

Plug-ins that filter and modify the nature and quality of a sound as it passes through them. See the Audio Unit Hosting Guide for iOS.

CoreMIDI

The CoreMIDI framework was introduced into iOS in version 4.2. It allows interaction with MIDI devices (but not, unfortunately, direct internal playback of ...