Basic Sensors in iOS

Recording and Playing Audio

The AVAudioRecorder class is part of the AVFoundation framework and provides audio recording capabilities for an application. The framework allows you to:

• Record until the user stops the recording

• Record for a specified duration

• Pause and resume a recording

The corresponding AVAudioPlayer class (also part of the AVFoundation framework) provides some fairly sophisticated functionality allowing you to play sound in your application. It can:

• Play sounds of any duration

• Play sounds from files or memory buffers

• Loop sounds

• Play multiple sounds simultaneously (one sound per audio player) with precise synchronization

• Control relative playback level and stereo positioning for each sound you are playing

• Seek to a particular point in a sound file, which supports such application features as fast forward and rewind

Recording Audio

Lets build a simple application to record some audio to a file and play it back later. Open Xcode and start a new View-based Application, naming it Recorder when requested.

When the Xcode project opens, add both the AVFoundation and CoreAudio frameworks to the project in a similar manner as we added the MediaPlayer framework to the Audio application earlier in the chapter.

Click on the RecorderViewController.h interface file to open it in the Standard Editor and make the following changes to the template file generated for you by Xcode:

#import <UIKit/UIKit.h>
#import <AVFoundation/AVFoundation.h>

@interface RecorderViewController : UIViewController ...