Programming iOS 4

Further Topics in Video

A large suite of AV Foundation classes was introduced in iOS 4 that provide detailed access to media components, analogous to QuickTime on Mac OS X. To access these, you’ll need to link to AVFoundation.framework (and probably CoreMedia.framework as well), and import <AVFoundation/AVFoundation.h>. For a list of classes, see the AV Foundation Framework Reference.

The AV Foundation class that performs actual playing of media is AVPlayer. An AVPlayer has an AVPlayerItem; this is its media. An AVPlayerItem comprises tracks (AVPlayerItemTrack), which can be individually enabled or disabled. It gets these from its underlying AVAsset; this is the basic media unit, as it were, providing you with access to tracks and metadata.

Starting in iOS 4.1, an AVPlayer can be an AVQueuePlayer, a subclass that allows multiple AVPlayerItems to be loaded up and then played in sequence. AVQueuePlayer also has an advanceToNextItem method, and its list of items can be changed dynamically, so you could use it to give the user access to a set of “chapters.”

To display an AVPlayer’s movie, you need an AVPlayerLayer (a CALayer subclass). You are unlikely to take this approach unless you need either the extended powers of AV Foundation or the sequential playing power of AVQueuePlayer or the flexibility of working directly with a layer and Core Animation. The AVPlayerLayer doesn’t even come with controls for playing a movie and visualizing its progress; you have to create these yourself. Nevertheless, ...