AVQueuePlayer is a subclass of AVPlayer used to play a number of items in a sequence.
An AVPlayer object can be used to implement controllers and user interfaces for single- or multiple-item playback. The multiple-item case supports advanced behaviors.
AVPlayer works equally well with local and remote media files, providing appropriate information about readiness to play or about the need to await additional data before continuing.
The visual content of items played can be displayed by an instance of AVPlayer in a CoreAnimation layer of class AVPlayerLayer; to synchronize real-time playback with other CoreAnimation layers, AVSynchronizedLayer can be used. An instance of AVVideoCompositionCoreAnimationTool cannot be used with an AVPlayer object; for offline rendering AVAssetExportSession should be used.
The status of a player can be observed using key-value observing. AVPlayer serializes notifications of changes that occur dynamically during playback on a dispatch queue so that remote observers can be added and removed safely. By default, this queue is the main queue (see dispatch_get_main_queue). To ensure safe access to a player’s nonatomic properties while dynamic changes in playback state may be reported, one must serialize access with the receiver’s notification queue. In the common case, such serialization is naturally achieved by invoking AVPlayer’s various methods on the main thread or queue.
