Requests the invocation of a block when specified times are traversed during normal playback.
- iOS 4.0+
- macOS 10.7+
- tvOS 9.0+
An array of
CMTimevalues representing the times at which to invoke
A serial queue onto which
blockshould be enqueued. Passing a concurrent queue is not supported and will result in undefined behavior.
If you pass
NULL, the main queue (obtained using
dispatch) is used.
_get _main _queue()
The block to be invoked when any of the times in
timesis crossed during normal playback.
An opaque object that you pass as the argument to
remove to stop observation.
Boundary times are arbitrary points of interest you define within the media timeline. As these times are traversed during normal playback, the block you provide to this method will be invoked. You must maintain a strong reference to the returned value as long as you want the time observer to be invoked by the player. Each invocation of this method should be paired with a corresponding call to
The player does not guarantee the callback block will always be invoked for each boundary time. If your times are very close together along the timeline (close enough that the execution of the block for one takes longer than the difference between them) or if a seek causes time to jump over one or more boundary times, time observation for any specific boundary time may not occur. The best practice is therefore to implement the callback block so it always performs its necessary calculations based solely on the player's
The following example shows how you could define boundary times for each quarter of playback.