Static AVAssetTrackTrackAssociationsDidChangeNotification 

pub unsafe static AVAssetTrackTrackAssociationsDidChangeNotification: &'static NSString

Available on crate feature AVAssetTrack only.

Posted when the collection of track associations of an AVAssetTrack changes, but only for changes that occur after the status of the value of “ availableTrackAssociationTypes“ has reached AVKeyValueStatusLoaded.

See also Apple’s documentation