The playback type.
- iOS 7.0+
- macOS 10.9+
- Mac Catalyst 13.0+
- tvOS 9.0+
- watchOS 2.0+
The playback type can be live, VOD, or from a file. If
nil is returned the playback type is unknown.
Corresponds to “s-playback-type”.
This property is not compatible with Key-value observing.