A Boolean value that indicates whether the asset is capable of being extended by fragments.
- iOS 9.0+
- macOS 10.11+
- Mac Catalyst 13.0+
- tvOS 9.0+
For QuickTime movie files and MPEG-4 files, the value of
true if an '
mvex' box is present in the '
moov' box. For those types, the '
mvex' box signals the possible presence of later '