The duration. The value for this key is of type NSValue, interpreted as a QTTime.
This attribute can be read but not written. This attribute can be read but not written when the movie containing this media has been initialized with QTMovieOpenForPlaybackAttribute set to YES.
Available in Mac OS X v10.4 and later.
Declaration Syntax Version Information- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)