The track layer of a QTTrack object; the value for this key is of type NSNumber, interpreted as a short.
This attribute can be read and written. This attribute can be read and written when the movie containing this track 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)