Along with the height parameter, this parameter defines the track's display rectangle. Together, the height and width parameters define the track's display rectangle. The height and width parameters therefore establish the lower-right corner of the track's display rectangle. If you are creating a track that is not displayed, such as a sound track, set the height and width parameters to 0. Volume values range from -1.0 to 1.0.
Negative values play no sound but preserve the absolute value of the volume setting.
Set this parameter to kFullVolume to play the track at its full, natural volume. Set this parameter to kNoVolume to set the volume to 0. The NewMovieTrack function returns a track identifier. If the function cannot create the track, it sets the returned identifier to nil . The DisposeMovieTrack function removes a track from a movie.