static moov(tracks, duration, timescale) {
        var
            i = tracks.length,
            boxes = [];

        while (i--) {
            boxes[i] = MP4.trak(tracks[i]);
        }

        return MP4.box.apply(null, [MP4.types.moov, MP4.mvhd(timescale, duration)].concat(boxes).concat(MP4.mvex(tracks)));
    }
@param tracks... (optional) {array} the tracks associated with this movie