1. A method of determining the quality of a three dimensional (3D) video stream, wherein the 3D video comprises at least one 3D view composition, each of the at least one 3D view composition defining a plurality of two dimensional (2D) views, the method comprising: determining a characteristic of each of the plurality of 2D views; calculating a variation in the characteristic, the variation calculated between the 2D views corresponding to the same one of the at least one 3D view composition; and calculating a quality score for the 3D video stream based upon the variation.