Facilitating motion estimation

An apparatus for facilitating a choice of a motion vector from a plurality of candidate motion vectors in a motion estimation device, the apparatus comprising:

• storage means for receiving and storing video image data from first, second and third consecutive groups of image data;
• and
• processing means for identifying a first image part of the first group of image data, a second image part of the second group of image data, and a third image part of the third group of image data, wherein the positions of the three image parts correspond to a motion trajectory indicated by a candidate motion vector;
• said processing means calculating a first error measure by testing for differences between the first image part and the third image part, and quantifying the differences as the first error measure;
• calculating a second error measure by testing for differences between either the first image part and the second image part, or the second image part and the third image part, and quantifying the differences as the second error measure;
• and outputting an output error measure, wherein the output error measure is derived from the first error measure and/or the second error measure in dependence on a vector length of the candidate motion vector.