1. A method of global motion estimation between frames of a motion-compensated inter-frame encoded video sequence, each frame of the sequence having a plurality of motion vectors encoded therein relating sub-parts of one frame to sub-parts of a preceding and/or succeeding frame of the sequence, the method comprising: using digital signal processing circuits including a computer-readable memory circuit connected to receive the sequence and configured to process the sequence by: a) decoding sub-part motion vectors for sub-parts of an input frame from the sequence; b) selecting N sets of the sub-part motion vectors with a sample size of at least 3, wherein N is an integer value greater than 1; c) calculating a motion estimation for each set of sub-part motion vectors; d) calculating a median squared error value for each motion estimation; e) selecting the motion estimation with the least median squared error value; and f) storing or outputting the selected motion estimation as representative of global motion between the entire input frame and an entire preceding or succeeding anchor frame for use in registering an image of the input frame with an image of the anchor frame.