1. A method for estimating global inter-frame motion between two video frames in a digital video sequence, comprising: comparing luminance data of a reference pixel subset of a first one of the video frames to luminance data of candidate pixel subsets within a search area in a second one of the video frames to determine a preliminary matching pixel subset from the candidate pixel subsets; determining an actual matching pixel subset from the other video frame based on a location of the preliminary matching pixel subset relative to said search area; calculating a global inter-frame motion vector characterizing global inter-frame motion based on a location of the actual matching pixel subset; checking the reliability of the actual matching pixel subset; and only calculating the global motion vector if the actual matching pixel subset is deemed to be reliable; wherein reliability of the actual matching pixel subset is based on at least one of a sum of absolute difference error calculated for the actual matching pixel subset and a ratio of a minimum to average sum of absolute difference error.