Patent ID: 6567469
Filing Date: 2003-05-20
Classification: H04N

Abstract:
A method for identifying an optimum motion vector for a current block of pixels in a current picture in a process for performing motion estimation, comprising:a first search phase for evaluating a subset of motion vector candidates for the current block of pixels, the subset including at least one motion vector candidate having an intrinsically high probability of being the optimum motion vector candidate, wherein evaluating the at least one motion vector candidate of the subset includes (i) calculating an error value for the at least one motion vector candidate that is representative of the differences between the values of the pixels of the current block of pixels and the values of a corresponding number of pixels in a reference block of pixels and (ii) responsive to the error value being less than a prescribed threshold error value, identifying the corresponding motion vector candidate as the optimum motion vector and aborting further evaluations of motion vector candidates; and a second search phase having at least two search levels and implemented only if further evaluations were not aborted in the first search phase, each search level including: evaluating each of a plurality of motion vector candidates at the search level for the current block of pixels by, for each motion vector candidate at the search level, calculating an error value that is representative of the differences between the values of the pixels of the current block of pixels and the values of a corresponding number of pixels in a reference block of pixels; while evaluating each motion vector candidate at the search level, checking the corresponding calculated error value, and aborting the evaluation for the corresponding motion vector candidate upon determining that the error value for that motion vector candidate exceeds a previous minimum error value for the plurality of motion vector candidates at the respective search level; and selecting as the optimum motion vector candidate for a respective search level, the motion vector candidate having the lowest calculated error value of the motion vector candidates of the respective search level, wherein identifying the optimum motion vector includes the lowest calculated error value of the motion vector candidates of the last search level of the at least two search levels of the second search phase.