Patent ID: 6914938

Claim:
A method for determining motion vectors in an interlaced video coding system for coding images comprising interlaced odd and even fields, the method comprising the steps of: (i) selecting a current odd field block and a current even field block that respectively comprise odd and even fields of a selected current image block of a current image; (ii) identifying differences between the current odd field block and reference blocks in a first search window that is one of either an even field search window of even fields or an odd field search window of odd fields that combined form part of a reference image, and errors between the current even field block and the reference blocks in a second search window that is the other one of the even field search window or odd field search window; (iii) determining, from the differences in the step of (ii) identifying, a suitable first odd field matching reference block for the current odd field block and a suitable first even field matching reference block for the current even field block; (iv) providing, from the suitable first odd field matching reference block and suitable first even field matching reference block, respective reduced search areas in the even field search window and odd field search window; (v) searching the reduced search areas for identifying the differences between the current odd field block and the reference blocks in the second search window and identifying the differences between the current even field block and the reference blocks in the first search window; (vi) determining, from the differences in the step of (v) searching, a suitable second odd field matching reference block for the current odd field block and a suitable second even field matching reference block for the current even field block; and (vii) selecting a respective field motion vector for both the current odd field block and current even field block, the respective motion vector being based on relative motion between the current odd field block and either the first or second odd field matching reference block and relative motion between the current even field block and either the first or second even field matching reference block.