Motion vector detecting circuit

Abstract

A motion vector detecting circuit is for detecting a motion vector in moving picture coding using motion compensation prediction in the unit of block composed of L pixels by block matching between a block in a prediction target image and a candidate block in a reference image. The motion vector detecting circuit comprises a calculating section for calculating a first prediction error between a block in a prediction target image and a candidate block in a reference image using L1 (<L) pixels in block, comparing the first prediction error thus calculated with a threshold, and calculating a second prediction error between a block in the prediction target image and a candidate block in the reference image using L2 (L1<L2.ltoreq.L) pixels in block if a first prediction error of the candidate block is not more than the threshold; and a comparing section for comparing the second prediction error with a predetermined value and, if the second prediction error is smaller than the predetermined value, replacing the predetermined value with the second prediction error, whereby a motion vector to a candidate block giving a minimum second prediction error is determined as an optimum motion vector.

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