Half-pixel accuracy fast search in video coding

An efficient and fast half-pixel accuracy motion estimation algorithm is introduced and its performance is evaluated in H.263 framework. With respect to motion estimation accuracy, sub-pixel accuracy methods such as 1/2 pixel and 1/4 pixel give more accurate motion estimation of moving object in the picture frame although it requires more computation overhead. Conventional half-pixel search algorithm evaluates cost measure at all of surrounding half-pixel locations of the target integer pixel. The proposed search algorithm, however, reduces the number of computation points to only a half of the conventional half-pixel full search algorithm. Through computer simulation using test video sequences, we demonstrate that the proposed half-pixel accuracy fast search algorithm outperforms the conventional full search method in computation speed by reducing the required number of computation to 50% while it shows only a slight degradation of the reconstructed image quality in terms of PSNR.