PPFPS - a paraboloid prediction based fractional pixel search strategy for H.26L

H.26L is a new recommendation for moving picture coding proposed by ITU-T, in which 1/4-pel and 1/8-pel fractional pixel motion compensation is added to achieve more accurate motion description and higher compression efficiency. However, at the same time the complexity of the fractional pixel motion estimation also increases, requiring a total of 24 fractional-pel positions to be checked in 1/8-pel motion vector search, while some fast integer pixel motion search algorithms have decreased the searching pixels to about ten. Therefore, reducing the computational load for fractional pixel motion search is both necessary and significant. A novel paraboloid prediction based fractional pixel search algorithm is first proposed in this paper. In any case (1/2 pixel, 1/4 pixel or 1/8 pixel resolution), roughly a computation reduction of 62.5% in fractional pixel motion estimation can be achieved compared with the full fractional pixel motion search algorithm. Experimental results prove that the strategy keeps good performance in preserving image quality and has little influence on the bit rate.