In an H.264 video encoder, motion estimation (ME) is the most
time-consuming component. The ME process consists of two
stages: integer pixel search and fractional pixel search. Since the
complexity of integer pixel search has been greatly reduced by
numerous fast ME algorithms, the computation overhead
required by fractional pixel ME has become relatively significant.
To reduce the complexity of fractional pixel ME, we propose a
prediction-based directional fractional pixel ME algorithm. We
utilize more accurate motion vector predictions and directional
search to achieve better computation reduction. We further
propose an early termination method to decrease the amount of
search. Experimental results show that compared to the full
search sub-pel ME and the fast sub-pel ME proposed in H.264,
the proposed method can reduce up to 84% and 74% of
fractional pixel search points respectively, with a negligible
degradation in quality.……