Fast sub-pixel motion estimation and mode decision for H.264

Motion estimation (ME) is one of the most time-consuming parts in video coding. The use of multiple partition sizes in H.264 makes the ME even more complicated. It is important to develop fast sub-pixel ME algorithms due to (1) The computation overhead by sub-pixel ME has become relatively significant while the complexity of integer-pel search has been greatly reduced by fast algorithms and (2) Reducing sub-pel searching points can save the computation for interpolating sub-pixel values. In this paper, a new fast sub-pixel ME algorithm is proposed which performs a ´rough´ sub-pel search before the partition selection and only performs the ´precise´ sub-pel search for the best partition. Experimental results show that our method can reduce the sub-pel search points by more than 50% compared to existing fast sub-pel ME methods with little quality degradation.