Half-pixel accurate motion-estimation using a flexible triangle search

In this paper, a technique for half-pixel motion estimation using the flexible triangle search (FTS) algorithm is presented. The FTS algorithm is based on the simplex algorithm and has been presented and analyzed in previous work by authors. The approach proposed in this paper for half-pixel motion estimation is based on combining full- pixel and half-pixel searches into a single stage instead of using two separate search stages as commonly used. The resulting half-pixel FTS, HP-FTS, is implemented and analyzed as part of an H.263 encoder. Results indicate that the computational complexity of the proposed HP-FTS is lower compared to a two-stage (full-pixel first and half-pixel second) FTS algorithm. Further, the compression ratios and the quality of the reconstructed sequences using the proposed HP-FTS are similar to those of the two-stage FTS.