Adaptive Variable Block-Size Early Motion Estimation Termination Algorithm for H.264/AVC Video Coding Standard

The variable block-size motion estimation (ME) process is the H.264/AVC encoder´s most time-consuming function. This letter proposes to reduce the complexity of the ME process with an early termination algorithm that features an adaptive threshold based on the statistical characteristics of rate-distortion (RD) cost regarding current block and previously processed blocks and modes. In this method, most motion searches can be stopped early, with a large number of search points saved. A region-based search is also suggested to further reduce the computation required for full search ME. A search point reduction scheme for the fast motion estimation of H.264/AVC is also introduced, and the experimental results illustrate how the proposed method reduces ME times for full search and fast motion estimation by about 77 and 31%, respectively, despite the insignificant degradation of RD performance.