An adaptive search ordering for rate-constrained successive elimination algorithms

This paper proposes a solution for the problem of unnecessary cost function evaluations, found when combining the successive elimination algorithm with a spiral scan search ordering. Our experiments show that the implementation of such a combination inside the HEVC reference software leads to unnecessary cost function evaluations. On the tested video sequences, an average of 3.46% unnecessary cost function evaluations was measured. Considering only small block sizes (e.g., 4×8 and 8×4), this average rises to 8.06%. To solve this problem, we propose an adaptive scan ordering of block matching candidates within the search area. When used with our early termination threshold, the proposed approach will only evaluate necessary cost functions, without impacting rate-distortion.