Reducing HEVC encoding complexity using two-stage motion estimation

We propose a technique for optimizing the High Efficiency Video Coding (HEVC) encoder by reducing the number of operations performed in the motion estimation stage. The technique is based on the fact that a significant number of motion estimation operations are performed repetitively for the same image samples, but for different block partition sizes. By decoupling the initial motion estimation and the block partitioning into different stages it is possible to remove a considerable number of redundant motion estimation operations. An implementation of the proposed technique on a SIMD optimized version of the HEVC reference encoder shows that, on average, a reduction of 79.02% SAD operations can be achieved, that results in an average reduction of 14.63% of the encoding complexity with negligible impact on the compression efficiency (BD-rate losses of less than 1%).