Memory Bandwidth Constrained Overlapped Block Motion Compensation for Video Coding

Overlapped block motion compensation (OBMC) is an inter prediction tool that improves coding performance by blending reference samples of the current and neighboring block across the block boundaries. For this mechanism, OBMC increases the reference samples fetched from the external memory on hardware decoders, i.e., memory bandwidth. This is a disadvantage when introducing OBMC to video coding standards such as VVC, especially for mobile devices with limited batteries, because the extended memory bandwidth increases decoders' power consumption. In this paper, we propose a memory bandwidth constrained OBMC method with adaptive number of motion vectors and interpolation filter taps of the neighboring blocks depending on the current block sizes. Simulation results show that the proposed method achieves-0.22 % performance improvements over VVC reference software without exceeding the maximum memory bandwidth of VVC, which is comparable to the full performance of OBMC (-0.33 %), requiring 3.8 times its memory bandwidth.