Low-Power Multiversion Interpolation Filter Accelerator With Hardware Reuse for AV1 Codec

Abstract

In modern video encoders, sub-pixel motion models are used to represent smoother transitions between neighboring frames, which is specially useful in regions with intense movement. The AV1 video codec introduces adaptive filtering for sub-pixel interpolation in the inter-frame prediction stage, enhancing flexibility in Motion Estimation (ME) and Motion Compensation (MC), using three filter types: Regular, Sharp, and Smooth. However, the increased variety of filters leads to higher complexity and energy consumption, particularly during the resource-intensive generation of sub-pixel samples. To address this challenge, this paper presents a hardware accelerator optimized for AV1 interpolation, incorporating energy-saving features for unused filters. The accelerator includes one precise version that can be used for both MC and ME and two approximate versions for ME, designed to maximize hardware efficiency and minimize implementation costs. The proposed design can process videos at resolutions up to 4320p at 50 frames per second for MC and 2,656.14 million samples per second for ME, with a power dissipation ranging between 21.25 mW and 40.06 mW, and an average coding efficiency loss of 0.67% and 1.11%, depending on the filter type and version.