A Resolution-adaptive Interpolation Filter for Video Codec

Abstract

The fraction-pel interpolation filter varies in the video coding standards such as H.264/AVC, AVS and HEVC. Since fractional-pel motion compensation plays an important role in the video encoder, the interpolation of fractional-pel pixels can be refined and designed better to enhance the coding efficiency. In this paper, we firstly propose the generation algorithm of interpolation filter coefficients, and four different tap filters, namely 4tap, 6 tap, 8 tap and 10tap, are tested. A resolution-adaptive interpolation filter for different resolution videos is then introduced based on this algorithm to achieve the maximum bitrate saving. In the proposed scheme, 4 tap filter is applied for the UHD (2560x1600 and above) videos, 6 tap filter and 10 tap filter are performed in the videos whose resolution ranging from 720P (1280x720) to 1080P (1920x1080) and the videos with the resolution below 720P, respectively. When 4 tap filter and 6 tap filter are used in high-definition video, the coding efficiency can increase and the computational complexity will reduce greatly, which is actually beneficial to make hardware optimization more effectively especially SIMD (Single Instruction Multiple Data) and VLSI design. Experiments show that the average BD-rate gains on luma Y, chroma U and V are 1.4%, 0.7% and 0.7% for LP-Main configuration, when conducted in HEVC reference software HM11.0. The coding efficiency gains are significant for some video sequences and can reach up to 6.1%.