Quality assessment of subsampling patterns for pel decimation targeting high definition video

Although pel decimation has been widely used to reduce the computational effort in video coding, there is no consensus about the optimal subsampling pattern. This paper presents an extensive analytical and statistical comparison of several different subsampling patterns using analysis of variance. The investigation includes commonly used patterns as well as seven proposed ones. The experiments were conducted on 19 video samples in a range of five resolutions (being nine videos at 1080p) and 30 bitrates by using the state-of-the-art x264 encoder running successive elimination exhaustive search. Two objective quality metrics were reported, PSNR and DSSIM, resulting in 10680 experimental points. The analysis of such amount of data allowed us to conclude that the proposed 4:3 ratio shows less than 5% in DSSIM and 1% in PSNR losses, being more than two times faster than full sampling. Compared with higher decimation, it presents a better trade-off between speedup and quality loss.