LAUSR

Perceptual video quality considerably affects the quality of experience (QoE) of watching television (TV) broadcasts. Viewing conditions, such as the screen size and viewing distance, impact the perceived quality. We performed subjective evaluation experiments on 8K (7, $680\times 4$ ,320) ultra-high definition (UHD) compressed videos under seven viewing conditions (combinations of 31.5-, 55-, and 85-inch displays and 0.75, 1.5, and 3.0 H (times of screen height) of viewing distance). Distorted videos compressed by the versatile video coding (VVC)/H.266 were used in four types of encoding resolution, from 2K (1, $920\times 1$ ,080) to 8K, at a wide bitrate settings range of 3–80 Mbps. We derived a simple regression equation predicting the mean opinion score (MOS) using the hierarchical linear model (HLM), investigating the factors influencing subjective video quality. In this equation, MOS is expressed as a linear combination of terms including intercept and bitrate associated with sequence and encoding resolution, screen size, and viewing distance; it indicates that the smaller the screen, or the further the viewing distance, the fewer artifacts are perceived, as following empirical rules. Furthermore, we confirmed that the derived model is accurate as the Pearson linear and Spearman rank order correlation coefficients between predicted and actual MOS values were more than 0.97.