Omnidirectional Video Quality Index Accounting for Judder

Abstract

Human visual system (HVS) strongly responds to motion information. In particular, neurons in middle temporal (MT) area of the brain are sensitive to certain velocities. Thus distortions appeared on moving stimuli, as visually salient information, are visually very important and can significantly affect the quality of experience (QoE). Judder is a visual artifact that manifests as non-smooth motion when tracking a moving object on a digital display. In particular, the effect of judder becomes more significant in the wide field of view (FoV) displays where objects can be observed in a longer trajectory and duration. Head mounted display (HMD) maximizes FoV by enabling full 360 degrees immersive experience and there has been rapid growth in the number of omnidirectional videos for HMDs. However, the impact of judder on visual QoE of the omnidirectional video has never been studied. In this paper, we first established a database of omnidirectional video sequences to study human responses on the visual effect of judder when watching videos on wide FoV HMDs. Two subjective tests were conducted to understand the impact of judder on video sequences compressed at different bit rates (i.e. different picture quality levels). Next, based on the subjective results, we proposed a novel QoE model considering the joint effect of judder, visual masking and picture quality. Experimental results indicate the effectiveness of the proposed model for accurate quality prediction of the videos with judder.