Modeling the User Experience of Watching 360° Videos with Head-Mounted Displays

Conducting user studies to quantify the Quality of Experience (QoE) of watching the increasingly more popular 360° videos in Head-Mounted Displays (HMDs) is time-consuming, tedious, and expensive. Deriving QoE models, however, is very challenging because of the diverse viewing behaviors and complex QoE features and factors. In this article, we compile a wide spectrum of QoE features and factors that may contribute to the overall QoE. We design and conduct a user study to build a dataset of the overall QoE, QoE features, and QoE factors. Using the dataset, we derive the QoE models for both the Mean Opinion Score (MOS) and Individual Score (IS), where MOS captures the aggregated QoE across all subjects, while IS captures the QoE of individual subjects. Our derived overall QoE models achieve 0.98 and 0.91 in Pearson’s Linear Correlation Coefficient (PLCC) for MOS and IS, respectively. Besides, we make several new observations on our user study results, such as (1) content factors dominate the overall QoE across all factor categories, (2) Video Multi-Method Assessment Fusion (VMAF) is the dominating factor among content factors, and (3) the perceived cybersickness is affected by human factors more among others. Our proposed user study design is useful for QoE modeling (specifically) and subjective evaluations (in general) of emerging 360° tiled video streaming to HMDs.