Impact of Alignment Edits on the Quality of Experience of 360° Videos

Optimizing user quality of experience (QoE) for 360° videos faces two major roadblocks: inaccurate viewport prediction and viewers missing the plot of a story. To tackle these issues simultaneously, alignment edits have emerged as a promising solution. These edits, also known as “re-targeting edits,” work by aligning the user’s field of view with a specific region of interest in the video content. Despite their potential benefits, there is limited knowledge about the actual impacts of alignment edits on user experience (UX). Therefore, we conducted subjective experiments following ITU-T P.919 methodology to explore their effects on QoE. We proposed an alignment edit based on gradual rotation of the 360° frame, aiming to replicate natural viewing behavior. We tested this approach under various conditions and thoroughly analyzed its impacts using both head motion data and feedback from observers, focusing on their sense of presence, comfort, and perceived experience. The results of our experiments are encouraging. Our proposed gradual alignment technique achieved a level of comfort and presence comparable to that of instant edits. Furthermore, all alignment edits tested led to a noticeable reduction in head movement speed after the edit, affirming their potential utility for on-demand video streaming. Notably, the gradual edits, in particular, induced a significant reduction of approximately 8% in head movement speeds when compared to the instant alignment technique. These findings shed light on the positive effects of alignment edits on user experience and firmly establish the viability of the proposed gradual alignment technique to enhance QoE during video consumption.