In this paper, we conducted two different studies. Our first study deals with measuring the flickering in HMDs using a selfdeveloped measurement tool. Therefore, we investigated several combinations of software 360° video players and framerates. We found out that only 90 fps content is leading to a ideal and smooth playout without stuttering or black frame insertion. In addition, it should be avoided to playout 360° content at lower framerates, especially 25 and 50 fps. In our second study we investigated the influence of higher framerates of various 360° videos on the perceived quality. Doing so, we conducted a subjective test using 12 expert viewers. The participants watched 30 fps native as well as interpolated 90 fps 360° content, whether we also rendered two contents published along with the paper. We found out that 90 fps is significantly improving the perceived quality. Additionally, we compared the performance of three motion interpolation algorithms. From the results it is visible that motion interpolation can be used in post production to improve the perceived quality.
In this paper, we compare the influence of a higherresolution Head-Mounted Display (HMD) like HTC Vive Pro on 360° video QoE to that obtained with a lower-resolution HMD like HTC Vive. Furthermore, we evaluate the difference in perceived quality for entertainment-type 360° content in 4K/6K/8K resolutions at typical high-quality bitrates. In addition, we evaluate which video parts people are focusing on while watching omnidirectional videos. To this aim we conducted three subjective tests. We used HTC Vive in the first and HTC Vive Pro in the other two tests. The results from our tests are showing that the higher resolution of the Vive Pro seems to enable people to more easily judge the quality, shown by a minor deviation between the resulting quality ratings. Furthermore, we found no significant difference between the quality scores for the highest bitrate for 6K and 8K resolution. We also compared the viewing behavior for the same content viewed for the first time with the behavior when the same content is viewed again multiple times. The different representations of the contents were explored similarly, probably due to the fact that participants are finding and comparing specific parts of the 360° video suitable for rating the quality.