Streaming 360{\deg} videos requires more bandwidth than non-360{\deg} videos.
This is because current solutions assume that users perceive the quality of
360{\deg} videos in the same way they perceive the quality of non-360{\deg}
videos. This means the bandwidth demand must be proportional to the size of the
user's field of view. However, we found several qualitydetermining factors
unique to 360{\deg}videos, which can help reduce the bandwidth demand. They
include the moving speed of a user's viewpoint (center of the user's field of
view), the recent change of video luminance, and the difference in
depth-of-fields of visual objects around the viewpoint. This paper presents
Pano, a 360{\deg} video streaming system that leverages the 360{\deg}
video-specific factors. We make three contributions. (1) We build a new quality
model for 360{\deg} videos that captures the impact of the 360{\deg}
video-specific factors. (2) Pano proposes a variable-sized tiling scheme in
order to strike a balance between the perceived quality and video encoding
efficiency. (3) Pano proposes a new qualityadaptation logic that maximizes
360{\deg} video user-perceived quality and is readily deployable. Our
evaluation (based on user study and trace analysis) shows that compared with
state-of-the-art techniques, Pano can save 41-46% bandwidth without any drop in
the perceived quality, or it can raise the perceived quality (user rating) by
25%-142% without using more bandwidth.

本文提出了一种名为 Pano 的 360 度视频流系统，它利用了 360 度视频的独特因素，包括用户视角的移动速度、视频亮度的变化和视角周围可视物体景深的差异，提出了一种变大小的铺砖方案以在视觉效果和视频编码效率之间取得平衡，以及一种最大化 360 度视频用户感知质量的新的质量自适应逻辑，通过用户研究和跟踪分析的评估表明，相比现有技术，Pano 可以节省 41-46％的带宽，同时不会降低感知质量，或者可以提高感知质量 25％-142％而不会增加带宽使用。