  The recent rise of interest in Virtual Reality (VR) came with the
availability of commodity commercial VR products, such as the Head Mounted
Displays (HMD) created by Oculus and other vendors. One of the main
applications of virtual reality that has been recently adopted is streaming
sports events. For instance, the last olympics held in Rio De Janeiro was
streamed over the Internet for users to view on VR headsets or using 360 video
players. A big challenge for streaming VR sports events is the users limited
bandwidth and the amount of data required to transmit 360 videos. While 360
video demands high bandwidth, at any time instant users are only viewing a
small portion of the video according to the HMD field of view (FOV). Many
approaches have been proposed in the literature such as proposing new
representations (e.g. pyramid and offset-cubemap) and tiling the video and
streaming the tiles currently being viewed. In this paper, we propose a tiled
streaming framework, where we provide a degrading quality model similar to the
state-of-the-art offset-cubemap while minimizing its storage requirements at
the server side. We conduct objective studies showing the effectiveness of our
approach providing smooth degradation of quality from the user FOV to the back
of the 360 space. In addition, we conduct subjective studies showing that users
tend to prefer our proposed scheme over offset-cubemap in low bandwidth
connections, and they don't feel difference for higher bandwidth connections.
That is, we achieve better perceived quality with huge storage savings up to
670%.
