360-degree video is an emerging medium that presents an immersive view of the environment to the user. Despite its potential to provide an immersive watching experience, 360-degree video has not achieved widespread popularity. A significant cause of this slow adoption is the high-bandwidth requirements of the format. The primary source of bandwidth inefficiency in 360-degree video streaming, un-addressed in popular transmission methods, is the discrepancy between the pixels sent over the network (typically the full omnidirectional view) and the pixels displayed in the head-mounted display's field of view. At worst, roughly 88% of transmitted pixels remain unviewed.

This artifact includes source code, scripts and datasets required to reproduce the experimental figures in the evaluation of the MM'18 paper, which is entitled "MiniView Layout for Bandwidth-Efficient 360-Degree Video". The artifact reports the comparison results among the standard cube layout (CUBE), the equi-angular layout (EAC), and the MiniView layout (MVL) in terms of compressed video size, visual quality of views and decoding and rendering time.

Today, 360-degree video streaming has become a popular Internet service with the rise of affordable virtual reality (VR) technologies. However, streaming 360-degree videos suffers from the prohibitive bandwidth demand. Existing bandwidth-efficient solutions mainly focus on exploiting the inherent spatial adaptability of 360-degree videos, delivering only video content (spatially-cut tiles) in the viewer's region of interest (ROI) with higher quality. Temporal adaptability, which has been widely leveraged in HTTP streaming, has not been well exploited to select proper quality for video segments according to the bandwidth variations. When these two dimensions of adaptability are jointly considered, bitrate selection for the tiles become more complicated and challenging. The importance of a tile with a spatial coordination played at a specific time should be quantified so that we can determine how to allocate bandwidth for improving the viewer's quality of experience. Furthermore, viewer's head orientation prediction is highly variable, which makes the determination of important tiles highly dynamic. In addition, network fluctuations are very common on the Internet. To overcome these challenges, we propose Bi-Adaptive Streaming for 360-degree videos (BAS-360°). In BAS-360°, both spatial and temporal adaptabilities are explored in the bitrate selection for different tiles. The objective is to minimize the bandwidth waste by allocating bandwidth to more important tiles (the tiles that are more likely to be watched). To tackle the high variability of visual region prediction and the unpredictable network fluctuations, we employ two features provided by HTT P /2: stream termination and stream priority, to efficiently organize tile delivery. Evaluation results show that BAS-360° outperforms naive tile-based 360-degree video streaming strategies when network fluctuations or errors in viewport predictions occur.

360-degree video has the potential to transform the video streaming experience by providing a more-immersive environment for users to interact with than standard streaming video. This experience is hampered, however, by high bandwidth requirements resulting from the extra information associated with the 360-degree frames. Because users cannot see this full 360-degree view, but the full view is transmitted in the majority of 360-degree streaming systems, there is much potential to reduce wasted bandwidth in this domain. We propose ClusTile, a tiling approach formulated to select a set of tiles that allows minimal bandwidth needed to be used when streaming 360-degree video over an expected set of views. These tiles are selected by solving a set of integer linear programs (ILPs) independently on clusters of collected user views. The clustering approach reduces computation requirements of the ILPs to practical levels. Tilings computed from ClusTile can save up to 76% bandwidth compared to standard 360-degree streaming and up to 52% bandwidth compared to best-performing fixed tiling schemes.

With the recent increase in popularity of VR devices, 360-degree video has become increasingly popular. As more users experience this new medium, it will likely see further increases in popularity as users experience its greater immersiveness compared to traditional video streams. 360-degree video streams must encode the omnidirectional view, and, with current encoding techniques, these views require significantly higher bandwidth than traditional video streams. These larger bandwidth requirements comprise the main barrier toward wider adoption by video streaming services.

A new generation of video streaming technology, 360-degree video, promises greater immersiveness than standard video streams. This level of immersiveness is similar to that produced by virtual reality devices—users can control the field of view using head movements rather than needing to manipulate external devices. Although 360-degree video could revolutionize the streaming experience, its large-scale adoption is hindered by a number of factors: 360-degree video streams have larger bandwidth requirements and require faster responsiveness to user inputs, and users may be more sensitive to lower quality streams. In this article, we review standard approaches toward 360-degree video encoding and compare these to families of approaches that distort the spherical surface to allow oriented concentrations of the 360-degree view. We refer to these distorted projections as offset projections. Our measurement studies show that most types of offset projections produce rendered views with better quality than their nonoffset equivalents when view orientations are within 40 or 50 degrees of the offset orientation. Offset projections complicate adaptive 360-degree video streaming because they require a combination of bitrate and view orientation adaptations. We estimate that this combination of streaming adaptation in two dimensions can cause over 57% extra segments to be downloaded compared to an ideal downloading strategy, wasting 20% of the total downloading bandwidth.

360-degree videos are encoded for adaptive streaming by first projecting the spherical surface onto two-dimensional frames, then encoding these as standard video segments. During playback of these 360-degree videos, the video player renders the portion of the spherical surface in the direction of the user's view. These user viewports typically cover only a small portion of the 360 degree surface, causing much of the downloaded bandwidth to be wasted. Tile-based approaches can reduce the wasted bandwidth by cutting video spatially into motion-constrained rectangles. Streaming logic then only needs to download the tiles necessary to render the viewport seen by the user. Existing tile-based approaches cut 360-degree videos into tiles of fixed sizes. These fixed-size tiling approaches, however, suffer from reduced encoding efficiency. Tiling cuts away portions of the video that can be copied by the encoder from adjacent frames or within the current frame that are needed for effective video compression.

360 degree video is anew generation of video streaming technology that promises greater immersiveness than standard video streams. This level of immersiveness is similar to that produced by virtual reality devices -- users can control the field of view using head movements rather than needing to manipulate external devices. Although 360 degree video could revolutionize streaming technology, large scale adoption is hindered by a number of factors. 360 degree video streams have larger bandwidth requirements, require faster responsiveness to user inputs, and users may be more sensitive to lower quality streams.; [email protected] this paper, we review standard approaches toward 360 degree video encoding and compare these to a new, as yet unpublished, approach by Oculus which we refer to as the offset cubic projection. Compared to the standard cubic encoding, the offset cube encodes a distorted version of the spherical surface, devoting more information (i.e., pixels) to the view in a chosen direction. We estimate that the offset cube representation can produce better or similar visual quality while using less than 50% pixels under reasonable assumptions about user behavior, resulting in 5.6% to 16.4% average savings in video bitrate. During 360 degree video streaming, Oculus uses a combination of quality level adaptation and view orientation adaptation. We estimate that this combination of streaming adaptation in two dimensions can cause over 57% extra segments to be downloaded compared to an ideal downloading strategy, wasting 20% of the total downloading bandwidth.