The delivery and display of 360-degree videos on Head-Mounted Displays (HMDs) presents many technical challenges. 360-degree videos are ultra high resolution spherical videos, which contain an omnidirectional view of the scene. However only a portion of this scene is displayed on the HMD. Moreover, HMD need to respond in 10 ms to head movements, which prevents the server to send only the displayed video part based on client feedback. To reduce the bandwidth waste, while still providing an immersive experience, a viewport-adaptive 360-degree video streaming system is proposed. The server prepares multiple video representations, which differ not only by their bit-rate, but also by the qualities of different scene regions. The client chooses a representation for the next segment such that its bit-rate fits the available throughput and a full quality region matches its viewing. We investigate the impact of various spherical-to-plane projections and quality arrangements on the video quality displayed to the user, showing that the cube map layout offers the best quality for the given bit-rate budget. An evaluation with a dataset of users navigating 360-degree videos demonstrates that segments need to be short enough to enable frequent view switches.
To deal with the cases of end-users consuming only a fraction of the video (navigable panorama @cite_16 @cite_17 @cite_11 and large-resolution video @cite_2 ), the most studied delivery solution leverages the concept of . The idea is to spatially cut a video into independent tiles. The server offers multiple video representations of each tile; the client periodically selects a representation for each tile and it has to reconstruct the full video from these tiles before the viewport extraction. In a short paper, have sketched a tile-based streaming system for @math -degree videos. In their proposal, the spherical video is mapped onto an video, which is cut into @math . More recently, proposed a -based tiling of a @math -degree video to take into account projection distortion. They also present an approach to describe the tiles with MPEG DASH SRD formatting principles. also propose the delivery of tiles based on a prediction of the head movements. evaluate the impact of different tiling scheme on the compression efficiency and on the transmission bit-rate saving.
@cite_16 @cite_2 @cite_11 @cite_17
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The mismatch between increasingly large video resolution and constrained screen size of mobile devices has led to the proposal of zoomable video systems based on tiled video. In the current system, a tiled video frame is constructed from multiple tiles in a single resolution stream. In this paper, we explore the perceptual effect of mixed-resolution tiles in tiled video, in which tiles within a video frame could come from streams with different resolutions, with the aim to tradeoff bandwidth and perceptual video quality. To understand how users perceive the video quality of mixed-resolution tiled video, we conducted a psychophysical study with 50 participants on tiled videos where the tile resolutions are randomly chosen from two resolution levels with equal probability. The experiment results show that in many cases, we can mix tiles from HD (1920×1080p) stream and tiles from 1600×900p stream without being noticed by the viewers. Even when participants notice quality degradation in videos combined with tiles from HD stream and tiles from 960×540p stream, the majority of participants still accept the degradation when viewing videos with low and medium motion; and greater than 40 of participants accept the quality degradation when viewing video with dense motion. While traditional multimedia applications such as games and videos are still popular, there has been a significant interest in the recent years towards new 3D media such as 3D immersion and Virtual Reality (VR) applications, especially 360 VR videos. 360 VR video is an immersive spherical video where the user can look around during playback. Unfortunately, 360 VR videos are extremely bandwidth intensive, and therefore are difficult to stream at acceptable quality levels. In this paper, we propose an adaptive bandwidth-efficient 360 VR video streaming system using a divide and conquer approach. In our approach, we propose a dynamic view-aware adaptation technique to tackle the huge streaming bandwidth demands of 360 VR videos. We spatially divide the videos into multiple tiles while encoding and packaging, use MPEG-DASH SRD to describe the spatial relationship of tiles in the 360-degree space, and prioritize the tiles in the Field of View (FoV). In order to describe such tiled representations, we extend MPEG-DASH SRD to the 3D space of 360 VR videos. We spatially partition the underlying 3D mesh, and construct an efficient 3D geometry mesh called hexaface sphere to optimally represent a tiled 360 VR video in the 3D space. Our initial evaluation results report up to 72 bandwidth savings on 360 VR video streaming with minor negative quality impacts compared to the baseline scenario when no adaptations is applied. While traditional multimedia applications such as games and videos are still popular, there has been a significant interest in the recent years towards new 3D media such as 3D immersion and Virtual Reality (VR) applications, especially 360 VR videos. 360 VR video is an immersive spherical video where the user can look around during playback. Unfortunately, 360 VR videos are extremely bandwidth intensive, and therefore are difficult to stream at acceptable quality levels. In this paper, we propose an adaptive bandwidth-efficient 360 VR video streaming system using a divide and conquer approach. We propose a dynamic view-aware adaptation technique to tackle the huge bandwidth demands of 360 VR video streaming. We spatially divide the videos into multiple tiles while encoding and packaging, use MPEG-DASH SRD to describe the spatial relationship of tiles in the 360-degree space, and prioritize the tiles in the Field of View (FoV). In order to describe such tiled representations, we extend MPEG-DASH SRD to the 3D space of 360 VR videos. We spatially partition the underlying 3D mesh, and construct an efficient 3D geometry mesh called hexaface sphere to optimally represent a tiled 360 VR video in the 3D space. Our initial evaluation results report up to 72 bandwidth savings on 360 VR video streaming with minor negative quality impacts compared to the baseline scenario when no adaptations is applied. We present a novel client-driven multiview video streaming system that allows a user to watch 3D video interactively with significantly reduced bandwidth requirements by transmitting a small number of views selected according to his her head position. The user's head position is tracked and predicted into the future to select the views that best match the user's current viewing angle dynamically. Prediction of future head positions is needed so that views matching the predicted head positions can be prefetched in order to account for delays due to network transport and stream switching. The system allocates more bandwidth to the selected views in order to render the current viewing angle. Highly compressed, lower quality versions of some other views are also prefetched for concealment if the current user viewpoint differs from the predicted viewpoint. An objective measure based on the abruptness of the head movements and delays in the system is introduced to determine the number of additional lower quality views to be prefetched. The proposed system makes use of multiview coding (MVC) and scalable video coding (SVC) concepts together to obtain improved compression efficiency while providing flexibility in bandwidth allocation to the selected views. Rate-distortion performance of the proposed system is demonstrated under different experimental conditions.