Abstract
Interactive 360° remote video applications have seen booming advancements due to the proliferation of smart display devices that enable a truly immersive experience. Compared to regular monoscopic videos, 360° videos have different requirements related to content preparation, packaging, transmission, specialized viewing equipment, and display factors (e.g., brightness, contrast, delay, frame rate, resolution, image quality, etc. In addition, 360° video requires substantial network and computational resources, which are challenging to achieve with conventional transmission and rendering infrastructure. Viewport-adaptive streaming is a common way to ensure visual quality under limited bandwidth resources. However, identifying, extracting, and rendering the true viewport in response to drastic head rotations can adversely affect user experience. This paper proposes two dynamic viewport selection approaches, which adapt the streamed regions based on content complexity variations and positional information to ensure viewport availability and smooth visual angles for VR users. They incorporate content information as well as user head movement patterns to support tile-based prioritized 360° video streaming. Moreover, a practical, prioritized bitrate adaptation approach, which requests selected tiles at appropriate quality levels, is also proposed to reduce the impact of inefficient bandwidth utilization in the VR scene. Experimental evaluations under real 4G bandwidth logs demonstrate that the proposed solutions outperform the closest state-of-the-art algorithms across multiple performance metrics, i.e., viewport overlap, perceived quality levels, quality fluctuations, and viewport bandwidth utilization.
Highlights
R ECENTLY, next-generation immersive multimedia applications such as Virtual Reality (VR) and 360° videos have increasingly penetrated various fields, including entertainment, healthcare, education, real estate, manufacturing, retail, transportation, sport, and other consumer-facing services
This paper proposes two innovative dynamic viewport selection (DVS) solutions for 360° adaptive video streaming, referred to as DVS1 and DVS2
For the Spotlight video, DVS1 and DVS2 methods achieve an average quality improvement of about 3.86% and 1.64% compared to uniform viewport (UVP), 7.4% and 5.18% compared to center tile first (CTF), 10.89% and 8.67% compared to HOS, and 11.67% and 9.45% compared to PET methods
Summary
R ECENTLY, next-generation immersive multimedia applications such as Virtual Reality (VR) and 360° videos have increasingly penetrated various fields, including entertainment, healthcare, education, real estate, manufacturing, retail, transportation, sport, and other consumer-facing services. The proposed solutions provide support for improved streaming tiles selection and bitrate adaptation based on content complexity and user engagement. Existing works [6]–[10], [15]–[17] only consider the viewing information to perform relevant tiles selection Unlike these schemes, DVS solutions include content information as well as viewing behaviors to proactively select the streaming regions. DVS solutions perform advanced streaming tiles selection in the context of three scenarios: (1) Fixed viewport; (2) Neighbor region; and (3) Extended viewport in order to improve the 360° video content visualization. He et al [30] performed a network response-based joint adaptation of the viewport coverage and bitrate under dynamic and congested network conditions. We compare the proposed solutions against the UVP, CTF [8], HOS [10], and PET [18] methods using three different motion videos prepared in different tiling patterns and segment lengths, which were shown to outperform others
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