Towards Viewport-dependent 6DoF 360 Video Tiled Streaming for Virtual Reality Systems

Previous studies of 360-degree video streaming with regard to virtual reality allowed users to move their head freely, while their position is fixed according to the camera's location in virtual reality. One of the approaches to overcome the problem is transmitting multiview video to provide six degrees of freedom (6DoF). However, 6DoF streaming system implementation is challenging because multiple high-quality video streaming requires several decoders and a high bandwidth. Therefore, this paper proposes a viewport-dependent high-efficiency video coding (HEVC)-compliant tiled streaming system on test model for immersive video (TMIV), MPEG-Immersive multiview compression reference software. This paper proposes a 6DoF viewport tile selector (VTS) for multiple 360-degree video tiled streaming. Furthermore, this paper introduces a viewport-dependent multiple-tile extractor. The proposed system detects the user's head movement, selects the tile sets that correspond to the user's viewport, extracts tile bitstreams, and generates single bitstream. The extracted bitstream is transmitted and decoded to render the user's viewport The proposed viewport-dependent streaming method can reduce the decoding time as well as the bandwidth. Experimental results demonstrated 12.04% bjontegaard delta rate (BD-rate) saving for the luma peak signal-to-noise ratio (PSNR) compared to those obtained via the TMIV anchor without tiled encoding and a 55.51% decoding time saving compared to those obtained via the TMIV anchor with the existing tiled streaming method.