Optimal Tile Size and Streaming Field of View for VR Streaming

Virtual reality (VR) video services require a high bitrate, and hence, viewport-adaptive streaming techniques like motion-constrained-tile-set (MCTS) have been found important to reduce streaming-rate and storage demands. The tiling scheme and streaming field of view (FOV) are among the key elements in designing an optimal VR viewport-adaptive streaming solution, in terms of rate-distortion (R-D) performance. The aim of this study is to propose an optimal configuration for the tile grid and streaming FOV, considering different VR viewing situations such as head motion speed, system delay, and head-mounted display FOV. To achieve this, a wide range of tiling schemes and streaming FOVs are examined to study the storage and streaming R-D performance of the MCTS-based technique in both viewport and non-viewport areas using a quality metric called Zonal-cubic PSNR. The findings demonstrate that for VR applications focused on preserving high viewport quality, fine tile grids lead to higher performance. In scenarios featuring small and large HMD FOV, the optimal configuration involves a small and medium streaming FOV, respectively.