Flexitile: A Flexible 360 Video Tiling and Streaming Method

Tiled-based streaming is a promising method for 360-degree video streaming that reduces transmission bandwidth while enhancing the quality of experience (QoE). However, the tiling layout and the bitrate of the tiles significantly affect the QoE. This paper proposes FlexiTile, a novel and flexible method that maximizes QoE in tiled-based 360-degree video streaming. FlexiTile achieves this through joint optimization of the tiling layout and bandwidth allocation for each tile. This optimization considers the rate-distortion characteristics of the video content and user viewing direction preferences. FlexiTile leverages a formulation based on the Set Cover problem and an efficient and accurate piece-wise linear estimation of the rate-distortion model for candidate tiles. FlexiTile is evaluated under various transmission constraints and a subjective quality test. Compared to the baseline Notile tiling scheme, FlexiTile achieves a 1.9 dB average improvement in viewport PSNR using the BD metric. Additionally, it outperforms other state-ofthe-art methods in terms of viewing quality. Furthermore, FlexiTile demonstrates improvement over existing tiled-based streaming methods by optimizing tile bandwidth allocation. Experiments show a 1.3 dB average improvement in Uniform tiling (4×2) when the bandwidth allocation is based on the FlexiTile optimization method. FlexiTile surpasses existing methodologies by providing adaptable tiling layout and bitrate allocation strategies, resulting in a notable enhancement of QoE.