TiCMP: A lightweight and efficient Tiled Cubemap projection strategy for Immersive Videos in Web-based players

The encoding, delivery and interactive consumption of omnidirectional videos still face many challenges. Traditional encoding techniques, based on Equirectangular formats, introduce significant pixel redundancy. This has prompted the appearance of advanced solutions based on the segmentation in separate regions or tiles, and their selective delivery depending on the users’ viewpoint. However, tiling techniques introduce further challenges. First, neighbouring pixels are encoded separately, which may result in a noticeable separation between regions. Second, they can involve synchronization problems when the users’ viewpoints change. Third, they may require further extensions to existing technologies, such as Dynamic Adaptive Streaming over HTTP (DASH), which makes their adoption in current web browsers very challenging. The use of Cubemap projection is alternatively gaining popularity due to its multiple advantages compared to Equirectangular projection. However, it requires the streaming of the whole 360º area. This paper proposes a novel tiled Cubemap (TiCMP) strategy that overcomes all the mentioned limitations. TiCMP is based on dividing the cube into two tiles, adaptively streaming them based on the users’ viewpoint, and playing them out in a synchronized manner in web-based players. Evaluation results demonstrate that TiCMP provides significant bandwidth savings, without negatively impacting the Quality of Experience when compared to traditional Equirectangular- and Cubemap-based strategies.