Low Bit-rate Mobile Cloud Gaming

In mobile cloud gaming, high-quality, high-frame-rate game images of immense data-size need to be delivered to the clients under stringent delay requirement. For good gaming experience, reducing the transmission bit-rate of the game images is necessary. In this work, we investigate a framework to achieve low bit-rate game image transmission. In particular, we extend our previously proposed layered coding to reduce transmission bandwidth and latency. In layered coding, we leverage the rendering capability of modern mobile devices to locally render low-quality game images, or the base layer. Instead of sending high quality game images directly, cloud servers can send enhancement layer information, which clients can utilize to improve the quality of the base layer. We investigate the design of a complexity-scalable base layer (BL) rendering pipeline that can be executed on a range of power-constrained mobile devices for layered coding. We focus on the popular Blinn-Phong lighting and formulate the design of BL Blinn-Phong lighting as an information-complexity optimization problem. Furthermore, we investigate a solution to remove the initialization latency of layered coding. Experiment results show that the information rate of the enhancement layer could be much less than that of the high quality game image; while the base layer can be generated with only a very small amount of computation. In particular, up to 84 percent reduction in bandwidth usage can be achieved by the proposed layered coding scheme.