Intra-Refresh Techniques for Mobile Video Streaming

Mobile devices are replacing the desktop computer in most spheres outside the workplace. This development brings a problem to video streaming services, as wireless channels are fundamentally error-prone, whereas video compression depends for most of its gains on predictive coding. The H.264 codec family has included a good number of error resilience facilities to counter-act the spatio-temporal error propagation brought on by packet loss. This chapter outlines these facilities before examining ways in which predictive coding can be temporally restrained. In particular, intra-refresh techniques are the focus, as these bring additional utility to the video stream. For example, the chapter compares periodic and gradual intra-refresh, each of which provides recovery points for the decoder and also allow stream switching or joining at these points. Thus, in intra-coding, the more normal temporal prediction is temporally replaced by spatial prediction, at a cost in coding efficiency but allowing a decoder in a mobile device to reset itself. After a review of research into this area, the chapter provides a case study in non-periodic intra-refresh before considering possible future research directions.