Source coding methods for robust wireless video streaming

As real-time video streaming moves to the mobile Internet, there is a greater need to protect fragile compressed bit-streams from the impact of lossy wireless channels. Though forward error correction (FEC) has a role, if it is applied without adaptation, it may introduce excessive communication overhead. Alternatively, error resilience methods provide additional protection at the application layer of the protocol stack, without replication of any protection already provided at the data-like layer. In this chapter, a case study shows that these resilience methods can be applied adaptively through stream switching according to channel conditions. Error resilience can work hand-in-hand with error concealment, again applied through source coding. There are many error resilience and concealment methods, which this chapter surveys at a tutorial level. The chapter also includes an overview of video streaming for those unfamiliar with the topic. Though error concealment is a non-normative feature of the H.264/AVC (Advanced Video Coding) codec standard, there is a range of new techniques that have been included within the Standard such as flexible macroblock ordering and stream switching frames. The chapter additionally reviews error concealment provision, including spatial, temporal, and hybrid methods. Results show that there are tradeoffs between the level of protection and the level of overhead, according to the severity of the wireless channel impairment.