Mobile Video Communications Based on Fast DVC to H.264 Transcoding

Nowadays, mobile devices demand multimedia services such as video communications due to the advances in mobile communications systems (such us 4G) and the integration of video cameras into mobile devices. However, these devices have some limitations of computing power, resources and complexity constraints for performing complex algorithms. For this reason, in order to establish a video communications between mobile devices, it is necessary to use low complex encoding techniques. In traditional video codecs (such as H.264/AVC (ISO/IEC, 2003)) these low complexity requirements have not been met because H.264/AVC is more complex at the encoder side. Then, mobile video communications based on H.264/AVC low complexity imply a penalty in terms of Rate – Distortion (RD). However, Distributed Video Coding (DVC) (Girod et al., 2005), and particularly Wyner-Ziv (WZ) video coding (Aaron et al., 2002), provides a novel video paradigm where the complexity of the encoder is reduced by shifting the complexity of the encoder to the decoder (Brites et al., 2008). Taking into account the benefits of both paradigms, recently WZ to H.26X transcoders have been proposed in the multimedia community to support mobile-to-mobile video communications. The transcoding framework provides a scheme where transmitter and receiver execute lower complexity algorithms and the majority of the computation is moved to the network where the transcoder is allocated. This complexity is thus assumed by a transcoder, which has more resources and no battery limitations. Nevertheless, for real time communications it is necessary to perform this conversion from WZ to H.264/AVC with a short delay, and then the transcoding process must be executed as efficiently as possible.