Wyner-Ziv to Baseline H.264 Video Transcoder

Mobile-to-mobile video communications is one of the most requested services which operator networks can offer. However, in a framework where one mobile device sends video information to another, both transmitter and receptor should employ video encoders and decoders with low complexity. On the one hand, traditional video codecs, such as H.264, are based on architectures which have encoders with higher complexity than decoders. On the other hand, Wyner-Ziv (WZ) video coding (a particular case of distributed video coding) is an innovative paradigm, which provides encoders with less complexity than decoders. Taking advantage of both paradigms, in terms of low complexity algorithms, a suitable solution consists in transcoding from WZ to H.264. Nevertheless, the transcoding process should be carried out in an efficient way so as to avoid major delays in communication; in other words, the transcoding process should perform the conversion without requiring the complete process of decoding and re-encoding. Based on all the algorithms and techniques we have proposed before, a low complexity WZ to H.264 Transcoder for the Baseline Profile is proposed in this article. Firstly, the proposed transcoder can efficiently turn every WZ group of pictures into the common H.264 I11P pattern and, secondly, the proposed transcoder is based on the hypothesis that macroblock coding mode decisions in H.264 video have a high correlation with the distribution of the side information residual in WZ video. The proposed algorithm selects one sub-set of the several coding modes in H.264. Moreover, a dynamic motion estimation technique is proposed in this article for use in combination with the above algorithm. Simulation results show that the proposed transcoder reduces the inter prediction complexity in H.264 by up to 93%, while maintaining coding efficiency.