Flexible GOP transcoding between DVC and H.264

Mobile to mobile video telephony is being one of the most attractive services that the newest generations of mobile communications system (such as 4G) are offering at the present time. This kind of service needs special requirements in terms of low complexity in both sides of the communication. By using traditional video encoders, such as H.264, those requirements are not satisfied due to the complexity of the encoder. Distributed Video Coding (DVC) deals with the problem of higher complexity constraints encoding algorithms at the expense of increasing the decoder complexity. In order to efficiently support video communications, this paper proposes an improved DVC to H.264 transcoder that maps different kind of GOPs, as well as different GOP lengths, between both paradigms. Moreover, the H.264 motion estimation is adjusted by using information gathered in the first step of the transcoders, offering a considerable reduction of the transcoding total time with a negligible rate-distortion penalty.