In mobile-to-mobile video communications, both the transmitting and receiving ends may not have the necessary computing power to perform complex video compression and decompression tasks. Traditional video codecs typically have highly complex encoders and less complex decoders. However, Wyner-Ziv (WZ) coding allows for a low complexity encoder at the price of a more complex decoder. We propose a video communication system where the transmitter uses a WZ (reversed complexity) coder, while the receiver uses a traditional decoder, hence minimizing complexity at both ends. For that to work we propose to insert a transcoder in the network to convert the video stream. We present an efficient transcoder from a simple WZ approach to H.263. Our approach saves a large amount of the computation by reusing the motion estimation performed at the WZ decoder stage, among other things. Results are presented to demonstrate the transcoder performance.
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