Network Image Coding for Multicast

We consider a new problem in network image coding for multicast. In a multihop mesh network, structured as a directed graph, all nodes decode and display reconstructions of the image (at possibly different qualities). Each node may also perform transcoding before transmitting data downstream in the network. The problem is the design of the coding and transcoding schemes to deliver the best image quality over the network. For a network with diamond topology, we show that multiple description coding combined with Wyner-Ziv transcoding is often superior to other methods. We argue further that the benefits are magnified for larger networks containing one or more diamond subnets. Our image coding experiments demonstrate that multiple description coding with Wyner-Ziv transcoding outperforms single description coding or multiple description coding with conventional transcoding, for both a diamond network and a two-hop mesh network with four branches.