The most recent literature indicates Multiple Description (MD) as a new coding approach to handle the problem of video transmission over unreliable networks. This technique describes the source information in equally important and independent streams named multiple descriptions, by introducing some kind of redundancy into each description. Recent works have shown the success of using motion compensation prediction also in an MD video coding scheme. Even though these MD systems have proved to be robust in an error-prone environment, they are in practice forced to use only two descriptions. This is a very strong constraint when more than two levels of reconstruction are required. For this reason this paper proposes two architectures of MD video coders; the first, that we call DC-MDVC, is based on the classical MD video codec architecture and the principle contribution is the use of a new MD algorithm based on a polyphase down-sampling technique. Since this architecture is suitable only in case of two descriptions, then a second architecture, called IF-MDVC, is given, where multi-level scalability is introduced by generating the multiple descriptions before the prediction loop. Results show that both architectures are appealing, and the second architecture seems to perform impressively well.
This work proposes and implements a system to transmit in real-time slow video signals - in particular video conference signal, that is head and shoulder sequences - over the public network. The proposed codec is based on a multiple description approach that gives N equally important and independent flows. The advantage of this codec is an intrinsic robustness to the transmission errors and to the packet loss, as the simulation results have proved. This feature results very suitable not only for IP-network, but also for every packet network like the next generation mobile systems. The approach is important also for the end user scalability since each device can decide the information to receive according to the resolution of the display and the bandwidth of the connecting link using the same source data stream.
Recently the problem of transmitting data over heterogeneous networks has received considerable attention. Our specific interest is the communication of still images. In this work we present a Multiple Description system based on Polyphase DownSampling algorithm (PDMD) that splits an image source in an arbitrary number of balanced descriptions. Our goal is to obtain both the best reconstruction quality from the received descriptions (also only one) and a subjective indistinguishable reconstruction from the original, if all the descriptions are available.
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