We study the performance of DPCM operating over lossy channels in cell-based networks such as ATM, when statistical multiplexing is used. Since the loss of data is mainly due to traffic congestion, and the minimum unit of loss is a cell which may contain multiple DPCM codewords, the loss process can be highly correlated. The contribution of this work comes in two parts. We first give a formulation which relates the performance of DPCM, in terms of signal-to-reconstruction-noise ratio, to the channel loss conditions. In particular we take into account any correlation that exists in the loss process. We then study in detail mechanisms which give rise to such correlation. Using simple source and multiplexing models, formulae are given which characterise the loss process as a result of statistical multiplexing. As a direct result of this treatment, we know that the maximum achievable performance of DPCM with reoptimised predictors further deteriorates when the loss process is correlated.>

Using simple multiplexer models, the performances of two prioritization mechanisms for the transmission of PCM coded signals modeled as exponential on/off sources are investigated and compared with nonprioritized transmission using statistical multiplexing and peak allocation. In both mechanisms the source traffic is partitioned into a low-priority stream and a high-priority stream. In the first approach independent channels of different quality of service are used to transport the two-priority streams. In the second approach a single channel is used in conjunction with a selective packet discarding procedure which attempts to restrict loss to the low-priority traffic. For a given source partitioning, new formulae are given to describe the average loss ratio for the low- and high-priority traffic. The effect of loss on quality for PCM coded signal is quantified by a new formula which relates signal-to-reconstruction-noise ratio to low- and high-priority-loss. The results of the investigation show that both methods of prioritized transmission can provide significant improvements in overall service quality when the channel utilization is high.>

Efficient video coding incorporating motion compensation and overlapped transforms requires different coding architectures and methods of motion estimation to those used in traditional DCT block based coding schemes. In this paper a transform domain motion estimation procedure is proposed for the MDCT. This method of motion estimation, while performed in the spatial domain, is equivalent to minimising the sum square error of transform coefficients. The application of the MDCT to frequency scalable video coding is investigated. A performance advantage is achieved over an equivalent DCT based coder for both the reconstructed low resolution and high resolution sequences of an open loop frequency scalable video coder.>

We propose a method of quantisation which explicitly minimises a generalised quadratic error measure. The method is applied to block based image and video coding schemes, and is shown to be useful in reducing block artefacts. Since no alteration to the decoding process is required, the method can be used in standards based coding in a fully compatible fashion.>