In this paper we present a high quality audio coding system based on a novel nonuniform modulated filterbank coupled with time-varying cosine modulated filterbanks in a cascade architecture. The system makes use of psychoacoustic thresholds in a natural way to adapt the resolution of the filterbank to achieve high coding gain on a wide range of signal types. Results show that the system provides excellent quality at 64 kb/s and good quality at 48 kb/s for monophonic coding.

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.>

In this paper a formal, quantitative approach to designing optimum Hough transform (HT) algorithms is proposed. This approach takes the view that a HT is a hypothesis testing method. Each sample in the HT array implements a test to determine whether a curve with the given parameters fits the edge point data. This view allows the performance of HT algorithms to be quantified. The power function, which gives the probability of rejection as a function of the underlying parametric distribution of data points, is shown to be the fundamentally important characteristic of HT behaviour. Attempting to make the power function narrow is a formal approach to optimizing HT performance. To illustrate how this framework is useful the particular problem of line detection is discussed in detail. It is shown that the hypothesis testing framework leads to a redefinition of the HT in which the values are a measure of the distribution of points around a curve rather than the number of points on a curve. This change dramatically improves the sensitivity of the method to small structures. The solution to many HT design problems can be posed within the framework, including optimal quantizations and optimum sampling of the parameter space. In this paper the authors consider the design of optimum I-D filters, which can be used to sharpen the peak structure in parameter space. Results on several real images illustrate the improvements obtained.>

We investigate the use of Robust Estimation in an application requiring the accurate location of the centres of circular objects in an image. A common approach used throughout computer vision for extracting shape information from a data set is to fit a feature model using the Least Squares method. The well known sensitivity of this method to outliers is traditionally accommodated by outlier rejection methods. These usually consist of heuristic applications of model templates or data trimming. Robust Estimation offers a theoretical framework for assessing such rejection schemes, and more importantly, provides an approach to parameter estimation in contaminated data distributions capable of greater accuracy.

A formal, quantitative approach to designing optimal Hough transform (HT) algorithms is proposed. This approach takes the view that a HT is a hypothesis testing method. This view allows the performance of HT algorithms to be quantified. The power function, which gives the probability of rejection as a function of the underlying parametric distribution of data points, is shown to be the fundamentally important characteristic of HT behavior. Attempting to make the power function narrow is a formal approach to optimizing HT performance. To illustrate how this framework is useful the particular problem of line detection is discussed. It is shown that the hypothesis testing framework leads to a redefinition of HT in which the values are a measure of the distribution of points around a curve rather than the number of points on a curve. The solution to many HT design problems can be posed within the framework, including optimal quantizations and optimum sampling of the parameter space. Consideration is given to the design of optimum 1-D filters which can be used to sharpen the peak structure in parameter space. Results on several real images illustrate the improvements obtained.>

An efficient method for finding straight lines in edge maps is described. The algorithm is based on a pyramid structure. At the bottom level of the pyramid, short line segments are detected by applying a Hough transform to small subimages. The algorithm proceeds, bottom up, from this low-level description by grouping line segments within the local neighborhoods into longer lines. Line segments which have local support propagate up the hierarchy and take part in grouping at higher levels. The length of a line determines approximately the level in the pyramid to which it propagates, and a hierarchical description of the line segments in a scene is obtained. The line-segment-grouping process is also based on a Hough transform. The method is quite efficient and has an attractive architecture which is suitable for parallel implementation.>

A new, oddly stacked, critically sampled, single side-band (SSB) [7] analysis/synthesis system based on Time Domain Aliasing Cancellation (TDAC) [1],[2] is described in this paper. The specifications for the analysis and synthesis filter responses are developed and a number of designs which satisfy the reconstruction requirements are described. The application of TDAC systems to Subband/Transform coding is also discussed and the objective performance of a 32 band coder using several different window designs is presented and compared with a coder based on Frequency Domain Aliasing Cancellation (FDAC) filter banks [3]-[5].