Mary L. Comer

Morphological operations for color image processing

In this paper operations based on mathematical morphology which have been developed for binary and grayscale images are extended to color images. We investigate two approaches for ‘‘color morphology’’—a vector approach and a component-wise approach. New vector morphological filtering operations are defined, and a set-theoretic analysis of these vector operations is presented. We also present experimental results comparing the performance of the vector approach and the component-wise approach for multiscale color image analysis and for noise suppression in color images.

Efficient Online WiFi Delivery of Layered-Coding Media Using Inter-layer Network Coding

A primary challenge in multi casting video in a wireless LAN to multiple clients is to deal with the client diversity -- clients may have different channel characteristics and hence receive different numbers of transmissions from the AP. A promising approach to overcome this problem is to combine multi-resolution (layered) video coding with interlayer network coding. The fundamental challenge in such an approach is to determine the strategy of coding the packets across different layers that maximizes the number of decoded layers at all clients. This paper makes three contributions. (1) We first show that even for one client, the previously proposed canonical triangular scheme for inter-layer network coding can perform poorly. We show how to enhance the triangular scheme by incorporating the estimated target number of layers which significantly improves its effectiveness. (2) We show that such an enhanced triangular scheme still performs poorly for multiple clients with diverse channel characteristics, which motivates the need for searching for the optimal coding strategy. The naive way of searching for the optimal strategy is computationally prohibitive. We present several optimizations that drastically reduce the complexity of exhaustively searching for the optimal strategy, making it feasible in real time. (3) Finally, we design and evaluate an on line video delivery scheme, Percy, to be deployed at a proxy behind the AP of a wireless LAN. Our simulation results show that Percy outperforms the previous inter-layer coding heuristic by up to 22-80% with varying numbers of clients.

Efficient Inter-Layer Motion Compensation for Spatially Scalable Video Coding

In this paper, an efficient inter-layer motion-compensation technique is proposed for enhancement layer in spatially scalable video coding. The proposed approach exploits the prediction residue correlation between consecutive spatial layers. In enhancement-layer motion compensation, it selects the method with the lowest rate-distortion (RD) cost from three schemes: pyramid motion compensation, subband motion compensation, and encoding the enhancement layer with no base-layer information. To reduce the block artifacts of the enhancement-layer prediction used in the subband method, extended edge prediction is introduced in the proposed approach. Compared with the current scalable H.264/AVC extension (SVC) motion-compensation scheme, our experimental results show that the proposed method exploits the redundancy between the base layer and the enhancement layer more efficiently and hence improves the coding performance. It achieves an improvement up to about 1dB in the enhancement-layer encoding for different coding parameters and video sequences.

Parameter estimation and segmentation of noisy or textured images using the EM algorithm and MPM estimation

Presents a new algorithm for segmentation of noisy or textured images using the expectation-maximization (EM) algorithm for estimating parameters of the probability mass function of the pixel class labels and the maximization of the posterior marginals (MPM) criterion for the segmentation operation. A Markov random field (MRF) model is used for the pixel class labels. The authors present experimental results demonstrating the use of the new algorithm on synthetic images and medical imagery.<<ETX>>

Rate Distortion Analysis for Spatially Scalable Video Coding

In this paper, we derive the rate distortion lower bounds of spatially scalable video coding techniques. The methods we evaluate are subband and pyramid motion compensation where temporal redundancies in the same spatial layer as well as interlayer spatial redundancies are exploited in the enhancement layer encoding. The rate distortion bounds are derived from rate distortion theory for stationary Gaussian signals where mean square error is used as the distortion criteria. Assuming that the base layer is encoded by a nonscalable video coder, we derive the rate distortion functions for the enhancement layer, which depend upon the power spectral density of the input signal, the motion prediction error probability density function and the base layer encoding performance. We will show that pyramid and subband methods are expected to outperform independently encoding the enhancement layer using motion-compensated prediction, in terms of rate distortion efficiency, when the base layer is encoded at a relatively higher quality or less accurate displacement estimation happens in the enhancement layer.

A four-description MDC for high loss-rate channels

One of the most difficult problems in video transmission is communication over error-prone channels, especially when retransmission is unacceptable. To address this problem, Multiple Description Coding (MDC) has been proposed as an effective solution due to its robust error resilience. Considering applications in scalable, multicast and P2P environments, it is advantageous to use more than two descriptions (which is designated multi-description MDC in this paper). In this paper, we present a new four-description MDC for high lossrate channel using a hybrid structure of temporal and spatial correlations. A Gilbert model is used as the channel model for burst packet loss simulation. Experimental results demonstrate the efficacy of the proposed method.

Chapter 8 – Multiple Description Coding *

Abstract With the development of 3G/4G and WiFi networks, there has been a growing demand for multimedia delivery over wireless channels. The dramatic increase in multimedia traffic over such lossy channels has driven the development of efficient, reliable, and adaptable coding techniques. Multiple description coding (MDC) has emerged as one of the most effective coding techniques to address such scenarios, especially in case of real-time applications when retransmission is unacceptable. In MDC, source data is coded into multiple descriptions containing controlled redundancy that is used to combat the unpredictable packet loss during delivery across a channel. Using the received descriptions, the source data is reconstructed by the decoder. Since its conception, many MDC based tools and systems have been developed for generic and specific applications. In this chapter, we review the development of MDC in the context of some selected applications.

Subband motion compensation for spatially scalable video coding

In this paper, a new enhancement layer motion compensation technique referred to as subband motion compensation is proposed for spatially scalable video coding. This approach is proposed as an alternative to a technique which we call pyramid motion compensation in this paper and which is referred to as inter-layer residual prediction in the H.264/MPEG4-AVC scalable extension, Scalable Video Coding (SVC) standard. The main difference between these two techniques lies in the way they use the base layer information to encode the enhancement layer. Experimental results comparing the two approaches show that for enhancement layer encoding, pyramid method is better when the corresponding base layer is encoded with a lower bitrate while subband method outperforms pyramid method when the base layer has a higher bitrate. This motivates future proposed work to adaptively choose between these two methods at the macroblock level or even at the transform coefficient level for spatially scalable video coding.

Efficient reduction of block artifacts in reduced resolution update video coding

This paper describes a new technique for reducing the blockiness that results from using the reduced-resolution update (RRU) video coding tool. In RRU coding, full resolution prediction error residuals are downsampled and coded at a reduced spatial resolution. In previous versions of RRU, such as that defined in Annex Q of the H.263 standard, each block of prediction errors is processed without using samples from any neighboring blocks. This can lead to severe blockiness in the decoded picture. To reduce this blockiness H.263 Annex Q RRU increases the deblocking filter strength to the maximum value. In the new technique presented here, referred to as RRU+, the downsampling and interpolation filters use residuals from neighboring blocks to prevent the blockiness that results from RRU. Experimental results comparing RRU+, RRU with normal deblocking filter strength (referred to simply as RRU in this paper), and RRU with maximum deblocking filter strength are presented. These results show that, while RRU+ and RRU with maximum deblocking strength both eliminate the blocking artifacts associated with RRU, RRU+ provides better peak signal-to-noise ratio (PSNR) performance than RRU, whereas RRU with maximum deblocking strength degrades the PSNR performance compared to RRU. Results comparing H.264 with RRU/RRU+ are also presented and the effectiveness of RRU/RRU+ as a tool for improving coding efficiency is discussed.

An automated segmentation for nickel-based superalloy

We investigate the automated segmentation of microstructures of a nickel-based superalloy using digital microscopy data. We study the combination of a region merging segmentation method called the stabilized inverse diffusion equation (SIDE), and a stochastic segmentation method, the expectation-maximization/maximization of the posterior marginals (EM/MPM) algorithm. We use the SIDE algorithm to segment the grain boundaries and we use the EM/MPM algorithm to classify two phases of the material within each grain. Experimental results demonstrate the effectiveness of our approach.