C. Nishan Canagarajah

Lossless Compression for Space Imagery in a Dynamically Reconfigurable Architecture

This paper presents a novel dynamically reconfigurable hardware architecture for lossless compression and its optimization for space imagery. The proposed system makes use of reconfiguration to support optimal modeling strategies adaptively for data with different dimensions. The advantage of the proposed system is the efficient combination of different compression functions. For image data, we propose a new multi-mode image model which can detect the local features of the image and use different modes to encode regions with different features. Experimental results show that our system improves compression ratios of space image while maintaining low complexity and high throughput.

Selection of image fusion quality measures: objective, subjective, and metric assessment

Accurate quality assessment of fused images, such as combined visible and infrared radiation images, has become increasingly important with the rise in the use of image fusion systems. We bring together three approaches, applying two objective tasks (local target analysis and global target location) to two scenarios, together with subjective quality ratings and three computational metrics. Contrast pyramid, shift-invariant discrete wavelet transform, and dual-tree complex wavelet transform fusion are applied, as well as levels of JPEG2000 compression. The differing tasks are shown to be more or less appropriate for differentiating among fusion methods, and future directions pertaining to the creation of task-specific metrics are explored.

Resource allocation for OFDMA-based cognitive radio networks with application to H.264 scalable video transmission

Resource allocation schemes for orthogonal frequency division multiple access- (OFDMA-) based cognitive radio (CR) networks that impose minimum and maximum rate constraints are considered. To demonstrate the practical application of such systems, we consider the transmission of scalable video sequences. An integer programming (IP) formulation of the problem is presented, which provides the optimal solution when solved using common discrete programming methods. Due to the computational complexity involved in such an approach and its unsuitability for dynamic cognitive radio environments, we propose to use the method of lift-and-project to obtain a stronger formulation for the resource allocation problem such that the integrality gap between the integer program and its linear relaxation is reduced. A simple branching operation is then performed that eliminates any noninteger values at the output of the linear program solvers. Simulation results demonstrate that this simple technique results in solutions very close to the optimum.

Spatial digital watermark for MPEG-2 video authentication and tamper detection

The widespread adoption of digital video techniques has generated a requirement for authenticity verification in applications such as criminal evidence, insurance claims and commercial databases. This work addresses problems that arise from a spatial digital watermarking technique developed to detect frame reordering and dropping scenarios. It discusses the differences between mutual frame types at different bit-rates. Many papers consider detection after MPEG-2 decoding as a naïve approach. However, this approach does offer significant advantages for a slight increase of computation load. This paper also establishes a link between the detector performance and the sequence content. The uniqueness of this work is the comparison of the test results using 18 different standard MPEG test-sequences. The functionality of the algorithm is demonstrated with a simulated attack.

Task-based scanpath assessment of multi-sensor video fusion in complex scenarios

The combining of visible light and infrared visual representations occurs naturally in some creatures, including the rattlesnake. This process, and the wide-spread use of multi-spectral multi-sensor systems, has influenced research into image fusion methods. Recent advances in image fusion techniques have necessitated the creation of novel ways of assessing fused images, which have previously focused on the use of subjective quality ratings combined with computational metric assessment. Previous work has shown the need to apply a task to the assessment process; the current work continues this approach by extending the novel use of scanpath analysis. In our experiments, participants were shown two video sequences, one in high luminance (HL) and one in low luminance (LL), both featuring a group of people walking around a clearing of trees. Each participant was shown visible and infrared (IR) inputs alone; and side-by-side (SBS); in an average (AVE) fused; a discrete wavelet transform (DWT) fused; and a dual-tree complex wavelet transform (DT-CWT) fused displays. Participants were asked to track one individual in each video sequence, as well as responding by key press when other individuals carried out secondary actions. Results showed the SBS display to lead to much poorer accuracy than the other displays, while reaction times in carrying out the secondary task favoured AVE in the HL sequence and DWT in the LL sequence. Results are discussed in relation to previous findings regarding item saliency and task demands, and the potential for comparative experiments evaluating human performance when viewing fused sequences against naturally occurring fusion processes such as the rattlesnake is highlighted.

Joint Call Admission Control and Resource Allocation for H.264 SVC Transmission Over OFDMA Networks

This paper aims to combine adaptive subcarrier allocation and bit loading with the transmission of the H.264 SVC (Scalable Video Coding) encoded video sequences in order to increase the number of supported users in the system and provide the best quality of service (QoS) to the subscribers. We initially assume that the number of calls at the base station can be supported, and present an integer program (IP) formulation of the problem that considers the frequency selective nature of the channel, bit error rate requirement and the discrete rate requirements of the different layers of the medium grain scalable (MGS) video. It is shown how the IP can be extended to perform call admission control (CAC). Due to the complexity involved with IP, a sub-optimal scheme is then presented. Results demonstrate that our proposed scheme performs better than systems with a fixed resource allocation strategy by supporting more users and by always achieving acceptable QoS. Furthermore, the low complexity of the proposed CAC schemes makes it suitable for practical application.

A Multicue Bayesian State Estimator for Gaze Prediction in Open Signed Video

We propose a multicue gaze prediction framework for open signed video content, the benefits of which include coding gains without loss of perceived quality. We investigate which cues are relevant for gaze prediction and find that shot changes, facial orientation of the signer and face locations are the most useful. We then design a face orientation tracker based upon grid-based likelihood ratio trackers, using profile and frontal face detections. These cues are combined using a grid-based Bayesian state estimation algorithm to form a probability surface for each frame. We find that this gaze predictor outperforms a static gaze prediction and one based on face locations within the frame.

Rapid block-based global motion estimation and its applications

This paper proposes a novel low-complexity block-based global motion estimation algorithm for real-time digital video processing applications. The algorithm involves an 8/spl times/8 block-based local motion estimation followed by a least square method to obtain the global motion vector parameters. The translation-zoom global motion model with 3 parameters was adopted and least square method computation is done after removing outliers. Blocks are considered outliers if: (i) the block is over-cluttered or (ii) the reference block has too little activity for an accurate motion vector to be estimated. The algorithm is used to estimate the global motion of 3 QCIF test streams at 10 fps and the parameters are used in 5 typical applications Respective simulations have produced favorable results emphasizing the usefulness of the proposed algorithm.

Exploiting spatial domain and wavelet domain cumulants for fusion of SAR and optical images

The aim of this paper is to introduce a novel statistical model-based\ image fusion method for Synthetic Aperture Radar (SAR) and optical images. The current fusion algorithms are effective only in specific areas of the scene. Hence, the fused image may not contain enough information for subsequent processing like classification and feature extraction. Our proposed method aims to keep the maximum contextual and spatial information from the source data by exploiting the relationship between spatial domain cumulants and wavelet domain cumulants. Our contributions are in integrating the relationship between spatial and wavelet domain cumulants of source images into an image fusion process as well as in employing these wavelet cumulants for optimization of weights in a Cauchy convolution based image fusion scheme. The superior performance of the proposed algorithm is demonstrated in comparison to existing fusion algorithms using real SAR and optical images.

Quality assessment of false-colored fused displays

Abstract— The problem of assessing the quality of fused images (composites created from inputs of differing modalities, such as infrared and visible light radiation) is an important and growing area of research. Recent work has shown that the process of assessing fused images should not rely entirely on subjective quality methods, with objective tasks and computational metrics having important contributions to the assessment procedure. The current paper extends previous findings, applying a psychophysical selection task, metric evaluation, and subjective quality judgments to a range of fused surveillance images. Fusion schemes included the contrast pyramid and shift invariant discrete wavelet transform (Experiment 1), the complex wavelet transform (Experiments 1 & 2), and two false-coloring methods (Experiment 2). In addition, JPEG2000 compression was applied at two levels, as well as an uncompressed control. Reaction time results showed the contrast pyramid to lead to slowest performance in the objective task, whilst the presence of color greatly reduced reaction times. These results differed from both the subjective and metric results. The findings support the view that subjective quality ratings should be used with caution, especially if not accompanied by some task.