Hong Ren Wu

Bio: Hong Ren Wu is an academic researcher from RMIT University. The author has contributed to research in topics: Adaptive filter & Human visual system model. The author has an hindex of 32, co-authored 196 publications receiving 5673 citations. Previous affiliations of Hong Ren Wu include National University of Singapore & Monash University.

A robust MIMO terminal sliding mode control scheme for rigid robotic manipulators

Abstract: In this paper, a robust multi-input/multi-output (MIMO) terminal sliding mode control technique is developed for n-link rigid robotic manipulators. It is shown that an MIMO terminal switching plane variable vector is first defined, and the relationship between the terminal switching plane variable vector and system error dynamics is established. By using the MIMO terminal sliding mode technique and a few structural properties of rigid robotic manipulators, a robust controller can then be designed so that the output tracking error can converge to zero in a finite time, and strong robustness with respect to large uncertain dynamics can be guaranteed. It is also shown that the high gain of the terminal sliding mode controllers can be significantly reduced with respect to the one of the linear sliding mode controller where the sampling interval is nonzero. >

Adaptive impulse detection using center-weighted median filters

Abstract: Previous median-based impulse detection strategies tend to work well for fixed-valued impulses but poorly for random-valued impulse noise, or vice versa. This letter devises a novel adaptive operator, which forms estimates based on the differences between the current pixel and the outputs of center-weighted median (CWM) filters with varied center weights. Extensive simulations show that the proposed scheme consistently works well in suppressing both types of impulses with different noise ratios.

Space variant median filters for the restoration of impulse noise corrupted images

Abstract: This brief proposes a generalized framework of median based switching schemes, called multi-state median (MSM) filter. By using a simple thresholding logic, the output of the MSM filter is adaptively switched among those of a group of center weighted median (CWM) filters that have different center weights. As a result, the MSM filter is equivalent to an adaptive CWM filter with a space varying center weight which is dependent on local signal statistics. The efficacy of the proposed filter has been evaluated by extensive simulations.

A generalized block-edge impairment metric for video coding

Abstract: A mew generalized block-edge impairment metric (GBIM) is presented in this paper as a quantitative distortion measure for blocking artifacts in digital video and image coding. This distortion measure does not require the original image sequence as a comparative reference, and is found to be consistent with subjective evaluation.

Digital Video Image Quality and Perceptual Coding

Abstract: PICTURE CODING AND HUMAN VISUAL SYSTEM FUNDAMENTALS Digital Picture Compression and Coding Structure . Introduction to Digital Picture Coding . Characteristics of Picture Data . Compression and Coding Techniques . Picture Quantization . Rate-Distortion Theory . Human Visual Systems . Digital Picture Coding Standards and Systems . Summary Fundamentals of Human Vision and Vision Modeling . Introduction . A Brief Overview of the Visual System . Color Vision . Luminance and the Perception of Light Intensity . Spatial Vision and Contrast Sensitivity . Temporal Vision and Motion . Visual Modeling . Conclusions Coding Artifacts and Visual Distortions . Introduction . Blocking Effect . Basis Image Effect . Blurring . Color Bleeding . Staircase Effect . Ringing . Mosaic Patterns . False Contouring . False Edges . MC Mismatch . Mosquito Effect . Stationary Area Fluctuations . Chrominance Mismatch . Video Scaling and Field Rate Conversion . Deinterlacing . Summary PICTURE QUALITY ASSESSMENT AND METRICS Video Quality Testing . Introduction . Subjective Assessment Methodologies . Selection of Test Materials . Selection of Participants-Subjects . Experimental Design . International Test Methods . Objective Assessment Methods . Summary Perceptual Video Quality Metrics-A Review . Introduction . Quality Factors . Metric Classification . Pixel-Based Metrics . The Psychophysical Approach . The Engineering Approach . Metric Comparisons . Conclusions and Perspectives Philosophy of Picture Quality Scale . Objective Picture Quality Scale for Image Coding . Application of PQS to a Variety of Electronic Images . Various Categories of Image Systems . Study at ITU . Conclusion Structural Similarity Based Image Quality Assessment . Structural Similarity Based Image Quality . The Structural SIMilarity (SSIM) Index . Image Quality Assessment Based on the SSIM Index . Discussions Vision Model Based Digital Video Impairment Metrics . Introduction . Vision Modeling for Impairment Measurement . Perceptual Blocking Distortion Metric . Perceptual Ringing Distortion Measure . Conclusion Computational Models for Just-Noticeable Difference . Introduction . JND with DCT Subbands . JND with Pixels . JND Model Evaluation . Conclusions No-Reference Quality Metric for Degraded and Enhanced Video . Introduction . State-of-the-Art for No-Reference Metrics . Quality Metric Components and Design . No-Reference Overall Quality Metric . Performance of the Quality Metric . Conclusions and Future Research Video Quality Experts Group . Formation . Goals . Phase I . Phase II . Continuing Work and Directions . Summary PERCEPTUAL CODING AND PROCESSING OF DIGITAL PICTURES HVS Based Perceptual Video Encoders . Introduction . Noise Visibility and Visual Masking . Architectures for Perceptual Based Coding . Standards-Specific Features . Salience/Maskability Pre-Processing . Application to Multi-Channel Encoding Perceptual Image Coding . Introduction . A Perceptual Distortion Metric Based Image Coder . Model Calibration . Performance Evaluation . Perceptual Lossless Coder . Summary Foveated Image and Video Coding . Foveated Human Vision and Foveated Image Processing . Foveation Methods . Scalable Foveated Image and Video Coding . Discussions Artifact Reduction by Post-Processing in Image Compression . Introduction . Image Compression and Coding Artifacts . Reduction of Blocking Artifacts . Reduction of Ringing Artifacts . Summary Reduction of Color Bleeding in DCT Block-Coded Video . Introduction . Detailed Analysis of the Color Bleeding Phenomenon . Description of the Post-Processor . Experimental Results-Concluding Remarks Error Resilience for Video Coding Service . Introduction to Error Resilient Coding Techniques . Error Resilient Coding Methods Compatible with MPEG-2 . Methods for Concealment of Cell Loss . Experimental Procedure . Experimental Results . Conclusions Critical Issues and Challenges . Picture Coding Structures . Vision Modeling Issues . Spatio-Temporal Masking in Video Coding . Picture Quality Assessment . Challenges in Perceptual Coder Design . Codec System Design Optimization . Summary Appendix: VQM Performance Metrics . Metrics Relating to Model Prediction Accuracy . Metrics Relating to Prediction Monotonicity of a Model . Metrics Relating to Prediction Consistency . MATLAB(R) Source Code . Supplementary Analyses INDEX

Higher-order sliding modes, differentiation and output-feedback control

Abstract: Being a motion on a discontinuity set of a dynamic system, sliding mode is used to keep accurately a given constraint and features theoretically-infinite-frequency switching. Standard sliding modes provide for finite-time convergence, precise keeping of the constraint and robustness with respect to internal and external disturbances. Yet the relative degree of the constraint has to be 1 and a dangerous chattering effect is possible. Higher-order sliding modes preserve or generalize the main properties of the standard sliding mode and remove the above restrictions. r-Sliding mode realization provides for up to the rth order of sliding precision with respect to the sampling interval compared with the first order of the standard sliding mode. Such controllers require higher-order real-time derivatives of the outputs to be available. The lacking information is achieved by means of proposed arbitrary-order robust exact differentiators with finite-time convergence. These differentiators feature optimal asymptot...

Mean squared error: Love it or leave it? A new look at Signal Fidelity Measures

Abstract: In this article, we have reviewed the reasons why we (collectively) want to love or leave the venerable (but perhaps hoary) MSE. We have also reviewed emerging alternative signal fidelity measures and discussed their potential application to a wide variety of problems. The message we are trying to send here is not that one should abandon use of the MSE nor to blindly switch to any other particular signal fidelity measure. Rather, we hope to make the point that there are powerful, easy-to-use, and easy-to-understand alternatives that might be deployed depending on the application environment and needs. While we expect (and indeed, hope) that the MSE will continue to be widely used as a signal fidelity measure, it is our greater desire to see more advanced signal fidelity measures being used, especially in applications where perceptual criteria might be relevant. Ideally, the performance of a new signal processing algorithm might be compared to other algorithms using several fidelity criteria. Lastly, we hope that we have given further motivation to the community to consider recent advanced signal fidelity measures as design criteria for optimizing signal processing algorithms and systems. It is in this direction that we believe that the greatest benefit eventually lies.

Robot vision

Abstract: A scheme is developed for classifying the types of motion perceived by a humanlike robot. It is assumed that the robot receives visual images of the scene using a perspective system model. Equations, theorems, concepts, clues, etc., relating the objects, their positions, and their motion to their images on the focal plane are presented. >