W.A.C. Fernando

University of Surrey, Guildford, ENG, United Kingdom

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Publications (156)65.6 Total impact

  • IEEE ICCE; 01/2014
  • H. Malekmohamadi, W.A.C. Fernando, A.M. Kondoz
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    ABSTRACT: A new reduced reference objective quality metric for stereoscopic video is proposed that incorporates spatial neighbouring information from grey-level co-occurrence matrices and edge properties. Extracted colour and depth features are combined unequally to maximise the performance of the proposed metric. The performance of this metric is validated through a series of subjective tests and the average correlation 0.82 is achieved when colour to depth importance ratio is near 0.80.
    Electronics Letters 05/2013; 49(11):701-702. · 1.04 Impact Factor
  • Zhiru Shi, W.A.C. Fernando, A.M. Kondoz
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    ABSTRACT: The H.264/AVC coding standard has achieved significant coding gain by using flexible block sizes inter prediction. However, the complexity of inter-mode decision is extremely high. In this paper, a fast inter-mode decision algorithm is presented by exploiting residual homogeneity for both macroblock and sub-macroblock levels. In this algorithm, the residual homogeneity indicators calculated in three directions are used to identify the block's homogeneous characteristic. Normalized motion vector activity is also considered to improve the performance. The experimental results illustrate that the proposed algorithm achieves about 49% of computational complexity saving in terms of encoding time, while with negligible quality degradation, compared to H.264/AVC reference software JM.
    Acoustics, Speech and Signal Processing (ICASSP), 2013 IEEE International Conference on; 01/2013
  • Source
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    ABSTRACT: In this paper, the sensitivity of the HVS towards binocular disparity depth cue, which is the most important cue in modern stereoscopic 3D displays, is investigated under different ambient illumination conditions. The experimental results indicate that as ambient illumination increases the sensitivity of the HVS for depth details increases or the Just Noticeable Difference in Depth (JNDD) decreases. It is expected that the investigation results will have important use cases in designing D display setups and 3D content production.
    01/2012;
  • Source
    R.M.T.P. Rajakaruna, W.A.C. Fernando, J. Calic
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    ABSTRACT: Compressed-domain content analysis enables fast content-based video applications. However, conventional encoder implementation, limited to optimising data compression, does not necessarily result in content representative compressed features. In this paper, we present a novel method for video encoder optimisation that enhances reliability of content representation in the compressed video. We propose a configurable encoder model to jointly optimise bit-rate, distortion and content representation of the encoded video. In encoder optimisation for motion estimation, we analyse the behaviour of motion representation and compression efficiency over a range of content complexities. A mathematical model to control the extent of noise in selected motion vectors is presented. We demonstrate that the compressed domain motion information can be enhanced without incurring a rate-distortion overhead. The computational overheads are marginal and can be eliminated by exploiting the inherently parallel nature of the proposed optimisation model.
    Multimedia and Expo (ICME), 2012 IEEE International Conference on; 01/2012
  • Zhiru Shi, W.A.C. Fernando, A.M. Kondoz
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    ABSTRACT: The video coding standard H.264/AVC although possesses the advantage of higher coding efficiency compared to previous ones, it would result in a high computational complexity due to various block sizes motion estimation for multi-modes decision. In this paper, a hybrid inter-mode decision algorithm is presented, combining coded block pattern (CBP) with motion activity and Rate-Distortion (RD) cost. In this algorithm, CBP and CBP4×4, which indicate none-zero coefficient block, is used to determine candidate modes at macroblock level and sub-macroblock level. Further, the normalized motion activity is used to identify the homogeneity of the block and target the candidate modes set more accurate. An early termination is also made between macroblock level and sub-macroblock level by RD cost comparing. The experimental results show that the proposed algorithm achieves approximately 60% of computational complexity saving in terms of encoding time, while with negligible quality degradation, compared to the conventional method in H.264/AVC.
    Multimedia and Expo Workshops (ICMEW), 2012 IEEE International Conference on; 01/2012
  • Zhiru Shi, W.A.C. Fernando, A. Kondoz
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    ABSTRACT: The new video coding standard, H.264/AVC, has achieved significant compression gain by utilizing several advanced techniques. Motion estimation (ME) is one of the most important elements to reduce the motion residual. However it results in heavy computational burden. In this paper, a novel fast ME search algorithm, which exposits the correlation character between predicted and optimal motion vectors (MVs), is presented for H.264/AVC. According to motion vector prediction, search window is adaptively divided into several regions with calculation of its motion correlation probability. Specifically, it combines MVs' direction correlation and locality correlation. A novel Priority Region List, which indicates search process and selects the number of search points, is dynamically updated. The simulation results show that the proposed algorithm reduces 23% of motion estimation encoding time and 60% of average search points while maintaining the same RD performance compared with that of UMHexagonS algorithm, which is adopted in H.264 reference software.
    Computer Science and Automation Engineering (CSAE), 2012 IEEE International Conference on; 01/2012
  • Source
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    ABSTRACT: Interest in 3D video has surged in recent years. However, efforts to improve the quality of compression and transmission schemes are severely hampered by a lack of effective quality evaluation metrics. This is a particularly severe problem for researchers trying to improve the robustness of video transmission to packet loss. Subjective tests for evaluating error robustness present huge requirements in terms of time and resources. To solve this problem, this paper presents a quality metric for 3D video, and evaluates its effectiveness for the measurement of quality in the presence of packet loss. A key feature of the work is the use of depth planes to enable the metric to better model how the Human Visual System (HVS) perceives 3D video. The quality metric results are compared with subjective test results. The correlation between the proposed quality metric and the subjective test results is shown to be stronger than standard quality metrics, such as Video Quality Metric (VQM).
    Digital Signal Processing (DSP), 2011 17th International Conference on; 08/2011
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    ABSTRACT: This paper addresses the sensitivity of human vision to spatial depth variations in a 3-D video scene, seen on a stereoscopic display, based on an experimental derivation of a just noticeable depth difference (JNDD) model. The main target is to exploit the depth perception sensitivity of humans in suppressing the unnecessary spatial depth details, hence reducing the transmission overhead allocated to depth maps. Based on the JNDD model derived, depth map sequences are preprocessed to suppress the depth details that are not perceivable by the viewers and to minimize the rendering artefacts that arise due to optical noise, where the optical noise is triggered by the inaccuracies in the depth estimation process. Theoretical and experimental evidences are provided to illustrate that the proposed depth adaptive preprocessing filter does not alter the 3-D visual quality or the view synthesis quality for free-viewpoint video applications. Experimental results suggest that the bit rate for depth map coding can be reduced up to 78% for the depth maps captured with depth-range cameras and up to 24% for the depth maps estimated with computer vision algorithms, without affecting the 3-D visual quality or the arbitrary view synthesis quality.
    IEEE Journal of Selected Topics in Signal Processing 05/2011; · 3.30 Impact Factor
  • Source
    R. M. T. P. Rajakaruna, W. A. C. Fernando, J. Calic
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    ABSTRACT: The proliferation of video consumption, especially over mobile devices, has created a demand for efficient inter- active video applications and high-level video analysis. This is particularly significant in real-time applications and resource- limited scenarios. Pixel-domain video processing is often inef- ficient for many of these applications due to its complexity, whereas compressed domain processing offer fast but unreliable results. In order to achieve fast and effective video processing, this paper proposes a novel video encoding architecture that facilitate efficient compressed domain processing, while maintaining com- pliance with the mainstream coding standards. This is achieved by optimizing the accuracy of motion information embedded in the compressed video, in addition to compression efficiency. In a motion detection application, we demonstrate that the motion estimated by the proposed encoder can be directly used to extract object information, as opposed to conventionally coded video. The incurred rate distortion overheads can be weighed against the reduced processing required for video analysis targeting a wide spectrum of computer vision applications.
    01/2011;
  • D. Varuna S. X. De Silva, Erhan Ekmekcioglu, Warnakulasuriya Anil Chandana Fernando, Stewart T. Worrall
    J. Sel. Topics Signal Processing. 01/2011; 5:335-351.
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    ABSTRACT: Wyner-Ziv video coding presents a new paradigm which offers low-complexity video encoding. However, the Wyner-Ziv paradigm accumulates high complexity at the decoder side and this could involve difficulties for applications which have delay requisites. On the other hand, technological advances provide us with new hardware which supports parallel data processing. In this paper, a faster Wyner-Ziv video decoding scheme based on multicore processors is proposed. In this way, each frame is decoded by means of the collaboration between several processing units, achieving a time reduction up to 71% without significant rate-distortion drop penalty.
    IEEE 13th International Workshop on Multimedia Signal Processing (MMSP 2011), Hangzhou, China, October 17-19, 2011; 01/2011
  • R. M. T. P. Rajakaruna, W. A. C. Fernando, J. Calic
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    ABSTRACT: Performance of real-time video processing appli- cations such as surveillance systems, content-based search, is limited by the complexity of video content analysis in the pixel domain. A low complex alternative is to analyse the video in the compressed domain, where content features already available in the compressed video are directly used in the analysis. However, this is achieved at the expense of output precision and reliability, due to compression-efficiency driven feature selection at the encoder. Therefore, video applications could benefit from enhanced reliability of data embedded in the compressed video. In this paper, we present a scalable optimization model that addresses the accuracy of content features in parallel with the conventional rate-distortion optimization criterion. We analyse and optimize rate-distortion performance of video encoder under content description accuracy constrain, using a motion calibrated synthetic data set containing a range of scene and motion complexity levels. Finally, using a natural video data set, we demonstrate that the proposed optimization framework can be used to enhance compressed feature accuracy without incurring a rate-distortion overhead.
    01/2011;
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    ABSTRACT: Depth maps are used for rendering novel views in 3-Dimensional (3D) Television systems. When depth maps are compressed using existing codecs, the compression artifacts will cause undesirable distortions in the rendered views. This paper proposes an adaptive bilateral filtering technique to eliminate such artifacts at the receiver end. The experimental results demonstrate that the proposed method significantly improves the quality of rendered views up to 1.5dB, with minimal increase in complexity.
    01/2011;
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    ABSTRACT: While the depth maps of D video are represented as luminance images, they are used to aid rendering of novel views and are not viewed by an end user. Therefore, metrics that measure the quality of images that are for end user viewing does not necessarily reflect the quality of depth maps in terms of its ability to render views. This paper investigates the relationship between the quality of the rendered views and different quality measures of the depth map. A novel depth map quality metric is proposed based on a distortion model that approximates rendering errors due to pixel errors in the depth map. The proposed depth map quality metric correlates very well with the quality of the rendered views, as compared to the PSNR and SSIM of the depth map. The application of the proposed depth map quality metric is further illustrated by incorporating the metric at the encoding mode selection stage of a video encoder. Experimental results suggest that with the proposed encoding mode selection scheme bit rate savings of up to 30% can be achieved compared to traditional encoding mode selection scheme based on sum of squared errors.
    01/2011;
  • Zhiru Shi, W. A. C. Fernando, A. Kondoz
    [Show abstract] [Hide abstract]
    ABSTRACT: The new video coding standard, H.264/AVC, has achieved significant compression gain by utilizing several advanced techniques. Block-Matching Motion Estimation is one of the most important elements to reduce the motion residual. However, it results in heavy computational burden and limits the application for real-time video service. In this paper, a fast motion estimation algorithm called Simulated Annealing Adaptive Search (SAAS) is proposed to reduce the computational load. The basic idea of the proposed scheme is based on adjusting search pattern not only for each frame, but also for each block. Initially, the adaptive search pattern is performed by statistical analysis of previous frame's Motion Vector Correlation. Then the search pattern is adjusted for each block according to Predicted Motion Vector. According to motion vector correlation statistics information, search region is adaptively divided and Simulated Annealing (SA) mechanism is adopted to select search power for each region and to avoid trapping into local minima. Experimental results indicate that the proposed algorithm offers considerable improvement in computing time and motion search points at the same rate-distortion performance, compared to the conventional fast motion estimation algorithm. 1
    IEEE Transactions on Consumer Electronics 01/2011; 57(3):1354-1361. · 1.09 Impact Factor
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    ABSTRACT: Depth maps, which can be represented as greyscale images, are used to aid rendering of novel views in three-dimensional (3D) video systems. However, compressing them using existing video codecs, such as H.264/AVC, leads to low quality rendered views. Presented is a sharpening method based on adaptive bilateral filtering to eliminate certain artifacts observed in compressed depth maps to improve the quality of rendered views. Experimental results demonstrate that significant rendering quality improvements of up to 1.9 dB can be achieved with the proposed method.
    Electronics Letters 12/2010; · 1.04 Impact Factor
  • D.V.S.X. De Silva, W.A.C. Fernando, S.T. Worrall
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    ABSTRACT: A technique to minimize distortions in synthesized virtual views, while encoding depth maps that are used in Depth Image Based Rendering (DIBR) applications is proposed. Depth maps are not viewed by end users, but are used for virtual view generation. Therefore, it is important to compress depth maps in a way that it minimizes distortion in views rendered with them. In doing so, it would be possible to generate high quality virtual views using compressed depth maps. Firstly, an error model to approximate rendering distortion caused by disparity changes is proposed. Thereafter, this error model is used at the encoding mode selection stage of coding depth maps. Experimental results illustrate an average bit rate saving of 19%-76%, compared with the mode selection method, which is based on minimizing pixel errors only of the depth map. Further, encoding depth maps with the proposed technique improves the overall visual quality of rendered views.
    IEEE Transactions on Consumer Electronics 12/2010; · 1.09 Impact Factor
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    ABSTRACT: The ability to provide a realistic perception of depth is the core added functionality of modern 3D video display systems. At present, there is no standard method to assess the perception of depth in 3D video. Existence of such methods would immensely enhance the progression of 3D video research. This paper focuses on the depth perception assessment in color plus depth representation of 3D video. In this paper, we subjectively evaluate the depth perceived by the users on an auto stereoscopic display, and analyze its variation with the impairments introduced during the compression of the depth images. The variation of the subjective perception of depth is explained based on another evaluation that is carried out to identify the Just Noticeable Difference in Depth (JNDD) perceived by the subjects. The JNDD corresponds to the sensitivity of the observers to the changes in depth in a 3D video scene. Even though only the effects of compression artifacts are considered in this paper, the proposed assessment technique, based on the JNDD values can be used in any future depth perception assessment work.
    Image Processing (ICIP), 2010 17th IEEE International Conference on; 10/2010
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    ABSTRACT: The most distinguishing feature of 3D display systems, compared to their traditional 2D counterparts, is their ability to provide an additional perception of depth to its viewers. Thus, the mechanisms behind human depth perception play a significant role in 3D video systems. While there has been significant amounts of research carried out to understand human depth perception, in the areas of physiology and psychology, its applicability to 3D display systems is seldom spoken. Understanding the mechanisms of depth perception is of utmost importance to the development of 3D video technologies that are heavily based on exploitation of human perception. In this paper, it is explained with the aid of existing physiological and psychological models how humans perceive depth in 3D video displays. Based on these explanations a mathematical model is derived to explain the just noticeable difference in depth (JNDD) as perceived by a viewer, watching 3D video. The derived model is experimentally validated on an auto-stereoscopic display. This model is expected to be useful in both 3D content productions as well as in 3D content processing and compression.
    Multimedia and Expo (ICME), 2010 IEEE International Conference on; 08/2010

Publication Stats

641 Citations
65.60 Total Impact Points

Institutions

  • 2008–2011
    • University of Surrey
      • Centre for Communication Systems Research (CCSR)
      Guildford, ENG, United Kingdom
    • Florida Atlantic University
      • Department of Computer and Electrical Engineering and Computer Science
      Boca Raton, FL, United States
    • University of Castilla-La Mancha
      • Instituto de Investigación en Informática de Albacete
      Ciudad Real, Castille-La Mancha, Spain
  • 2004–2007
    • Brunel University
      • • School of Engineering and Design
      • • Department of Electronic and Computer Engineering
      London, ENG, United Kingdom
  • 1998–2006
    • Asian Institute of Technology
      • School of Engineering and Technology (SET)
      Krung Thep, Bangkok, Thailand
  • 2005
    • University of Hertfordshire
      • School of Computer Science
      Hatfield, ENG, United Kingdom
  • 2003
    • University of Saskatchewan
      • Department of Electrical and Computer Engineering
      Saskatoon, Saskatchewan, Canada
  • 1999–2001
    • University of Bristol
      • Department of Electrical and Electronic Engineering
      Bristol, ENG, United Kingdom