Rapid developments in display technologies, digital printing, imaging sensors, image processing and image transmission are providing new possibilities for creating and conveying visual content. In an age in which images and video are ubiquitous and where mobile, satellite, and three-dimensional (3-D) imaging have become ordinary experiences, quantification of the performance of modern imaging systems requires appropriate approaches. At the end of the imaging chain, a human observer must decide whether images and video are of a satisfactory visual quality. Hence the measurement and modeling of perceived image quality is of crucial importance, not only in visual arts and commercial applications but also in scientific and entertainment environments. Advances in our understanding of the human visual system offer new possibilities for creating visually superior imaging systems and promise more accurate modeling of image quality. As a result, there is a profusion of new research on imaging performance and perceived quality

Larabi, M.C.

Triantaphillidou, S.

Watson, A.B.

WestminsterResearch

    WestminsterResearch http://www.westminster.ac.uk/research/westminsterresearch   Special Section Guest Editorial: Image/Video Quality and System Performance  Mohamed-Chaker Larabi Sophie Triantaphillidou Andrew B. Watson     This is a copy of the final published version of an article published in Journal of Electronic Imaging, Volume 23 (6) (2014), pp. 061101-1 - 061101-2.  © 2014 by the authors, SPIE and IS&T.  This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.  The published version is available at: http://dx.doi.org/10.17645/mac.v3i2.207     The WestminsterResearch online digital archive at the University of Westminster aims to make the research output of the University available to a wider audience.  Copyright and Moral Rights remain with the authors and/or copyright owners.     Whilst further distribution of specific materials from within this archive is forbidden, you may freely distribute the URL of WestminsterResearch: (http://westminsterresearch.wmin.ac.uk/).  In case of abuse or copyright appearing without permission e-mail repository@westminster.ac.uk Image/Video Quality and SystemPerformanceMohamed-Chaker LarabiSophie TriantaphillidouAndrew B. WatsonDownloaded From: http://electronicimaging.spiedigitallibrary.org/ on 01/08/2015 Terms of Use: http://spiedl.org/termsImage/Video Quality and System PerformanceMohamed-Chaker LarabiUniversité de PoitiersXLIM Signal Image and Communication DepartmentBvd. Marie Et Pierre CurieBP 30179, 86962 FranceE-mail: chaker.larabi@univ-poitiers.frSophie TriantaphillidouUniversity of WestminsterFaculty of Media, Arts and DesignWatford Road, HarrowHA1 3TP, United KingdomE-mail: triants@westminster.ac.ukAndrew B. WatsonNASA Ames Research CenterMS 262-2Moffett Field, California 94035-1000, United StatesE-mail: andrew.b.watson@nasa.govRapid developments in display technologies, digital printing,imaging sensors, image processing and image transmissionare providing new possibilities for creating and conveying vis-ual content. In an age in which images and video are ubiqui-tous and where mobile, satellite, and three-dimensional (3-D)imaging have become ordinary experiences, quantification ofthe performance of modern imaging systems requires appro-priate approaches. At the end of the imaging chain, a humanobserver must decide whether images and video are of a sat-isfactory visual quality. Hence the measurement and model-ing of perceived image quality is of crucial importance, notonly in visual arts and commercial applications but also in sci-entific and entertainment environments. Advances in ourunderstanding of the human visual system offer new possibil-ities for creating visually superior imaging systems and prom-ise more accurate modeling of image quality. As a result, thereis a profusion of new research on imaging performance andperceived quality.During the last decade important research efforts havebeen put to understand and model human visual attention.This yielded several computational saliency models that tryto find the most attractive objects based on image/videocharacteristics. Most existing models are low-level feature-oriented (bottom-up) approaches; only a few are or task-oriented (top-down). The interest in such models is due tothe potential optimization that can be obtained when thesalient areas are known. This likely helps preserve the qualityof some of the scene objects when applying processinglike compression, watermarking, transmission, and so on.Moreover, the performance of image processing algorithmsand the quality of experience linked to them, are fundamen-tally associated with the salient information. Impairments fall-ing in the salient areas will have a disproportionate impact onthe quality.Quality assessment has been a challenge in the last de-cade and many issues are still open in this field. An impres-sive number of full reference metrics dedicated to imageshave been developed. Many of them are well correlated tohuman judgment in the framework of multimedia applications.However, only a few metrics have attempted blind (no refer-ence) or semi-blind (reduced reference) image qualityassessment. First, because these type of metrics are highlydependent upon the impairment type. Second, it is always dif-ficult to select side information that is both reduced and effi-cient in representing the original image. These problemsincrease when dealing with video content, where the temporalvariation of both content and quality makes the scope verydifferent from the image one. Furthermore, with the advent ofnew technologies like 3-D or multiview, quality is facing newchallenges since the involvement of the visual perception isincreased. Moreover, depth is not only an additional dimen-sion but is also a feature changing the full interpretation of ascene. Therefore, the research community has to improve itsunderstanding of the binocular vision mechanisms such asthe binocular rivalry, suppression and fusion, in order to beable to predict the perceptual impact of the various impairments.High dynamic range (HDR) is expected to be the nextstage of multimedia imaging. It allows avoidance of the prob-lems caused by tone mapping operators and other grayscaleprocessing. However, as a new technology, little is knownabout how to assess the quality of HDR images and video.An important research effort is now under way to understandHDR and to develop tools and quality metrics that fulfill thechallenges of the quality of experience.This special section presents some of the recent advancesin image and video quality assessment and system perfor-mance with applications to multimedia, consumer camera,image and video coding, and other related topics. The papersof this special section can be grouped into four categories,according to the addressed subject.The first category addresses image and video quality met-rics. First, a psychometric study evaluates a number of no-reference image quality metrics, based on natural scene sta-tistics, which were previously shown to predict successfullythe subjective quality of digital image processing algorithms.The best performing metrics, BIQI and NIQE, are shown toperform equally well on two tests with four printed imagesand different graded papers, while NIQE is also robust toscene content variations. In the second study concernedwith the measurement of image quality, a no-referenceimage quality metric uses image features derived from theimage’s contourlet transform to obtain structural imageJournal of Electronic Imaging 061101-1 Nov∕Dec 2014 • Vol. 23(6)Special Section Guest EditorialDownloaded From: http://electronicimaging.spiedigitallibrary.org/ on 01/08/2015 Terms of Use: http://spiedl.org/termsinformation and a singular-value decomposition is proposed.The advantage of the metric is that it does not require trainingor learning and is shown to deliver predictions that correlatewell with human observations. Finally, multimodal qualityassessment is very important since it corresponds to thereal-life experience with visual content. Despite the relevanceof this field, few approaches have been proposed in the liter-ature. One contribution of this special section addresses thisproblem by running psychophysical experiments to clarify theinteraction between audio and video. Based on their subjec-tive findings, authors propose objective metrics combiningaudio and video quality in various ways.Three papers in this issue consider visual saliency andattention. In the first, the problem of saliency detection isapproached by selecting image features from multipleimage views with different contributions. A multimanifold rank-ing algorithm determining final saliency is presented andtested using qualitative and quantitative comparisons and dif-ferent image databases. In the second, a number of full-refer-ence video quality metrics were assessed with and without theincorporation of visual saliency models. It is shown that, over-all, computational models of attention benefit all selected met-rics, but predominantly those designed to predict spatialdegradations. Finally, authors of the third paper exploredtwo different visual tasks related to quality, i.e. quality estima-tion and difference estimation. Eye-tracking results showed adifferent strategy for each of the tasks. Visual characteristics(e.g. fixations) are different in position, duration, and role,leading to the conclusion that instructions may might havea noticeable influence on the strategy used.Image and video coding is the focus of another set ofpapers. In the first, authors propose an optimized parallelimplementation of the DCT transform using OpenCL (opencomputing language). The results show interesting speed-upfactors in heterogeneous environments. Authors of the sec-ond paper propose a Wyner-Ziv video coding scheme withlow bit-rate fluctuations based on a symmetric coding structure.The bit-rate stability is seen as a great advantage for manyapplications with constrained communication bandwidth.Recently, a joint effort between ITU and ISO allowed the devel-opment of a new video coding standard called HEVC (high effi-ciency video coding) based on a quad-tree structure to providevariable transform sizes in the transform coding process. Thethird paper proposes a similarity-check scheme to efficientlyreduce the transform unit (TU) candidate modes. The proposedoptimization allowed an important saving of the TU encodingtime for almost invisible impairments. Finally, the effect of cod-ing and transmission is evaluated on the performance of astate-of-the-art pedestrian detection algorithm. “Quality aware”spatial image statistics are used to blindly categorize distortedvideo frames by distortion type and level in a blind way.In a paper concerned with feature subsets that predictimage quality of consumer cameras, the authors have usedthe new CID2013 large database with consumer camera pho-tographs, to classify images using principal component analy-sis. Images were classified in terms of sharpness and noiseenergy, with the sharpness dimension including lightness, res-olution and contrast. A feature subset model is proposed thatsuccessfully predicts human observations. The second paperproposes a benchmark to solve the problem of how to combinequality and speed metrics for mobile phone camera evaluation.Vergence-accommodation conflict has been studied for 3-D inorder to understand the accumulation of visual fatigue. A paperin this special issue has been dedicated to investigate this con-flict for holographic stereograms. It showed that improved full-parallax holographic stereogram can control the focusingdepths of points and guarantee consistency between the ver-gence and accommodation distances.Several people deserve to be acknowledged for the suc-cess of this special section. We would like to thank authors forsubmitting their high-quality papers, and reviewers for dedi-cating their time and expertise to selecting the best papersfor publication. Special thanks go to Editor-in-Chief Dr.Gaurav Sharma and the editorial staff for their full supportthroughout the process of this special section.Mohamed-Chaker Larabi received his PhD from the University ofPoitiers (2002). He is currently the associate professor in charge ofthe perception, color, and quality activity at the same university.His actual scientific interests deal with image and video coding andoptimization, 2-D and 3-D image and video quality assessment,and user experience. He published over 100 papers in computervision, image quality, and human perception. He acted as chair/co-chair of the program committee of several conferences and guest edi-tor for special issues. He is a member of MPEG and JPEG committee(since 2000), and chair of the Advanced Image Coding Group and theTest and Quality Subgroup. He serves as a member of divisions 1 and8 of CIE, is a member of IS&T, and a senior member of IEEE.Sophie Triantaphillidou is an associate professor in imaging scienceand the director of the Imaging Technology Research Group of theUniversity of Westminster, UK. She received her PhD from theUniversity of Westminster in imaging science in 2002. She has pub-lished over 40 papers relating to imaging system performance, imagequality, and human vision and is the co-editor and a main contributorof the 10th edition of Manual of Photography, published by FocalPress in 2010. She has been the co-chair of the SPIE/IS&TElectronic Imaging: Image Quality and System Performanceconference since 2012 and has been involved in several nationaland international program committees relating to imaging. She wasthe recipient of the Davis Medal of the Royal Photographic Societyin 2012, awarded for her contributions to digital imaging science.Andrew B. Watson is the Senior Scientist for Vision Research atNASA Ames Research Center in California. He was an undergradu-ate at Columbia University, received his PhD in psychology from theUniversity of Pennsylvania, and did postdoctoral work at the Univer-sity of Cambridge in England. He is the author of over 100 papers andseven patents on topics in vision science and imaging technology. In2001, he founded the Journal of Vision (http://journalofvision.org),where he served as editor-in-chief. He is a fellow of the Optical Soci-ety of America, of the Association for Research in Vision and Ophthal-mology, and of the Society for Information Display. He is vice chair forvision science and human factors of the International Committee onDisplay Measurement.Journal of Electronic Imaging 061101-2 Nov∕Dec 2014 • Vol. 23(6)Special Section Guest EditorialDownloaded From: http://electronicimaging.spiedigitallibrary.org/ on 01/08/2015 Terms of Use: http://spiedl.org/terms

Special Section Guest Editorial: Image/Video Quality and System Performance

Larabi, Mohamed-Chaker

Triantaphillidou, Sophie

Watson, Andrew B.

Archive Ouverte en Sciences de l'Information et de la Communication

Image/Video Quality and System Performance: Guest Editorial

Mohamed-Chaker Larabi

Sophie Triantaphillidou

Andrew B. Watson

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Journal of Electronic Imaging

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Special Section Guest Editorial: Image/Video Quality and System Performance

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