Understanding user experience of mobile video: Framework, measurement, and optimization

Since users have become the focus of product/service design in last decade, the term User eXperience (UX) has been frequently used in the field of Human-Computer-Interaction (HCI). Research on UX facilitates a better understanding of the various aspects of the user’s interaction with the product or service. Mobile video, as a new and promising service and research field, has attracted great attention. Due to the significance of UX in the success of mobile video (Jordan, 2002), many researchers have centered on this area, examining users’ expectations, motivations, requirements, and usage context. As a result, many influencing factors have been explored (Buchinger, Kriglstein, Brandt & Hlavacs, 2011; Buchinger, Kriglstein & Hlavacs, 2009). However, a general framework for specific mobile video service is lacking for structuring such a great number of factors. To measure user experience of multimedia services such as mobile video, quality of experience (QoE) has recently become a prominent concept. In contrast to the traditionally used concept quality of service (QoS), QoE not only involves objectively measuring the delivered service but also takes into account user’s needs and desires when using the service, emphasizing the user’s overall acceptability on the service. Many QoE metrics are able to estimate the user perceived quality or acceptability of mobile video, but may be not enough accurate for the overall UX prediction due to the complexity of UX. Only a few frameworks of QoE have addressed more aspects of UX for mobile multimedia applications but need be transformed into practical measures. The challenge of optimizing UX remains adaptations to the resource constrains (e.g., network conditions, mobile device capabilities, and heterogeneous usage contexts) as well as meeting complicated user requirements (e.g., usage purposes and personal preferences). In this chapter, we investigate the existing important UX frameworks, compare their similarities and discuss some important features that fit in the mobile video service. Based on the previous research, we propose a simple UX framework for mobile video application by mapping a variety of influencing factors of UX upon a typical mobile video delivery system. Each component and its factors are explored with comprehensive literature reviews. The proposed framework may benefit in user-centred design of mobile video through taking a complete consideration of UX influences and in improvement of mobile videoservice quality by adjusting the values of certain factors to produce a positive user experience. It may also facilitate relative research in the way of locating important issues to study, clarifying research scopes, and setting up proper study procedures. We then review a great deal of research on UX measurement, including QoE metrics and QoE frameworks of mobile multimedia. Finally, we discuss how to achieve an optimal quality of user experience by focusing on the issues of various aspects of UX of mobile video. In the conclusion, we suggest some open issues for future study

A real-time content adaptation framework for exploiting ROI scalability in H.264/AVC

In many application scenarios, the use of Regions of Interest (ROIs) within video sequences is a useful concept. It is shown in this paper how Flexible Macroblock Ordering (FMO), defined in H.264/AVC as an error resilience tool, can be used for the coding arbitrary-shaped ROIs. In order to exploit the coding of ROIs in an H.264/AVC bitstream, a description-driven content adaptation framework is introduced that is able to extract the ROIs of a given bitstream. The results of a series of tests indicate that the ROI extraction process significantly reduces the bit rate of the bitstreams and increases the decoding speed. In case of a fixed camera and a static background, the impact of this reduction on the visual quality of the video sequence is negligible. Regarding the adaptation framework itself, it is shown that in all cases, the framework operates in real time and that it is suited for streaming scenarios by design

Analysis and Comparison of Modern Video Compression Standards for Random-access Light-field Compression

Light-field (LF) 3D displays are anticipated to be the next-generation 3D displays by providing smooth motion parallax, wide field of view (FOV), and higher depth range than the current autostereoscopic displays. The projection-based multi-view LF 3D displays bring the desired new functionalities through a set of projection engines creating light sources for the continuous light field to be created. Such displays require a high number of perspective views as an input to fully exploit the visualization capabilities and viewing angle provided by the LF technology. Delivering, processing and de/compressing this amount of views pose big technical challenges. However, when processing light fields in a distributed system, access patterns in ray space are quite regular, some processing nodes do not need all views, moreover the necessary views are used only partially. This trait could be exploited by partial decoding of pictures to help providing less complex and thus real-time operation. However, none of the recent video coding standards (e.g., Advanced Video Coding (AVC)/H.264 and High Efficiency Video Coding (HEVC)/H.265 standards) provides partial decoding of video pictures. Such feature can be achieved by partitioning video pictures into partitions that can be processed independently at the cost of lowering the compression efficiency. Examples of such partitioning features introduced by the modern video coding standards include slices and tiles, which enable random access into the video bitstreams with a specific granularity. In addition, some extra requirements have to be imposed on the standard partitioning tools in order to be applicable in the context of partial decoding. This leads to partitions called self-contained which refers to isolated or independently decodable regions in the video pictures. This work studies the problem of creating self-contained partitions in the conventional AVC/H.264 and HEVC/H.265 standards, and HEVC 3D extensions including multi-view (i.e., MV-HEVC) and 3D (i.e., 3D-HEVC) extensions using slices and tiles, respectively. The requirements that need to be fulfilled in order to build self-contained partitions are described, and an encoder-side solution is proposed. Further, the work examines how slicing/tiling can be used to facilitate random access into the video bitstreams, how the number of slices/tiles affects the compression ratio considering different prediction structures, and how much effect partial decoding has on decoding time. Overall, the experimental results indicate that the finer the partitioning is, the higher the compression loss occurs. The usage of self-contained partitions makes the decoding operation very efficient and less complex

Description-driven Adaptation of Media Resources

The current multimedia landscape is characterized by a significant diversity in terms of available media formats, network technologies, and device properties. This heterogeneity has resulted in a number of new challenges, such as providing universal access to multimedia content. A solution for this diversity is the use of scalable bit streams, as well as the deployment of a complementary system that is capable of adapting scalable bit streams to the constraints imposed by a particular usage environment (e.g., the limited screen resolution of a mobile device). This dissertation investigates the use of an XML-driven (Extensible Markup Language) framework for the format-independent adaptation of scalable bit streams. Using this approach, the structure of a bit stream is first translated into an XML description. In a next step, the resulting XML description is transformed to reflect a desired adaptation of the bit stream. Finally, the transformed XML description is used to create an adapted bit stream that is suited for playback in the targeted usage environment. The main contribution of this dissertation is BFlavor, a new tool for exposing the syntax of binary media resources as an XML description. Its development was inspired by two other technologies, i.e. MPEG-21 BSDL (Bitstream Syntax Description Language) and XFlavor (Formal Language for Audio-Visual Object Representation, extended with XML features). Although created from a different point of view, both languages offer solutions for translating the syntax of a media resource into an XML representation for further processing. BFlavor (BSDL+XFlavor) harmonizes the two technologies by combining their strengths and eliminating their weaknesses. The expressive power and performance of a BFlavor-based content adaptation chain, compared to tool chains entirely based on either BSDL or XFlavor, were investigated by several experiments. One series of experiments targeted the exploitation of multi-layered temporal scalability in H.264/AVC, paying particular attention to the use of sub-sequences and hierarchical coding patterns, as well as to the use of metadata messages to communicate the bit stream structure to the adaptation logic. BFlavor was the only tool to offer an elegant and practical solution for XML-driven adaptation of H.264/AVC bit streams in the temporal domain

Ukufundisa ukufunda okubhaliwe ngesiZulu ulimi lwasekhaya ngohlelo lwe CAPS kubafundi bebanga le 10 ezikoleni ezimbili esiyingini saseMhlathuzana.

Master of Education in Education Studies. University of KwaZulu-Natal, Edgewood 2016.Aphansi amazinga okufunda okubhaliwe kubafundi baseNingizimu Afrika futhi kuseyinkinga engakasitholi isisombululo. Kuze kube yimanje awukho umbiko usuke wabika ubungcono kule nkinga, nakuba ikhona imizamo eyenziwayo ukulwa nale nkinga kodwa asikabi bikho isisombululo. Inhloso yalolu cwaningo ukubheka Ukufundisa ukufunda okubhaliwe ngesiZulu uLimi Lwasekhaya ngokohlelo lwe-CAPS kubafundi bebanga le-10. Ucwaningo luhlose ukuphendula imibuzongqangi emithathu elandelayo: (i) Othisha besiZulu ulimi lwasekhaya bebanga le-10 basezikoleni zaseMhlathuzana bakuqonda kanjani ukufundisa ukufunda okubhaliwe belandela uhlelo lwe-CAPS? (ii) Othisha besiZulu ulimi lwasekhaya bakufundisa kanjani ukufunda okubhaliwe ebangeni le-10 ezikoleni ezisesiyingini zaseMhlathuzana? (iii) Zizathu zini ezenza othisha besiZulu uLimi lwaseKhaya bafundise ukufunda okubhaliwe ngendlela abenza ngayo ebangeni le-10 lapho belandela uhlelo lwe-CAPS ezikoleni ezisesiyingini saseMhlathuzana? Ucwaningo lwenziwe elokishini lakwaNdengezi ePinetown, lapho isiZulu siwulimi olukhulunywa emphakathini, kanti nasezikoleni zamabanga aphezulu kusetshenziswa sona njengolimi lwasekhaya ekufundeni. Ucwaningo lwenziwe ezikoleni ezimbili ezisesiyingini saseMhlathuzana. Othisha ababeyingxenye yocwaningo babebane, isikole nesikole kwakuba othisha ababili. Ucwaningo lulucwaningo lobunjalo besimo (qualitative case study), ngaphansi kwe-interpretivist paradigm. Kusetshenziswe izingxoxo ezisakuhleleka (semi-structured interviews) nokubukela othisha befundisa (observations), njengezindlela zokuqoqa ulwazi locwaningo. Kusetshenziswe insizakuhlaziya i-schema theory (Bartlett, 1932) njengohlaka lwenjulalwazi kanye nohlaka lwemicabango ukuhlaziya ulwazi olutholakele. Kugqama izindikimba ezinhlanu olwazini olutholakalayo. Kukhona emayelana nolwazi ngesifundo sokufundisa okubhaliwe kothisha abafundisa isiZulu uLimi Lwasekhaya ngohlelo lwe-CAPS. Lapha kuvela ukuthi sengathi othisha badinga ukulekelelwa ngolwazi lwesifundo ikakhulukazi ukufunda okubhaliwe nokufundisa. Enye imayelana namasu okuzakhela izinsizakufundisa. Lapha kuvela ukuthi othisha bathembele ezincwadini ezifundwa ngabafundi zemibhalo efundwa ekilasini. Enye imayelana nezinselelo ezimayelana nokuqeqesheka kothisha ohlelweni lwe-CAPS. Othisha baveza ukuthi abaqeqeshekile ngokwanele ekulandeleni uhlelo lwe-CAPS ezifundweni abazifundisayo. Enye imayelana nobude besikhathi sokufundisa. Kutholakale ukuthi isikhathi sokufundisa ukufunda okubhaliwe asanele uthisha uze angakwazi ukuhlola abafundi esifundweni sokufunda okubhaliwe. Enye indikimba imayelana nokungasebenzi kwebhodi uma kufundwa isifundo sokufunda okubhaliwe. Lokhu akujwayelekile ukusebenzisa ibhodi uma ufundisa ukufunda okubhaliwe. Imiphumela yocwaningo ikhombisa ukuthi abakwenzayo othisha kunomthelela ongemuhle kubafundi abafundisayo ekufundiseni kwabo ukufunda okubhaliwe