An emerging area of database system research is to investigate techniques that ensure a continuous display of video objects. As compared to the traditional data types, e.g., text, a video object must be retrieved at a prespecified rate. If it is retrieved at a lower rate then its display may suffer from frequent disruptions and delays, termed hiccups. This paper describes two alternative approaches to representing video objects (stream-based and structured) and the issues involved in supporting their hiccup-free display. For each approach, we describe the existing solutions and the future research directions from a database systems perspective. I want to thank Martha Escobar-Molano, Seon Ho Kim, Cyrus Shahabi, and Roger Zimmermann for contributing to the presented material. This paper is to appear as a book chapter in Multimedia Database Systems: Issues and Research Directions, Editors: S. Jajodia and V.S. Subrahmanian, Springer Verlag, 1995. This research was supported in part by th...

Most multimedia servers reported in the literature are designed to serve multiple and independent video/audio streams. We think that, in future, multimedia servers will also serve complete presentations. Multimedia presentations provide unique opportunities to develop algorithms for buffer management and admission control, as execution-time consumption requirements of presentations are known a priori. In this paper, we examine presentations in three different domains (heavyweight, middleweight, and lightweight) and provide buffer management and admission control algorithms for the three domains. We propose two improvements (flattening and dynamic-adjustments) on the schedules created for the heavyweight presentations. Results from a simulation environment are presented. Keywords: Multimedia presentations, buffer management,admission control, flattening. 1.

With the structured approach to representing video clips, a presentation consists of a collection of background objects and actors (3-D representations) constrained using spatial and temporal constructs along with rendering features (e.g., shading, audiences' view point). While the spatial constraints define the position of displayed objects on the screen, the temporal constraints describe when the objects are rendered. As compared with an alternative approach (termed stream-based) that conceptualizes a video clip as a sequence of frames, the structured approach provides for both re-usability of objects in other presentations and effective query processing techniques for retrieval of relevant data. The display of a structured presentation is termed coordinated when the display of objects respects the pre-specified temporal and spatial constraints. Otherwise, the display might suffer from failures that translate into meaningless scenarios. For example, a chase scene between a dinosaur a...

A multimedia presentation can be represented as a collection of objects with temporal constraints that define when the objects are rendered. The display of a presentation is termed coordinated when the display of its objects respects the pre-specified temporal constraints. Otherwise, the display might suffer from failures that translate into meaningless scenarios. For example, a chase scene between a dinosaur and a jeep becomes meaningless if the system fails to render the dinosaur when displaying the scene. A previous study [EMGI96] introduced a resource scheduling technique that guarantees a coordinated display of a presentation for single-disk architectures. This technique minimizes both latency and memory requirements and has a worst case time complexity O(n lg n). This paper extends the previous study to multi-disk architectures and demonstrates the following: (1) the computation of a resource schedule that supports a coordinated display and yields the minimum latency is NP-Hard, ...

With the structured approach to representing video clips, a presentation consists of a collection of background objects and actors (3-D representations) constrained using spatial and temporal constructs along with rendering features (e.g., shading, audiences' view point). While the spatial constraints define the position of displayed objects on the screen, the temporal constraints describe when the objects are rendered. As compared with an alternative approach (termed stream-based) that conceptualizes a video clip as a sequence of frames, the structured approach provides for both re-usability of objects in other presentations and effective query processing techniques for retrieval of relevant data. The display of a structured presentation is termed coordinated when the display of its objects respects its pre-specified temporal and spatial constraints. Otherwise, the display might suffer from failures that translate into meaningless scenarios. For example, a chase scene between a dinosa...

Abstract not found

Multimedy applications arecharacterized bytheir strong timing requirementsand constraintsand thusmultimedy dul storage is a critical issue in the overall system's performanceand functionality. This paperdpery)%% multimedfi dul representationmodre that e#ectivelyguid dec placementtoward the improvement of the Qualityof Presentation for the considxyw multimedw applications. The performance of both constructive iterative improvement placement algorithms isevaluated and dduated Emphasis is given on placement schemes which arebased on the simulatedannealing optimization algorithm. A placement policy,based on a self-improving version of thesimulated annealing (SISA) algorithm isapplied and evaluated Performance of the placement policies is experimentallyevaluated on asimulated tertiarystorage subsystem. As proven bythe experimentation, the proposed approach shows considI5:yw gain in terms of seekand service times. The improvements of theproposed SISA approach are in the range of 40% whencompared torand5 placementand at the range of 15--35% whencompared to the typicalsimulated annealing algorithm,dgorithm a lot on the initial configurationand theneighborhood search.

Video applications are characterized by their increased requirements for hug storag spaces andtiming synchronization. Video data storag is a critical issue due to the so-called I/O bottleneck problem in relation to the quality of service while accessing video applications. The main contribution of the paper is that it considers video data dependencies, access frequencies andtiming constraints in order to introduce a video data representation model whichg ides the storag policies. Two video data representation levels are considered to capture the frequencies of accesses at external (video objects) and internal (video clips) levels. A simulation model has been developed in order to evaluate the placement strateg2C-- Video data placement is performed on a tertiary storag subsystem by both constructive and iterative improvement policies. Iterative improvement placement has been proven to outperform the other video data placement approaches.

Navigat1/ has added intx'&M1q it in nowadaysmult imedia applicatpli whichsupport e#ectxx accessingt oobject s of various format and presen tesen requir ement1 Stnt1 issues needt be reconsidered for tr new tw1 ofnavigatq)/` mult(&/x` applic in order t improvesyst m's performance. This paper addresses t1 problem ofmultM& dia dat st))D t))D improving da access ibilit and request servicing undernavigat ional applicatplic Anavigat)x' l graph-based model (forto mult imedia da t representes1M ) is proposedt guideti dat placement under a hierarchicalstl1fi/ tl1fi/` . The multul - iadat dependencies, access frequencies andt)M'D const aint are usedt charact&1q) tr graph nodes which correspondt mult(` dia obj ect allocato at t to iary sty1 ge level. Based oncertfifi defined popularit critri a,dat areelevat ed and placed on secondary leveltvel1fi improvingbot tt request servicing and dat accessibilit y. The proposedmult imediadat elevat ion is aprefet1 ing approach sinceit is performed "apriori"(not on demand) based on previously extusly1 user accesspats rns. Appropriat dat placement policies are also employedat t secondary level, and a simulat(D model has been developed based on current commercialtommer y and secondaryston ge devices. This model is usedt evaluat et/ proposed popularit based da televat'1 approach as employed under a hierarchical stcal1 subsyst em. Experimenti ion is performed underartr1)`M dat workloads andit is showntow to proposed hierarchical da t placement approach considerably improves dat accessing and request servicing in navigati nal mult/) dia applic atlic1 Theit1)'DM( improvement placement is provent out erform earlier relati mult imediadat placement policieswit respect t commonly used performancemet ics.

Advances in computer graphics, authoring tools and the explosive growth of the Internet has increased the use of multimedia presentations. This article presents a new retrieval scheduling technique to support the display of multimedia presentations in a multi-user environment. A multimedia presentation consists of a collection of objects with temporal constraints that define when the objects are rendered. A scheduling algorithm must determine when objects are retrieved from disk to satisfy the temporal constraints of the presentation. The time elapsed between the arrival of a request and the onset of its display (latency) depends upon the resources (CPU, disk, and memory) available to the system. The resources available depend upon those consumed by other presentations already being displayed. Therefore, the latency must be computed when the new request for a presentation arrives and that latency must include its computation time. Prior scheduling techniques applicable to arbitrary resource requirements have quadratic time complexity. Unlike prior work, our scheduling algorithm has linear time complexity. We compare the performance of our scheduling technique with one that exhaustively searches for the earliest time to schedule a presentation. Our simulation results show that our technique significantly reduces the latency of a presentation as compared with the exhaustive search. 1