Browsing by Author "Prabhakaran, B."
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Item CHIMP: A Framework for Multimedia Documents(1997) Candan, K. Selcuk; Prabhakaran, B.; Subrahmanian, V.S.; ISRA multimedia document consists of different types of media objects that are to be presented at different instants of time and for different durations. The media objects may be stored in computer systems connected by a network, thereby rendering the document distributed. The authors may wish to collaborate in a distributed manner to edit a multimedia document. Hence, an authoring system needs to identify a retrieval schedule that describes the time instants at which the objects have to be retrieved as well as the logical paths to be followed by the objects. In this paper, we consider a collaborative multimetia document authoring system with the above mentioned features. We propose a difference constraints based temporal specification for the multimedia document. This approach allows us to generate flexible schedules for retrieving objects over the computer network. This flexible retrieval schedule can handle variations in system parameters such as available network throughput and buffer resources.Item Collaborative Multimedia Documents: Authoring and Presentation(1998-10-15) Candan, K.S.; Prabhakaran, B.; Subrahmanian, V.S.Multimedia documents are composed of different data types such as video, audio, text and images. Authoring a multimedia document is a creative exercise. Unlike traditional computer supported collaborative work where documents are composed of static objects, multimedia documents have temporal, spatial and quality of service (QoS) requirements that must be supported by any collaborative multimedia platform. In this paper, we show that most requirements (including temporal, spatial, and QoS requirements) for collaborative multimedia systems can be expressed in terms of a highly-structured class of linear constraints called difference constraints that have been well-studied in the operations research literature. As a consequence, well known algorithms for solving difference constraints may be used as a starting point for creating multimedia documents. Based on our difference-constraint based characterization, we develop efficient, incremental algorithms for creating and modifying multimedia documents so as to satisfy the required temporal, spatial and QoS constraints. We further develop methods to identify inconsistent requirements, and show how such inconsistencies may be removed through constraint relaxation techniques. (Also cross-referenced as UMIACS-TR-96-9)Item Presentation Planning for Distributed Video Systems(1998-10-15) Hwang, Eenjun; Prabhakaran, B.; Subrahmanian, V.S.A distributed video-on-demand system is one where a collection of video data is located at dispersed sites across a computer network. In a single-site environment, a local video server retrieves video data from its local storage device (or devices). However, in the setting of a distributed VoD system, when a customer requests a movie from his/her local server, the server may need to interact with other servers located across the network. In this paper, we present three types of presentation plans, that a local server must construct in order to satisfy the customer's request. Informally speaking, a presentation plan is a detailed (temporally synchronized) sequence of steps that the host server must perform at given points in time. This involves obtaining committments from other video servers, obtaining committments from the network service provider, as well as making committments of local resources, within the limitations of available bandwidth, available buffer, and customer/client data consumption rates. The three types of plans described in this paper all work at different "levels of abstraction" in this planning process. Furthermore, we introduce two measures of how good a plan is: minimizing wait time for the customer, and minimizing a quantity called access bandwidth (which informally speaking, specifies how much network/disk bandwidth is used). We develop algorithms to compute optimal (w.r.t. the above measures) plans for all three types, and show experimentally that in all three cases, one of the three types of plans (called a hybrid presentation plan) systematically outperforms the other two. In addition to these new concepts, our framework has the advantage that many results that had previously been verified experimentally in the literature can now be conclusively proved mathematically. (Also cross-referenced as UMIACS-TR-96-91)Item Resource Lock Commit Protocol (RLCP) for Multimedia Object Retrieval(1998-10-15) Candan, K. Selcuk; Hwang, Eenjun; Prabhakaran, B.; Subrahmanian, V.S.Many multimedia presentation applications involve retrieval of objects from more than one collaborating server. Presentations of objects from different collaborating servers might be inter-dependent. For instance, we can consider distributed video servers where blocks of movies are distributed over a set of servers. Here, blocks of a movie from different video servers have to be retrieved and presented continuously without any gaps in the presentation. Such applications first need an estimate of the available network resources to each of the collaborating server in order to identify a schedule for retrieving the objects composing the presentation. A collaborating server can suggest modifications of the retrieval schedule depending on its load. These modifications can potentially affect the retrieval schedule for other collaborating applications. Hence, a sequence of negotiations have to be carried out with the collaborating servers in order to commit for a retrieval schedule of the objects composing the multimedia presentation. In this paper, we propose an application sub-layer protocol, Resource Lock Commit Protocol (RLCP), for handling the negotiation and commitment of the resources required for a collaborative multimedia presentation application. (Also cross-referenced as UMIACS-TR-97-08)Item Retrieval Schedules Based on Resource Availibility and Flexible Presentation Specifications(1998-10-15) Candan, K. Selcuk; Prabhakaran, B.; Subrahmanian, V. S.A distributed multimedia document presentation involves retrieval of objects from the document server(s) and their presentation at the client system. The presentation of the multimedia objects have to be carried out in accordance with the specification of temporal relationships among the objects. The retrieval of multimedia objects from the document server(s) is influenced by the factors such as: temporal specification of objects presentations, throughput offered by the network service provider, and the buffer resources on the client system. Flexibility in the temporal specification of the multimedia document can help in deriving an object retrieval schedule that can handle variations in the network throughput and buffer resources availability. In this paper, we develop techniques for deriving a flexible object retrieval schedule for a distributed multimedia document presentation. The schedule is based on flexible temporal specification of the multimedia document using the difference constraints approach. We show how the derived retrieval schedule can be validated and modified to ensure that it can work with the offered network throughput and the available buffer resources. (Also cross-referenced as UMIACS-TR-96-21)