Integrating symbolic images into a multimedia database system using classification and abstraction approaches

Symbolic images are composed of a finite set of symbols that have a semantic meaning. Examples of symbolic images include maps (where the semantic meaning of the symbols is given in the legend), engineering drawings, and floor plans. Two approaches for supporting queries on symbolic-image databases that are based on image content are studied. The classification approach preprocesses all symbolic images and attaches a semantic classification and an associated certainty factor to each object that it finds in the image. The abstraction approach describes each object in the symbolic image by using a vector consisting of the values of some of its features (e.g., shape, genus, etc.). The approaches differ in the way in which responses to queries are computed. In the classification approach, images are retrieved on the basis of whether or not they contain objects that have the same classification as the objects in the query. On the other hand, in the abstraction approach, retrieval is on the basis of similarity of feature vector values of these objects. Methods of integrating these two approaches into a relational multimedia database management system so that symbolic images can be stored and retrieved based on their content are described. Schema definitions and indices that support query specifications involving spatial as well as contextual constraints are presented. Spatial constraints may be based on both locational information (e.g., distance) and relational information (e.g., north of). Different strategies for image retrieval for a number of typical queries using these approaches are described. Estimated costs are derived for these strategies. Results are reported of a comparative study of the two approaches in terms of image insertion time, storage space, retrieval accuracy, and retrieval time. Received June 12, 1998 / Accepted October 13, 1998     

A data model and a query languagefor multimedia documents databases

A multimedia application involves information that may be in a form of video, images, audio, text and graphics, need to be stored, retrieved and manipulated in large databases. In this paper, we propose an object-oriented database schema that supports multimedia documents and their temporal, spatial and logical structures. We present a document example and show how the schema can adress all the structures described. We also present a multimedia query specification language that can be used to describe a multimedia content portion to be retrieved from the database. The language provides means by which the user can specify the information on the media as well as the temoral and spatial relationships among these media.     

An algebra for creating and querying multimedia presentations

Over the last few years, there has been a tremendous increase in the number of interactive multimedia presentations prepared by different individuals and organizations. In this paper, we present an algebra for creating and querying interactive multimedia presentation databases. This algebra operates on trees whose branches reflect different possible playouts of a set of presentations. The algebra not only extends all the classical relational operators to such databases, but also introduces a variety of novel operators for combining multiple presentations. As our algebra supports merging parts or all of existing presentations, this algebra can also be used as an authoring tool for creating multimedia presentations. We prove a host of equivalence results for queries in this algebra, which may be used to build query optimizers for interactive presentation databases.     

Intelligent multimedia data: data + indices + inference

In this paper, we present a novel approach for multimedia data indexing and retrieval that is machine independent and highly flexible for sharing multimedia data across applications. Traditional multimedia data indexing and retrieval problems have been attacked using the central data server as the main focus, and most of the indexing and query-processing for retrieval are highly application dependent. This precludes the use of created indices and query processing mechanisms for multimedia data which, in general, have a wide variety of uses across applications. The approach proposed in this paper addresses three issues: 1. multimedia data indexing; 2. inference or query processing; and 3. combining indices and inference or query mechanism with the data to facilitate machine independence in retrieval and query processing. We emphasize the third issue, as typically multimedia data are huge in size and requires intra-data indexing. We describe how the proposed approach addresses various problems faced by the application developers in indexing and retrieval of multimedia data. Finally, we present two applications developed based on the proposed approach: video indexing; and video content authorization for presentation.     

Dynamic playout scheduling algorithms for continuous multimedia streams

In this paper, we investigate a playout scheduling framework for supporting the continuous and synchronized presentations of multimedia streams in a distributed multimedia presentation system. We assume a situation in which the server and network transmissions provide sufficient support for the delivery of media objects. In this context, major issues regarding the enforcement of the smooth presentation of multimedia streams at client sites must be addressed to deal with rate variance of stream presentations and delay variance of networks. We develop various playout-scheduling algorithms that are adaptable to quality-of-service parameters. The proposed algorithms permit the local adjustment of unsynchronized presentations by gradually accelerating or retarding presentation components, rather than abruptly skipping or pausing the presentation materials. A comprehensive experimental analysis of the proposed algorithms demonstrates that our algorithms can effectively avoid playout gaps (or hiccups) in the presentations. This scheduling framework can be readily used to support customized multimedia presentations.     

Adaptive multimedia synchronization in a teleconference system

In this paper, we present an adaptive buffering scheme for implementing intra-stream and inter-stream synchronization in real-time multimedia applications. The essence of the proposed scheme is to dynamically enforce equalized delays to incoming media streams, in order to piece-wise smooth the network delay variations and to synchronize the streams at the sink. An adaptive control mechanism based on an event-counting algorithm is employed to calibrate the PlayOut Clocks (POCs), which manages the presentations of multimedia data. The algorithm does not rely on globally synchronized clock and makes minimal assumption on underlying network delay distribution. Also, the user defined quality of service (QoS) specifications can be directly incorporated into the design parameters of the synchronization algorithm. The proposed synchronization scheme has been experimentally implemented in a teleconference system which consists of separately controllable audio, video, and data channels. The modular structure of the synchronization control provides the flexibility to maintain an arbitrary synchronization group in conjunction with a distributed conference management scheme. This paper also shows the experimental results of the test implementation and the suitability of the proposed scheme with respect to the multimedia traffic across an FDDI/Ethernet network.     

Delivering presentations from multimedia servers

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. Received June 9, 1998 / Accepted October 13, 1998     

Dynamic end-to-end QoS management middleware for distributed multimedia systems

In this paper, we present a separable, reusable middleware solution that provides coordinated, end-to-end QoS management over any type of service component, and can use existing (legacy) QoS management solutions (by using wrappers) in a distributed multimedia system. Our middleware solution incorporates strategic and tactical QoS managers, and supports protocols and messages between tactical managers and managed application components, and between QoS managers in the management hierarchy. Strategic QoS managers take a global view of QoS provided by a set of application components within the manager's policy domain. Tactical QoS managers provide local control over application components. We introduce the concept of QoS policy domains to scope the authority of a strategic QoS manager. We describe how the management hierarchy is dynamically configured and reconfigured based on runtime needs of the application.     

Presentations for databases in multimedia environments

The problem of presenting database query results has not been investigated sufficiently. This work proposes an approach to identify effective presentations for the results of database queries. This will be done by considering different kinds of information, such as user goals, the characteristics of the data to be presented, and the relationships among them. Our approach is based on the definition of composition operations which, on the basis of elementary presentation types, allow us to obtain designs of complex final presentations. Some effectiveness criteria are considered in order to identify those presentations which best match the user's goals and cognitive abilities. We consider multimedia environments at both the data and presentation level.     

The multimedia multicasting problem

This paper explores the problems associated with the multicasting of continuous media to support multimedia group applications. The interaction between multicasting and the delivery of multiple time-correlated continuous-media streams with real-time delay requirements poses various new and interesting problems in research on communication protocols and architectures. We describe these problems, and identify where the opportunities are for effective solutions, all in the context of providing an overview of the current state of research in multimedia multicasting. The issues we discuss include quality of service, resource reservations, routing, error and traffic control, heterogeneity, and the use of hierarchical coding and open-loop control techniques.     

Synchronized delivery and playout of distributed stored multimedia streams

Multimedia streams such as audio and video impose tight temporal constraints for their presentation. Often, related multimedia streams, such as audio and video, must be presented in a synchronized way. We introduce a novel scheme to ensure the continuous and synchronous delivery of distributed stored multimedia streams across a communications network. We propose a new protocol for synchronized playback and compute the buffer required to achieve both, the continuity within a single substream and the synchronization between related substreams. The scheme is very general and does not require synchronized clocks. Using a resynchronization protocol based on buffer level control, the scheme is able to cope with server drop-outs and clock drift. The synchronization scheme has been implemented and the paper concludes with our experimental results.     

MING-I: a distributed interactive multimedia document development mechanism

The next generation of interactive multimedia documents can contain both static media, e.g., text, graph, image, and continuous media, e.g., audio and video, and can provide user interactions in distributed environments. However, the temporal information of multimedia documents cannot be described using traditional document structures, e.g., Open Document Architecture (ODA) and Standard Generalized Mark-up Language (SGML); the continuous transmission of media units also raises some new synchronization problems, which have not been met before, for processing user interactions. Thus, developing a distributed interactive multimedia document system should resolve the issues of document model, presentation control architecture, and control scheme. In this paper, we (i) propose a new multimedia document model that contains the logical structure, the layout structure, and the temporal structure to formally describe multimedia documents, and (ii) point out main interaction-based synchronization problems, and propose a control architecture and a token-based control scheme to solve these interaction-based synchronization problems. Based on the proposed document model, control architecture, and control scheme, a distributed interactive multimedia document development mechanism, which is called MING-I, is developed on SUN workstations.     

Interactive authoring of multimedia documents in a constraint-based authoring system

As multimedia applications spread widely, it is crucial for programming and design support systems to handle “time” in multimedia documents effectively and flexibly. This paper presents a set of interactive system support tools for designing and maintaining the temporal behavior of multimedia documents. The tool set provides mechanisms for anomaly detection, temporal query processing, and interactive scheduling. It is based on a fast incremental constraint solver we have developed, which can be adapted by any constraint-based system. The incremental constraint solver provides immediate feedback to the user, supporting a highly interactive design process. Combined with existing optimal layout generation mechanisms proposed in the literature, our tools effectively utilize the flexibility provided by constraint-based systems.     

View management in multimedia databases

Abstract. Though there has been extensive work on multimedia databases in the last few years, there is no prevailing notion of a multimedia view, nor there are techniques to create, manage, and maintain such views. Visualizing the results of a dynamic multimedia query or materializing a dynamic multimedia view corresponds to assembling and delivering an interactive multimedia presentation in accordance with the visualization specifications. In this paper, we suggest that a non-interactive multimedia presentation is a set of virtual objects with associated spatial and temporal presentation constraints. A virtual object is either an object, or the result of a query. As queries may have different answers at different points in time, scheduling the presentation of such objects is nontrivial. We then develop a probabilistic model of interactive multimedia presentations, extending the non-interactive model described earlier. We also develop a probabilistic model of interactive visualization where the probabilities reflect the user profiles, or the likelihood of certain user interactions. Based on this probabilistic model, we develop three utility-theoretic based types of prefetching algorithms that anticipate how users will interact with the presentation. These prefetching algorithms allow efficient visualization of the query results in accordance with the underlying specification. We have built a prototype system that incorporates these algorithms. We report on the results of experiments conducted on top of this implementation. Received June 10, 1998 / Accepted November 10, 1999     

Checking the temporal integrity of interactive multimedia documents

Abstract. When authoring multimedia scenarios, and in particular scenarios with user interaction, where the sequence and time of occurrence of interactions is not predefined, it is difficult to guarantee the consistency of the resulting scenarios. As a consequence, the execution of the scenario may result in unexpected behavior or inconsistent use of media. The present paper proposes a methodology for checking the temporal integrity of interactive multimedia document (IMD) scenarios at authoring time at various levels. The IMD flow is mainly defined by the events occurring during the IMD session. Integrity checking consists of a set of discrete steps, during which we transform the scenario into temporal constraint networks representing the constraints linking the different possible events in the scenario. Temporal constraint verification techniques are applied to verify the integrity of the scenario, deriving a minimal network, showing possible temporal relationships between events given a set of constraints. Received June 9, 1998 / Accepted November 10, 1999     

Transformation and exchange of multimedia objects in distributed multimedia systems

One of the challenges in the design of a distributed multimedia system is devising suitable specification models for various schemas in different levels of the system. Another important research issue is the integration and synchronization of heterogeneous multimedia objects. In this paper, we present our models for multimedia schemas and transformation algorithms. They transform high-level multimedia objects into schemas that can be used to support the presentation and communication of the multimedia objects. A key module in the system is the Object Exchange Manager (OEM). In this paper, we present the design and implementation of the OEM module, and discuss in detail the interaction between the OEM and other modules in a distributed multimedia system.     

Embedding interactive sounds in multimedia applications

We describe a system for generating and controlling sound effects from within applications. We discuss performance demands and current technology constraints on sound synthesis methods, highlight several distinct interactive control strategies, and demonstrate a development environment for making a large database of heterogeneous sound models manageable by developers who are not sound synthesis experts.     

Scheduling and data layout policies for a near-line multimedia storage architecture

Recent advances in computer technologies have made it feasible to provide multimedia services, such as news distribution and entertainment, via high-bandwidth networks. The storage and retrieval of large multimedia objects (e.g., video) becomes a major design issue of the multimedia information system. While most other works on multimedia storage servers assume an on-line disk storage system, we consider a two-tier storage architecture with a robotic tape library as the vast near-line storage and an on-line disk system as the front-line storage. Magnetic tapes are cheaper, more robust, and have a larger capacity; hence, they are more cost effective for large scale storage systems (e.g., video-on-demand (VOD) systems may store tens of thousands of videos). We study in detail the design issues of the tape subsystem and propose some novel tape-scheduling algorithms which give faster response and require less disk buffer space. We also study the disk-striping policy and the data layout on the tape cartridge in order to fully utilize the throughput of the robotic tape system and to minimize the on-line disk storage space.     

Retrieval scheduling for collaborative multimedia presentations

The single-system approach is no longer sufficient to handle the load on popular Internet servers, especially for those offering extensive multimedia content. Such services have to be replicated to enhance their availability, performance, and reliability. In a highly replicated and available environment, server selection is an important issue. In this paper, we propose an application-layer broker (ALB) for this purpose. ALB employs a content-based, client-centric approach to negotiate with the servers and to identify the best server for the requested objects. ALB aims to maximize client buffer utilization in order to efficiently handle dynamic user interactions such as skip, reverse presentation, go back in time. We also present details of a collaborative multimedia presentation platform that we have developed based on ALB.     

Optimizing database architecture for the new bottleneck: memory access

In the past decade, advances in the speed of commodity CPUs have far out-paced advances in memory latency. Main-memory access is therefore increasingly a performance bottleneck for many computer applications, including database systems. In this article, we use a simple scan test to show the severe impact of this bottleneck. The insights gained are translated into guidelines for database architecture, in terms of both data structures and algorithms. We discuss how vertically fragmented data structures optimize cache performance on sequential data access. We then focus on equi-join, typically a random-access operation, and introduce radix algorithms for partitioned hash-join. The performance of these algorithms is quantified using a detailed analytical model that incorporates memory access cost. Experiments that validate this model were performed on the Monet database system. We obtained exact statistics on events such as TLB misses and L1 and L2 cache misses by using hardware performance counters found in modern CPUs. Using our cost model, we show how the carefully tuned memory access pattern of our radix algorithms makes them perform well, which is confirmed by experimental results. Received April 20, 2000 / Accepted June 23, 2000