| General note |
This is a book about advanced multimedia systems, what constitutes a distributed multimedia system, current and emerging technologies that support advanced multimedia systems, and how to design and implement a multimedia system. The technologies at the core of the computing revolution have reached a point where one can envision a distributed computing system composed of a number of elements strung together by various communications methodologies, all striving to serve the user in a semi-intelligent manner. The system understands and knows how to interpret and combine data elements of various types and present them to the user in the desired mode set by the user. Multimedia systems, especially distributed multimedia systems, present extraordinary design challenges. This book discusses the characteristics of multimedia systems, identifies these design challenges, and presents design approaches to address them in an efficient manner. Technologies discussed in this book include those required for distributed multimedia messaging. The way technical and business documents are compiled, written, distributed, and read has undergone a radical transformation to computer-based electronic hypermedia documents. Distributed computing networks link a variety of platforms with different operating systems and applications that must interact to allow storage and transmission of hypermedia documents. Hypermedia documents encapsulate storage, compression, and format conversion information to allow adapting documents for the specific user location and desktop environment. Desktop videoconferencing, video messaging, and hypermedia repositories require a combination of technologies including communications, decompression at high rates, high-resolution display systems, and storage and rapid dissemination of multidimensional objects consisting of text, image, voice, audio, and full-motion video components. With transmission bandwidths at a premium, techniques for the compression and decompression of data take on a very important and visible role. Compression techniques have been standardized for digitized objects like binary images, gray-scale images, color images, video images, audio, and full-motion video data. These compressed objects need to be stored, retrieved, and transmitted over LANs and WANs, and decompressed before being displayed. Lossy compression is used for compressing objects for which absolute data accuracy is not required. For example, when a video image is decompressed on a frame- by-frame basis at 30 frames/sec, the loss of one frame will not be perceived by a user. For higher-quality rendering, DSP chips may be used for performing such tasks as compression and decompression, vector quantization, and data pacing to provide higher-quality video. This book is intended to help you design a real-world multimedia solution for an enterprise. Businesses have networked systems that span facilities, cities, and nations, and have integrated applications running on these networks. There is a growing need to manage widely distributed data in a timely and effective manner. The following describes three important design issues for a well-designed distributed multimedia system: 1. The underlying data management system and how well it handles diverse and complex data types, high data volumes, fast and controlled transfer rates, data integrity under access from distributed users, and updates from distributed sour ces of data. 2. Specialized hardware and software for managing creation, retrieval, recomposition, and display of hypermedia documents and multimedia database records, and supporting a variety of storage, compression, and decompression standards. 3. An advanced user interface provided by a graphics workstation or PC with the capability of integrating text, graphics, pictures, sound, and video. These three components form an important group of topics for discussion in this book. As we said earlier, this book is about what constitutes distributed multimedia systems, and how to design and implement an advanced distributed multimedia system. Readers are assumed to be students of computer programming or to have a professional interest in information systems and multimedia applications, especially in the design of advanced multimedia systems. We expect that the readers will have some understanding of the C and C++ languages (although that is not really necessary for understanding the examples) and MS Windows programming (again, not necessary but beneficial). This book is divided into four major groupings of chapters that present relevant technologies—development methodologies, data modeling, and design—in a congruous manner. The progression in these chapter groups, especially Groups 1, 2, and 3, is important. These three groups are informative as well as tutorial in nature, especially when approached in sequence. At a more detailed level, the contents of the twelve chapters are as follows: Group 1 Introduction to Multimedia Systems: Group 1, comprising Chapter 1, concentrates on our definition of an advanced distributed multimedia system and an introduction of the prominent technologies and design features that contribute to a good multimedia system. Chapter 1 presents our basic definition of the various data elements and application sources associated with multimedia and the requirements of the universal multimedia application. We introduce the object types as well as specialized technologies used in multimedia systems. Th is chapter also introduces multimedia standards and compression and decompression technologies. Group 2 Key Technologies for Multimedia Systems Group 2, comprising Chapters 2, 3, 4, and 5, presents the key technologies consisting of input and output technologies, compression and decompression techniques, and storage technologies. In Chapter 2 we present a detailed discussion of compression and decompression techniques, including CCITT Group 3 and 4 as well as JPEG and MPEG (and quantization). A coded example shows how compression and decompression are performed. In Chapter 3 we present file and data formats such as the RTF, TIFF, RIFF, and AVI standards. Chapter 4 is a detailed discussion of techniques, standards, and key design issues for input and output technologies, including display systems, image scanners, digital voice and audio components, and full-motion video cameras. Chapter 5 provides a detailed analysis of the various storage technologies, including magnetic storage, RAID, CD-ROM, rewriteable optical media, and jukeboxes. Group 3 Architectural and Multimedia Application Design Issues Group 3, comprising Chapters 6, 7, 8, 9, and 10, presents a detailed discussion of the architectural and design issues that determine the functionality and the design strengths of a distributed multimedia system. Chapter 6 is dedicated to technologies and architectural issues comprising DSPs, processor and memory issues, connectivity via LAN and WAN (including ISDN), and overall architectural issues for multimedia systems. In Chapter 7 we discuss data flow control and other application design issues, including virtual reality for multimedia systems. Chapter 8 provides a discussion of authoring systems and user interface issues for multimedia systems. Chapter 9 presents an analysis of the design issues for multimedia messaging technologies i ncluding e-mail interface and addressing standards such as VIM, X.400, and X.500. In Chapter 10 we discuss the key design issues for distributed multimedia systems. The discussion includes design issues for multiserver networks, organizing a distributed multimedia database, managing objects in a distributed database, replication of objects, and storage optimization. |
