Multimedia 多媒体 More Usage Likely To Immediately Make Every Day Into Another [1] On Multimedia Applications Definition Multimedia—the combination of text, animated graphics, video, and sound—presents information in a way that is more interesting and easier to grasp than text alone. It has been used for education at all levels, ibb training, and games by the entertainment industry. It is becoming more readily available as the price of personal computers and their accessories declines. Multimedia as a human-computer interface was made possible some half-dozen years ago by the rise of affordable digital technology [2] . Previously, multimedia effects were produced by computer-controlled analogy devices [3] , like videocassette recorders, projectors, and tape recorders. Digital technology's exponential decline in price and increase in capacity has enabled it to overtake analogy technology. The Internet is the breeding ground for multimedia ideas and the delivery vehicle of multimedia objects to a huge audience [4] . This paper reviews the uses of multimedia, the technologies that support it, and the larger architectural and design issues. Introduction Nowadays, multimedia generally indicates a rich sensory interface [5] between humans and computers or computer-like devices—an interface that in most cases gives the user control over the pace and sequence of the information. We all know multimedia when we see and hear it, yet its precise boundaries elude us. For example, movies on demand, in which a viewer can select from a large library of videos and then play, stop, or reposition the tape or change the speed, [6] are generally considered multimedia. However, watching the movie on a TV set attached to a VCR [7] with the same abilities to manipulate the play is not considered multimedia. Unfortunately, we have yet to find a definition that satisfies all experts. Recent multimedia conferences, such as the IEEE International Conference on Multimedia Computing and Systems [8] , ACM Multimedia [9] , and Multimedia Computing and Networking [10] , provide a good start for identifying the components of multimedia. The range of multimedia activity is demonstrated in papers on multimedia authoring (i. e. specification of multimedia sequences), user interfaces, navigation (user choices), effectiveness of multimedia in education, distance learning, video conferencing, interactive television, video on demand, virtual reality [11] , digital libraries, indexing and retrieval, and support of collaborative work. The wide range of technologies is evident on papers on disk scheduling [12] , capacity planning, resource management, optimization, networking, switched Ethernet LANs [13] , ATM [14] networking, quality of service in networks, MPEG [15] encoding, compression, caching, buffering, storage hierarchies, video servers, video file systems, machine classification of video scenes, and Internet audio and video. Multimedia systems need a delivery system to get the multimedia objects to the user. Magnetic and optical disks [16] were the first media for distribution. The Internet, as well as the Transmission Control Protocol/lnternet Protocol (TCP/IP) [l7] protocol suite or Net BIOS [18] on isolated or campus LANs [19] , became the next vehicles for distribution. The rich text and graphics capabilities of the World Wide Web browsers are being augmented with animations, video, and sound. Internet distribution will be augmented by distribution via satellite, wireless, and cable systems. General Uses and Applications Multimedia applications are primarily existing applications that can be made less expensive or more effective using multimedia technology. In addition, new, speculative applications, like movies on demand, can be created with the technology. We present here a few of these applications. 1. Home applications ① Video on demand Video on demand (VOD), also called movies on demand, is a service that provides movies on an individual basis to television sets in people's homes. The movies are stored in a central server and transmitted through a communication network. A set-top box (STB) [20] connected to the communication network converts the digital information to analog and inputs it to the TV set. The viewer uses a remote control device [21] to select a movie and manipulate play through start, stop, rewind, and visual fast forward buttons. The capabilities are very similar to renting a video at a store and playing it on a VCR. The service can provide indices [22] to the movies by title, genre, actors, and director. VOD differs from pay per view [23] by providing any of the service's movies at any time. Instead of requiring that, all purchasers of a movie watch its broadcast at the same time. Enhanced pay per view, also a broadcast system, shows the same movie at a number of staggered starting times. ② Home shopping and information systems Services to the home that provide video on demand will also provide other, more interactive, home services. Many kinds of goods and services can be sold in this way. The services will help the user navigate through the available material to plan vacations, renew driver's licenses, purchase goods, etc. ③ Networked games The same infrastructure that supports home shopping could be used to temporarily download video games with graphic-intensive functionality to the STB, and the games could then be played for a given period. Groups of people could play a game together, competing as individuals or working together in teams. Action games would require a very fast, or low-latency, network. 2. Video conferencing Currently, most video conferencing is done between two specially set-up rooms. In each room, one or more cameras are used, and the images are displayed on one or more monitors. Text, images, and motion video are compressed and sent through telephone lines. Recently, the technology has been expanded to allow more than two sites to participate. Videoconferences can also be connected through LANs or the Internet. In time, videoconferences will be possible from the home. 3. Education A wide range of individual educational software employing multimedia is available on CD-ROM. One of the chief advantages of such multimedia applications is that the sequence of material presented is dependent upon the student's responses and requests. Multimedia is also used in the classroom to enhance the educational experience and augment the teacher,s work. Multimedia for education has begun to employ servers and networks to provide for larger quantities of information and the ability to change it frequently. ① Distance learning Distance learning is a variation on education in which not all of the students are in the same place during a class. Education takes place through a combination of stored multimedia presentations, live teaching [24] , and participation by the students. Distance learning involves aspects of both teaching with multimedia and video conferencing. ② Just-in-time training Another variation on education, called just-in-time training, is much more effective because it is done right when it is needed. In an industry context, this means that workers can receive training on PCs at their own workplaces at the time of need or of their choice. This generally implies storing the material on a server and playing it through a wide-area network or LAN. 4. Digital libraries Digital libraries are a logical extension of conventional libraries, which house books, pictures, tapes, etc. Material in digital form can be less expensive to store, easier to distribute, and quicker to find. Thus, digital technology can save money and provide better capabilities. The Vatican [25] Library has an extraordinary collection of 150,000 manuscripts, including early copies of works by Aristotle [26] , Dante [27] , Euclid [28] , Homer [29] , and Virgil [30] . However, only about 2000 scholars a year are able to physically visit the library in Rome. Thus, the IBM Vatican Library Project, which makes digitized copies of some of the collection available to scholars around the world, is a very valuable service, especially if the copies distributed are of high quality. 5. Virtual reality Virtual reality provides a very realistic effect through sight and sound, while allowing the user to interact with the virtual world. Because of the ability of the user to interact with the process, realistic visual effects must be created "on the fly" [31] . 6. Telemedicine Multimedia and telemedicine can improve the delivery of health care in a number of ways. Digital information can be centrally stored, yet simultaneously available at many locations. Physicians can consult with one another using videoconference capabilities, where all can see the data and images, thus bringing together experts from a number of places in order to provide better care. Multimedia can also provide targeted education and support for the patient and family. Notes [1] 此处将各个单词的第一个字母组合后，即可拼出multimedia，意为多媒体。 [2] digital technology数字技术。 [3] ...computer-controlled analogy devices...计算机控制的模拟装置。 [4] The Internet is the breeding ground for multimedia ideas and the delivery vehicle of multimedia objects to a huge audience．因特网是多媒体技术这一思维的繁殖地，同时，网络又是把多媒体对象传送给诸多观众的工具。 [5] a rich sensory interface感官丰富的界面。 [6] 此分句为插入语，本句主语是movies on demand。 [7] VCR videocassette recorder录像机。 [8] International Conference on Multimedia Computing and Systems多媒体处理及系统国际会议。 [9] ACM Multimedia美国计算机学会多媒体(大会)。其中，ACM是Association for Computing Machinery的缩写，指美国计算机学会。 [10] Multimedia Computing and Networking多媒体处理与网络。 [11] virtual reality虚拟现实。 [12] disk scheduling磁盘列表。 [13] Ethernet LANs以太局域网，其中LANs见本课注解[19]。 [14] ATM Asynchronous Transfer Mode异步传输模式。 [15] MPEG Moving Picture Expert Group运动图像专家组。 [16] optical disk光盘。 [17] TCP/IP Transmission Control Protocol/Internet Protocol传输控制协议/网间协议。 [18] BIOS Basic Input Output System基本输入输出系统。 [19] LANS Local Area Networks局域网。 [20] set-top box(STB)置顶盒，机顶盒。 [21] remote control devic