Unit10 Digital Multimedia Systems
Lesson 28 Digital Storage Media
《电子技术专业英语教程》冯新宇 主编 电子工业出版社
28 Digital Storage Media
• Backgrounds • Text tour • Language in use
2013-6-27
《电子技术专业英语教程》
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What is digital storage media?
• "digital storage media" refers to both storage and communication capabilities • These have increased in capacity more than a thousand fold in the past decade, allowing digital multimedia to emerge as a cost effective competitor for analog approaches. • In 1985, CD-ROM (compact disc read-only memory) with a capacity of more than 600 Mbytes but a manufactured cost under a dollar was first applied to electronic publishing. Similarly, fiber-optic cable now makes gigabitper-second communication channels a reality worldwide.
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CDROM development
• An elaborate system of optics, servos, and signal decoding circuits allows data to be accessed within a second. ISO 9660 (based on the High Sierra standard ) specifies the volume and file characteristics, allowing access through nearly any CD-ROM drive and operating system. Efforts of the Rock Ridge Group have extended the utility of ISO 9660 for UNIX systems and servers.
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《电子技术专业英utline
- What is digital storage media? - Storage
• CDROM • CDROM development
- Network • Why should the introduction of network storage? • The realization of networked storage
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《电子技术专业英语教程》
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CD-ROM
• CD-ROMs, the most cost effective storage medium for distributing large quantities of digital data, are related to regular compact discs-that is, CD-DA, or compact-disc digital audio. • Both support direct access to individual sectors of data that can store 1/75 second of CD-quality digital audio in CDDA format, using 2,336 bytes, or 2,048 bytes of arbitrary digital data in CD-ROM format with the rest of the space for error correction. Thus, CD-ROM data transfer speed is 150 Kbytes per second or 1.2 Mbits per second.
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Network
Why should the introduction of network storage?
– While fiber-optic connections are the most cost-effective scheme for rapidly transmitting large volumes of digital data，a great deal of research regarding networked multimedia is required. – The Fiber Distributed Data Interface operates at 100 Mbps, and connection costs dropped below $5000 in the early 1990s. Gigabitper-second networks are being tested, and will form the backbone for national telecommunication. However, research regarding network protocols, local area network and workstation architectures, and operating-system support software for digital multimedia is still in its infancy. The first international workshop exclusively on these topics was held late in 1990.
– High performance and reliability are also important. Research is proceeding on object-oriented models to handle the various classes of multimedia, abstractions for continuous media (for example, an audio stream) I/O, and connection architectures for networks and workstation. – There is a trade-off between network reliability, how closely the network approximates providing a constant rate stream, and other factors. – Without buffering, the stream of data must be carefully prepared, such as by interleaving data on storage units. – That is especially important with CDROM, where seek times are one to two orders of magnitude slower than with magnetic disks. As memory prices decline, however, buffering of multimedia data will allow fast processors to compensate for many performance problems in digital storage media.
– Vocabulary – Structure – Reading/writing techniques
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《电子技术专业英语教程》
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Backgrounds
• Terminology – fiber-optic 【计】光导纤维 – servo n.伺服，伺服系统；【计】伺服装置 – Hypermedia 【计】多介质的，超媒体 – CD-DA 数字音频光盘 – compact-disc 激光唱片，压缩磁盘，光盘 – CD-ROM 只读存储器，只读光盘 – Fiber Distributed Data Interface 光纤分布式数据接口 – seek time 寻道时间 – orders of magnitude 数量级
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《电子技术专业英语教程》
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CDROM development
• Compact discs are part of the family of optical media. There are prospects for further improvement, including write-once and erasable discs of varying sizes. For example, announcements indicate that in 1992, write-once CD-ROM drives will cost under $3000, and minidisk (2.5inch, 128-Mbyte) drives will cost about the same as those for CD-ROMs, handling both formats. • Magnetic disks are readily available with capacities on the order of a gigabyte, but they are not low-cost，removable, or produced by mass replication. Use of caching, memory hierarchies, and minimal perfect hashing will make all storage units even more effective contributors to digital multimedia.