Introduction
A data storage device is a device for recording (storing) information (data). Recording can be done using virtually any form of energy. A storage device may hold information, process information, or both. A device that only holds information is a recording medium. Devices that process information (data storage equipment) may both access a separate portable (removable) recording medium or a permanent component to store and retrieve information.
Electronic data storage is storage which requires electrical power to store and retrieve that data. Most storage devices that do not require visual optics to read data fall into this category. Electronic data may be stored in either an analog or digital signal format. This type of data is considered to be electronically encoded data, whether or not it is electronically stored. Most electronic data storage media (including some forms of computer storage) are considered permanent (non-volatile) storage, that is, the data will remain stored when power is removed from the device. In contrast, electronically stored information is considered volatile memory.
Memory and Storage Devices
By adding more memory and storage space to the computer, the computing needs and habits to keep pace, filling the new capacity.
To estimate the memory requirements of a multimedia project- the space required on a floppy disk, hard disk, or CD-ROM, not the random access sense of the project’s content and scope. Color images, Sound bites, video clips, and the programming code that glues it all together require memory; if there are many of these elements, you will need even more. If you are making multimedia, you will also need to allocate memory for storing and archiving working files used during production, original audio and video clips, edited pieces, and final mixed pieces, production paperwork and correspondence, and at least one backup of your project files, with a second backup stored at another
location.
Floppy and Hard Disks
Adequate storage space for the production environment can be provided by largecapacity hard disks; a server-mounted disk on a network; Zip, Jaz, or SyQuest removable cartridges; optical media; CD-R (compact disc-recordable) discs; tape; floppy disks; banks of special memory devices; or any combination of the above.
Removable media (floppy disks, compact or optical discs, and cartridges) typically fit into a letter-sized mailer for overnight courier service. One or many disks may be required for storage and archiving each project, and it is necessary to plan for backups kept off-site.
Floppy disks and hard disks are mass-storage devices for binary data-data that can be easily read by a computer. Hard disks can contain much more information than floppy disks and can operate at far greater data transfer rates. In the scale of things, floppies are, however, no longer “mass-storage” devices.
A floppy disk is made of flexible Mylar plastic coated with a very thin layer of special magnetic material. A hard disk is actually a stack of hard metal platters coated with magnetically sensitive material, with a series of recording heads or sensors that hover a hairbreadth above the fast-spinning surface, magnetizing or demagnetizing spots along formatted tracks using technology similar to that used by floppy disks and audio and video tape recording. Hard disks are the most common mass-storage device used on computers, and for making multimedia, it is necessary to have one or more large-capacity hard disk drives.
As multimedia has reached consumer desktops, makers of hard disks have been challenged to build smaller profile, larger-capacity, faster, and less-expensive hard disks. In 1994, hard disk manufactures sold nearly 70 million units; in 1995, more than 80 million units. And prices have dropped a full order of magnitude in a matter of months. By 1998, street prices for 4GB drives (IDE) were less than $200. As network and Internet servers increase the demand for centralized data storage requiring terabytes (1 trillion bytes), hard disks will be configured into fail-proof redundant array offering built-in protection against crashes.
Zip, jaz, SyQuest, and Optical storage devices
SyQuest’s 44MB removable cartridges have been the most widely used portable medium among multimedia developers and professionals, but Iomega’s inexpensive Zip drives with their likewise inexpensive 100MB cartridges have significantly penetrated SyQuest’s market share for removable media. Iomega’s Jaz cartridges provide a gigabyte of removable storage media and have fast enough transfer rates for audio and video development. Pinnacle Micro, Yamaha, Sony, Philips, and others offer CD-R “burners” for making write-once compact discs, and some double as quad-speed players. As blank CD-R discs become available for less than a dollar each, this write-once media competes as a distribution vehicle. CD-R is described in greater detail a little later in the chapter.
Magneto-optical (MO) drives use a high-power laser to heat tiny spots on the metal oxide coating of the disk. While the spot is hot, a magnet aligns the oxides to provide a 0 or 1 (on or off) orientation. Like SyQuests and other Winchester hard disks, this is rewritable technology, because the spots can be repeatedly heated and aligned.
Moreover, this media is normally not affected by stray magnetism (it needs both heat and magnetism to make changes), so these disks are particularly suitable for archiving data. The data transfer rate is, however, slow compared to Zip, Jaz, and SyQuest technologies. One of the most popular formats uses a 128MB-capacity disk-about the size of a 3.5-inch floppy. Larger-format magneto-optical drives with 5.25-inch cartridges offering 650MB to 1.3GB of storage are also available.
Digital versatile disc (DVD)
In December 1995, nine major electronics companies (Toshiba, Matsushita, Sony, Philips, Time Waver, Pioneer, JVC, Hitachi, and Mitsubishi Electric) agreed to promote a new optical disc technology for distribution of multimedia and feature-length movies called DVD.
With this new medium capable not only of gigabyte storage capacity but also full-motion video (MPEG2) and high-quantity audio in surround sound, the bar has again risen for multimedia developers. Commercial multimedia projects will become more expensive to produce as consumer’s performance expectations rise. There are two types of DVD-DVD-Video and DVD-ROM; these reflect marketing channels, not the technology.
DVD can provide 720 pixels per horizontal line, whereas current television (NTSC) provides 240-television pictures will be sharper and more detailed. With Dolby AC-3 Digital surround Sound as part of the specification, six discrete audio channels can be programmed for digital surround sound, and with a separate subwoofer channel, developers can program the low-frequency doom and gloom music popular with Hollywood. DVD also supports Dolby pro-Logic Surround Sound, standard stereo and mono audio. Users can randomly access any section of the disc and use the slow-motion and freeze-frame features during movies. Audio tracks can be programmed for as many as 8 different languages, with graphic subtitles in 32 languages. Some manufactures such as Toshiba are already providing parental control features in their players (user’s select lockout ratings from G to NC-17).
CD-ROM Players
Compact disc read-only memory (CD-ROM) players have become an integral part of the multimedia development workstation and are important delivery vehicle for large, mass-produced projects. A wide variety of developer utilities, graphic backgrounds, stock photography and sounds, applications, games, reference texts, and educational software are available only on this medium.
CD-ROM players have typically been very slow to access and transmit data (150k per second, which is the speed required of consumer Red Book Audio CDs), but new developments have led to double, triple, quadruple, speed and even 24x drives designed specifically for computer (not Red Book Audio) use. These faster drives spool up like washing machines on the spin cycle and can be somewhat noisy, especially if the inserted compact disc is not evenly balanced.
CD Recorders
With a compact disc recorder, you can make your own CDs using special CDrecordable (CD-R) blank optical discs to create a CD in most formats of CD-ROM and CD-Audio. The machines are made by Sony, Phillips, Ricoh, Kodak, JVC, Yamaha, and Pinnacle. Software, such as Adaptec’s Toast for Macintosh or Easy CD Creator for Windows, lets you organize files on your hard disk(s) into a “virtual” structure, then writes them to the CD in that order. CD-R discs are made differently than normal CDs but can play in any CD-Audio or CD-ROM player. They are available in either a “63 minute” or “74 minute” capacity for the former, that means about 560MB, and for the latter, about 650MB. These write-once CDs make excellent high-capacity file archives and are used extensively by multimedia developers for premastering and testing CDROM projects and titles.
Videodisc Players
Videodisc players (commercial, not consumer quality) can be used in conjunction with the computer to deliver multimedia applications. You can control the videodisc player from your authoring software with X-Commands (XCMDs) on the Macintosh and with MCI commands in Windows. The output of the videodisc player is an analog television signal, so you must setup a television separate from your computer monitor or use a video digitizing board to “window” the analog signal on your monitor.
