Page 113 - DCAP303_MULTIMEDIA_SYSTEMS

Unit 6: Hardware

A floppy disk is made of flexible Mylar plastic coated with a very thin layer of special magnetic notes
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 however 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. 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.
6.3.4 Zip, Jaz, syQuest and optical storage Devices

SyQuest’s 44 MB 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 100 MB 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 CDs, 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.
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 128 MB-capacity disk-about the size of a 3.5 inch floppy.
Larger-format MO drives with 5.25 inch cartridges offering 650 MB to 1.3 GB of storage are also
available.
6.3.5 Digital versatile Disc (DvD)
With this (DVD) 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.
The 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. 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 eight different languages, with graphic subtitles in 32 languages.

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