Data storage devices-Optical disks drives

What are the Optical disk drives

CD-ROM drives. CD-ROM is an acronym for Compact Disk Read-Only Memory. CD-ROMs are used to store applications or data in such forms as video, sound and animation. CD-ROM drives can only read information from compact disks (CD).

CD-R and CD-RW drives (burners). With CD-ROM drives you can play CD-ROMs on your computer, CD-R drives allow you to create your CD-ROMs. CD-R is short for "CD-Recordable". Recordable CDs are called also as WORM (Write Once, Read Multiple) media that work just like standard CD-ROMs. The main disadvantage of CD-R drives is that you can't rewrite CD-ROM. CD-RW (Rewritable) drives allows you to write discs, then erase and rewrite. They are also called CD-E (compact disk-erasable). CD-Rewritable drives are able to write both CD-R and CD-RW discs. Media for CD-R and CD-RW drives are blank CD-R or CD-RW.

Features and characteristics. Most CD-ROM drives come with convenient features to allow you to use the drive to play and listen to audio CDs. Drives seem to vary drastically in terms of what they provide on their front panels, but you will usually see some combination of the following:

Design: CD-ROM players can be either internal, in which case they fit in a bay , or external., in which case they generally connect to the computer's I/O interface such as a parallel port, SCSI, IDE/EIDE, Firewire, USB etc. If your computer doesn't already contain such an interface, you will need to install one.

Speed: The number in front of the X in reference to CD-ROMs indicates how many times the data speed of the drive is faster than an audio CD. For example a 24X CD-ROM player is supposed to spin CD-ROMs 24 times faster than an audio CD spins. For CD 1X equals 150 KBps; for DVD, 1X equals 1.38 MBps. CD-ROM can work on base of the CLV or CAV technology. With CLV (Constant Linear Velocity), the rotation speed of the disk changes based on how close to the center of the disk the data is. Short for Constant Angular Velocity, a technique for accessing data off of rotating disks. With CAV (Constant Angular Velocity), the disk rotates at a constant speed regardless of what area of the disk is being accessed. Usually on a driver label you may see 2-3 speeds (for example, 24X/10X/40X, for Read, Write and Rewrite processes).

Access time: The access time measures how long, on average, it takes the drive to access a particular piece of information.

Data transfer rate. The data transfer rate measures how much data can be read and sent to the computer in a second.

Functions

Stereo Headphone Output: A mini headphone jack that allows you to plug headphones directly into the drive to listen to the CD audio being played back. This is found on virtually every CD-ROM drive.
Volume Control Dial: Most drives include a dial control to allow you to select the volume of the CD audio output.
Start and Stop Buttons: Many drives include control buttons to start and stop the play of the CD. On some drives these are the only controls found on the front panel.
Next Track and Previous Track Buttons: The addition of these buttons makes listening to CD audio on the CD-ROM drive much more practical. Unfortunately many drives save 79 cents or whatever by leaving these off.

Capacity: CD as media usually hold about 74 minutes of audio, or about 650MB of data. Some CD-R blanks can hold 80 minutes of audio, or about 700MB of data.

DVD Digital video (versatile ) disk (DVD) drives realize the next generation of optical disc storage technology. DVD is essentially a bigger, faster CD that can hold cinema-like video, better-than-CD audio, and computer data. DVD aims to encompass home entertainment, computers, and business information with a single digital format, eventually replacing audio CD, videotape, laserdisc, CD-ROM, and video game cartridges. You can meet six recordable versions of DVD-ROM: DVD-R for General, DVD-R for Authoring, DVD-RAM, DVD-RW, DVD+RW, and DVD+R. All DVD recorders can read DVD-ROM discs, but each uses a different type of disc for recording. DVD-R and DVD+R can record data once (sequentially only), like CD-R, while DVD-RAM, DVD-RW, and DVD+RW can be rewritten thousands of times, like CD-RW. DVD-RAM is more of a removable storage device for computers than a video recording format. The other two erasable format families (DVD-R/RW and DVD+R/RW) are essentially in competition with each other. The market will determine which of them succeeds or if they end up coexisting or merging.

Features and characteristics:

Speed: Usually on a DVD label you may see 2-3 speeds (for example , for Read, Write and Rewrite processes

Storage capacity: 2.6-9.4 GB. In nearest future it can be 17 GB.

Data-transfer rates are higher than for most CD-ROM drives. For entertainment applications (such as movies on-disk), the transfer rate is about 600 KBps (kilobytes per second), which is four times as fast as the standard rate for audio CDs and equivalent to the speed of a 4X CD-ROM drive. For data applications, expect rates of 1.3 MBps or more, roughly equivalent to the speed of a 10X CD-ROM drive.

Formats: It's important to understand the difference between the physical formats (such as DVD-ROM or DVD-R) and the application formats (such as DVD-Video or DVD-Audio). DVD-ROM is the base format that holds data. DVD-Video (often simply called DVD) defines how video programs such as movies are stored on disc and played in a DVD-Video player or a DVD computer . The difference is similar to that between CD-ROM and Audio CD. DVD-ROM includes recordable variations DVD-R/RW, DVD-RAM, and DVD+R/RW . The application formats include DVD-Video, DVD-Video Recording, DVD-Audio. DVD-Audio Recording, DVD Stream Recording, and SACD. There are also special application formats for game consoles such as Sony PlayStation 2. DVD -RAM is a new type of rewritable compact disc that provides much greater data storage than today's CD-RW systems.

Compatibility: One of the best features of DVD-ROM drives is that they are backward-compatible with CD-ROMs. This means that DVD-ROM players can play old CD-ROMs, CD-I disks, and video CDs, as well as new DVD-ROMs. Newer DVD players can also read CD-R disks.

Request to computer's hardware and software: Computer must be fast enough to handle software decoding. Good-quality software-only playback requires no less than 350-MHz Pentium II or a Mac G4. You may also need software that can read the UDF file system format used by DVDs. Almost all new computers with DVD-ROM drives use software decoding instead of hardware decoding, since it's now possible on even the cheapest new models.

High Density Digital Versatile Disc or High Definition Digital Video Disc is a digital optical media format which can hold high definition video or other data. HD DVD is similar to the competing Blu-ray Disc, which also uses the same CD-size (120 mm diameter) optical data storage media and 405 nm wavelength blue laser. HD DVD is promoted by Toshiba, NEC, Sanyo, Microsoft, and Intel, among others. In terms of major studios, HD DVD is currently exclusively backed by Universal Studios, and is non-exclusively backed by Paramount Pictures, Warner Bros, etc.

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