How Does Optical Media How Does Optical Media Technology Work?Technology Work?

By Wayne He Period 2

Common File Systems Common File Systems for CDs and DVDsfor CDs and DVDs

High SierraHigh Sierra In 1985, representatives from several

companies met at High Sierra Hotel at Lake Tahoe, Nevada. Created a logical format and file structured

for CD-ROMs.Was later submitted to the International

Organization for Standardization (ISO).

ISO 9660ISO 9660 Adapted from the High

Sierra format. Level 1 Interchange:

Filenames may only have uppercase letters, digits, and underscores ( _ ).

8 characters max. for filenames and 3 chars max for extensions.

Directory names may only have 8 characters maximum.

Directories are limited to 8 levels deep.

Files must be contiguous.

Level 2 Interchange: Allowed the filename

and extension to have a total of 30 characters maximum.

Level 3 Interchange: “Files must be

contiguous” restriction removed.

JolietJoliet Extension of ISO 9660 CDs can be recorded with filenames with 64

characters max. Specifications:

Filenames and directories can have 64 characters maximum (as stated above)

Directories may have extensions. Directories can be deeper than eight levels. Supports multisession recording.

Universal Disk Format (UDF)Allows an operating system to read,

write, and modify dataDVDs are based on this format.

Lands and Pits on CDs Lands and Pits on CDs and DVDsand DVDs

A land is a layer that reflects light.Pits look like bumps.

Data Bits and Channel BitsLand – 1 data bitPit – 0 data bitChannel bits:

A “1” refers to a change from a land to a pit, or from pit to land.

A “0” refers to no change between a land and a pit.

CLV and CAV

Circular Angular VelocityAccesses data off

of rotating disksUsed by disk

drivesDisk motor does

not need to change speed

Constant Linear Velocity Used by older CD-

ROM players Rotational speed

changes depending on the data’s location

Ensures constant data rate regardless of the data’s location

Speeds of different optical media technologies

CD-ROM CD-ROM CD-i/XA CD-i/XA

Mode 1 Mode 2 Form 1 Form 2

Speed (CLV)

(2,352 Bytes/Block)

(2,048 Bytes/Block)

(2,336 Bytes/Block)

(2,048 Bytes/Block)

(2,324 Bytes/Block)

1x 176,000 153,600 175,200 153,600 174,300

2x 352,800 307,200 350,400 307,200 348,600

4x 705,600 614,400 700,800 614,400 697,200

6x 1,058,400 921,600 1,051,200 921,600 1,045,800

8x 1,411,200 1,228,800 1,401,600 1,228,800 1,394,400

12x 2,112,000 1,843,200 2,102,400 1,843,200 2,091,600

16x 2,816,000 2,457,600 2,803,200 2,457,600 2,788,800

20x 3,520,000 3,072,000 3,504,000 3,072,000 3,486,000

Read/Write Audio

Color Books

(not to be confused with children’s coloring books)

RedRed books define CD-Audio “father” of all CD-formatsCompact Disc-Digital Audio (CD-DA)

defined by Philips N.V. and Sony in 1980

Yellow “mother” of all CD formatsDefines CD-ROMsDeveloped by Philips N.V. and Sony in

1983Allows storing of digitalized content

OrangeCD-Recordable (CD-R)Created by Philips N.V. and Sony in

1988Can now record (as where the name

“CD-Recordable” came from)

GreenCompact Disc Interactive (CD-i)Stores an entire hardware and software

systemStores special compression methods for

audio and visual data Interleaves audio, video, and text data

BlueCD PlusMultisession disc with two sessions

Music Data

WhiteVideo CDDeveloped by JVC, Philips, Sony, and

Matsushita in July 1993Stores MPEG-1 (Motion Picture Experts

Group) videos (maximum of 74 minutes)Playable on a personal computer (PC)

or a DVD player