[A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q-R] [S] [T] [U] [V] [W] [Y]

[A]

About this Glossary

See, Z-Author.

 

A-D Conversion

Analog to digital conversion, also known as modulation, involves special chips to convert analog signals to digital strings, or vice-versa. A-D conversion is necessary to send computer data through regular telephone lines, to convert analog audio and video to digital video, to have computerized telecommunications, to display data on analog displays, and so on. 

 

A-Time

Absolute Time is used to access sectors of data from the CD- ROM, identifying or addressing them from the beginning of the disc, using the drive's internal clock (min:sec:sector). It allows access of random amounts of data, such as video and audio segments, especially if the disc will include more than 98 individual audio segments. In Mixed-Mode discs, since only 98 tracks of CD-DA are allowed, track access is not workable. A- Time access involves mapping the audio portions in the CD-ROM (start and stop of each) using time addresses (Min-Sec-Sector), mapped relative to the beginning of the disc. This requires special care in determining the 'offset'--the amount of time used by all the components of Track 1 (pregap, post gap, application, etc.). Track relative time, on the other hand, involves mapping the times relative to the beginning of its track--which is a much easier option, and widely used in Mixed-Mode discs. 

 

Access Time

Amount of time it takes a CD-ROM drive to find and display the requested information. Although specified widely, access times must be used with care because there is no measuring standard. It is generally regarded to include radial positioning time (the head moves to the appropriate track), plus settling time (stops vibration), plus latency (wait for beginning of block with the wanted data)--all of which take much more time than the final read and display step. The faster hard disk drives claim access speeds of 12 milliseconds or even lower, while current CD- ROM drives claim access times of about 150 milliseconds--and some SCSI drives claim even lower access times.

 

Active Movie

Active Movie (Microsoft, 1996) was announced as the replacement of Video for Windows and MCI (Media Control Interface). Active Movie has a 32-bit architecture, with enhanced video playback capabilities( for higher frame rates)--which should help MPEG-2 video. Some DVD playback card manufacturers plan to use Active Movie in the Windows95 and NT platforms. Major developers (Adobe, Matrox, Mediamatics, and others) planned to announce Active Movie implementations in the first half of 1997.

 

Adapter Cards

In computers, adapter cards (a.k.a. controller cards, expansion cards, interface cards, etc.) are installed or plugged into slots of the motherboard, or bus extensions such as Local Bus. They are also necessary for networking computers. The cards 'adapt' the flow of data and instructions between the CPU and the device (peripheral), thus enhancing the computer's capabilities (memory expansion, fax-modem, advanced graphics, sound, I/O expansion, etc.).

 

ADPCM

Adaptive Differential Pulse Code Modulation is an audio encoding procedure (often referred to as compression algorithm) that takes about half the space of standard PCM, and involves different sampling rates and bits per sample, algorithms and chips to produce up to 20 hours of Level C, monaural audio in one CD. 'Differential' (often called 'Delta') refers to the way the algorithms determine and record only the differences between one signal and the next, using 4-bit numbers--thus reducing the total length of code. It is implemented with interleaving in CD-I and CD-ROM-XA applications. 

 

Analog Signal

A continuous signal that reflects the variation in the phenomenon being measured or represented, such as voice, temperature, pressure, intensity of light, electrical flows, etc. To be used in computers, analog signals, such as those in communications, must first be modulated into digital code strings. 

 

Application

In computer circles, it is a complete package of software and data designed to work in a particular computing platform. Main applications today involve: fulltext search and retrieve, databases, encyclopedias and other reference works, games, graphics libraries, multimedia products, etc. 

 

ASCII

The American Standard Code for Interchange of Information, better known as the ASCII ('askey') character set, is the binary, 7-bit, 128-character set implemented as the standard in communications, and in mini and microcomputers. Because data is transferred as bytes, ASCII codes are added an eight bit (generally a 1-bit) to make up the standard eight-bit byte--which is generally used as a parity bit.

 

Aspect Ratio

The height to width ratio in PC and TV monitors. In DVD-Video, the video display frame can have different rectangular shapes, determined by its recording aspect ratio (4:3 or 16:9). DVD-Video also offers panoramic and letter-box display formats (options). Obviously, not all TV sets offer a 'wide screen' option, and viewing a film using the improper aspect ratio leaves dark (unused) areas or bands in the screen.

 

ASPI

Advanced SCSI Programming Interface is, essentially, a driver that helps the operating system translate application program commands so that they are understood by the hardware--such as SCSI devices, CD-Recordable drives (dealing with the bus, ports, DMA channels, interrupts, other SCSI devices, etc.). ASPI drivers are loaded by the CONFIG.SYS, and there are versions for various bus architectures.

 

Audio

Traditionally, audio signals were recorded and played back as analog signals. In today's computer circles, audio refers to files of digital (binary) codes that are produced by converting analog signals to digital audio. The quality of digital audio depends on the sampling rate and the sample size. Humans hear dound in the range of 15 to 20,000 Hz. 

 

AUDIO_TS

This is the specified directory name for the audio files in a DVD volume using the Universal Disk Format (UDF). 

 

Average Access Time

Average time, in milliseconds, it takes for a CD-ROM drive to complete a request to read task--the word to note here is 'average.' Some manufacturers specify their 1/3 stroke access time, and others specify random access time (also referred to as random seek time), or a combination of them--reason why using access times for comparisons should not be considered reliable and sufficient.

[B]

Bandwidth

Originally a range of frequencies, in current computer circles it describes the capacity or amount of traffic (data, voice, video, etc) per unit of time. In computerized communications it is expressed in Mbits/sec. Some of the new microcomputer buses and local buses have bandwidths of about 132 MBytes/sec. 

 

Bi-directional Prediction

Some compression programs have this capability, which means that the Codec (coder-decoder) keeps track of what has been processed, and reads ahead to prepare appropriate procedures to process the data more efficiently, and to preclude sudden surges in data transfer rates--such as would take place when the action involves sudden changes in scene, or fast actions of the objects in the screen. Bidirectional prediction is implemented in both the compression and the decompression procedures, and is a key capability for preserving image quality in full-motion video.

 

Binary Code

Computers are based on binary code; binary digits (bits), 0s and 1s that form bytes and files. Information is stored in binary files, in specific formats. Optical devices, such as CD-ROM, involve physical 'pits' and 'lands' on the coded track of the disc. But, in the end, they are decoded into 1s and 0s of binary files that can be used by the computer.

 

Birefringence

In CDs and other optical discs, it means double refractive ability. It is caused mainly by improper cooling of the substrate during the injection-molding process. In optical applications, substrate birefringence is unwanted, since it interferes with the read function. Users, however, can not determine that it is birefringence that is causing read errors or poor performance of their CD-ROM applications--it is detected by special equipment and tests.

 

Bit

A compressed form of 'binary digit.' Therefore, a bit can be a 1 or a 0. A standard byte has eight bits (256 possibilities). Bits are used mostly when dealing with bandwidth rates (bits/sec), graphics resolutions, and related topics. Bytes are used when talking about data and file lengths in general.

 

BLER

Block Error Rates indicate the number of blocks that contain erroneous bytes (error bursts) during a read from the CD-ROM. BLERs also serve to gage effectiveness of mastering, replication, and CD-R encoding processes. Analysis of BLERs require understanding the basic Reed-Solomon error correction code, and the Cross-Interleaved Reed Solomon Code (CIRC)--which are basic for error detection and correction in CDs. An average BLER of less than 220 is considered within the specifications.

 

Block

Unlike the blocks used in regular magnetic storage devices, in ISO 9660 CD-ROMs, logical blocks are subdivisions of the sectors in the track. But, in most applications, the logical block is considered to be the same size as the user data area of the sector--which has led to the common notion that blocks and sectors are the same thing, and which is not true for all cases.

 

Block Structure

See, CD Sector Structures.

 

Blue Book

Released by Philips-Sony (Dec 1955), the Blue Book was also known as the CD-Extra format (in the Mixed-Mode family). It provides for including data and audio in the same disc--using CD- ROM-XA sector structure for graphics and data. CD-Plus was a somewhat similar product that is no longer mentioned. Microsoft released an Enhanced CD Sampler in CD-Extra format (Music Industry Conference, Mar96). The Recording Industry Association of America endorsed the Enhanced CD format. The Blue Book fixes the 'track one' problem (awful screech when CD-Audio players play the data track), and this format can be read by current CD-Audio and CD-ROM drives. (See, CD-ROM XA)

 

Blue Laser

The development of a blue-light emitting diode (based on gallium nitride) in Japan (1993), opened the way for the production of short-wavelength (@16nm) blue laser optical devices. Philips, Sony and Toshiba demonstrated the blue laser in 1996. Obviously, since the blue laser will make smaller pits and use narrower tracks--disc capacities should increase even more. (Current red lasers are @ 600+ nanometers.) It seems that cooling requirements for the blue laser have not been resolved so that it could be implemented in consumer drive architectures.

 

Bonding Film

Single and double-layer DVDs require bonding two substrates (0.6mm), which have the recorded pits in the inside face, to make the standard 1.2mm DVD. The bonding materials and technology have presented challenges, but the experience with LaserDisc and other products should serve well. (This bonding layer is not the same as the semi-transmissive layer that is placed in between the two coded layers of a double-layer disc--which allows the laser light through.) Two bonding methods are in use, Hotmelt Adhesive, and UltraViolet Curing.

 

Books

In DVD, Books A to E include the specifications for the five different implementations of DVD. (See, DVD-Audio,  DVD-ROM,  DVD-Video ,  DVD-R,  DVD-RAM)

 

Boolean Search

One of the various logical constructs (Boolean Operator, Logic, Modifier, etc.) named after George Boole (1815-65), a British mathematician who developed a system of algebraic logic that has been applied beneficially in various areas, including computer logic circuits and software applications. Most text search and retrieve software use the Boolean operators And, Or, Not, ButNot, etc. Boolean logic for database or numerical fields includes operators such as 'Less than,' 'More than,' 'Equal or More than,' 'Equal or Less than,' and so forth. With the advent of powerful processors and affordable memory, there is interest in other logical systems that produce faster text searches, some quite sophisticated indeed, especially in large and very large textbases. Boolean searching, however, remains predominant.

 

Bootable CD

Some operating systems recognize and can use an ISO file structure, and therefore the CD can be configured with a boot record descriptor and operating system files (boot file), so the PC can boot from it--as some CDTV systems do. But, the Microsoft CD-ROM Extensions do not recognize the boot record descriptor in the CD, so MS-DOS PCs can not boot from it. As an alternative, in 1995, IBM and Phoenix Technologies announced an open Bootable CD-ROM format specification that would allow placing bootable images of floppies or hard disks on the CD-ROM, and a bootable CD-ROM BIOS in the system. To boot-up, the BIOS (one that recognizes bootable CDs) enables the system to read the preconfigured 'boot image' and proceed with the rest of the configuration. There was some talk about controller cards that would recognize or support bootable records in CD-ROMs, but nothing of the sort seems yet available. The El Torito Bootable CD-ROM Format Specification (an 'open' specification) provides for placing one or more 'bootable images' in a CD, and allows the PC to select the desired bootable image. Publisher HyCD (Creative Digital Research) is advertised as able to create bootable CDs. It was expected that applications with special configurations, games, multimedia applications and others would use the 'bootable CD' option, but it seems that it has not caught on.

 

Buffer

A usually small amount of memory that holds momentarily either instructions or other information for it, and which is directly available to the CPU. Buffers should to be confused with memory cache. Buffering is used to overcome factors that affect direct access of instructions or data to the CPU; such as speed differences, interface delays, and other variations between a device and the CPU.

 

Buffer Underrun

During recording, a CD-Recordable drive requires data to be provided in an uninterrupted stream at a the drive's specified recording rate. If the stream is interrupted by any reason, and the available buffer can not supply enough data to cover the interruption, the recording stops--reporting a buffer underrrun, ending the session, and wasting a blank disc. The Packet Writing option helps reduce buffer underruns.

 

Bundling

The practice of selling hardware or software, with additional items that, supposedly, do not add to the total price. Initially, minor software products were bundled with PCs and some peripherals. Since, DOS, Windows, Modems, speaker sets, and especially CD-ROMs and Multimedia applications of various types were bundled with hardware and major software packages. This practice, however, has helped the growth of CD-ROM.

 

Bus

In computers, a bus is the main or continuous channel of electrical connection between the CPU, the system memory (RAM), and the peripheral devices. (See, ISA Bus,  EISA Bus,  MCA Bus,  PCI Local Bus,  HPSB)

 

Byte

Bytes are strings of bits, operated upon as a unit. Until recently, PCs were designed to use 8-bit bytes. The 128 characters of the ASCII character set are represented by 8-bit bytes, (seven plus a parity bit--thus only 128 characters). Bytes are also basic for the Hex and Octal notation used in computer programming. PC file lengths are measured in bytes. Current PCs are implementing 32-bit buses, with 16 and 32-bit processors (that handle 4 or 8 bytes at a time). For encoding CD-ROM discs, the magnetic 8-bit byte is modulated to the 14-bit optical byte. In DVD, the magnetic 8-bit byte is modulated to a 16-bit optical byte. (See, Bit,  EFM)

 

[C]

 

Caddy

A 'caddy' is a special plastic case that holds and protects the CD during operation--especially when the drive is mounted on its side. Caddies are not used for shipping. For WORM and Erasable media, they are called cartridges--probably because they do not allow extraction of the disc itself. DVD-RAM (phase change) will also use a cartridge. (See, Jewel Case)

 

Capacity of CD-ROM

In general, the term capacity refers to the capacity of a CD, in megabytes of user data. Currently, there are CD-ROM media that can hold 63 or 74 minutes of data (74 min. is the maximum designed capacity). Before, because of equipment and other considerations, CD-Audio and CD-ROM did not use the outer area of the disc, and 60 to 63-minute discs were the rule. Today, because current equipment can encode and drives can read the outer area of the disc, 74-minute discs are common. The capacity of the CD- ROM is the number of user bytes per sector, times 75 sectors per second, times the total time recorded in the disc. Furthermore, the total, in Megabytes, will depend on the definition of Megabyte. Using 2(exp 20), or 1,048,576, we will arrive to the figure of 527 MBytes for a 60 minute CD-ROM. Obviously, this figure will be much higher for a 74-minute CD-ROM. Moreover, with multimedia CD-ROMs, all figures of capacity have to take into consideration that Mode 2 allows more space for user data (2336 user bytes). It is therefore possible to produce a 74-minute disc, in Mode 2, with about 778 million bytes, or about 741 Megabytes of user data in it--and still remain within the ISO 9660 specifications. Users must take these variables into account when discussing CD capacities. (See, CD Sector Structures,  Raw Capacity)

 

Capacity of DVD

The DVD specifications include single and double-layer discs, as well as single and double-sided discs, as shown in the following chart. The generic designations are: DVD-5, DVD-9, DVD-10 and DVD-18. DVD-R is implemented with a capacity of 3.86GB, and DVD-RAM with a capacity of 2.66GB--although it is expected that those capacities will increase in their 'second generation.'

                       Single-Layer    Double-Layer



                       ----------------------------



        Single-Side    DVD-5           DVD-9         



                         4.7 GB          8.5 GB



                       ----------------------------



        Double-Side    DVD-10          DVD-18



                         9.4 GB          17.0 GB



                       ----------------------------

CAV/CLV

See, Constant Angular Velocity....

 

CCITT

The International Consultative Committee for Telegraphy and Telephony, now the Telecommunications Sector, established by the United Nations within the International Telecommunications Union (ITU), is based in Europe, and recommends worldwide telegraph and telephone (including fax) transmission standards. CCITT derives from its French name.

 

CD

The Compact Disc was developed by Philips and Sony, and was first implemented commercially for storing digital audio data (CD-Digital Audio). The physical specifications for the 12cm disc, since known as CD, were issued in the now famous Red Book. The CD is made up of a polycarbonate substrate, a thin reflective metallic layer (the mirror-like is aluminum), and a lacquer coating. The encoded data track is a continuous spiral track of about 1.6 to 2.2 microns wide, and the pits are about 0.6 microns wide. Essentially, any other size or type of disc is not a CD. (See, Red Book,  CD Sector Structures,  DVD)

 

CD-Audio

See, CD-Digital Audio.

 

CD-Bridge Disc

A Bridge disc is defined as a CD-ROM XA disc that includes Mode 2 user data that can also be played by a CD-I player. Additional codes in the CD-ROM XA tracks allow the output to be shown on a TV screen (CD-I players), and on a computer monitor (with CD-ROM XA players). The specifications for the CD-Bridge disc are known as the White Book. (See, CD-I Ready ,  CD-ROM Specifications ,  White Book)

 

CD-Digital Audio

Philips and Sony developed the necessary technology for storing digital audio signals on a Compact Disc, and introduced the CD-Digital Audio (1982). This new product was based on the now famous Red Book (1981)--which specified the physical structures for the track and sectors in the disc. CD-Digital Audio was implemented to hold about 60 minutes of audio data, in up to 99 tracks (songs) at a sampling rate of 44.1 KHz and a sample size of 16 bits, to produce high quality stereo sound. The success of CD-Digital Audio has been key for the growth and success of CD-ROM and other CD implementations. (See, CD-ROM Specifications,  DVD-Audio)

 

CD-Extra

See, Enhanced CD.

 

CD-I

Compact Disc-Interactive was developed by Philips and Sony, who issued the specifications in 1986, in what is known as the Green Book. CD-I employs the CD, with a sector structure similar to CD-ROM-XA, and addresses issues of synchronization to implement interleaved data, compressed audio, different character sets, still frames, full-motion video, and special effects, complying with the ISO 9660. CD-I was advertised as the upcoming interactive multimedia platform, but current CD-I products aim mainly towards business and education multimedia interactive applications. A mayor drawback was that CD-I uses proprietary hardware, operating system (OS9), and data compression solutions- -mainly MPEG-1. The keyboard-less CD-I drives range from the basic player to the professional set, and can display to NTSC and PAL monitors. CD-I players can play CD-Audio and Bridge discs (Kodak Photo CDs, and Video CD) compliant with the White Book. PCs, with a special add-on board, can read CD-I discs. (See, CD Bridge Disc, CD-ROM Specifications)

 

CD-I Ready

A CD-I Ready disc is defined as a CD-Audio disc that includes a CD-I application, and can be played with a modified CD-I player. It involves extending the pre-gap space of CD-Audio, and including in it data that only the CD-I player can recognize and use. This additional functionality allows CD-I to present additional information about its contents. (See, CD-Bridge Disc,  CD-ROM Specifications)

 

CD-Plus

See, Enhanced CD.

 

CD-Recordable

CD-Recordable technology allows production of CD-ROMs on the desktop ('one-offs'). It requires a PC, a CD-R recorder or drive, appropriate software, and 'recordable' media. The reduction of prices for this hardware and software, and their ease of use, have helped the growth of CD-ROM production in-house. The 'one-off' is very different from the mass- reproduced or 'hot-pressed' CDs. It is sold pregrooved, in 63 or 74 minute capacities, and it involves a layered structure--with a sensitive chemical recording layer, and almost always with a gold reflective layer. Once recorded, the CD-R disc (one-off) performs in the same way as the mass-reproduced CDs. (See, DVD-R)

 

CD-RDx

The CD-ROM Read-Only Data Exchange Standard, developed by the CIA, Intelligence Community Staff, aimed to achieve "...system and software interoperability for CD-ROMs," which was further explained as the "...ability to publish a single integrated collection of data and indexes on a CD-ROM disc and make it accessible on any ISO 9660-compatible computer system." A final draft circulated in early 1993.

 

CD-ROM

The Compact Disc-Read Only Memory is the standard 12cm CD formatted according to the ISO 9660. Although the physical characteristics and track structure of a CD-ROM are the same as that of CD-Audio, a CD-ROM is used to store computer data (text, graphics). It also involves additional error detection and correction--as specified in the Yellow Book. The logical volume and file structure of CD-ROM, specified in the ISO 9660 allows it to be used in the computer arena. Therefore, a CD with computer data that is not structured according to the ISO 9660 is not a standard CD-ROM. (See, ISO 9660)

 

CD-ROM Drives

The growth of the industry is reflected in the types of CD- ROM drives offered today. The original drives had a transfer rate of 150 KBytes/second, and no audio plug. Recent drives offer 6X, 12X, 16X and even higher transfer rates, can handle audio tracks, and have connections for the sound card used by multimedia applications. Most current drives support CD-ROM XA and Photo-CD (including multiple session discs).

 

CD-ROM Extensions

The MS-DOS operating system (just as other operating systems) was developed before optical technology became available for the PC platform. Therefore, Microsoft had to add appropriate capabilities to MS-DOS, so that the PC could acknowledge an ISO- compliant CD-ROM as another storage device. The program, MSCDEX.EXE, is known as CD-ROM Extensions, and must be loaded by the Autoexec.Bat file. Apple also has Apple Extensions for its Hierarchical File System, and Commodore has CDFS extensions for CDTV. (See, MSCDEX.EXE)

 

CD-ROM Specifications

In the industry, most people speak of standards when they really mean industry specifications. With respect to CD-based products, the specifications have a common genesis and a close historical relationship, as is summarily charted below.

           ------------------------



       ---|CD-AUDIO (Red Book,1981)|-------------- 



      |    ------------------------               |



  Mixed-Mode**        |                           |



  (Blue Book,1995)    |                           |



      |   ---------------------------             |



      |   |CD-ROM (Yellow Book,1983)*|            |



      |   ---------------------------            CD-I



      |   |                     |               Ready



      Mode 1          -------Mode 2               |



         |           |          |                 |



  ------------------ |   --------------------     |



  ISO 9660*  Non-ISO |  |     CD-ROM XA      |    |



                     |   --------------------     |



                     |       |    |-- Form 1*     |



             Bridge Disc**   |    |-- Form 2      |



          (White Book,1993)  |                    |



                     |       |                    |



                    -----------------------       |



                   | CD-I (Green Book,1986)|<-----  



                    ----------------------- 



                                 |-- Form 1*



                                 |-- Form 2



        ------------------------------------ 



       |      Orange Book (1990)            | 



       | -Part 1, Magneto-Optical (CD-MO)   |



       | -Part 2, Write-Once (CD-WO)        |



       | -Part 3, Rewritable (CD-RW) PD***  |



        ------------------------------------



         * Implements Third Layer of Error Detection &



           Error Correction codes.



        ** Kodak Photo-CD and Video-CD are White Book Bridge Discs.  



       *** PD is used to mean Phase Change Technology, as oppossed 



           to M-O (magneto-optical) technology.

 

CD-ROM Tower

This is a configuration of CD-ROM drives in one box, known as a tower. CD-ROM towers are usually implemented in networks, usually with an appropriate CD-ROM server. They work well in busy multiuser environments because all the drives in the tower are accessible at all times, while jukeboxes access only one disc at a time. Recently, some manufacturers have introduced tower models with CD-Recordable units, and LAN-ready configurations.

 

CD-ROM XA

CD-ROM Extended Architecture, developed by Sony, Philips and Microsoft, involves extensions to the Yellow Book, and defines two new types of sector (CD-ROM Mode 2 sectors are 'extended' into CD-ROM XA Form 1 and Form 2 sectors). The new CD-ROM XA sectors are used for data, graphics, video, and ADPCM compressed audio, in an interleaved scheme (CD-I structure)--making it possible to read and display jointly text, graphics and audio files of various sample sizes, up to 20 hours of 4-bit monaural sound. Kodak's Photo CD for example, uses XA tracks, and it can therefore be read by an XA drive. (See, Multi-session)

 

CD-RW

See, Orange Book.

 

CD Sector Structures

The sector structures shown here refer to the logical structures derived from the Yellow Book--the user data areas are not subdivided into logical blocks. Therefore, the first two levels of Red Book ED/EC (784 bytes), and the 98 closing control bytes, are outside the box. In general, it is the size of the user data area (2048 or more bytes) that is used for the computations of transfer rates (at 75 blocks/sec) and the capacities of the various CD products.

     Red Book Specifications (Philips and Sony, 1981)



       CD-Audio Sector = 2352 bytes.* 



      _________________________________________________



     | User Data                                       |



     | 2352 Bytes                                      |



     |_________________________________________________|











     Yellow Book Specifications (Philips and Sony, 1983)



       CD-ROM, Mode 1 Sector = 2352 bytes.* 



      _________________________________________________



     | Sync  Header  User Data      EDC   Blank   ECC  |



     | 12    4       2048           4     8       276  |



     |_________________________________________________|











       CD-ROM, Mode 2 Sector = 2352 bytes.*



      _________________________________________________



     | Sync  Header  User Data                         |



     | 12    4       2336                              |



     |_________________________________________________|











     CD-ROM XA (Extended Architecture).



     (All tracks are CD-ROM, Mode 2) 







       CD-ROM XA Sector, Form 1 = 2352 bytes.* 



      _________________________________________________



     | Sync  Header  Sub-Header  User Data  EDC  ECC   |



     | 12    4       8           2048       4    276   |



     |_________________________________________________|











       CD-ROM XA Sector, Form 2 = 2352 bytes.*



      _________________________________________________



     | Sync  Header  Sub-Header  User Data       EDC   |



     | 12    4       8           2324            4     |



     |_________________________________________________|











     Green Book Specifications (Philips and Sony, 1986)



     (All tracks are CD-ROM, Mode 2)** 







       CD-I Sector, Form 1 = 2352 bytes.* 



      _________________________________________________



     | Sync  Header  Sub-Header  User Data  EDC  ECC   |



     | 12    4       8           2048       4    276   |



     |_________________________________________________|







       CD-I Sector, Form 2 = 2352 bytes.*



      _________________________________________________



     | Sync  Header  Sub-Header  User Data       EDC   |



     | 12    4       8           2324            4     |



     |_________________________________________________|











     Notes.



     ---------



     *  There follow the Red Book 1st and 2nd layer EDCs and      



        ECCs, plus 98 Control Bytes.



     **  As can be seen CD-ROM XA and CD-I sectors employ the     



         same structure.  Moreover, CD-ROM XA and CD-I tracks are 



         CD-ROM Mode 2 tracks, where 3rd level EDCs and ECCs are  



         added only as needed.

CD Singles

In the early 90s, the 8cm music 'CD-singles' were popular in Japan. Formatted under ISO 9660, the 8cm disc can hold up to 200 KB of data and be played by the Sony Data Discman. Some CD-ROM-XA applications have been ported to 8cm discs. This 8cmm disc should not be confused with the Sony 8cm MiniDisc, which is an M-O rewritable disc (Orange Book).

 

CDTV

Commodore Dynamic Total Vision, released in 1991, involved CD-ROM for multimedia applications for Commodore PCs that displayed to a TV monitor. Its particular file system (CDFS) is set to use the ISO 9660 (Interchange Level 2) file format. But, CDTV discs that implement Interchange Level 2 (allowing smaller logical blocks, different filename lengths and character set conventions) are incompatible with the IBM-compatible platform. CDTV also is capable of booting from the CD. For various reasons, CDTV weakened as Commodore lost market share in the US-- though they seem to be holding on in some foreign markets.

 

CD-V

Compact Disc-Video (Philips, 1986) is an implementation of the CD to store full motion video (analog, about 5-6 minutes) and CD-Audio tracks (about 20 minutes). CD-V requires a special CD-V drive, and is used mostly in the music industry and commercial video production arena. This format is implemented in other platforms as well, as video discs in 20cm (8in) and 30cm (12in) formats--these are not CDs, obviously. Pioneer seemed to sell the only players that supported this format, and its DVD multifunction players may still support it. (See, DVD,  Video CD)

 

CD-WO

Compact Disc-Write Once is rather recent, but is often confused with the older WORM (Write Once Read Many) optical technology. More appropriately, CD-WO is defined by the Orange Book, Part 2 (1990). It involves the 12cm CD, with a recordable layer that can be written to, but not erased and rewritten. Therefore, once the tracks have been encoded, a Table of Contents is created and placed in the appropriate place (the track's Lead- in). CD-ROM players use that TOC to read the contents. CD-R implements the Orange Book, Part 2, Write Once specifications. A CD-WO Hybrid disc involves an area where Read-Only files can be placed, and the rest of the disc is the W-O area, which can be written to in one or more sessions (each session creates its own Table of Contents). Multi-session discs need multi-session capable drives, such as the Kodak Photo CD drive and the newer multi-session ready drives. (See, W-O Technology)

 

Channel Bits

The optical bytes, after the eight-to-fourteen modulation, are recorded in channel bits--which are encoded as pits and lands on the data track. In another context, channel bits refer to the bits that make up each of the 98 Control Bytes included in each sector. Those channel bits are named P, Q, R, S, T, U, V, and W, and each of them represents a subcode channel, and include important information for timing, types of information, tracking, etc.

 

CIRC

Cross-Interleaved Reed-Solomon Code is used in compact discs for the first two levels of error detection and correction. CIRC in CD-Audio, implemented at the frame level, provides an integrity of one erroneous byte in a gigabyte (two CDs). In CD- ROM, which has an additional and more sophisticated third level 'layered' error detection and correction in CD-ROM claims an integrity of one byte in 2,000 CD-ROMs. (See, Integrity,  Reed-Solomon Product Code.)

 

Cladding

Special material used to line or cover an optical fiber, to reflect and confine the light waves to the core.

 

Clamping Area

See, Hub.

 

CMP

A joint Committee on Multimedia Technology formed by the Interactive Multimedia Association (IMA) and the Society of Motion Picture and Television Engineers (SMPTE) to deal with issues about multimedia, to produce technical papers, propose standards and distribution guidelines, and promote product interchange and interoperability in the multimedia industry.

 

Codec

Derived from COder-DECoder, a Codec is a software program that implements algorithms that are central to compression- decompression packages, especially those that deal with digitized streams produced from analog video source. Most of the reliable codecs maximize their power by using specific compression decompression boards (such as "MPEG boards"), especially since pure software compression-decompression packages have hardware requirements beyond what comes in standard PCs. Well-known codecs include, Intel's Indeo, MPEG, Cinepak, PLV, etc.

 

COLD Technology

COLD is the industry term for Computer Output to Laser Disk. The term COLD reflects the fact that optical disks (or laser disks) were the archival media utilized in the early systems. Current optical technology, however, offers CD-ROM-based archival subsystems, RAID subsystems, various optical disc jukeboxes or autochanger systems, and others--with an assortment of software for their use. Most people are familiar with COM (Computer Output to Microfiche), which is being replaced by COLD technology. But, in the imaging industry, COLD may be replaced soon by COAR (Computer Output Archival and Retrieval) which is more representative of the current archival and search and retrieve technologies--which will add more value and broad accessibility to applications based on computer output.

 

Compression

The large file size of audio, graphics and video files for CD-ROM applications reinforced the development of hardware and software compression-decompression procedures. Most compression algorithms are designed with specific types of files in mind (text, audio, video, graphics, etc.). Some of them involve intraframe compression (reducing the size of an individual frame), and interframe compression (reducing the amount of repetitive information from one frame to the next). There are even products that aim to compress the entire contents of a CD-ROM before mastering and, decompress when accessed-- 'on-the-fly'. Current compression CD-based products have implemented various options, indeed. But, in DVD, the compression options have been narrowed down--and they are specified in the DVD Books. (See, Codec,  DVD Specifications,  JPEG,  MPEG,  Lossy/Lossless Compression)

 

Compression Frame Rate

This expresses the frame rate used during the compression of the video--which is not the same as the Display Rate. (See, Display Rate,  Frame Rate)

 

Connectors

These are the physical cables, receptacles and plugs used to connect devices in and to a computer. Although they are designed for specific types of connection (serial, parallel, SCSI-1, SCSI-2, SCSI-SCA, etc.), most CD-ROM and other optical devices use different connectors and cables--depending on the manufacturer, operating system, and even model.

 

Constant Angular Velocity (CAV) and Constant Linear Velocity (CLV)

Magnetic and optical storage drives can rotate with constant angular velocity (CAV), or constant linear velocity (CLV). CAV, used by magnetic drives (and record players), is measured in RPM, and means that the read head sweeps the same angle, for the same amount of time, at all radii. CLV, used in CD-ROM, allows the head to read the same length of track at all times and radii, at a rate of 1.3 m/sec--also called 'reference speed, or scan rate.' CLV requires that the disc spin slower as the head moves to the outer edge of the disc; a CD-ROM, for example, spins from 539 RPM at the inner edge, to 210 RPM at the outer edge. DVDs also use CLV, at a reference speed of 4.0 m/sec. (See, Rotation)

 

Control Bytes

The CD-ROM physical block structure specifies a data user area of 2048 bytes and other sets of bytes, to make a full sector--including the 98 control bytes. These control bytes, with sub-channels at the bit level, are specified in the Red Book. They are key for much of the functionality of CD implementations. (See, CD Sector Structures)

 

Convergence

A term in the industry that tries to explain the pressures on optical technology, mainly CD-ROM development, to bridge the gap between computer users and television viewers. The aim is, ostensibly, to produce multimedia applications that would serve and satisfy the needs of both groups, with one hardware device. In some circles, the term currently includes conjunction of CD-ROM technology with the Internet and other network services.

 

Conversion

Generally used to mean conversion of computer files from one system to another, or from one format to another (DOS to Mac, EBCDIC to ASCII, PCX to TIFF, and so on). In some cases, conversion is used to mean putting the information on another media--as in digitizing information that is on paper, in microfiche, video, etc. Conversion is usually a key and expensive part of the data preparation process. In fact, the growth of the conversion industry is a reliable reflection of the growth of the CD-ROM, optical imaging, and multimedia industries. (See, Data Preparation)

 

Copy Protection

The movie industry's concerns about unrestricted copying or piracy of their DVD-Video content led to imposing copy protection measures in the DVD-Video specifications. The current main option is Macrovision, which implements Analog Protection System (APS) --which degrades the video stream that is being copied. There are other options as well--of varying sophistication or complexity, such as the Content Scrambling System. Moreover, the industry is working hard to make it illegal everywhere to defeat copy protection measures.

 

Country Codes

See, Regional Codes.

 

CPU

The Central Processing Unit, or processor chip, is the 'brains' of the computer. For floating point computations, the CPU employs the co-processor chip--and current CPUs include the co-processor unit. Database, spreadsheet, CAD-CAM and other vector graphics applications, and most software decompression algorithms benefit from the use of a co-processor. That is why some multimedia applications work smoother with a fast CPU and its coupled co-processor. Recently, Intel is promoting its new line of CPUs that implement MMx instruction sets--which will help multimedia applications.

 

CRC

Cyclic Redundancy Check is a method for detecting errors in data transfers. A special polynomial algorithm produces and uses a coefficient and a remainder (16 or 32 bits long) to check if the transmission proceeded without problems. CRC values change even if only one bit in the file changed--which makes it extremely reliable for checking integrity of files transmitted between computers.

 

CRT

Originally, somewhat appropriately, computer monitor screens were dubbed CRTs, because the Cathode Ray Tube was its biggest component. Current CRTs offer ever-increasing resolutions and sophistication. Flat display technology, however, does not employ the CRT and is becoming a competitor because it is no longer used only in portable or notebook computers.

 

[D]

 

Daisy Chain

Peripheral devices connected serially are said to be 'daisy chained,'--as in SCSI configurations. While a SCSI card uses only one slot in the bus, all the devices in the daisy chain are available, because each has a specific address, and the devices in the chain respond only to the instructions addressed to them.

 

DAT

Digital Audio Tape, generally high-quality 4mm magnetic tape in a cassette, with capacities up to over 1 Gigabyte, that has been used in the computer arena mainly as an archival and back-up medium. For CD-ROM, it is used as a transfer medium. For DVD, which deals in gigabytes, DAT has been replaced by DLT. (See, Transfer Media)

 

Data

Plural of datum, in the sciences, refers to sets of figures, measurements, expressions, etc. that, when expressed in a defined framework, acquire meaning that makes then information. For example, 45, 35, 75, are essentially meaningless figures (data); but, when expressed in terms of degrees Fahrenheit, they mean specific levels of temperature (information). In computer terminology, however, data generally is used to mean files with user information.

 

Data Area

This is the space in the track, specified by the ISO 9660 specifically for the sectors with user data. It is recorded after the System Area, and is followed by the Lead out. In DVD, this area is named Recorded Data Area.

 

Database

In traditional computing, databases are structured collections of fielded data sets that can be updated, manipulated, indexed and used as sources of appropriate information. With the advent of large collections of text, graphics, and other types of information incorporated in single applications, the concepts of database, media and information are expanding.

 

Data DiscMan

A Sony portable drive that plays Sony's 8cm discs, media that was used initially for audio 'CD-singles.' Since 1990, the Data Discman plays 'mini-CDs' or 'mini-discs' formatted according to the ISO 9660--which can hold up to 200 Kb of information. More recent implementations include compressed audio--using the CD- ROM-XA format. For some reason, the DataDiscman has not become popular in the US. (See, CD Singles)

 

Data Preparation

This is usually the most time-consuming and also the most expensive part of the application production process. Since, with rare exceptions, all the necessary data is usually in a mix of media, file formats, databases and others, it takes a lot of preparation and work to get them in the shape and formats appropriate for use in the CD-ROM application. In DVD, the specifications at the application level have specific requirements as to the preparation of the content (amounts, formats, compression, etc.). Therefore, data preparation must be a carefully planned step in the process. (See, Conversion)

 

Data Rate

In video applications, this is the quantity of data, usually expressed in megabits per second (Mbits/sec), that the hardware needs to receive either to compress or to display a video clip of a specified quality (bits/pixel), at a specified frame rate and resolution. Should not be confused with hardware transfer rates.

 

Data Search Information

In DVD-Video, DSI involves the codes for navigation, angle changes, jumps, etc. DSI includes sector addressing codes for the key reference frames of the video (such addressing helps the seamless display or playback of video streams).

 

Data Transfer Rate

Generally, this is the reading speed of the drive. The first CD-ROM drives had a transfer rate of 150 KB/sec. Since then, manufacturers kept multiplying that rate, and are now offering even 12X drives--and even higher speed drives are in the news. DVD specified a raw or minimum transfer rate of about 1.2 GB/sec (equivalent to 8X in CD-ROM). DVD-Video specifies a user data transfer rate of 11.08 Mbits/sec, and a constant Mux_rate of 10.08 Mbits/sec. The difference (1 Mbit/sec) is the system overhead, and is composed of PGCI and DSI codes. (See, Mux_rate,  Data Search Information,  Program Chain Information)

 

DBMS

A Database Management System generally involves policies about the coordination of data entry, database operations, output, access, and information security in an organization. Systems vary in size and sophistication, and there are many appropriate software DBMS front-ends in all platforms, and more and more DBMS include CD-ROM as their archival medium.

 

DCI

Display Control Interface (Intel-Microsoft) was produced for the PC platform, to provide Windows with better software decompression capabilities and support of video display cards. It improved Windows' capabilities to play multimedia and video applications.

 

DCT

Discrete Cosine Transform is a mathematical algorithm used in compression/decompression programs, especially for color graphics and motion video--such as in JPEG and MPEG. MPEG uses DCT for intraframe compression. MPEG's high rates of compression, however, are due mainly to interframe compression.

 

Delta Frame

In video compression, most algorithms maximize efficiency by comparing two frames in sequence, and recording and compressing only the bits or areas changed from one to the otherframe--which is called the 'delta frame.' The concept is implemented similarly in audio compression. (See, Compression,  Key Frame)

 

Demodulation

In data communications, transmission through telephone lines involves modulation at one end, and demodulation at the other end. The modem (MOdulator-DEModulator) is the device used for computers. (See, Modem)

 

Digital

Generally contrasted to analog, digital refers to the use of digits (0-9), in specific code schemes. The binary coding scheme uses 1s and 0s, and is the basis for digital computers. Although analog computers were developed, binary processors rule technology--from cheap consumer items to Cray supercomputers.

 

Digital Audio

Although digital audio can have a variety of sampling rates and quantization, the Red Book specifies CD-Digital Audio as being sampled at 44.1KHz, and quantized at 16 bits/sample, for high quality stereo sound (65,536 values). Therefore, sound of different quality, even if it is placed in a CD, is not Red Book Digital Audio. (See, CD-Digital Audio,  DVD-Audio)

 

Digital Linear Tape

DLT is the preferred or prescribed transfer or input medium-- so that the client's application or title (magnetic) can be input to the Laser Beam Recorder (LBR) at DVD-Video mastering plants.

 

Digital Versatile Disc

The DVD industry seems at odds about the meaning of DVD. While in some of the literature DVD is used to mean or imply Digital Video Disc, others use it to mean Digital Versatile Disc. Some have observed that the literature from Sony, for example, uses DVD to mean DVD, and that is that (maybe because Toshiba and Time Warner came up first with the Digital Video Disc name, to replace their SuperDensity CD). Although both usages seem to coexist, the trend seems to favor Digital Versatile Disc. (See, DVD)

 

Digital Video

In general, digital video is a coded binary string that is read by a computer (PC or other device) to produce and display the pixels that make up the frames of a video sequence. In general, the higher the frame rate the better the motion; and the higher the bits per pixel, the better the quality of color.

 

Digital Video Disc

See, DVD.

 

Digitization

Digitization generally refers to the process of converting data and information (in paper, analog sound tracks, graphics, etc..) into binary coded files for use in computers. Text can be keystroked or OCR'd, graphics are scanned, analog video signals are digitized, sound is sampled and quantized, and so on. (See, Conversion)

 

Direct Cut

This process, essentially, 'masters' a 'DVD one-off' on glass substrate. Generally, this is done for testing and demonstrations. A Direct Cut disc can not be used to produce the metal stampers for replication.

 

Directory Structure

Book B, specifications for DVD Video, outlines the required directory structure (such as the Root, Audio_TS and Video_TS, and user defined subdirectories) for the files that will make up a DVD-Video title.

 

DiscMan

See, Data DiscMan.

 

Disc Read Head--Disc Write Head

Storage drives (magnetic and optical) have a head or heads that float over the recorded area to read and write. Obviously, CD-ROM drives have only a read head, which involves a low-intensity red laser diode (a.k.a. infrared laser diode), lenses that focus the laser on the track, and others that redirect the reflections to one of the photodiodes for appropriate decoding. Some Write-Once and Rewritable optical drives involve two heads (to write and read), while other drives, including CD-Recordable, use only one head to do both--using a high-intensity blue argon laser for the write function. For mass replication of CD-Audio, CD-ROM, and DVDs, the glass master is produced by encoders that have special recording heads.

 

Disk Sector

In magnetic disks, formatting, provides a geography of the platters; which are divided into concentric circles, and these circles are further subdivided into sectors. Although sectors vary in size depending on their position in the disk, they have a specific capacity in bytes. This sectored framework is found in constant angular velocity (CAV) drives, and is compatible with the FAT used in PCs. When discussing optical discs (with c), 'sector' is used to refer to discrete amounts of data with a specific layout or structure along the single spiral track. (See, CD Sector Structures)

 

Display Rate

In video, the display rate is the number of frames per second actually being displayed. This display rate has usually been limited by the processing power of the hardware. 80386 and 80486 multimedia PCs can achieve, at best, a rate of 15 frames/sec. The newer Pentium multimedia PCs can achieve full-motion output, at 30 frames/sec.

 

DMA

Direct Memory Access takes place when an input/output device (hardware), or an application (software), issues calls or writes directly to system memory--while the CPU, essentially, lets that happen. MS-DOS implements a table of DMA channels for that purpose.

 

Dolby AC-3

This is Dolby Digital audio, using AC-3 compression (from a source PCM stream), sampled at 48 kHz, and 16 bits. This is one of the digital audio formats that are included in the DVD-Video specifications--required for DVD-Video titles for NTSC countries. It involves 1 to 5.1 channel sorround-sound, and is of higher quality than the CD-Digital Audio.

 

DOS

Disk Operating Systems pertain to microcomputers. In fact, early microcomputers operated with one of various operating systems. When IBM chose the operating system developed by Microsoft, which could handle hard and floppy disks, it was called Microsoft Disk Operating System. Since then, all operating systems for microcomputers, especially IBM-compatibles, are called DOS (MS-DOS, IBM-DOS, Dr. DOS, 4-DOS, etc.).

 

Double-layer Discs

The technology was developed by 3M, and enabled production of a CD with two recordable layers on the same side. To read it, the single head shifts the laser's focal length appropriately. The specifications for DVD include double-layer discs, and they should become common when appropriate technical aspects are perfected and available in mastering plants (especially bonding materials and technology).

 

Double Spin

See, Transfer Rate.

 

Double Density CD

This was the name for the CD format proposed by Nimbus Technology and Engineering (1994). It claims to encode more than two hours of a CD, by increasing the number of tracks (narrower tracks)in the disc. Double density, and more, was also demonstrated by Optical Disc Corporation (ODC), which proposed its own High Density CD specifications in late 1993. These efforts, however, did not attracte the attention that Philips, Sony, Matshushita, Toshiba and the other major players received for their own proposals--which led to the industry's initial DVD Specifications in late 1995. (See, DVD)

 

DRAW

Direct Read After Write was an expression originally used to differentiate W-O and Rewritable from CD-ROM technology. DRAW implied that W-O and Rewritable disks could be accessed or read immediately after being written to, while CD-ROM could not--because, by design, it had to be mass replicated first.

 

Driver

In computers, driver refers to a device driver, which is software that, under CPU control, implements device I/O functions or other functionality (video, sharing, graphics, printer, mouse, etc.).

 

DSP

Digital Signal Processors are specialized processor chips used for diverse functions, especially in modems, sound boards and serial ports.

 

DVD

It is used to mean Digital Video Disc, Digital Versatile Disc, or just DVD. DVD is the final product of the race for a high-capacity CD that started when Nimbus and Optical Disc Corporations (ODC) showed their capabilities to master double density CDs, and Philips demonstrated quad-density CDs. The emphasis turned, however, on what the industry leaders would support--and they were not of one mind. One camp, headed by Sony and Phillips, first promoted the MultiMedia CD, and then the High Density CD (HDCD, 1994)--which included single and dual-layered, single and dual-sided CDs, with corresponding capacities from 1.3 to 7.4 GB, and playing times from 47 to 270 minutes. The other camp, headed by Toshiba and Time Warner, promoted the SuperDensity CD (SDCD) and after changing the name, proposed the DVD (Jan95)--which included single and double-sided CDs, with capacities of 5 to 10 GB, and playing times from 135 to 270 minutes. It was understood that MPEG-1 was included. To keep within the traditions of the industry, and after the compulsory maneuvering, with help and pressure from the movie entertainment industry, the two camps compromised on one set of specifications. The announcement of the DVD specifications (Sep95) mentioned a double-layer single-sided disc, same size as the CD (12 cm), with a capacity of 4.7GB per layer, including double-sided, double-layer options, the use of EFM+ modulation, and an even more precise version of the Reed-Solomon error detection and correction scheme. Although the books of specifications cover five different products (ROM, Audio, Video, Recordable, and RAM), most analysts thought the emphasis on the video specifications satisfied the video industry's need for a disk with sufficient playing time for a full-length movie, using MPEG-2, backward compatible, and other features. Moreover, the physical specifications include double- layer and double-sided DVDs; but the first products in late 1996 were all single-side single-layer titles. Moreover, the delays were due to copy protection and regional code requirements demanded by the movie and video industry. There have been scheduled 'roll-outs' of DVD all over the world and, in March 1997, scores of DVD-Video titles and drives were officially rolled out in selected US metropolitan centers. (See, Copy Protection,  Regional Codes)

 

DVD-Audio

Book C (not yet final) will provide the specifications for DVD-Audio. The initial specifications allow use of Red Book CD- Digital Audio sound (44.1 KHz, 16 bit sample), as well as 'true' DVD-Audio of two types: Audio sampled at 48 KHz, 20 bit samples, and 8 channels for 96 minutes per layer, and audio sampled at 96 KHz, 16 bit samples, and 8 channels for 86 minutes per layer. Both can be output as Dolby AC-3, Subcode, or LPCM. The DVD-Audio players will have MPEG2/Dolby AC-3 decoder boards, and it is expected that all DVD-players will have the capability to play DVD-Audio--at least in the second generation models. There are, however, other audio (compression) formats being proposed as well--especially those pushed by Sony-Philips engineers. Also, some audio copy protection issues remain unresolved. Unavoidably, the movie industry has its hands in these matters as well.

 

DVD Capacity

See, Capacity of DVD.

 

DVD Consortium

Now DVD Forum, this is the broad industry group that achieved the compromise DVD specifications in 1995. It includes: Hitachi, Matshushita, Mitsubishi, Philips, Pioneer, Sony, Thompson, Time Warner, Toshiba and JVC. They were required a serious capital contribution, and continue the work on the specifications. The Consortium, through its members (mainly Philips, Thomson & Toshiba), also licenses the specifications. Encryption technologies (Matsushita), copy-protection technologies (Macrovision), and other technologies are generally licenced free of charge to hardware manufacturers (others pay).

 

DVD Player

This is a generic term, since there are DVD-Audio, DVD-ROM, DVD-Video players--while DVD-Recordable and DVD-RAM drives are not yet ready for the market. DVD-Video has complex hardware and firmware requirements on the player, and the DVD Player Reference Model specifies the capabilities for a DVD-compliant player for consumer market--outlining the standard and optional sets of features. DVD-Video displays to a TV monitor, but DVD-ROM players will have the hardware (boards) to play DVD-Video and DVD-Audio titles. But, DVD-Video copy protection and regional code issues further complicated and delayed the marketing of players, precluding the implementation of some otherwise acceptable software options, or external devices. It is expected that newer players will implement the required copy protection and regional codes.

 

DVD-R

Book D, will provide the specifications for DVD-R (DVD- Recordable), which aims to replace the surprisingly popular CD-R. It is expected in different models in early 1998. The announced capacity of DVD-R is 3.86 GB per side. While double-sided products are envisioned, current DVD-R technology seems to preclude double-layer implementation.

 

DVD-RAM

Book E provides the specifications for DVD-RAM. This is essentially a rewritable disc, using phase change technology-- although final specifications are not out. The capacity of DVD- RAM will start at about 2.66 GB per side. While double-sided products are promised, current phase-change technology seems to precllude double-layer implementation. Although the first DVD players may not be able to read DVD-RAM, the industry expects second and later generation players to read both DVD-R (Recordable) and DVD-RAM.

 

DVD-Recordable

See, DVD-R.

 

DVD Regional Codes

See, Regional Codes.

 

DVD-Rewritable

See, DVD-RAM.

 

DVD-ROM

Book A will provide the specifications for DVD-ROM. Currently, there seem to be no limiting application format requirements, but some are expected. It looks like DVD-ROM will be the replacement of CD-ROM and all its varied implementations--although video applications will undoubtedly use the DVD-Video format. It is expected that DVD-ROM will outpace DVD-Video and DVD-Audio early in the game.

 

DVD Specifications

            -----------------------------------------------------------



Application      ?        Video      Audio       ?            ?



Formats                   Spec.      Spec.     



            -----------------------------------------------------------



Logical     UDF-Bridge (Micro UDF+ISO 9660)     UDF           UDF 



Format



            -----------------------------------------------------------          



                  Physical Format              Physical      Physical            



Physical                                       Format        Format 



Format      -----------------------------------------------------------          



                    Disc Specifications        Disc Specs.   Disc Specs.         



                      (Read-Only Disc)         Write-Once    Rewritable



            -----------------------------------------------------------



Specs.      Read-Only     Video      Audio     Write Once    Rewritable          



            Specs.        Specs.     Specs.    Specs.        Specs. 



            -----------------------------------------------------------



Book.       Book A        Book B     Book C    Book D        Book E  



            -----------------------------------------------------------

DVD-Video

Book B includes the specifications for DVD-Video, which influenced the key aspects of the specifications for the DVD family. DVD-Video supports high quality full motion MPEG-2 video of 720x480 pixels/frame, at 30 frames/sec (NTSC), and 720x576 pixels/frame at 25 frames/sec (PAL). It provides for high quality audio (MPEG-2, 7-1; Dolby AC-3, 5-1; or Linear PCM), with up to 32 sub-picture elements such as captions and stills (to a TV monitor). In addition, it offers the user choices of languages, various navigation and interactive controls (including random access for interactive games), and regional coding, copy protection and other features demanded by the movie industry. All DVD players will support a basic set of options. A single-side, single-layer DVD-Video can contain a 133 minute full-featured movie title.

 

DVI

Digital Video Interactive, developed by Intel and IBM, is conceptually similar to CD-I. DV-I, however, emphasizes a compression scheme that employs proprietary chip sets on add-on boards (to compress and decompress audio and video). These DV-I boards display VHS quality full-motion video, and use the CD as the storage medium. But, the surge of applications implementing the MPEG specifications affected the growth of DVI. It is, however, still used in public information, education and training.

 

[E]

 

EBCDIC

Extended Binary Coded Decimal Interchange Code, is an 8-bit, no parity, 256 character code (in several variations), used mainly in IBM mainframes and related platforms. Unlike the 'extended' ASCII character sets, EBCDIC variants are not standard. Conversion between EBCDIC and ASCII platforms is therefore not an automatic process. (See, ASCII)

 

ECC Constraint Length

In DVD, the ECC constraint Length is 16, which is the number of sectors that are interleaved to provide more efficient error correction. Since interleaving 'spreads' the codes in sectors, it is expected to make it easier for the corrrection codes to 'reconstruct' the bytes--such as the erroneous reads produced by scratches, BLERs, etc. (See, Interleaving)

 

EFM

Eight to Fourteen Modulation is used during encoding, because the 8-bit 'magnetic' byte has to be modulated to a 14-bit 'optical' byte. Technically, this modulation is necessary to allow encoding of two consecutive 1s--which would be impossible with the scheme of pits and lands using 8-bit bytes (1s and 0s). In fact, the changes in reflectivity (as the laser light moves along the sequence of pits and lands) are coded as 1 channel bits. Two consecutive 1s are therefore not possible. Moreover, the 'lands' in between the 1s are represented by 0 channel bits, and the number of 0s represent the run-length. The bits in an optical byte are known as 'channel bits' to avoid confusion, and because they are transferred to the controller board through a specific channel. Furthermore, the fourteen-bit optical byte is provided three additional channel bits, known as merging bits--to eliminate transition conflicts between consecutive optical bytes. During the read process, the interface card demodulates the 14- bit optical code to the 8-bit code used by the computer--and all channel bit-level modulation and processing remain transparent to the user.

 

EFM Plus

EFM Plus Modulation is truly an 'eight to sixteen' modulation of magnetic to optical channel code during the encoding to produce a DVD master. Although it is implemented in the same manner as the Eight to Fourteen Modulation, the two additional bits (and the 'three merge bits' in EFM) are used for transitions between sectors, especially in multilayer DVD applications. For some reason, the odd EFM Plus designation is broadly used instead of the more precise 'Eight to Sixteen Modulation.' (See, EFM)

 

EISA Bus

The Extended ISA Bus, was introduced by PC manufacturers as their alternative to the IBM MCA bus. It is also a 32-bit bus, supports high speed data transfers, allows post-installation configuration of adapter cards, and can access higher amounts of system RAM. Unlike the ISA bus, the EISA bus does not support 8- bit adapter cards. PCI buses with Pentium CPUs have overtaken EISA technology.

 

Electroforming

In jewelry, it is used to lay fine gold or silver surfaces on complicated pieces, or on extremely fine shapes and surface configurations, because the electromagnetic field sets the fine metallic particles in place. In the CD industry, where the pits in the glass master are measured in tenths of microns, electroforming is used to 'form' the initial metallic (nickel) mold that is used to produce the stampers for the injection molding machines. (See, Mastering,  Metallic Coating)

 

Encoding

In the computer arena, programmers and users see and work with higher level languages, but the processors deal with machine languages and binary code. To use optical technology, it was necessary to develop an encoding scheme that would produce the 8- bit computer bytes, while using the pits and lands produced by the laser on the disc surface. The resulting optical encoding scheme, uses a 14-bit byte modulated from the 8-bit byte--in which the 1s represent the transitions between lands and pits, and the 0s represent the run-lengths. In addition, there are various other sets of system and error detection and correction bits that are encoded so that the technology works as designed-- but the user does not deal with these. The mastering machines do the encoding, and the controller card of the drive does all the decoding.

 

Encoding Technologies

See, Optical Recording Technologies.

 

Enhanced-CD

A format that uses the Red Book to produce a CD-Audio that includes data and/or grahics in Track 1--addressing most of the problems of the Mixed-mode disc. There are variations of the Enhanced CD (CD-Extra or CD-Plus, Hidden Track, etc.), and Windows 95 apparently supports it.

 

EPROM

Erasable Programmable Read Only Memory is found mainly in PC motherboards. Until recently, all important hardware configuration, BIOS, and other defined information was stored in ROM chips--to prevent accidental erasures or modifications. But, with EPROMs, knowledgeable users can reprogram ('burn') the code in those chips as deemed necessary. EPROMs are also used to provide firmware for higher-end hardware configurations.

 

Erasable

In optical technology, erasable generally referred to optical drives that allow the user to write and erase at will--just as with magnetic hard drives. Currently, however, the preferred term is rewritable, as in magneto-optical rewritable technology. (See, Optical Recording Technologies,  Orange Book)

 

Error Detection Codes (EDCs) and Error Correction Codes (ECCs)

For data integrity, CD-Audio includes two levels of CIRC error detection and correction, as specified in the Red Book. Because computer data requires higher that audio levels of integrity, the Yellow Book specified a third level of such codes in each CD-ROM sector (4 bytes EDC and 276 bytes ECC). This third level involves a layered error detection and correction scheme, and is sometimes referred to as the Block Error Correction codes. (See, Integrity,  CIRC,  CD Sector Structures,   Reed-Solomon Product Code)

 

Error Rate

See, BLER.

 

Exabyte

Originally a brand name, it is used commonly to refer to the high quality, 8mm wide, magnetic tape (designed for video), in special cassettes, of capacities up to over 2 GBytes, currently used in the computer arena mainly as an archival medium, and in tape libraries--also manufactured by Exabyte. In CD-ROM, 8mm Exabyte tapes are used as a transfer medium. (See, Transfer Media)

 

Expansion Bus

Because of the growth in computer devices, some users fill all available slots in the main bus. Especially in portables and luggables, expansion buses, some of them proprietary, allow users to connect other controller cards and devices to the main bus.

 

[F]

 

Fielded Database

Some years ago, this phrase would have been considered redundant, since databases were composed of data in fields. But, since the advent of large collections of text, and since the noun textbase did not catch on, 'fielded databases' and 'fulltext databases' are widely used. Fielded databases are, essentially, those that do things with data in fields--the way dBase and others do. (See, Full-text Database)

 

Floptical Disk

The name implies the combination of a floppy disc and optical technology, but the floptical disk is a magnetic disk. It uses optical technology only to align the head along the tracks, which are at a much higher density than regular floppy disks. That density accounts for its capacity--about 20 MBytes. But, floptical disks did not fare as well as first expected.

 

Foreign File Access

The Apple operating system provides Foreign File Access to allow reading of CD-Audio and CD-ROM (ISO 9660 and HSF) discs. In a quite different option, ISO 9660 discs can be read by Apple computers that have the Apple Extensions for ISO 9660--which, essentially, make the CD-ROM look like an HFS-formatted disc. (See, MSCDEX.EXE)

 

Format

In the computer arena, storage devices involve physical and logical formats. Magnetic storage devices implement a physical structure (MFM, RLE, IDE, SCSI, etc.). A high level formatting program establishes its physical layout, and a low level format assigns logical identities and file allocation tables to all its partitions. CD-ROM discs use the physical format defined by the Red Book (which defines the size, tracking, sector contents, etc.). The standard logical format is defined by the ISO 9660, the volume and file structure that was the key for the growth of CD-ROM. Because DVD involves capacities above 4GB (limit of sector addresses in ISO 9660), other format options are part of the DVD specifications. (See, ISO 9660,  CD-ROM Specifications,  DVD Specifications,  UDF)

 

Frame

During mastering, the CD-ROM sector is subdivided into 98 frames, and the bytes in those frames are modulated from 8 to 14 bit structures and provided with three merging bits, to insure fluid concatenation. All this manipulation of frames and bits is done by the equipment, and is transparent to the user. Obviously, in video parlance, frame refers to the unit of graphic display. (See, Encoding)

 

Frame Rate

Commonly, frame rates are used to imply video speeds, and the higher the frame rate (video speed) the better the motion (30 frames/sec as opposed to 8 frames/sec). But, users must be aware that a video clip involves two frame rates: a compression frame rate and a display frame rate, and these can be different due to hardware, type of video, and other variables.

 

Frankfurt Group

A group of the industry's top firms met in Frankfurt, in 1991, and proposed an ISO 9660-compatible standard for multi-session recording--which was not part of the ISO 9660. They also supported the Rock Ridge Proposal, which deals with multi-platform volumes. The Frankfurt Group's proposal, published by ECMA as Working Paper TC 15, deals with logical specifications for the Orange Book, Part II (W-O). It establishes two types of file structures: Type 1 is compatible with other ISO 9660 discs, and can be read by a standard drive. Type 2 allows 'incremental multi-session recording' in a CD-WO volume. Hybrid Discs include both types of file systems, but standard drives could only read the Type 1 area--but, more importantly, the Type 2 areas would allow recording applications that can be used by different operating systems or platforms. (See, Multi-session)

 

Full-motion Video

In general terms, it implies video display of continuous movement, at a frame rate that minimizes interframe delays (jerkyness of movement in the picture). More and more, however, it is used to mean full-screen video that plays at 30 frames/sec in NTSC format, or 25 frames/sec in PAL format.

 

Full-text Database

Essentially, this is a large collection of textual information or documents--ready to be managed by a full-text retrieval software package. Therefore, a large collection of text files alone does not a full-text database make. If however, they are configured and indexed for software that can perform searches across all of them, and perform output functions, then and only then you have a full-text database.

 

[G]

 

Glass Master

This product of the mastering process involves a large glass disc, duly prepared and coated with a recording layer--usually Photoresist. After recording, the glass master goes through a special chemical process (akin to development), and is then metallized. The metallized glass master, also referred to as the 'positive,' is submitted to electroforming, to produce the metallic (usually nickel) master--which is necessary for producing the stampers for the injection molding machines. (See, Mastering)

 

Green Book

Published by Philips and Sony in 1986, the Green Book establishes the block structure for CD-I (Yellow Book compatible), addressing problems of synchronization and use of file compression for multimedia applications (which involve CD- Audio, other audio, data, graphics and video). Although it looks like a CD-ROM XA sector, a CD-I sector makes use of the area (8 bytes) left unused in the Yellow Book CD-ROM sector structure. (See, CD-I)

 

GUI

Graphical User Interfaces are becoming predominant. Computer operating systems are designed to work, out of the box, implementing the command line (prompt), in the basic text mode screen (80x25 for PCs and 80x24 for Unix terminals, etc.). But, the growth and popularity of graphical applications led to the implementation of graphical user interfaces. GUIs work in graphics mode; that is, they display everything on the screen as a graphic and, instead of the command line, they implement menus and other graphic objects that are operated with special keystrokes or a pointer device--the ubiquitous mouse. Microsoft Windows is the predominant graphical user interface in the IBM-compatible platform, and others predominate in the OS/2, UNIX, and other operating systems.

[H]

 

Hard Drives

Originally known as Winchester drives, these magnetic storage devices have one or more non-removable solid platters--as opposed to the floppy-disk drives. Hard drives come in various types, different capacities and configurations--and are connected to the bus through a controller or interface card. There are removable hard drives, which allow removal of the component that contains the platters--a workable option for users with security concerns. (See, Format)

 

HDTV

High Definition Television has been in use in Japan and Europe for some time. The US tried (unsuccessfully) to convince all (especially the Japanese) to use the HDTV specifications developed by the US industry, which only delayed the implementation of HDTV in the US. The FTC approved the Digital TV (DTV) standards (1150 scan lines, 4-channel audio, aspect ratio 16:9). Some expect new DTV sets by the end of 1998. Apparently, the NTSC and PAL video resolutions and frame rates supported by DVD can be upgraded to support HDTV. The DVD data tranfer rate, however, would have to double to support the 19 Mbits/sec required by DTV. There is expectancy to find out what DTV will really implement.

 

Header

In computer circles, headers meant a set number of bytes at the 'head' of the file--with information about the file, especially necessary when dealing with large numbers of files in tapes. In current PC usage, the term refers more often to headers of graphics files. A TIFF file, for example, can have extensive functionality because the TIFF header has broad features and flexibility. Graphics headers, however, can become problematic, because specifications about headers are rather liberal, and developers tend to include in the headers additional information useful to their applications--often causing problems to others.

 

High Density CD

The technical specifications of a High Density CD (HDCD), proposed by the Optical Disc Corporation (ODC), were submitted to the International Electrotechnical Commission (IEC) as a draft standard. It described the use of a new higher definition red laser to achieve a capacity of up to 3.3 gigabytes of user data in a CD. It apparently also claimed that, using MPEG compression, it could output at a data transfer rate of 3.3 Mbits/sec, making the HDCD able to store a 135-minute full-length movie. The race towards DVD seems to have sidelined the HDCD effort. (See, DVD,  Double Density CD)

 

High Sierra Format

The development of the High Sierra Format is an essential element of the industry's folklore. After the publication of the Yellow Book, facing the growth of CD-ROM applications in proprietary formats, representatives of TMS, DEC, Microsoft, Hitachi, LaserData, Sony, Apple, Philips, 3M, Video Tools, Reference Technology and Xebec, met at the Del Webb's High Sierra Hotel and Casino, in Lake Tahoe, Nevada, to agree on basic specifications for a common logical format and file structure for CD-ROM. Soonafter, theypublished the "Working Paper for Information Processing: Volume and File Structure of CD-ROM Optical Discs for Information Exchange (1986)," since known as the High Sierra Format (HSF). Their unprecedented effort proved to be key for the effective role of standards in the CD-ROM industry. And, to their credit, the ISO 9660 is essentially their Working Paper with some pertinent modifications and extensions. Today, only organizations that do not distribute their CD-ROM application beyond their organization produce HSF discs. (See, ISO 9660)

 

Hit

In search and retrieve applications, hits refer to the matches or instances found by the software. Most applications remind the user to combine search parameters appropriately to generate efficient (narrowed-down) searches and produce the most relevant results or matches.

 

Hollywood Digital Video Advisory Group.

A committee of representatives of the entertainment industry (Columbia, Disney, MCA/Universal, MGM, Paramount, Viacom, Warner Bros., et al.) that met in 1994, and proposed their guidelines for a desired DVD product. Those guidelines were important for the compromises towards the final DVD specifications. (See, DVD)

 

HPSB

The High Performance Serial Bus, developed by the IEEE, specifies a no-loop bus that can connect up to 63 devices on a single bus. The base transfer rate is 100Mbits/sec, and highest expected transfer rate is 400Mbits/sec--to accommodate future devices and PCMCIA features. HPSB, as an interface between devices, does not specify its own packet protocol; it will use other protocols. ANSI was considering the SCSI-3 specifications (command, transfer and control schemes) for its own HPSB specifications. (See, Bus,  SCSI)

 

Hub

This is the area about the central hole of the optical disc-- it is also called clamping area. The spindle of the drive clamps the disc by this hub, which should fit rather precisely to provide reliable centering and eliminate flutter as it transfers the rotational movement imparted by the motor. For obvious reasons, this area must be kept clean to prevent any slippage.

 

Hypercard

Interface card and software for Macintosh computers, to use and produce multimedia applications. The software development tool in the recent version 2.3 includes text-to-speech (with Plain-talk software) and other up-to-date capabilities. Since Hypercard was bundled with the Macintosh, its users have been spared the problems of compatibility and upgradability of the multimedia kits and peripherals in the IBM-compatible world.

 

HyTime

Hypermedia/Time-based Structured Language is an international standard (ISO/IEC 10744:1992) for an SGML-based set of semantic extensions to SGML. They help structure or represent hypertext and multimedia elements in SGML documents--recent proposed extensions involve maps, music scores and others.

[I]

ID

In DVD, Identification Data is a four-byte field that identifies each individual sector, providing for direct sector addressing or access.

 

IDE Interface

The Intelligent Device Electronics interface supports ISA, EISA or MCA buses, and is much smaller than the original disk controller cards. IDE hard drives include most of the circuitry that previously resided in the interface card. The growth of multimedia helped the growth of sound cards and of IDE controller cards that support CD-ROM drives.

 

IEC

In DVD titles, ID Error Correction involves two error correction bytes in the header of each sector.

 

Image

After the CD-ROM application works as desired in the PC, the data, retrieval software, indexes, interface, and other files are placed in the desired order--aiming for their most efficient location in the eventual CD-ROM. Usually, the application is tested at this stage. And, then, this collection of files, in appropriate block sizes, along with descriptors, etc., is written as a large file, an 'image' to be sent for mastering. More precisely, an 'ISO image,' refers to the contents of a disc, premastered in ISO sectors, that will be used to master an ISO 9660 volume. (See, Premastering)

 

Imaging

This now popular term refers to the use of computers to work with graphics, as well as conversion of documents to computer usable graphics formats. The imaging hardware and software industries have been high growth industries these past years. In fact, the multimedia, archiving, online document management, and business forms processing and other arenas are certainly poised to keep it that way.

 

Implementation Levels

The ISO 9660 specifies three Interchange Levels--which deal with file naming and their use by different operating systems. But, since some operating systems can not implement the interchange levels effectively, the ISO 9660 defines two levels of implementation. Implementation Level 1 allows producers to limit their implementation of the features of the chosen interchange level. Level 2 specifies that all the features of the ISO 9660 interchange levels must be supported. In the IBM- compatible world, for example, because MSCDEX.EXE supports only Implementation Level 1, some features specified in the interchange levels are generally not used, and others are used with some limitations (path lengths, characters to be used in filenames, number of directory levels, and others). (See, Interchange Levels)

 

Indeo Video

This codec, introduced by Intel, supports high quality video (320x240) that is used in multimedia applications, and allows software-only playback with PCs with 486 or Pentium CPUs. It is also supported by Microsoft's Video for Windows and Apple's Quick Time--which also has a Windows version. Intel's Indeo supported vector quantization technology, but the recently introduced version 3.2, Indeo VI (video interactive), is said to support a new hybrid wavelet-based technology. As with previous versions, developers can use Indeo VI royalty-free. (See, QuickTime)

 

Indexing

In CD-ROM, indexing involves assigning searchable 'addresses' within a track--which can be up to 99. But, in data management, indexing involves creating sets or tables of pointers to the records or information in the database. With the new processors, complex indexing is used for search and retrieve functions in large and sophisticated databases or large collections of text. Nevertheless, indexes or the 'indexing overhead' for large full-text databases can take up considerable space in the CD. (See, Full-text Database)

 

Injection Molding

This is a common industrial process to produce plastic products of all shapes. The mastering and replication plants require costly equipment and highly clean environments. The injection molding machines fitted with appropriate stampers, stamp or press the molten polycarbonate. Thus, the replicate (or substrate) is allowed to cool before it is moved for metallizing and given a coat of protective lacquer. Some injection molding machines produce 7 to 10 replicates per minute, while some of the newer machines claim even higher rates. There is a new method in testing, which uses photolithography, and a continuous roll of metallized polyester, to produce the CDs (by exposing, developing, cutting and bonding to the substrate). But, injection molding is here to stay for the foreseeable future, specially since current replication plants claim that they will be able to handle DVD replication--with some adjustments or new equipment.

 

Integrity

Integrity is another conceptualization of reliability. It is often expressed as a number of erroneous bytes (characters) read per number of bytes read--after error detection and correction. The Yellow Book specifies a much more effective scheme than that in the Red Book. In fact, the industry's figures for CD-ROM integrity are 1 in 10 exp(13)--or about one erroneous byte in ten trillion (an erroneous byte in about 5,000 CD-ROMs. In DVD, the use of the Reed-Solomon Product Code is supposed to increase that integrity by a factor of 100. (See, CIRC,  Error Detection Codes,  Reed-Solomon Product Code)

 

Interchange Levels

The ISO 9660 defines three downward compatible levels of interchange--which define the length of filenames, and the ways they can be recorded in a CD-ROM. Level 1, which is more restrictive but compatible with MS-DOS, is obviously the most commonly implemented. The expectation is that the increasing demand for multi-platform applications will push the implementation of levels 2 and maybe even level 3 features. (See, Implementation Levels)

 

Interface

In computers, a user interface is that software component that the user sees, interacts with, and employs to control and navigate the application. In more sophisticated database environments, common interfaces refer to software programs that enable users and operators in different computer environments, when appropriately connected, operate a specific program on a main computer or network.

 

Interlacing

In interlaced video display, a field refers to the frame made up by each other scan line (rows) during a vertical (full) refresh of the frame, reason why a field is considered a 'half- frame.' Therefore, when the two fields (half-frames) are interlaced, refreshing the frame sequentially, it is supposed to give the user the impression that the entire frame has been refreshed twice--sharpening the image. However, with the advent of more powerful video display cards, and video memory at lower prices, non-interlaced monitors are more common today.

 

Interleaving

In terms of CD-ROM encoding, where the track is a single spiral line, it means the appropriate interposition of portions of files, of different data types (text, video, audio, graphics, etc.), so that the application can use it for the most coordinated display or output (making it seem as displaying varied data types at the same time). The process is performed at the sector or logical block level (if the sector has been broken down to that level). The ISO 9660 provides specifications for interleaving, and CD-ROM-XA applications have implemented them.

 

ISA Bus

The Industry Standard Architecture bus, introduced by IBM in the early 1980s, was a motherboard with a 16-bit data bus that was freely copied for the manufacturing of IBM-compatible PCs. Although never approved by a standards-setting organization, the ISA bus was common to most 286, 386, and 486 Pcs. Its limitations became clear in face of the new faster CPUs (486, Pentium, etc.), and it was replaced by EISA and PCI buses.

 

ISO

The International Standards Organization, composed of scores of international specialized committees, with main Secretariats worldwide, is the accepted source of standards for electronic and computerized data communications and information processing within the Open Systems Interconnection (OSI) framework.

 

ISO 9660

Issued by the International Standards Organization, its formal title is ISO 9660: Information Processing--Volume and File Structure of CD-ROM for Information Exchange (1988). This multi-platform logical structure has been the key standard for the growth and worldwide acceptance of CD-ROM as a publishing and information distribution media and, since then, as the basic format structure for other implementations of CD-ROM in the computer arena. (See, CD-ROM Specifications)

 

[J]

 

Jewel Case

This is the plastic shipping and storage case for CDs. Although the original practical design of the jewel case received no compliments, it is still used throughout the industry. There is, however, a veritable growth industry in light CD-ROM mailers, storage packets, and colorful mailers--especially for promotional mailings. DVD products, specially DVD-Video, will add to the variety with their special requirements

 

JPEG

A versatile and commonly used color graphics compression specification adopted by the Joint Photographic Experts Group. Hardware and software JPEG implementations allow setting the desired compression, from 24-bit lossless (usually 2:1) to smaller bit size lossy compression rates (up to 60:1 in some cases). This allows users to insure retention of detail and precision of the original. For everyday graphics work, recommended JPEG compression ratios range between 25 and 35:1.

 

Jukebox

CD-ROM jukeboxes allow users to access collections of CD-ROMs. There are various types of CD-ROM jukeboxes, with different capacities (Pioneer has one with 500 CDs, and Disc has one with 1478 CDs.). Some implement one or more drives, some include CD-Recordable drives, and most recent products come with software that supports major LAN configurations. In some circles, 'optical jukebox' refers to jukeboxes with WORM and Rewritable optical discs. (See, CD-ROM Tower)

 

[K]

 

Kbps

Kilobits per second, also Kbits/sec, which means 1000 bits per second, is used mainly in computer communications, for transmission rates and hardware bandwidths.

 

Key Frame

Video Compression algorithms start with a Key Frame, which contains data of all the pixels in the frame, and does not depend on another reference frame when addressed. The subsequent frames are compared to it, and only the difference is processed. In video clips where the frames change drastically (as in changes of scene, change of direction, etc.), the compression program will define another key frame. (See, Compression ,  Delta Frame)

 

Kilobyte

In computer usage, this basic number means 1024 bytes, which is 2 to the tenth power. It is used to account storage capacity, file lengths, and other byte-related amounts. Today, larger multiples are in everyday use (Megabyte, Gigabyte and so on), but they are often wrongly interpreted to mean multiples of 1000. (See, Kbps)

 

Kodak Photo CD

See, Photo CD.

[L]

Label

CD-ROM, and other optical discs, are usually labelled on the 'back' side. Earlier, the label was generally screen-printed at the replication plant, in up to three colors, as part of the basic price. Today, there are various printing options, including some do-it-yourself kits for CD-R one-offs. While labels have specific information about the product, they should also include the industry's 'DISC' logo that identifies the disc as an CD-Audio, CD-ROM, CD-I, etc.

 

LAN

Local Area Network (LAN) and Wide Area Network (WAN) technologies have incorporated optical devices into most of their architectures. Some sophisticated servers now enable multi-user access to CD-ROM drives and CD-R recorders throughout the network.

 

Lands

During recording of a glass master disc, a high power concentrated blue argon laser beam burns pits in a spiral track on the specially prepared recording surface. The 'lands' are the clear spaces between those pits.

 

Laser

Light Amplification by Stimulated Emission of Radiation was demonstrated about half a century ago, with an original ruby laser. Today, lasers abound to suit diverse technologies and applications. Some magazines have reported tests of blue, blue- green, and blue-purple lasers of higher precision, which will make possible higher density optical discs. Ultraviolet lasers produce heat and require cooling--just as do the barely visible violet Krypton gas lasers. Cooling and size requirements are key to the implementation of a laser to optical disc technologies. (See, Blue Laser)

 

LaserCard

A small card that has a special backing (includes a recordable layer), and can be recorded and read by special drives (optical card readers). Some cards employs ablative write-once technology, and can store about 3MB of data.

 

LaserVision

Introduced in 1978 (Philips), the LaserVision disc was one of the original implementations of optical technology. It was used to record video (analog), and became prominent in the interactive video training and educational market. Pioneer remains in this arena with its LaserDisc, and there is no sign that Pioneer will abandon it.

 

Lead-In--Lead-Out

These are lengths of track before the beginning and after the end of the coding. In single session applications, they serve as 'markers;' the lead-in includes the Table of Contents, and the lead-out can include code to stop the player. CD-Audio tracks (songs) implement lead-in and lead-out to help song selection. In mixed-mode applications, each track with different type of data (text, video, audio) is required to include pre-gap and post-gap spaces. DVD also uses lead-in and lead-out.

 

Linear PCM

Linear Pulse Control Modulation is a string of sampling codes for an audio file, a code for each sample. Linear PCM does not involve compression, and can be used in DVD. (See PCM,  ADPCM,  DVD-Audio)

 

Logical Structure

In the computer industry, operating systems are designed to use a particular logical structure for data storage. For CD-ROM, however, the ISO 9660 specified the standard volume and file format to serve various computer platforms or operating systems. With appropriate modifications, and implementing two modes, the ISO 9660 made it possible for CD-ROM to involve text, graphics, audio and video in various implementations. (See, ISO 9660)

 

Lossy/Lossless Compression

Certain compression algorithms can produce outstanding compression ratios, but often at the cost of imperfect decompression; that is, the decompressed data is not identical to what it was before compression. Imperfect decompression (even if only a few bits per millions of bits) is called lossy--because of the loss of bits in the process. Lossless compression, on the other hand, employs algorithms that do not lose data in decompression, and although they may not produce great compression ratios, they provide integrity or reliability. When working with graphics and sound, some lossy compression is considered adequate, especially when storage and bandwidths are serious considerations. (See, Compression)

 

[M]

Mass storage

This is a relative concept. When PCs were introduced, 10 MB hard drives were considered adequate mass-storage devices. For current PCs, magnetic disks of one gigabyte or two, CD-ROMs and optical discs are common mass storage options. Indeed, the pressure for larger storage devices will continue.

 

Mastering

Mastering involves producing a glass master disc that is necessary for the mass reproduction process. Mastering takes place in a 'clean' environment, where the encoders use a high power blue argon laser beam to 'burn' pits on a large glass disc coated with a sensitive recording layer (usually photoresist). Once treated or 'developed' (chemically), the glass disc is referred to as the master or positive. Using electroforming technology, this glass master serves for the production of a metallic master (usually nickel), generally known as the 'father.' (It is also called a stamper, if it is used for reproduction of small runs.) For large mass reproduction jobs, the 'father' is used to produce intermediate 'mother' molds which are used to produced the necessary metal stampers ('sons' or production stampers) that are used in the injection molding machines. Mastering and reproduction are usually done at the same plant. For DVD, double-layer, and double-sided products will require sophisticated replication, bonding, lacquering and drying procedures. (See, Injection Molding)

 

Matches

See, Hit.

 

MCA Bus

Micro-Channel Architecture Bus, introduced by IBM in 1987, is a 32-bit bus that can allow access to over 64 MBytes of system RAM. The versatile MCA bus, also allows post-installation configuration of adapter cards using a software program. At the outset, CD-ROM drives with controller cards for the MCA bus were higher priced. But, for various reasons, the PC industry has not followed IBM in the use of micro-channel technology.

 

Media

In the computer arena, media refers to storage media. Optical technology uses various types of media or discs. CD-Audio and CD-ROM use the polycarbonate substrate for mass replication, but CD-Recordable and CD-Rewritable discs require multi-layer media, with specially designed compounds and coatings. (See, Image)

 

Media Control Interface

This interface (by Microsoft and Intel), developed as an API for Windows, handles multimedia elements (audio, video, graphics) in different media (videodiscs, CDs, etc.) so that they can be played effectively in PCs.

 

Megabyte

In computer circles, a Megabyte (MB) is 1024 KBytes, or 1,048,576 bytes.

 

Metallic Coating

After injection-molding and cooling, each disc undergoes metallizing--a process that gives the CD a metallic coat and its typical shiny surface. This shiny surface reflects the laser light during the read process. For mass reproduced CDs, this coating is generally aluminum, but CD-Recordable, Write-Once and Rewritable discs use a gold-based coating for the same purposes.

 

Micron

One millionth of a meter, or a thousand of a millimeter. For example , the CD-ROM track pitch is 1.6 microns wide, and the pits are about 0.6 microns wide. In DVD, the track pitch is 0.74 microns and the pits are 0.4 microns wide. (See, Track)

 

Microsecond

One millionth of a second.

 

Middle Area

A DVD can be single-layer or double-layer, and single-sided or double-sided. The transition area in between the layers is the middle area (space at the end of layer 0 and beggining of layer 1).

 

MIDI

Musical Instrument Digital Interface, provides a coding format for reproduction of sound in MIDI instruments. MIDI interface cards allow computers and other equipment use the MIDI coding. Most sound cards support the MIDI format. Because it does not involve sounds, but instructions and codes about the properties of the sound, the MIDI format is platform independent, and computer users can manipulate MIDI files to great advantage. Plenty of MIDI files are available in public bulletin boards and other sources.

 

Mini-CD

See, Data Discman.

 

Mini-Disc

See, Data Discman.

 

Mixed-Mode Disc

Mixed-mode refers to a CD-Digital Audio disc with data. Generally, the application (programs, data, indexes, etc.) are in Track 1, which is Mode 1 (ISO 9660). Audio begins in Track 2, and can be up to 98 CD-DA tracks. But, the earlier CD-DA players did recognize the first data track, and would 'play' it--which resulted in loud harsh sounds. There have been various implementations of the mixed-mode disc, of which the Enhanced CD is the better known. (See, Enhanced CD)

 

MMx

Announced in early 1996, MMx is Intel's new set of x86 instructions for Pentium and Pentium-Pro CPUs and, apparently, it is the most meaningful change to the x86 instruction set in many years. MMx will improve video decompression, 3-D graphics display, handling communications, and others. Some editors noted that MMx is, essentially, "...hardwiring multimedia capabilities into the x86 architecture." Applications, however, must be "MMx aware" to profit from MMx.

 

M-O Technology

Magneto-optical technology is the most used recording technology in the Rewritable (a.k.a. Erasable) line of optical products. The substrate is covered with a complex stack of thin films or layers--one of them the recording layer (of iron, cobalt and terbium), in which the pits are recorded. Two such discs are glued together to make the 5.25in, double-sided M-O disc. M-O discs can be rewritten millions of times, because the technology employs a magnetic field to realign (polarize) the molecular structure of the pit to its original unwritten state. This process exploits the Curie and Kerr effects, and does not cause degradation in the coding layer. The major drawback some see in M-O is that the process takes multiple passes to seek the area, erase, write, and verify--which, according to detractors, make it a slow performer. Under the Orange Book, Part 1 (M-O), magneto- optical technology is employed on the 12cm CD, formatted following the ISO 9660 specifications. Unlike the optical M-O discs (proprietary formats in various sizes), the standard CD-MO product has given rise to new types of drives. The multi- function drives, for example, are able to read and write the CD- MO ('Rewritable CD') and read a standard CD-ROMs as well. Recently, CD-Rewritable phase change discs are poised to challenge M-O's market share. (See, Optical Recording Technologies)

 

Mode

Under the ISO 9660, a CD-ROM sector can be Mode 1 or Mode 2. Mode 1 allocates 2048 bytes for user data, plus a third layer of error detection and error correction codes. This is the Mode that provides the highest integrity for computer data. Mode 2 allocates 2336 bytes for user data, and no third layer of error detection and error correction. This mode is considered appropriate for segments of music, graphics and video, specially in CD-ROM-XA and CD-I implementations. (See, CD Sector Structures,  Integrity)

 

Modem

A computer peripheral device that employs a digital to analog converter (DAC) to MOdulate and DEModulate the data stream from binary to analog and viceversa. Modems enable transmission of computer data through telephone lines. (See, A-D Conversion)

 

Modulation

Modulation generally refers to analog to digital conversion. There are however, various other modulation schemes. For example, CD Audio players use a Digital to Analog converter to produce the stereo analog music signals. To produce the appropriate mix of sounds in the signal, the system uses Pulse Code Modulation (PCM)--although Adaptive Digital Pulse Code Modulation (ADPCM), and others, have been implemented in other audio applications. (See, ADPCM,  EFM,  PCM)

 

MPEG

A Codec adopted by ISO's Motion Pictures Expert Group for compression and playback of full-motion video and audio streams-- often referred to as 'MPEG video.' MPEG-1 is now an open standard (ISO/IEC 11172, 1991)--which establishes the structure for a standard MPEG file, and specifies a transfer rate of 1.5Mb/sec, with a resolution of 352x240 at 30 fps. MPEG-2 accepts transfer rates up to 15Mb/sec, with a high resolution of 720x480 at 30 fps, and it also requires a 2MB buffer. Today, most of the demands of multimedia and full-motion video are met by various MPEG add-on boards. Incidentally, CD-I uses MPEG-1, and Video CD was promoted as the first MPEG-1 optical disc for multiple platforms. MPEG add-on boards use special chip sets for compression and decompression--but there are various software-only MPEG decoding programs. High-end hardware solutions claim compression ratios up to 50 to 1. But, since MPEG is lossy, such high compression rates often signify lower quality playback at 30 fps. MPEG-2 (ISO 13818-1, 1994) offers higher quality and speeds than MPEG-1. In certain circles, it is considered a temporary solution in the wait for a software solution (which will require CPUs to provide code streams above 10 Mbits/sec). DVD, however, uses MPEG-2 primarily, and all DVD-players will include hardware to handle MPEG-2 contents.

 

MPEG Audio

This is a digital multi-channel audio format, which uses a source PCM stream to compress it at a sample rate of 48kHz, sample size 16 bits. DVD supports MPEG-1 and MPEG-2 audio formats, and can have up to 7.1 sorround-sound channels.

 

MSCDEX.EXE

Known as the Microsoft CD-ROM Extensions, the MSCDEX.EXE program became necessary when CD-ROM drives were introduced to the PC platform--thus also stopping the growth of proprietary extensions and CD-ROM file managers. With the appropriate CD-ROM device driver loaded, MSCDEX.EXE enables the PC to configure the drive (by giving it a drive lettername), and to access the contents of ISO 9660 CD-ROMs. Other platforms have equivalents to MSCDEX. The Apple/Mac platform, although it can use HFS and Apple CD-ROM extensions, it can also use its Foreign File Access to deal with ISO 9660 CD-ROMs. MSCDEX.EXE is now included in MS-DOS and Windows. But, because it can only address up to 2GB in a volume, it will likely give impetus to the implementation of UDF in DVD products. Microsoft announced a new version of CDFS for Windows 95 upgrades. (See, CD-ROM Extensions)

 

Multimedia

This is the exciting and still growing arena of applications that use CD-ROM. Multimedia applications include text, sound, and motion video in what are mostly new categories of informational, educational, and entertainment products--and which have also helped define the new arena of 'infotainment.' Multimedia uses CD-ROM as its main file storage device. But, since video files can be very large, multimedia has led to the growth of specialized software, efficient hardware, and compression solutions. Multimedia authoring tools have achieved recognition, and some aspects of multimedia are subject to specifications issued by the Multimedia PC Marketing Council. Multimedia implementations in CD-I, however, use DYUV for graphics, MPEG for video, and ADPCM for audio--and display in a rather low resolution (340x240). IBM's proposed specifications for multimedia, known as Ultimedia, have not taken hold. In the Mac arena, users have been less hampered by hardware problems because the Mac comes configured to deal with CD-ROM and multimedia demands--and some Mac users think Hypercard is also a satisfactory multimedia authoring tool. (See, Hypercard)

 

Multi-read

In DVD, multiread applies specifically to the capability of DVD players to read DVD-R and DVD-RAM products, as well as CD-R and CD-RW. In similar vein, CD-ROM and CD-R players can not read CD-RW discs either. The problems involve low reflectivity of CD-RW on the one hand, and the higher laser wavelengths in DVD on the other. Therefore, read-heads have to be given multiread capability, or the player has to use two heads. The industry (mainly OSTA) has promised multi-read specifications to make DVD players fully compatible with all CD and rewritable products.

 

Multi-session

In optical technology, this refers to a disc that has been encoded in more than one session. Therefore, the disc has more than one 'volume'--reason why it is also known as multi-volume. During recording, the volumes are provided their own Lead-In and Lead-Out areas. The multi-session disc, however, has a overall Table of Contents (TOC) that is written at 'closing'--after the last session is recorded. In some implementations, individual volumes (sessions) write their tables of contents in their Lead- in area, and other implementations update the overall TOC. A multisession drive has to be able to read the contents of all the volumes in the disc (regular drives can only read the first TOC). Kodak Photo CD, and CD-ROM-XA and CD-I implement multi-session features, but only some recent XA drives are truly multi-session capable. Multi-session specifications were proposed by the Frankfurt Group, and were circulated by the European Computer Manufacturers' Association as Working Paper TC 15. (See, Frankfurt Group)

 

MUX_RATE

This is the total data transfer rate for DVD Video, and is defined at 10.08 Mbits/sec (ISO/IEC 13818-1?), as opposed to 1.4 Mbits/sec for Video-CD. Mux_rate, also known as the User Data Rate, implies that the addition (rather, the multiplexed rate) of all elements of the video, audio, subpictures, and text streams can not surpass that figure. Also, it seems that this is the optimal rate for the track buffer in DVD Video. (See, Transfer Rate)

 

[N]

 

Nanometer

A thousand of a micron. Laser wavelengths are usually measured in nanometers. (See, Wavelength)

 

Non-ISO 9660 CDs

This category includes CD-ROM products in other proprietary formats, and as test products for other platforms. There are, for example, CDs formatted as Apple HFS products. Since mastering and replication can be done for any format, and new CD-Recordable hardware is proliferating, non-ISO applications can be produced in all computer platforms--with the appropriate formatting software.

 

NTSC

The National Television Standards Committee supports the NTSC signal and display technology used in the TV industries of North America, Japan, and a few other countries. It specifies 525 lines/screen, and 29-30 frames/sec. (See, HDTV ,  PAL)

 

Numerical Aperture

In Optics, NA is a number that represents the light gathering capacity of a lens system--which determine the depth of field and resolving power. The base or reference is a vacuum, whose NA = 1.0; and the higher the number the better the quality of the lens system. For CD-ROM, the NA= 0.45; for DVD, the NA=0.60.

[O]

OCR

In computing circles, Optical Character Recognition involves scanning hardware and software to produce computer usable text files from printed pages--as opposed to producing a graphic image of the page. Essentially, the OCR software recognizes the dot patterns and produces characters. OCR technology has improved remarkably, and with more powerful CPUs, it will increase its reliability and other factors. For documents with complex layout, uncommon or unclear fonts, and in old or dark color paper, keystroking anew is often the best option.

 

One-off Discs

See, CD-Recordable,  DVD-R.

 

Operating Systems

Generally, an operating system refers to the set of internal (kernel) and external commands and subroutines that allow the computer to manage its components. Most operating systems require (cards or software) interfaces to deal with peripheral devices (MS-DOS, Mac, OS/2, Unix, etc). CD-ROM drives, and most other optical devices, are usually packaged with the necessary interface card and drives for the operating system. SCSI CD-ROM drives either come ready to connect to a 'standard' SCSI-2 card, or come with a SCSI card of their own--for the appropriate operating system.

 

Optical Byte

See, EFM,  EFM Plus.

 

Optical Discs

Technically, optical discs are those that are 'written' (encoded) and read using a laser optical device. In the computer arena, the optical industry is clearly divided; with the mastered and mass-reproduced 12cm CD-ROM implementations in one camp, and all the other discs in the 'optical' camp. Some types of discs are mastered and mass-reproduced (i.e. CD-Audio and CD-ROM), and others are produced individually by the apropriate drive (i.e. Write-Once, Rewritable, and CD-Recordable).

 

Optical Recording Technologies

Although often referred to as encoding, optical recording technologies are varied and quite sophisticated--the main ones are summarized below. For CD-Audio and CD-ROM, which are mass-replicated products, a glass disk, coated with photoresist, undergoes recording, development, and a special process to produce the metallized glass master--which is then used to produce the stampers for the reproduction equipment. On the desktop, Write-Once (W-O) and Rewritable drives record the optical discs in real time. CD-Recordable drives encode either in Track-at-Once (TAO), or Disc-at-Once (DAO) mode in the same CD-Recordable media. All those 'one-off' discs have a recording layer prepared for the specific recording technology to be applied. W-O uses Ablative, Phase Transition, Bubble Formation, Alloy Formation, and Texture Change recording technologies. Ablative technology, which is the most common, uses a recording layer with tellurium alloy (low melting point) that allows formation of holes when the high power laser beam is applied--thus forming holes or 'pits.' In similar fashion, the other technologies produce some sort of 'pit' by a phase, color, or texture change. Rewritable discs implement Magneto-Optical (M-O), Dye Polymer, or Phase Change technology. M-O is the most common, and it uses a magnetic film (of rare earths) for the recording layer, an appropriate magnetic field, and a high power laser beam to record or 'rewrite'--applying the Curie and Kerr principles about changes in structure when heat is applied, and the realignment of particles (polarization) when a magnetic field is present. Dye polymer and phase change also use special recording films or layers, on which the write laser produces the pits. The pits in these technologies are, however, erasable--they can be reverted to their original state. In phase-change, for example, a pulse from the laser changes a spot from crystalline to amorphous (which has different reflectivity), and another pulse of the laser heats it up and changes the spot back to crystalline (erasing, as it were, the previous pit). Some important vendors are marketing phase change drives (which can erase and write in one pass), and are becoming serious competitors of M-O drives. (See, Orange Book)

 

Optical Technology

Technically, optical technology refers to all processes that involve light, lenses and other devices dealing with transmission of light (cameras, the eye, microscopes, etc.). In computing circles, however, optical technology refers to that used in CD- ROM, Write-Once and Erasable drives. All these devices use high power lasers to encode the data on the disc, and low power lasers and photodiodes to read the codes. The 'heads' employed to 'write' and 'read' the code involve sets of precise lenses and servo-mechanisms that guide the laser beam as well as focus it with great precision. Obviously, any type of coding that can be converted to digital code can be transferred to an optical disc. CD-Audio and CD-ROM are mass reproduced optical products, while Write-Once, Erasable and CD-Recordable discs are produced individually. Current optical devices need only appropriate interface cards to work with computers.

 

Orange Book

The Recordable Compact Disc Standard was published by Philips, in 1990, reportedly in a binder with Orange Covers. The Orange Book defined two new 12cm CD products: the Magneto-Optical and the Write-Once. Recently, Part 3 was released, which covers Rewritable (Phase Change) products. Part 1, Magneto-Optical (CD-MO), defines tracks that can be erased and rewritten--reason why this format is more appropriately known as Rewritable. M-O drives implement magneto- optical recording technology, on 12cm CDs that are rated to allow millions of rewrites. These drives are however slower than other optical drives, because they use two heads--one to erase and the other to write, in a double-pass process. Some CD-MO products include a small premastered Read-Only area that usually contains system and other information--but which can also be read by a regular CD-ROM drive. The remainder space is the Recordable User Area, and the user can reuse this area at will. Part 2, Write-Once (CD-WO), defines tracks that can be written to, but not erased and rewritten--in the tradition of WORM (write-once read-many) discs. A Write-Once drive records appropriate 12cm CDs--which involve special recording layers, pregrooved tracks and, generally, a gold reflective layer. The initial tracks include a Program Calibration Area, are followed by a Lead-In area (where the Table of Contents will be written), and by the Program Area--for the user data. The recording session is finished with the Lead Out. A CD-WO 'Hybrid' disc involves an area where Read-Only files can be placed, and the rest of the disc is the W-O area. Part 3, Rewritable (CD-RW). Some brands designate it as Rewritable PD (for Phase Change). Developed by Philips and Sony (Oct 96), these specifications implement Phase Change technology and the Universal Disc Format(UDF) promoted by OSTA, to produce a CD that can be rewritten in one pass. Currently, CD-RW can not be read by CD-ROM and CD-R drives, because CD-RW media has much lower coefficients of reflectivity (15-25 compared to 65-70%). But, while drives with multiple heads are considered one solution, the industry is working towards a 'single-head multiread drive.' Nevertheless, CD-RW phase change drives seem poised to challenge the CD-MO drives, and the optical 5.25in products as well. (See, Optical Recording Technologies,  Phase-Change Technology , CD-ROM Specifications)

 

OS-9

This is an operating system, implemented in microcomputers dedicated to CD-I.

 

Overhead

Full-text search and retrieve applications that involve large collections of text rely mainly on indexing to produce speedy results. Some database applications with superior functionality rely heavily on indexing. Indexes, however, can be very large, averaging between 30 and 50 percent of the textbase, and in some cases much more. Those indexes are often thought of as overhead, and provisions must be made for it in the arithmetic of disc capacity and design. In DVD, the overhead is that amount of code that is in the tracks, and is used in the process, but is not part of the video output.

 

[P]

 

Packaging

Once the CD-ROM is produced, it has to be prepared for distribution. Generally, besides the labelling of the CD-ROM itself, most replication plants offer printing services for jewel case inserts, manuals, and other information to fit in or accompany the jewel case. Once all the items are ready and assembled as desired, they are either shrinkwrapped or stuffed into appropriate envelopes or mailers. Obviously, the artwork for the disc label and insert, the masters for printing, mailing lists, and all other necessary items must be provided in advance, in the format specified by the plant. DVD products will have different packaging. Promoters and vendors try to make sure authors recognize the role of packaging for the success of the product, and they have been proved right too often to ignore their recommendations. (See, Label)

 

Packet Writing

This is the newest software that allows CD-Recordable drives to encode entire volumes in a more efficient process (such as reducing buffer underruns)--allowing for multisession, efficient buffering, 'drag and drop,' hybrid discs, and other options. Packet writing software also implements UDF, and is available for most platforms.

 

Packs and Packets

In multimedia and DVD, where MPEG compression is implemented, the MPEG audio and video code streams are processed as 'packs' that are coded into sectors (one pack per sector). A pack consists of packets, which are individual streams of code 2048 bytes long (for the up to 8 audio channels, video, VBI streams, system and compression bytes).

 

PAL

Phase Alternation Line, a television standard, is used by European, Asian and some Latin American Countries. It specifies 768 pixels/line, 576 lines/screen and 25 frames/sec. (See, NTSC)

 

PCI Local Bus

The Peripheral Communications Interconnect Local Bus, introduced by Intel and associated manufacturers (1993), is a sophisticated local bus--considered superior to the VESA local bus. It is a 32-bit bus, with a maximum transfer rate of 132 MBytes/sec., that can handle up to ten devices (three of which can be add-on boards). It is currently used in most Pentium PCs, but the expected PCI interfaces for optical devices has not been announced yet.

 

PCM

Pulse Code Modulation is used to sample analog audio into digital code (generally, 8000 samples/sec), and to structure the analog signal that is produced by the digital-analog converter of the CD-Audio player. PCM makes it possible to hear the various instruments, their different ranges and depth of sound, etc. It was the basis for ADPCM, which was implemented in CD-ROM-XA and CDI. (See, ADPCM)

 

PCMCIA

The Personal Computer Memory Card International Association addressed the need for small and portable devices for the growing portable, notebook and other hand-held computer production lines. The PCMCIA developed a new interface (with connectors in three sizes), which essentially senses the device connected, identifies it, and makes it available to the user. Since the devices implement PCMCIA electronics, they can be attached to or removed from the bus at any time.

 

Phase-Change Technology

This rewritable technology employs a recording layer that shifts phase, from amorphous to crystalline. A pulse from the 'write' laser beam changes a spot to the amorphous state. To 'erase', a laser beam of higher power heats up the area and, essentially, melts it--which then cools to the crystalline state, and is therefore ready to be written again. Since phase-change made possible 'single pass' erasing and rewriting, vendors claim that phase-change drives provide faster operation than M-O drives, and that its slight advantage in storage capacity will play a bigger role when discs of over one Gigabyte become common. Some industry magazines claim that it has already reached about 30 percent of the rewritable market, challenging the popular M-O drives. In 1995, Panasonic introduced a Phase-Change multifunction drive. In 1966, phase change drives, drives in CD-Rewritable format, compliant with Orange Book, part 3, were introduced by Panasonic, Pioneer, Pinnacle Micro, and others.

 

Photo-CD

This product, was introduced by Kodak and Philips, in 1992. The Photo CD is a hybrid disc that uses the CD-ROM XA Form 1 sector structure to store up to 100 35mm photographs in one disc, in one or more sessions. The photographs are scanned into digital files (18 MBytes--compressed to about 4.5 MBytes, each), in five different resolutions. The Kodak Photo CD player displays on a TV monitor, but a multi-session CD-ROM XA drive, with appropriate software, can display on a PC monitor. When issued as a Bridge Disc, it can be played by Photo CD and CD-I drives connected to a TV set. Photo-CD allows multisession recording, with one TOC per session (Orange Book, Part II, Hybrid disc). CD-ROM XA players need an appropriate interface (or a software patch) to display multi-session contents. Kodak also licensed a consumer product that takes film rolls (or color photos), and processes them into a Photo CD. (See, Multi-session)

 

Physical Format

Media-specific structure that dictates how the data is laid out in the disc, data modes, error detection and correction, physical sector addressing, and other characteristics necessary to manage the type of data intended for the media. The volume and file structure for the contents are dealt with by a logical format. (See, Logical Structure,  Red Book)

 

Pits

During optical encoding, pulses of a high power laser beam 'burn' microscopic 'pits' on the recording layer. The untouched spaces between such pits are called 'lands.' During the read process, the laser light focuses on the spinning spiral track, and since the pits reflect light less intensely, the read head detects the changes in reflectivity, and those changes are processed as 1s to produce a binary data stream. In CD-ROM, the track pitch is 1.6 microns, and the pits are .83 microns wide. In DVD, the track pitch is 0.74 microns, and the pits are 0.4 microns wide.

 

Pixel

A Picture Element, used mainly in graphics and video circles, is the smallest unit of display that can be given color and intensity values or codes. The larger the number of bits per pixel, the higher the range of colors that can be displayed.

 

Pre-gap/Post-gap

These are empty lengths of track (two seconds, or equivalent, of nothing but 0s), which are placed before and after the data track.

 

Premastering

Too often, this term is used quite broadly. Data preparation, indexing, testing (also called simulation), and creating the 'image' are done before premastering. Premastering involves taking the 'image' of the application and producing the premastered file--one large ISO 9660 volume file (a chain of CD- ROM sectors, with sector addresses, header, synchronization, error correction and detection, mode, and other required bytes). The premastered file is further processed for the production of the glass master. The hardware and software used for premastering are usually known as 'ISO formatters,' and they vary in capabilities and features. When using a CD-Recordable drive premastering takes place as the program records the 'one-off.' (See, Image,  Mastering)

 

Presentation Control Information

In DVD-Video, PCI involves specific information about timing and presentation options of a program (aspect ratio, angle, other user selection options, subpicture choices, etc.).

 

Pressed Discs

Some circles in the industry use these terms to distinguish the mass reproduced discs from the rewritable, write-once, and CD-Recordable discs (which are produced one by one, by an appropriate drive, on the desktop).

 

Program Area

This term, introduced in CD-Audio production, refers to the area of the disc where the user files (music) are stored. The program area is between the Lead-in and the Lead-out. In CD-ROM, the user data, indexes, and other files that go in the program area are usually placed in the most appropriate order--to reduce seek and access times.

 

Program Chain Information

PGCI involves information that is part of the user data overhead (1 Mbit/sec)--which is not decoded for display. But, PGCI information involves pointers to the physical location of the program sectors in the tracks, and serve to insure program continuity for the display stream.

 

Protective Coating

Optical discs are given a clear plastic or lacquer coat that protects the metallic layer. Even with this coating, small scratches, pressure, dirt and other markings can make the disc unreadable. The coating also prevents air from reaching and oxidizing the metallized layer--which would render the disc unreadable.

[Q-R]

QuickTime

Initially an Apple only product, now found in Windows and being ported to other platforms, QuickTime is a multifeatured program that plays sounds, animation, and video files in a time- based programmed mode--although the display is only about one- third of the screen (.MOV files). QuickTime movie authoring involves file compression and on-the-fly decompression (up tp about 15frames/sec)--without additional hardware requirements. It supports Intel's Indeo decompression, and MPEG-1, but not MPEG2.

 

RAID

Redundant Array of Inexpensive Disks is a large storage scheme used increasingly more in large imaging systems, and industrial multimedia developing systems. The newer RAID systems offer high reliability and claim (fiber channel) transfer rates near 100 MBytes per second, and expect to transfer above that figure soon. RAID's versatility, software and hardware dependent, includes levels of security, recovery after network or drive failure, 'hot swapping,' compression and other sophisticated options.

 

RAM

Random Access Memory, also known as 'system memory,' is that amount of physical memory that is addressable by and directly accessible to the CPU--chips on the motherboard, or on an add-on board on the bus. RAM in DVD-RAM stresses the random access capability of this rewritable product--mainly to differentiate it from other 'rewritable' products, and to compete with magnetic hard drives.

 

Raw Capacity

Optical discs include substantial overhead in the encoding, to work effectively, and to provide the integrity required for computer data. For any CD-ROM, in percentages, the overhead includes: the bytes used by the required eight-to-fourteen modulation (34%), the merging bits (17%), the error detection and correction codes (11%), and synchronization and subcodes (5%). This leaves about 33% net space for user data (in a 73 minute CD- ROM, that is about 680 MBytes of usable data.) Efforts to improve the capacity of optical products are also focusing on these overhead areas. In DVD, additional codes in the track, which are used for processing the video title, but which are not part of the output stream, are also called overhead.

 

Read Error Rate

See, BLER,  Integrity.

 

Recording Layer

This is the sensitive layer, deposited over the substrate, which reacts in a specific way when a high power laser beam is focused on it. Each recording technology uses an appropriate recording layer--which can be Photoresist, a special dye, special alloy, or a sandwich of sensitive films. The initial glass disc or master (for reproducing CD-ROMs) usually has a Photoresist recording layer.

 

Red Book

Philips and Sony, developers of the CD technology, and of the 12cm CD, published their specifications for CD-Audio in 1980-- reportedly in a binder with red covers. The Red Book addressed the physical specifications for the CD; the tracks, the sector and block layout, coding and sampling of digital audio files, and other specifications. The Red Book was key for the high quality sound of CD-Audio, which became a standard and key for the worldwide CD-ROM industry. The International Electrotechnical Commission published the Red Book as their Doc IEC 908 (1987). (See, CD-ROM Specifications)

 

Reed-Solomon Codes

These are error detection and error correction codes, based on mathematical algorithms and binary structural logic. The Red Book implemented the basic two levels of error detection and correction using Cross Interleaved Reed Solomon Codes (CIRC). The Yellow Book specified a third level of 'layered' error detection and error correction codes, to attain the level of integrity that computer data require. DVD implements the Reed- Solomon Product Code (RSPC), which is said to be about ten times effective. (See, Error Detection Codes,  Integrity)

 

Reed-Solomon Product Code

The RSPC is a compression algorithm that expands the Reed-Solomon Cyclic Redundance compression algorithm by generating a product (row x colums) as a final code. This product code algorithm is said to be ten times more robust than the CIRC algorithms used in CD-ROM. (See, CIRC)

 

Reflectivity

A measurable property of a surface. In optical technology, baseline reflectivity refers to the reflectivity of the 'lands'-- the clear spaces between the pits in the data track. The pits have lower than baseline reflectivity. In optical discs, the changes in reflectivity are detected and decoded, and then converted to magnetic coding. The differences in reflectivity between rewritable and mass reproduced and/or one-off discs can be substantial (15-25% compared to 65-70%). In fact, CD-RW media (Orange Book, III) can not be read by CD-ROM players (without additional hardware fixes). In the same vein, DVD players have wavelength problems with CD-R, because CD-R media does not reflect at all the DVD laser beam. The industry is working to overcome this problem of 'invisibility' in second generation and in multifuntion players. The key promise is that they will be 'multiread.' (See, Multi-read)

 

Regional Codes

Also referred to as Country Codes, or Zone Locks, these are optional codes that the movie industry imposed on DVD-Video specifications. Players will be coded by region, and these players will not play DVDs coded for a different region. It is expected that only first release DVD-Video titles will have those codes. DVDs with no regional codes will be played by any DVD player. The six regional codes are: 1: North America, 2: Japan, Europe, Middle East, South Africa, 3: Southeast Asia (plus Hong Kong), 4: Australia, New Zealand, Central & South America, 5: Northwest Asia, North Africa, and 6: China.

 

Replication

In optical technology, replication refers to mass replication, as in CD-Audio and CD-ROM. Mass replication made CD-Audio a competitive product. Moreover, since the same CD- Audio mass replication plants produced CD-ROMs, they made possible low CD-ROM production costs--which were certainly crucial during the first years of the CD-ROM industry.

 

Resolution

In general, display devices support standard resolutions (EGA, VGA, XVGA, etc.), which specify the number of pixels of the width and height of the screen (i.e. 640x480). Video resolution, however, usually includes a third element: the quality or depth of the pixel (in bits/pixel). For example, 640x480x24 means a VGA resolution (640x480) by 24 bits/pixel--which means each pixel has over 16 million color possibilites.

 

Rewritable Optical Discs

Rewritable optical technology involves drives that aim to replace magnetic storage devices. Vendors claim that their rewritable optical disks can be erased and rewritten over a million times. There are three main types of recording technologies for rewritable optical discs. Magneto-Optical (M-O) technology is predominant. Phase Change technology follows far behind, but its adoption by new manufacturers keeps it in contention. The third is Dye Polymer technology, adopted by some manufacturers. For some reason, vendors use M-O to refer to M-O rewritable drives, and Rewritable to refer to phase-change rewritable drives--although both are rewritable technologies. Until recently, the optical M-O discs were mainly 3.5 and 5.25 inches in diameter, double sided, and of various capacities and proprietary formats. Recently, the Orange Book, 12cm CD-MO was introduced to the market--but without much promotion. In that context, more recently, Panasonic released a new Phase-Change drive that is supposed to read all rewritable (M-O, Phase-change, and Dye Polymer) discs, and is making phase change drives more noticeable. PhaseWriter Dual drives claim to read CD-Audio, CD-ROM and CD-Rewritable discs, and Pinnacle Micro's Apex Rewritable 4.6 GB drive claims to read CD-ROMs at 16X speed, and so on. Rewritable technology is indeed showing its maturity. (See, Optical Recording Technologies)

 

 

RIFF

Resource Interchange File Format is used to store multimedia files, because it also allows their use in various platforms. (See, Multimedia)

 

Rockridge Group

This is an industry group that developed extensions to the ISO 9660 to produce ISO-compliant applications that could be played by multiple operating systems, emphasizing Unix-based or POSIX-compliant systems. Some saw the need for those extensions, especially since implementation of ISO 9660 interchange levels was more problematic than first perceived. The proposed extensions, System Use Shared Protocol (SUSP), and the Rockridge Interchange Protocol (RRIP), allow for support of multi-platform formats, tables of contents with deeper levels of hierarchy, and the use of filenames larger than those allowed by MS-DOS. Essentially, those extensions make the ISO-compliant contents of the disc appear like a Unix File System to Unix machines configured to support Rockridge Extensions. Incidentally, in a different approach, there are applications for the Unix platform that include translation tables to show the contents of the CD- ROM with Unix-like file and directory names--but that is not what the Rockridge Group proposal specifies. It was expected that the Rock Ridge specifications be approved by the end of 1995. (See, Interchange Levels)

 

ROM

Read Only Memory. The term originally applied to read-only memory chips used in computers. With the growth of optical storage, the term read-only memory now applies to compact disc products (CD-ROM, CD-I, CD-ROM XA, CD-Recordable, etc.). In the case of WORM, now referred to as Write-Once, after a recording session, the disc is essentially a read-only disc. (See, RAM)

 

Rotation

CD and DVD use clockwise rotation. All single layer discs are read from the inside out. In double-layer discs, DVD reads both layers from the same side, and there are two ways of doing so. Opposite track reading is when the top or outside layer (layer 0) is read radially from the inside out, and the inside layer (layer 1) is read radially from the outside in--after transfering at the transition area. That is why the tracks are 'running' in opposite directions. But, this implementation is used to provide for reading continuity--which is important for video applications. Parallel track reading is when the layers can be read non-sequentially during a session--tracks 'running in the same direction.' For text and data applications, the parallel track layout is preferred, because it allows random access to data anywhere in the tracks. (See, Constant Angular Velocity (CAV)...)

 

Run-Length

In CD-ROM, run-length specifies the number of contiguous 0s in the optical byte--between the 1s. This usage is related but not the same as run-length encoding (RLE), which is a compression algorithm used widely to compress graphics files.

 

[S]

 

Sampling

Sampling is part of analog to digital conversion. Essentially, the analog signal is sampled at an specific rate and quantized--which means a numerical value is matched to each sample, and that value is converted to binary code. Although the frequency of sampling is important for continuity, the size of the sample (in bits) is important for depth of quality. CD-Audio involves sampling rate of 44.1 KHz, and sample size of 16 bits.

 

Scaling

When working with video, scaling is the process that reduces the frame rate of the source video to a lower rate, by a certain scale (2-1, 5-4, etc.). For example, full-motion video, at 30 fps, is generally scaled to 15 fps (2-1 scaling), so it can be shown under Windows, by Quicktime, or Video for Windows. Resolutions are also scaled in the same framework (640x480 to 320x240, etc.).

 

Scan Rate

This is the rated speed at which the code travels when it passes under the read head. In CD-ROM the base scan speed was 1.2 m/sec (constant linear velocity). In DVD, the base scan speed is 4.0 m/sec (constant linear velocity). In some circles, the scan rate is provided in terms of X. For example, for a basic CD-ROM, 1X=75 sectors/sec. DVD players scan at a rate equivalent to 8X of CD-ROM (@1.2 MB/sec).

 

Scanning

Scanning involves hardware and software. Essentially, scanners apply a light (laser, and recently LED) to the source page, so that a set of sensors (charge-coupled devices) can detect the presence of black areas (or colors) and produce codes for each pixel, and those codes are processed into raster scan files. High end scanners, using appropriate chips and hardware, produce high resolution graphic files. Earlier desktop scanners popularized the 300 bpi resolution, while fax specifications use 170 bpi resolution. With appropriate software, some scanners can produce scan files in vector graphics formats. Most scanners, with appropriate software, can also scan documents for optical character recognition (OCR). The same principles guide the specialized scanners such as the hand-held scanners, bar code readers, slide and microfiche scanners, card scanners, pattern recognition scanners, and others. (See, OCR)

 

SCSI

The Small Computer System Interface was introduced as the 'intelligent interface for intelligent devices.' A SCSI card can operate in 8 and 16-bit buses, and serve up to seven (or even more) devices connected in a 'daisy chain'. The interface issues commands to the chain, where each device recognizes the commands addressed to it. SCSI hard disks store data in sequential blocks, and transfer (in parallel) at rates between 3.3 and up to 40 MBytes/sec (the newer implementations offer faster rates). Nevertheless, despite its many flavors, the fact that SCSI is an ANSI standard has made for solid commitments to it among some manufacturers. Currently, SCSI-2 (Fast, Wide, Fast and Wide) are popular. Ultra SCSI can support up to 15 devices, and is backward compatible. Upcoming SCSI specifications are said to involve asynchronous (serial) mode implementations for fiber channels, HPSB and other new bus designs in the market.

 

Search and Retrieve

Software operating on large amounts of data (full-text, databases, spreadsheets, multi-media, etc.) provide search and retrieve functions to help find the appropriate information efficiently. Most CD-ROM full-text applications use the now popular Boolean search and retrieve. (See, Boolean Search)

 

Sector

Unlike the sectors and blocks used in regular magnetic storage devices, the sectors in CD-ROM are prescribed by the Yellow Book, in the physical format of the data track. The logical sector, on the other hand, is defined by the ISO 9660, and is the smallest addressable unit. In technical circles the difference between physical and logical sectors is clear. But, in general parlance it is not so clear because, under the ISO 9660, the physical sector (data user area of 2048 bytes) can be subdivided into Logical Blocks of 512, 1024 or 2048 bytes. And, since MSCDEX supports only logical blocks of 2048 bytes, each Mode 1 sector's user data area is one logical block. This usage has caused many to consider physical and logical blocks as one and the same. DVD specifies the sector much the same as it is in CD-ROM. (See, CD Sector Structures)

 

Sequence

In video parlance, a sequence is the group of frames that were prepared and processed as a continuous whole. That means that the individual frames in the sequence share a common bitrate (CBR), buffer size, picture size, aspect ratio and frame rate.

 

Servo Mechanisms

These precise electro-mechanical devices with sophisticated components are employed for precise shifting of the read (and write) heads to specific tracks on the disc, to detect variations in the tracking of the pits and correcting any off-centering, to position the heads to the appropriate focal length for the laser as the disc rotates, and so on. The sophistication and precision of these devices can be appreciated better when one realizes that the CD-ROM tracks are 1.6 microns wide and that, in an 8X drive, the DVD tracks are 0.7 microns wide, and that the laser is discerning pits and lands at a rate of about 1.2 GB per second.

 

SIGCAT

The Special Interest Group for CD Applications and Technology, based in Reston, VA, is a non-profit Foundation dedicated to the promotion of CD technology in government and industry. SIGCAT is open to all; it has gained broad government and corporate support (government policies and CD-ROM implementation, private hardware, software and application developers and vendors), and has a subscription list of over 10000. DISCourse, its newsletter, is mailed to subscribed members. The BLER (Bimonthly Listing of Events and Resources) is mailed to all who sign up for it. SIGCAT has a Training Center that offers a varied program of courses and workshops, and its CIRC (CD-ROM Information Resources Center) serves vendors, software developers and mostly government users. The yearly SIGCAT National Conference is a major event in the CD-ROM arena.

 

Simulation

Developers 'simulate' the application, when it is considered finished, but still in the computer. It involves testing the software, interface and data, as if it were in the CD-ROM. There are simulation software packages that can measure retrieval speeds, output features, screen building, and other features. If some features are found lacking, they can be improved and retested until they are satisfactory. Simulations are cost- effective, because they are performed before the expensive mastering and replication. In some CD-Recordable drives, simulation is a feature that transfers the data but does not encode the disc--thus simulating the process. It shows that all is fine, or that the recording is creating errors or underruns-- and saves ruining a clean disc. For DVD, given the capacities involved, simulation hardware and software (most of it in development or upgrading) carry higher price tags.

 

SMPTE

This is a timing code implemented by the Society of Motion Picture and Television Engineers. It employs hours, minutes, seconds, and frames to address the individual frames in a videotape--a framework not too dissimilar from that of CD-ROM. To use (NTSC) television signals, which flows at a rate of about 30 frames per second, appropriate SMPTE timing marks must be included for their use in CD applications.

 

Stamper

A metallic mold (usually nickel) produced by electroforming, during the mastering process. For small runs, the 'father' (the first electroformed master) is used in the injection-molding machine. For large runs, the 'father' is used to produce intermediate molds and the final stampers that are placed in the injection-molding machines. (See, Glass Master ,  Injection Molding,  Mastering)

 

Standards

See, CD-ROM Specifications,  DVD Specifications,  ISO 9660.

 

Stopwords

In search and retrieve applications, stopwords are those words that the application designer wants the search and retrieve software to ignore altogether. A generic stopword list includes about 100 common articles, adverbs, adjectives and other modifiers that are of no use in the logic of a full-text search. Also, eliminating these common words reduces clutter in the index tables--which also helps the search process.

 

Subcodes

See, Control Bytes,  Channel Bits.

 

Sub-picture

A graphic element that is superimposed to the running video display. It can be of any size, up to the size and resolution the video frame (NTSC or PAL standards). DVD-Video can use up to 32 subpicture streams.

 

Substrate

This is the core of CDs and DVDs. In the injection molding machines, it starts as molten, clear polycarbonate. After pressing and cooling, the core disc or substrate is metallized, given a lacquer protective coating, and labelled. CD-Recordable media has the same substrate, but different recording layers on it. In optical 5.25in W-O and M-O media, the substrate is often glass. DVD Recordable and RAM (rewritable) will apparently use polycarbonate substrate. There have been tests on other materials, one of them, polyolyphine. But, despite better qualities shown by other materials, it seems that polycarbonate is still the cost-effective option. (See, Injection Molding)

 

Synchronization

The Synch bytes help the synchronization of the read head onto the coding in the block (to engage it to begin reading at the right place). There are 12 synch bytes in a CD-ROM block. In addition, DVD products will use coding and firmware to synchronize video and audio output. (See, CD Sector Structures)

 

[T]

 

TAR

Tape Archival and Retrieval format, used extensively during the reign of the mainframes, served to place files on tapes that could be retrieved by computers with a different operating system. Some government information, for example, was sold to the public in TAR format.

 

Telecine Process

This is a video conversion process that is used to convert video of 24 frames/sec, to video of 30 frames/sec, or viceversa.

 

Termination Resistors

These small plastic contraptions are placed at both ends of the chains of devices in a SCSI configuration. Their role is, essentially, to signal that there are no other devices beyond that point, and prevent excess signal noise on the SCSI bus.

 

Title

In DVD Video, a title is an independent or self-contained program--usually a whole movie or TV program episode. A DVD can contain more than one title--obviously, that depends only on the size of the titles.

 

TOC

Table of Contents generally implies a list of the files and addresses of a CD-ROM application. In current multi-session applications, each session involves its own table of contents-- and the application scans the disc and begins to read the last table of contents first. In magnetic drives, since file sizes can change and be broken into parts, the FAT (file allocation table) is the system's TOC, because it is an updatable table of file locations (addresses and distribution) for the entire drive (logical partition).

 

Track

Optical technology uses Constant Linear Velocity rotation, which involves a spiral track of coding that begins near the center of the disc. In CD-ROM, the track has a pitch of about 1.6 microns and, in a 63-minute disc, it is about 3 miles long. DVD specifies a track of 0.74 microns. The pits in a CD-ROM track are 0.83 microns wide, and in a DVD they are 0.4 microns wide. At another level, in mixed-mode or multimedia applications, we say that data types are in 'separate' tracks--but they are placed sequentially in the same physical track, and accessed using appropriate interleaving.

 

Track Access

This is the common method to access 'songs' by track number in CD-Digital Audio. Under the Red Book, a disc can have 99 tracks, and under the Yellow Book, it can have up to 98 tracks of CD-DA tracks (the first track must be Mode 1 data track). Therefore, mixed mode discs implement other access methods. (See, A-Time)

 

Track Buffer

In the DVD player, the track buffer receives the user bitstream (which fluctuates due to irregular disc access in the program), and releases a smoothed bitstream regulated to a variable MPEG stream (mux_rate from 1 to 10.8 Mbits/sec).

 

Transfer Media

Initially, mastering plants accepted the image of CD-Audio or CD-ROM applications in a few specific magnetic transfer media: 9- track, 1/2in. tapes were the most popular. In time, large capacity 8mm. Exabyte tapes, 4mm Digital Audio Tapes, and similar media became acceptable transfer media. Recently, CD-Recordable 'one-offs' became the popular transfer medium. But, with DVD, Digital Linear Tape (DLT) will be the preferred transfer medium.

 

Transfer Rate

This usually refers to the player's capacity to deliver data. The first CD-ROM drives were designed to read 75 sectors of data per second, which means that it transferred 150 KBytes of user data per second to the computer's CPU. This basic transfer rate is now thought of as 1X, because current drives specify theirs as multiples of that rate--i.e. 6X, 8X, etc. In fact, some multimedia applications recommended quad-speed (4X) drives as a minimum. Current literature mentions 16X drives. In DVD, the base transfer rate is about 1.2 MB/sec (equivalent to that of an 8X CD drive). Incidentally, a DVD reads (scans) about 3 times more amount of track than CD-ROM does, for the same amount of time. But, more importantly, due to video and audio compression, buffering and overhead, the transfer rates are much higher, and can be differently stated. (See, Track Buffer ,  Mux_rate)

 

 

[U]

 

UDF

The Universal Disc Format was promoted by the Optical Storage Technology Association (OSTA), as a single file system for interchange of information in the computer arena. It is referred to as a subset or domain of ISO/IEC 13346/ OSTA aimed to develop a UDF-based file format for CD-ROM, write-once and rewritable products, including multi-surface sets. UDF is expected to eliminate the addressing limitations of the ISO 9660, the file-size limitations of redirectors (MSCDEX & CDFS), provide for cross-platform products, and also help eliminate the broad incompatibility among CD and DVD mass-reproduced and write-once and rewritable applications.

 

UNIX

This relatively old and powerful operating system, matured and spawned various versions in mostly academic, industry, and government research institutions. Recently, because of the Internet, the power available on desktop hardware, the growth of worldwide computer communications, and the efforts to standardize its code, UNIX (and Linux) is becoming another option on the PC platform.

 

User Data

In CDs, the sectors include an specific space allocated for data used by the application--which is called user data. (See, CD Sector Structures)

 

User Data Rate

See, Mux_rate.

 

[V]

 

VESA

The industry group, Video Electronic Standards Association, produced a non-proprietary response to IBM's Microchannel architecture. They did so with the VESA Local Bus architecture--known as the VL Bus. It is a 32-bit bus, with a maximum bandwidth of 132 MBytes per second. It was designed to aid high speed video devices. The VL Bus Interface (additional circuitry and chips) extends the CPU bus, and thus can interact directly with the CPU and memory. However, In the 486 platform, this 32-bit interface was usually limited to only three VL Bus peripherals--and only two of them could be add-on boards. The power in the Pentium architecture, and the PCI bus, have reduced the need for the VESA LB.

 

Video CD

The Video CD specifications ('White Book') were proposed by JVC and Philips (Aug93), and supported by other major players in the industry (apparently, it was derived from the 'Karaoke video' concept). The CD is used to store 72-74 minutes of full motion video and digital audio (2 channels), using an MPEG-1 decompression board, in a CD-ROM XA 'bridge disc.' It has a video data transfer rate of 1.44 Mbits/sec. Because CD-I players can play Video CD discs, it was considered another version of CD-I. The menace of DVD-Video seems to have cooled Video CD plans for the future. (See, CD-ROM Specifications)

 

VL Bus

See, VESA.

 

Volume

A volume is defined as a complete CD-ROM. Often, 'ISO volume' refers to a CD-ROM produced according to the ISO 9660. If the data, or large files, need to use more than one disc, then the entire product is known as a Volume Set. We must point out, however, that under the ISO 9660, Volume Sets can not be produced under Implementation Level 1. Moreover, multi-volume disc sets are not supported by MSCDEX. (See, ISO 9660 ,  Implementation Levels ,  Title)

 

Volume Descriptor

The Primary Volume Descriptor is an area of 2 Kbytes, at the beginning of the track, that includes data and identifiers about the volume, the publisher, data origination, copyright, dates, etc.

 

[W]

 

Wavelength

Laser wavelengths (usually in nanometers) define precision; the shorter the wavelength, the more precise the laser. The infrared laser used in CD-ROM has a wavelength or 780 nm. The red lasers in DVD have wavelengths of 635 and 650 nm (double layer disc).

 

W-O Technology

Write-Once Technology, started with WORM (Write Once, Read Many) computer applications--which involved generally proprietary formats and hardware options. Philips developed the specifications for the implementation of Write-Once technology in the 12cm CD, in the Orange Book, Part 2. Essentially a W-O drive, with appropriate software, 'writes' the code onto the W-O disc, in one or more sessions, until the disc is filled. From then on, the disc is read-only--reason for the 'write-once' name. Currently, Ablative, Phase Transition, Bubble Formation, Alloy Formation, and Texture Change technologies are used for recording W-O discs--ablative technology being the most used. All these technologies involve a specially designed recording layer, which undergoes a specific physical change at the spot where the high power laser beam is focused--forming a 'pit'. As with all optical technologies, those pits cause changes in reflectivity, and those changes are decoded to produce the 1s and 0s of the code stream. Orange Book, W-O applications (12cm CDs), are found in enterprise document archival, audit trails, scientific record archival, imaging and imaging archival, and others. Currently, the growth of multifunction drives (M-O and CD-ROM), and of CD- Rewritable (CD-RW), seems to have added options to a growing market, making it rather difficult to discern current trends in Write-Once technology.

 

White Book

The White Book, produced by JVC and Philips (1993), used the sector structure of CD-ROM-XA to produce a Video-CD ("bridge disc,' or a hybrid CD derived from the Karaoke-CD concept). Video-CDs can be played in CD-ROM-XA and CD-I drives as well. Video-CD uses interleaved full-motion MPEG video. Another implementation of the White Book is the Kodak Photo-CD. (See, Video CD,  Photo-CD)

 

WORM

Stands for Write Once, Read Many, the usage for optical technology that was applied since the late 70s, in media of various sizes (5.25in, 12in, and even 14in). Most WORM media was double-sided, with capacities from 140MBytes to over 3 GB per side, depending on formats and encoding. The growth of WORM technology was hampered by the various proprietary hardware and software solutions, as well as by their price. Nevertheless its 5.25in disc format, with increased capacities, became predominant in archival (imaging) applications, especially for large enterprises and government agencies. Recently, however, Orange Book, Write-Once products (12cm CD), seem poised to slowly replace optical WORM products. (See, W-O Technology)

 

[Y]

 

Yellow Book

Published by Philips and Sony, in 1983, in a binder with yellow covers, the 'Yellow Book' used the Red Book as its basis for the physical specifications of sectors in a CD-ROM--designed for computer data. The Yellow Book specified two types of sector layout (Mode 1 and Mode 2), additional 'layered' error detection and correction to insure higher integrity of the contents, and much more. CD-ROM-XA is defined in supplements to the Yellow Book. In 1989, the Yellow Book was issued by the ISO as ISO/IEC 10149, Data Interchange on Read-Only 120mm Optical Discs (CD-ROM). (See, High Sierra Format,  ISO 9660,  CD-ROM Specifications)

 

Z-Author

 

* Leo F. Pozo is a Member of the SIGCAT Board of  Directors. For information on this copyrighted Glossary of  CD and DVD Technologies, or on other related published material, please write to: 2801 Fort Drive,  Alexandria, VA 22303-1324. E-Mail: leopozo@cpcug.org 

Copyright © 2000 HARGROVE PRODUCTIONS. All Rights Reserved.