CD Glossary

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

A/D Converter A device that takes analog inputs and converts them to digital signals. For example, a sine wave input can be converted into a series of numbers that represents the value of the input curve at any given point on the curve. The resolution of the converter is determined by the number of bits (the more the better) and the sample rate (the faster the better). 

AF - Audio Frequency. Frequencies in the audible range, from 20 Hz to 20 KHz. 

Audio Premastering

Audio premastering comprises those processes needed to convert the incoming audio into a format ready for mastering :

• Audio editing and compiling from any audio source. This can include cross fades, sample rate conversion, equalization and dynamic range compression as well as track compilation.
• PQ encoding which involves adding a table of contents comprising time codes for the start of each track, therefore allowing individual tracks to be cued. It informs the CD player when to start and when to stop. Audio transfer from the input media to a media and/or format more suitable for mastering. The Digital Audio Tape (DAT) format usually needs transferring to Exabyte or U-matic tape. Sample rate conversion from 48 kHz sample rate to 44.1 kHz needed for CD mastering.

Bitstream - Refers to the 1-bit pulse density modulated (PDM) code output from the quantizer in the noise-shaping stage. 

BOOK SPECIFICATIONS:

• Blue Book

• The Blue Book defines the Enhanced Music CD (also known as CD EXTRA - the term CD Plus is not now recommended to avoid confusion with similar formats) specification for multisession pressed disc (ie not recordable) comprising audio and data sessions. Enhanced Music CD discs are intended to be played on any CD audio player, on PCs and on future custom designed players. The current version 1.0 was released in Jan 1996. 

  The Blue Book comprises of: 

  Disc specification and data format including the two sessions (audio and data). The second, data session must be a CD-ROM XA session. Directory structure (to ISO 9660) including the directories for CD Plus information, pictures and data. It also defines the format of the CD Plus information files, picture file formats and other codes and file formats. MPEG still picture data format.

• Green Book

• The Green Book, written originally in 1987, describes the CD-interactive (CD-i) disc, player and operating system and contains the following information: 
  • CD-I disc format (track layout, sector structure). Data retrieval structure which is based on ISO 9660 with some additions. Audio data using ADPCM levels A, B and C (cf CD-ROM XA) Real-time video data which describes the disc coding of different types of still images, the video decoder and visual effects available. Program related data, which defines the 68000 processor instruction set, the character sets to be used and phonetic coding. Compact Disc Real Time Operating System, which is the operating system used in every CD-i player. The Green Book specifies the OS kernel, file managers, drivers and all the system calls available. Base case system which is a specification of the minimum CD-i hardware configuration. Full motion extension which defines the functions provided by the MPEG cartridge and the software calls available for MPEG decoding.

• • The Green Book is the most comprehensive specification of all the colored books, specifying in detail not just the disc but the coding of data and the architecture of the player hardware and software.
     
• Orange Book

• The Orange Book defines CD-Recordable discs with multisession capability. It is in three parts:
  1. Part I defines CD-MO (Magneto Optical) re-writable discs, last updated in November 1990.
  2. Part II defines CD-WO (Write Once) discs, last updated in January 1994.
  3. Part III defines the CD-E (Erasable) disc format. The tentative version 0.8 was released in September 1995.

• All three parts contain the following sections: 

  Disc specification for the unrecorded disc and the recorded disc. Pre-groove modulation which is necessary for motor control information needed during writing. Data organization including linking to allow writing at different times. Multisession and hybrid discs 

  Recommendations for measurement of reflectivity, optimum power control, environment, light fastness, push pull magnitude, measurement of groove wobble amplitude, wavelength dependency, jitter, use of pre-gap, serial copy management and others.

• Red Book

• The Red Book describes the physical properties of the compact disc and the encoding of the digital audio data. It comprises the following information: 

  Audio specification for 16-bit PCM Disc specification, including physical parameters Optical stylus and parameters including laser wavelength, numerical aperture, pit sizes and track pitch. Deviations and block error rate. Modulation system and error correction. Control and display system (ie subcode channels) 

  A more recent addition to the Red Book describes the CD graphics option using the subcode channels R to W. This describes the various applications of these subcode channels including graphics and MIDI, both of which can be used for Karaoke applications.

• White Book

• The White Book defines the Video CD specification. First published in 1993, there have been several versions:
  • version 1.0: Karaoke CD specification, MPEG-1 data in tracks
  • version 1.1: Video CD: as 1.0 but chapter marks and multi-volume album facilities added
  • version 2.0: Video CD: addition of stills, generic menus, playlists, closed caption text.
  • The White Book (version 2.0) comprises:
  • • Disc format including use of tracks, Video CD information area, segment play item area, audio/video tracks and CD-DA tracks. Data Retrieval Structure, compatible with ISO 9660. MPEG audio/video track encoding including image sizes allowed, video/audio bit rate, sector interleaving and examples of MPEG packets. Segment play item encoding for video sequences, video stills and CD-DA tracks. Play sequence descriptor to allow the playback of preprogrammed sequences. User data fields for scan data (enabling fast forward/reverse) and closed captions. Examples of play sequences and playback control.

• Yellow Book

• The Yellow Book was written in 1984 to describe the extension of CD to store computer data, ie CD-ROM. This specification comprises the following content: 

  Disc specification which is a copy of part of the Red Book. Optical stylus parameters (from Red Book) Modulation and error correction (from Red Book) Control & display system (from Red Book) Digital data structure, which describes the sector structure and the ECC and EDC for a CD-ROM disc. 

  As a separate extension to the Yellow Book, the CD-ROM XA specification comprises the following:

  • Disc format including Q channel and sector structure using Mode 2 sectors. Data retrieval structure based on ISO 9660 including file interleaving which is not available for Mode 1 data. Audio encoding using ADPCM levels B and C. Video image encoding (ie stills)

CAV: Constant angular velocity where the rotational speed remains constant. This mode used in laserdics for interactive applications. 

CD: Compact disc. 

CD Plus: For mixed mode discs including Blue Book Discs. 

CD-E: CD Erasable disc format currently being standardized. 

CD-EXTRA: New name for Enhanced Music CDs (see Blue Book) which are multisession CDs. 

CD-G/CD-Graphics: CD Graphics using the subcode channels on an audio CD. 

CD-i: Compact Disc interactive (CD-i) - a multimedia standard introduced by Philips in 1987. The standard covers both disc and player. Approximately 1m CD-i players have been sold world-wide. 

CD-i Bridge: A bridge standard allowing CD-ROM XA discs to play on CD-i. 

CD-i Ready: CDs which can be played on audio players (audio only) and CD-i players (CD-i data & audio) 

CD-MO: Compact Disc - Magneto Optical format for re-recordable discs 

CD-R, CD-Recordables: Recordable CD used where small quantities are required. 

CD-ROM: Compact Disc Read Only Memory. 

CD-ROM XA, CD-XA: Compact Disc Read Only Memory Extended Architecture. 

CD-RTOS: Compact Disc - Real Time Operating System for CD-i Players 

CD-V: Compact Disc - Video; CD audio with analogue video. This format was launched on the market in 1988 but has not been successful. CD-V discs should not be confused with Video CDs which contain up to 74 minutes of digital video on a compact disc. 

CD-WO: Compact Disc - Write Once. One type of CD-recordable disc. 

CD-XA: Compact Disc - Extended Architecture (a shortening of CD-ROM XA). 

CD32: Amiga CD32 CD-ROM based games console developed by Commodore 

CDDA: Compact Disc Digital Audio 

CDTV: Commodore Dynamic Total Vision. Consumer multimedia system from Commodore, the forerunner of the Amiga32. 

Clock Jitter - An FM modulation of the clock signals that are then used by the DAC; will cause intermodulation distortion components in the audio band.

D/A: Digital to Analogue 

DAC: Digital to Analogue Converter 

DAO: Disc At Once recording. Refers to the ability of certain CD-Recorders to record a disc in one continuous operation. This is necessary to avoid glitches when playing recordable audio discs. (cf Track at Once) 

DAT: Digital Audio Tape, used to record audio in digital form at sampling rates from 32kb/s to 48kb/s. Can be used to master compact discs from. 

Data Fork: The part of a Macintosh HFS file containing the actual data. 

Dynamic Range - Full scale (RMS) signal to broadband noise ratio. The broadband noise is measured over the specific bandwidth and with an input signal 60 dB below full-scale. Units measured in dBs. 

Electroforming and Stamper Finishing

The electroforming stage involves creating one or more nickel stampers from the glass master as follows:

• The metallized glass master is electroplated with nickel in a class 1000 clean room environment to produce a nickel father. For glass masters metallized with silver, the silver is recovered for future use. If nickel, this becomes part of the father.

• The mother is electroformed in a similar way from the father but its surface comprises pits which are identical to the surface of the original glass master and to the CDs to be manufactured. The stamper(s) are then electroformed from the mother producing a nickel disc identical to the father. When the stamper has been electroformed from the mother, it requires finishing before any discs can be replicated from it. Each stamper is checked visually, the back polished, it is cut to the required outside diameter, a hole accurately cut in the center and finally it is checked on a stamper player before being fitted to the press. The father can be used as the stamper for pressing the finished discs but this would only allow one stamper to be produced per glass master. For large runs several stampers are needed. These are usually electroformed from one mother.

Enhanced Music CD: CD EXTRA specification for audio and data contained in separate sessions (see Blue Book). 

Exabyte: A digital tape format based on 8mm video tape and used for transferring CD-ROM files for mastering and for backup purposes 

Father: A nickel disc which has been electroformed from the glass master. 

Glass Mastering:

CD Glass Mastering comprises a number of stages needed to create a metallised glass master from which the stampers are produced. The processes are carried out in a class 1,000 clean room. Operators wear special clothing including face masks and footwear to minimize any particles.

• Glass Master Preparation of the 200 cm (8 inch) diameter 6mm thick glass master starts by stripping the old photo resist from its surface (since the glass blanks can be recycled). This is followed by cleaning and final washing using de-ionised water. The blank master is then dried carefully ready for the next stage. The surface of the clean glass master is then coated with a photo resist layer 150 microns thick by spin coating. The uniformity of the layer is measured with an infra red laser. The photo resist coated glass master is then baked at about 80º C for 30 minutes. This hardens the photo resist layer ready for exposing by laser light. Laser Beam Recording where the photo-resist layer is exposed with laser light in a class 100 controlled environment using a blue gas laser directly from the source audio or CD-ROM data. The photo-resist is exposed where pits are to be pressed in the final disc. The photo-resist surface is then developed to remove the photoresist exposed by the laser and therefore create pits in the surface. These pits should extend right through the photoresist to the glass underneath to achieve good pit geometries as specified in the Red Book. The glass itself is unaffected by this process.

• The active surface (ie containing pits) of the developed glass master is then metallized either with silver by evaporation or a nickel or nickel alloy created by sputtering. The glass master is then played on a disc master player (DMP) to check for any errors. Audio masters are actually listened to at this stage.

Green Book: Defines the CD-interactive (CD-i) standard. See BOOK SPECIFICATIONS

GUI: Graphical User Interface. An application, such as Microsoft Windows, that lies on top of other applications and provides a user interface based on graphical icons 

HDCD: High Definition Compatible Digital, an enhanced version of PCM encoding. 

Header: The bytes in a CD-ROM sector which contain the time-code and mode 

Hz: Abbreviation for Hertz; cycles per second. 

ISO: International Standardization Organization. Worldwide group responsible for establishing and managing various standards committees and expert groups, including several image-compression standards. 

ISO 9002: ISO standard for quality in manufacturing. 

ISO 9660 File Structure

• A group of interested parties formed the High Sierra Group and agreed on a proposal for a file structure for CD-ROMs. This was then ratified, in a slightly modified form, by the International Standards Organization as recommendation ISO 9660. ISO 9660 is compatible with MSDOS, for example filenames can be in upper case only with 8 characters plus 3 character extension. The ISO 9660 data starts at track time 00:02:16 or sector 166 of track one. The first 150 sectors comprise the Pause. The next 16 sectors are empty. The ISO 9660 data are followed by the user data.

ISRC: International Standard Recording Code, for uniquely labeling audio and audio/visual recordings. Should be included on every track of an audio CD. 

JOLIET Extensions to ISO 9660

The Joliet specification was designed to resolve a number of deficiencies in the original ISO 9660 file system. These include:

• Character Set limitations to upper case characters, numbers and underscore.
• File Name Length limited to 8 characters plus three-character extension
• Directory Tree Depth limitations
• Directory Name Format limitations

The Joliet specification uses the supplementary volume descriptor (SVD) feature of ISO 9660 to solve the above problems. At the same time compatibility is maintained with ISO 9660. 

Jewel Case: A plastic case commonly used for CDs and CD-ROMs which contains the CD plus booklet. 

Jitter: On a CD defines the changes in velocity needed when reading the pits. 

Joliet: Microsoft's extension to the ISO 9660 file system to handle long filenames which are part of the features of Windows 95. 

Lacquering: All CDs after metallizing are protected with a lacquer by spin coating. 

LASER: Light Amplification by Stimulated Emission of Radiation; a means of generating coherent light which can be focused to a very small spot size and ideal for reading compact discs, in laser beam recording and for writing CD-R discs. 

LBR: Laser Beam Recorder used in glass mastering CDs and CD-ROMs. 

Lead-in: The starting area of a CD, audio or CD-ROM, or of each session of a multisession disc. It contains the Table of Contents (TOC). 

Lead-out: The last area of a CD or session of a multisession disc. It comes after the program area. 

MIDI: Musical Instrument Digital Interface. An industry-standard connection for computer control of musical instruments and devices. 

Mixed mode disc: A CD which comprises tracks of two or more different types, eg. one or more data tracks followed by one or more audio tracks.

MMCD: Multimedia CD, the Philips & Sony high density disc format. 

Mode 1: CD-ROM sectors containing 2048 bytes of data per sector plus error correction. 

Mode 2: CD-ROM XA sectors which are Form 1 (2048 bytes + error correction) or Form 2 (2324 bytes, no error correction). 

Mode 2 Sectors

Mode 2 sectors are designed for the interleaving of multimedia data. They can be form 1 or form 2 and comprise the following:

• Header consisting of Minutes, Seconds, Sectors (frames) and Mode (= 2).
• Subheader comprising the file number, channel number, trigger bits and data type.
• 2048 bytes of Form 1 data or 2324 bytes of Form 2 data.
• Error correction data (only Form 1).
• Error detection data.

Mother: A nickel disc which has been electroformed from a nickel Father. 

Multisession: CD which comprises more than one session, each of which comprises Lead-in, Program area and Lead-out and (for a recordable CD) can be written at different times (ie sessions). 

Multimedia: Refers to the delivery of information that combines different content formats (motion video, audio, still images, graphics, animation, text, etc.). 

Orange Book: Defines the specification for CD-Recordables. See BOOK SPECIFICATIONS

Oversampling - 1) A/D conversion - for an A/D process oversampling is used to redistribute the quantization noise (error) power over the nFs bandwidth. Thus, it reduces the noise power in the audio band. 2) D/A conversion - for a D/A process, oversampling is used in conjunction with noise shaping techniques to redistribute the additional quantization noise introduced by the requantization (reduction of bits) of the sigma delta modulator. NOTE: for any digitized analog signal, the resulting digital word contains quantization noise that is indistinguishable from the true signal. 

It is this inherent quantization noise and the original sampling frequency that will limit the dynamic range and S/N ratio performance specification for any DAC. Therefore, there is no amount of oversampling that can be employed to increase these performance specifications beyond the theoretical limit set by the original sampling frequency and the number of bits per word. For CD applications: for high input signals, a sampling rate of 1Fs, and 16-bit words yields a theoretical limit of -6 dB (16-bits)-1.7dB or -97.7 dB. 

Photo CD: CD format defined by Kodak and Philips for storing photographs for display and/or subsequent printing. 

PQ-Encoding: An audio CD premastering process that is used to identify and transfer index points, song duration and CD running times. This information is stored in the master tape or disc header file and is read in the glass mastering stage. 

Premastering: process needed to convert the data representing audio or a CD-ROM application into the data to be stored on the CD. For PC CD-ROMs it will involve adding the ISO 9660 file structure data. 

CD-ROM Premastering comprises those processes needed to convert the incoming CD-ROM data into a format ready for mastering. The premastering process depends on the CD-ROM format used but include:

• ISO 9660 premastering most commonly used for CD-ROMs for Windows or MS-DOS applications. (See ISO 9660 File System) Premastering Photo CDs and Video CDs which are CD-ROM XA discs and use ISO 9660 but where certain files must be placed in fixed physical positions on the disc. Normal ISO 9660 premastering tools are not usually suitable. Premastering (also called disc-building) CD-i, CD32 and other proprietary formats require special software since they use variants of ISO 9660. Also CD-i uses Mode 2 sectors. Premastering Mixed Mode which require audio and CD-ROM tracks to be combined on the same disc usually using ISO 9660 file system. CD Extra discs are multisession discs using CD-ROM XA (mode 2) sectors and need special premastering software. Premastering CD Graphics requires adding the R to W data files from magnetic disk or some other media to CDDA audio.

Printers Glossary

Program area: The largest area on a CD containing the audio or CD-ROM information. On a multisession disc there will be one program area per session. 

Red Book: The specification which describes the audio CD. See BOOK SPECIFICATIONS

RGB: Red-Green-Blue, the three primary colors used to output video signals to a computer monitor. 

ROM - Read Only Memory. A memory that stores data and instructions permanently. Contents are placed into memory at the time of manufacture and cannot be altered. Widely used in microcontroller applications. 

Sampling: The first step in the process of converting an analogue signal into a digital representation. This is accomplished by measuring the value of the analogue signal at regular intervals called samples. These values are then encoded to provide a digital representation of the analogue signal 

Sampling rate: The number of samples taken of a signal per unit time. 

Scan Velocity: Velocity (speed) of a CD when being read at normal speed. This should be constant from start to finish of the disc 

Screen Printing: A process used for printing multi-colour labels on CDs. 

Sectors: Units of data on a CD-ROM disc containing 2048 or 2324 bytes of data plus header information. At normal speed, 75 sectors per second are read from a CD-ROM. 

SMPTE: Society of Motion Picture and Television Engineers 

SMPTE Time Code: An 80-bit standardized edit time code adopted by SMPTE. 

Sputtering: A process for coating molded CDs with aluminum whereby an aluminum target is bombarded with particles in a vacuum causing the aluminum to be deposited on the CD surface. 

Stamper: A nickel disc created by electroforming from the mother and used to mould CDs. 

Subcode: A separate low speed data channel on every CD. The subcode comprises 8 channels. The R to W channels are used for CD Graphics. 

Subheader: Subheader is one of the fields in a mode 2 sector and is used to describe the contents of the sector. 

Table of Contents: Table of Contents of a CD, listing the start time code of every track on the disc. 

TAO: Track At Once. Refers to the way most CD-Recorders write discs, where the laser beam stops at the end of each track and then restarts. This can cause a glitch when playing audio CDs recorded in this way. 

Time Code: A frame-by-frame address code time reference recorded on the spare track of a videotape or inserted in the vertical blanking interval. It is an eight-digit number encoding time in hours, minutes, seconds, and video frames (e.g.: 02: 04: 48: 26). 

TOC: Table of Contents of CD, listing the start time code of every track on the disc. 

Track Pitch: The distance between consecutive 'tracks' on a disc measured in a radial direction. 

Tracks: Sub-divisions of the program area of a CD. Each disc may have up to 99 tracks each at least 4 seconds in length. Each track can contain data of only one type. 

WAV: File extension for PCM Wave audio files. 

White Book: Defines the Video CD standard for up to 74 minutes of VHS quality MPEG-1 video on one CD. See BOOK SPECIFICATIONS

Yellow Book: Defines the CD-ROM specification for mode 1 CD-ROM discs See BOOK SPECIFICATIONS

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