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Glossary about DVD

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

AC-3 ( now Dolby Digital)
Dolby Digital Surround Sound System. This is a digitally compressed audio format characterized by its ability to offer up to 6 separate or discrete digital audio channels. AC-3 is used for DVD-Video titles in the NTSC format. Standard digital PCM data such as used on CD would take up too much data on a DVD-Video hence the adoption of a compressed audio format. AC-3 5.1 is the five surround sound channels plus a 1/10 bandwidth channel to drive a sub-woofer. When a 6-channel master is not available, an AC-3 2-channel is used to compress stereo PCM for DVD-Video. PAL titles will use MPEG2 audio compression standard.

AES/EBU

AES/EBU (Audio Engineering Society/European Broadcasting Union) is the name of a digital audio transfer standard. The AES and EBU developed the specifications for the standard. The AES/EBU digital interface is usually implemented using 3-PIN XLR connectors, the same type connector used in a professional microphone. One cable carries both left- and right-channel audio data to the receiving device.

Artifacts
As used in DVD, "artifacts" refer to "video artifacts." These are unusual or unwanted effects caused by the technology and processes used to display motion pictures. Examples are flicker, color shift, loss of resolution, changes in aspect ratio, etc. Broadcast standards such as NTSC and PAL have their own inherent artifacts which affect the motion picture image. DVD, or more accurately MPEG coding/decoding, can introduce its own characteristic artifacts, the most notable of which is "blocking" or "pixelating" where insufficient data describing a picture causes it to be represented in many discrete blocks across the screen.

Authoring
The process of taking data assets such as video, audio, and text, and combining them into a DVD-Video or DVD-ROM compliant disc image. The inputs to this process might consist of compressed video files in MPEG2, compressed audio files in AC-3 and subtitles as bitmap images; the output or end result of the authoring process would typically be a DLT tape with a DVD disc-image file and DDP descriptors.

Bandwidth
The amount of data that can be transferred or processed per unit of time. In simple terms, bandwidth is like pipe size; a 1-inch water hose has a higher bandwidth than an-inch hose since it can pass more water in the same time.

Betacam (Digital Betacam, Betacam SP)
Widely-used component digital video formats suitable for Digital Video Compression work. Each has separate and different PAL and NTSC versions.

Birefringence
A technical term used to describe how a reading laser will be affected by the molded stresses and composition of an optical disc. DVD discs are generally made of polycarbonate, which is prone to taking up "stresses" during the injection molding process. The laser light is "retarded" by non-ideal polycarbonate polymer orientation and this has a bearing on the readout characteristics of a DVD disc.

Bitmap
An image consisting of an array of pixels (picture-cells) that can be displayed on a computer monitor having color/brightness information.

Bit Testing / Bit-to-Bit Test
An automated data verification between a replica DVD disc and the DLT Master tape used to create the Master disc.

Brightness
The value of a pixel along the black-white axis.

CBR - Constant Bit-Rate
This type of compressed video signal uses the same amount of data to describe the video signal regardless of complexity. This is standard MPEG technology used on satellite broadcasts and the like where bandwidth or storage capacity is less of a problem. CBR will most likely be used for short programs on DVD where a higher bit-rate can be allocated to the entire program thereby making the compression process automatic.

CD
Compact Disc: a 120mm (approx. 5") disc used to store optical, machine-readable, digital data that can be accessed with a laser-based reader such as a CD player.

CD-ROM
Compact Disc Read-Only Memory: a compact disc used for computer data and applications that cannot be modified and can be accessed with a CD-ROM drive. See CD.

Chapters
(see titles)

Check Disc Package
Twenty DVD replica discs as a sample Test Pressing for clients to check the authoring and compression of their DVD projects. Cost includes a full Mastering charge and QC verification of disc data to customer-supplied Master. This is thought to be an essential service until DVD-R technology arrives.

CODEC
A software driver used to compress and decompress video originally digitized from an analog source. Literally "COmpression DECompression."

Color Model
Any of several means of specifying colors according to their individual components. See RGB, YUV.

Component Video
A video signal format that separates chrominance and luminance into two waveforms. See S video. Compare composite video. Component video (e.g., D1) is the preferred format for video compression work.

Composite Video
A video signal format that includes all the visual information in one waveform, including chrominance, luminance, blanking pedestal, field, line, color sync pulses and field equalizing pulses. Compare component video. D2 is an example of this. For video compression work composite video source formats are often transferred to a component video source format.

Compression
The process of converting video and audio data into a more compact form for storage or transmission. Compare decompress.

Contrast
The range between the darkest tone and the lightest tone in an image.

CSS
"Content Scramble System." The officially licensed DVD-Video digital encryption scheme. CSS is applied during Glass mastering such that the data on the DLT Master is scrambled and the final discs are encrypted. Only a CSS-licensed DVD player can unscramble the video data.

Custom Pit-Art
See pit-art. A pit-art design created from customer e-file image. Involves a CD Mastering process to create the pit-art stamper.

Data Rate
The speed of a data transfer process, usually expressed in kilobytes (thousands of bytes) per second. CD-ROM drives expressed as 10X drives are designed to have a data rate 10 times that of a standard CD-ROM drive.

D1
An industry standard component video digital video standard. The D1 format is designed to carry PAL and NTSC programs plus PCM audio. A D1 VTR can record either a PAL or NTSC program- they are two different things. A D1 conforms to CCIR-601 and is a world standard for high resolution digital video editing. D1 masters are housed in large format cassettes. D1 is the preferred master format for DVD-Video due to its being a component video format and its high resolution.

D2
A digital video standard. D2 is composite video and PCM audio. Less suitable for DVD-Video due to being composite.

DDP
Disc Description Protocol. A small computer file or files describing data to be Mastered onto an optical disc. This standard was developed by Doug Carson and Associates and later adopted as an ANSI standard. DVD Master Tapes on DLT feature a disc image consisting of the data required to be placed on the DVD disc; the DLT may also contain DDP files instructing the Laser Beam Recorder Data Formatter how to process the data, for example, how to make the disc a DVD-Video

DDP 2.0 DLT Master
A de facto standard for authored DVD Master images supplied to glass mastering houses. The authoring system produces a tape with three files: DDPID (see DDP) , CONTROL.DAT with manufacturing information, and MAIN.DAT the main program. These Masters work directly in a glass mastering machine with no pre-mastering at the disc plant needed.

Decode
The process of decompressing a video clip and then converting its color space from YUV to RGB. See decompress, RGB, YUV. Compare encode.

Decompress
The process of converting video and audio data from its compact form back into its original form in order to play it. Compare compress.

Delta Frame
A frame containing only the data that has changed since the last frame. Delta frames are an efficient means of compressing image data. Compare key frame.

Digitize
The process of turning an analog signal into digital data.

Digital Video
A video signal represented by computer-readable binary numbers that describe colors and brightness levels.

DLT
Digital Linear Tape. A square-shaped tape used as a master tape for DVD. It can hold 10-20 Gigabytes (or more for newer generations of DLT) and can be used directly in mastering. The DLT system is available at various data capacities and densities. Media designated "Compact Tape Type III" and "Compact Tape Type IV" is commonly compatible with DVD Authoring and Mastering systems.

Dolby Digital
The correct name for AC-3. See AC-3.

DVD
An acronym for Digital Versatile Disc, a new optical-disc technology developed by the DVD Consortium, a collection of 10 companies who contributed to the DVD standard and specification. There are five specified DVD disc varieties: DVD-ROM, DVD-Video, DVD-Audio, DVD-R (recordable), DVD-RAM (eraseable).

DVD-5
A single-sided, single-layer DVD capable of holding 4.7GB of data.

DVD-10
Double-sided, single-layer DVD capable of holding 9.4GB of data.

DVD-9
Single-sided, dual-layer DVD holding 8.5GB of data. This unique format allows both molded DVD data halves to be read from the same side of the disc by using a clear bonding agent, a semi-reflective metal layer on the first data disc, and by adjusting the focus point of the player to read two layers.

DVD-18
Dual-layer, dual-side. Capacity 17GB of data.

DVD-Audio
A pre-recorded DVD disc conforming to the yet-to-be-released Book C or the Audio Application specification in the DVD Audio specification.

DVD-ROM
A pre-recorded DVD disc conforming to the DVD File system and specification but not to the DVD-Video or DVD-Audio specified application layer.

DVD-Video
A pre-recorded DVD disc conforming to Book B or the Video Application specification in the DVD Video specification.

Emulation
DVD disc masters are authored and created as a hard disc image. DVD emulation software programs are designed to access the hard disc image under the same conditions that a DVD-Video player accesses the final DVD disc image. The emulator copies the functions of a DVD-Video player to ensure the authored master image is compatible with the DVD specification and that the resulting discs will be compatible with DVD-Video players.

Encode
In the context of digital video and MPEG2, the process of converting the color space of a video clip from a full-bandwidth source to a compressed MPEG2 file.

Field
One half of a video frame, consisting of every other row (scan line). See frame, interlacing.

FLP
Warner/Ivy Hill "Flip" or "Snapper Box" DVD-Video packaging configuration with Home Video form factor.

Formatter
The system on a glass mastering laser beam recorder that takes the raw program data on the DLT master tape and formats it to the DVD specification for creating the glass disc master.

Frame
One video or film image in a clip. Film is shot at 24 frames per second. PAL TV is viewed at 25fps and NTSC at 30fps.

Frame Rate
The number of frames per second at which a video clip is displayed.

Full Motion Video
Video that plays at thirty frames per second (NTSC) or 25 frames per second (PAL).

Generic Face Pit-art
See pit-art. Discs can be printed with title and catalog number information in plain black text for identification. This option removes the custom pit-art mastering process.

Gigabyte
Literally a billion bytes. A Gigabyte in DVD nomenclature represents exactly 1 billion bytes of data (one byte being 8 binary bits). In some computer references a Gigabyte is referred to as 1024*1024*1024 bytes or 1.074 billion bytes.

Glass Mastering
The initial formation of the 120mm DVD disc image from the DLT master tape. A glass master is an extremely fragile part in which the DVD disc image exists in a sub-micron film of "photoresist" material similar to the material used in the manufacture of integrated circuits/silicon chips. See LBR.

Hot-Melt Bonding
A process in which DVD disc halves are bonded using a glue which is heated and allowed to harden after assembly. A well-established technology used for Laserdisc and MO.

Hue
Color.

Interlacing
The process of drawing a frame by alternately drawing the rows of each field, creating the illusion that the image is being redrawn twice as often as it actually is. See field. This is a non-ideal artifact of both PAL and NTSC broadcast systems, e.g., an NTSC broadcast, although thought of as 30 frames per second, is actually made up of 60 half-frames displayed one after the other per second; each half-frame is consecutive black/video lines that interlace to complete full frames. The alternative is progressive scan where only complete frames are drawn on the screen; this is used on computer monitors, HDTV, and in most cases where high quality is important and the application is not tied to an interlaced broadcast standard.

Inverse Telecine Process
See Telecine process.

JPEG
Joint Photographic Expert Group: a standard for compressing single images with high quality. Motion-JPEG is a way of expressing moving images using this technology.

Jewel Case
The standard plastic case used for the majority of audio CDs.

Jitter
This term is used throughout the signal processing world and can refer to many different problems in audio and video alone. In DVD manufacturing, jitter relates to the fidelity of the disc and player's data signal to the clock signal in the player. The DVD and CD technology relies on the disc and player producing data at discrete timing intervals in relation to the player clock. Jitter is a true measure of manufactured disc quality. Low jitter implies that the pits on a DVD disc are consistent in length and allow the player to deliver data close to the system clock pulses thereby minimizing the chance of misreading data.

Laserfile
A VHS form-factor packaging configuration for DVD.

LBR (Laser Beam Recorder)
The machine that creates the DVD disc master on a disc master. The DLT master tape is the input to this machine. The glass master that is made is the master image of the DVD disc.

Luminance
The component of a video signal that includes information about its brightness. See brightness. Compare chrominance.

Macrovision
A publicly traded US company with an analogue copy protection technology for PAL and NTSC video signals. This is widely used on VHS media and works by maladjusting the recording circuitry in a VHS recorder such that the copied program is unwatchable. Macrovision exists on VHS media but is applied by the hardware for DVD after being instructed by the disc. For DVD (NTSC) Macrovision comes in three flavors, AGC (Automatic Gain Control ? as VHS), 2-line, and 4-line color stripe.

Mbps - (Megabits per second)
A mnemonic to express the amount of binary 1s and 0s being used to express a digital data signal. The 133-minute video capacity of a DVD which is often quoted is derived from assuming that the video stream needs an average of 3.5Mbps to describe it. The average Mbps required for the individual video, audio, and subtitle assets determines ultimate runtime since the "bit capacity" of a disc is fixed.

Mother
An inverse master image of a DVD disc that is used to create stampers. A mother is a 9" nickel plate with a DVD disc image in the center. Mothers are thin nickel electroforming plates used to grow stampers in an electroforming or electroplating process. See Stamper.

MPEG
Motion Picture Expert Group: a standard for compressing motion pictures. MPEG1 and MPEG2 are two different standards catering to digital video on CD and DVD respectively. MPEG1 is used on VideoCD and CDI as a sub-VHS quality video distribution medium. MPEG2 and DVD offer better-than-laserdisc quality and twice the runtime per disc.

MPEG Audio
Compressed audio in stereo, six, or eight channel form for use on DVD projects. PCM or MPEG stereo audio is mandated in PAL countries for DVD. Multi-channel MPEG2 audio is optional worldwide.

Multimedia
Information that combines some or all of text, still images, sound, animation, and video.

Navigation
The process of accessing the features of a DVD-Video disc using the specified commands built into the DVD-Video specification. See Titles and Chapters.

NTSC
National Television Systems Committee: a committee of the Electronic Industries Association that prepared the standards for commercial television broadcasting in the United States, Canada, Japan, and parts of Central and South America.

NTSC Format
A color television format having 525 scan lines (rows) of resolution at thirty frames per second (30 Hz). See NTSC. Compare PAL format.

PAL
Phase Alteration Line: the standard for commercial television broadcasting in most of Europe, Australia, parts of Central and South America, and other countries.

PAL format
A color television format having 625 scan lines (rows) of resolution at 25 frames per second (25 Hz). See PAL. Compare NTSC format.

Palette
A look-up table of 256 color values.

PCM Audio
Pulse-code-modulated audio. This is the uncompressed native digital audio commonly used on the Video master tapes. It is often 16-bit 48kHz stereo which is 1.536Mbps or nearly half the bandwidth of a typical VBR MPEG2 video stream. For this reason, PCM audio is usually compressed to 2-channel AC-3 or MPEG audio in NTSC and PAL countries respectively.

Pit-Art
A decorative treatment for a DVD-5 dummy or top disc. A stamper is created with mirrored areas defining a graphic image in a regular CD pit-pattern. Customer supplies a black-on-white e-file image preferably 300dpi plus.

Pixel
Picture element (lit. picture-cell): the smallest independently accessible unit of a digital image.

Pixel Depth
The number of bits of color information per pixel. A system using eight bits per pixel can display 256 (28) colors. A system using 16 bits per pixel can display 65,536 (216) colors. A system using 24 bits per pixel can display over 16.7 million colors. Twenty-four-bit color is often called true color because the human eye can distinguish among approximately six million different colors, fewer than are available in a 24-bit color system.

Regional Coding
A provision in the DVD specifications such that DVD players can be hard-coded to accept DVD discs that are authored and encoded for use in one of six designated world regions. Legislation will exist to ensure that only regionally-coded players are produced. Therefore when a DVD disc is manufactured, a region code is applied at the authoring stage such that the final disc will play only on those players distributed in the designated world region. This technique was developed to enable motion picture companies to release movies at different times in different regions.

Seven regions (also called locales or zones) have been defined. Each one is assigned a number:

Resolution
The width and height of the video window, in pixels.

Reverse Print
In DVD context, see Sandwich Print.

RGB
A color model used chiefly for computer displays in which colors are specified according to their red, green, and blue components. Compare YUV.

S Video
See component video.

Saturation
The amount of gray, as opposed to hue, in a color-the intensity of the hue. See hue.

Sandwich Print
DVD discs may be printed on the bonded surface prior to bonding such that the printed image is viewed through the polycarbonate and appears wet or extremely glossy. Only possible on DVD-5. Also known as reverse-, wetlook-print.

SDI

SDI (Serial Digital Interface) is a standard for digital video transmission over coaxial cable. The most common data speed is 270 megabits per second (Mbps). However, speeds of up to 540 Mbps are theoretically possible. Standard 75-ohm cable is used. This is the same type of coaxial cable used in most home television installations. The SDI standard uses data words that are 8 or 10 bits in length. Signals are uncompressed and are self-synchronizing between the transmitter and receiver. Most errors caused by noise or interference can be detected, and the lost data recovered by means of a specialized code called the Hamming code. A signal in SDI can contain up to four independent digital audio signals along with the video signal.

Stamper
A 6" Nickel DVD disc master used as an insert in the DVD injection molding process. Individual disc replicas are "pressed" off a stamper during injection molding. The clear discs produced take up the image of the stamper which is the DVD disc image created during glass mastering.

Telecine Process
The process of creating a video master from a film master including the step up from 24 film frames per second to 30 NTSC video frames per second. Inverse telecine deals with retracing back to 24fps to reduce the amount of digital compression work needed.

Tilt
A measure of the flatness of a DVD disc. A critical quality parameter for DVD; tilt defines at what angle the reading laser of the player will return to the players detector to read the data. A non-flat disc will cause the reading laser to stray away from the reading detector and for information to be lost.

Titles and Chapters
The DVD-Video specification allows video programs to be split up into titles and chapters. This allows a two-level "directory" structure. For example, a DVD-Video disc may contain three sporting events; each event may be designated as a separate title. Each period in the individual sporting event or title may be designated a chapter. DVD-Video allows the creation of menus to access both titles and the individual chapters in the title.

Trac-Pac
A VHS form-factor DVD packaging configuration.

UV Bonding
A process in which the two halves of a DVD are bonded together with a bonding agent activated or cured by ultra-violet light. Radical UV bonding utilizes a clear bonding agent and has applications with all DVD formats; the bond is cured after assembly. Cationic UV bonding features an opaque bonding agent that restricts its use to single-layer DVD applications; curing is begun prior to assembly and takes hours to reach final strength.

VBR (Variable Bit-Rate)
A feature of DVD allowing the authoring facility to allocate a video compression bit-rate that varies with picture complexity. Still scenes require a lower data rate or bit-rate to describe the video than scenes with a great deal of action.

Video Title Set (VTS)
A term used for DVD Video to denote a set of .VOB files which make up a title. One DVD-Video disc may have multiple titles or title sets on it.

VOB ( .VOB or "video object")
The file format and extension specified for DVD-Video containing the MPEG2 video, AC3 audio and navigation commands. A DVD-Video title must have .VOB files in a directory called Video_ts. Associated files are extension .bup, .ifo.

Wetlook Print
See Sandwich Print.

YUV color model used chiefly for video signals in which colors are specified according to their luminance - the Y component, and their hue and saturation - the U and V components. See hue, luminance, saturation. Compare RGB.