DVD Glossary - Part 2 (C

caption - A textual representation of the audio information in a video program. Captions are usually intended for the hearing impaired, and therefore include additional text to identify the person speaking, offscreen sounds, and so on.

CAV - Constant angular velocity. Refers to rotating disc systems in which the rotation speed is kept constant, where the pickup head travels over a longer surface as it moves away from the center of the disc. The advantage of CAV is that the same amount of information is provided in one rotation of the disc. Contrast with CLV and ZCLV.

Cb, Cr - The components of digital color-difference video signals carrying blue and red color information, where the brightness (Y) has been subtracted from the blue and red RGB signals to create B-Y and R-Y color-difference signals. (See Chapter 3.)

CBEMA - Computer and Business Equipment Manufacturers Association. (See Appendix C.)

CBR - Constant bit rate. Data compressed into a stream with a fixed data rate. The amount of compression (such as quantization) is varied to match the allocated data rate, but as a result quality may suffer during high compression periods. In other words, data rate is held constant while quality is allowed to vary. Compare to VBR.

CCI - Copy control information. Information specifying if content is allowed to be copied.

CCIR Rec. 601 - A standard for digital video. The CCIR changed its name to ITU-R, and the standard is now properly called ITU-R BT.601.

CD - Short for compact disc, an optical disc storage format developed by Philips and Sony.

CD+G - Compact disc plus graphics. A variation of CD which embeds graphical data in with the audio data, allowing video pictures to be displayed periodically as music is played. Primarily used for karaoke.

CD-DA - Compact disc digital audio. The original music CD format, storing audio information as digital PCM data. Defined by the Red Book standard.

CD-i - Compact disc interactive. An extension of the CD format designed around a set-top computer that connects to a TV to provide interactive home entertainment, including digital audio and video, video games, and software applications. Defined by the Green Book standard.

CD-Plus - A type of Enhanced CD format using stamped multisession technology.

CD-R - An extension of the CD format allowing data to be recorded once on a disc by using dye-sublimation technology. Defined by the Orange Book standard.

CD-ROM XA - CD-ROM extended architecture. A hybrid version of CD allowing interleaved audio and video.

CD-ROM - Compact disc read-only memory. An extension of the Compact disc digital audio (CD-DA) format that allows computer data to be stored in digital format. Defined by the Yellow Book standard.

CDV - A combination of laserdisc and CD which places a section of CD-format audio on the beginning of the disc and a section of laserdisc-format video on the remainder of the disc.

cDVD - DVD-Video content stored on a CD (or CD-R/RW). Also called mini DVD. Most consumer DVD players can't play a cDVD.

cell - In DVD-Video, a unit of video anywhere from a fraction of a second to hours long. Cells allow the video to be grouped for sharing content among titles, interleaving for multiple angles, and so on.

CEMA - Consumer Electronics Manufacturers Association. A subsidiary of the Electronics Industry Association (EIA). (See Appendix C.)

CGMS - Copy guard management system. A method of preventing copies or controlling the number of sequential copies allowed. CGMS/A is added to an analog signal (such as line 21 of NTSC). CGMS/D is added to a digital signal, such as IEEE 1394.

challenge key - Data used in the authentication key exchange process between a DVD-ROM drive and a host computer, where one side determines if the other side contains the necessary authorized keys and algorithms for passing encrypted (scrambled) data.

channel bit - The bits stored on the disc, after being modulated.

channel data - The bits physically recorded on an optical disc after error-correction encoding and modulation. Because of the extra information and processing, channel data is larger than the user data contained within it.

channel - A part of an audio track. Typically there is one channel allocated for each loudspeaker.

chapter - In DVD-Video, a division of a title. Technically called a part of title (PTT).

chroma (C´) - The nonlinear color component of a video signal, independent of the luma. Identified by the symbol C´ (where ´ indicates nonlinearity) but usually written as C because it’s never linear in practice.

chroma subsampling - Reducing color resolution by taking fewer color samples than luminance samples. (See 4:1:1 and 4:2:0.)

chrominance (C) - The color component (hue and saturation) of light, independent of luminance. Technically, chrominance refers to the linear component of video, as opposed to the transformed nonlinear chroma component.

CIE - Commission Internationale de l’Éclairage/International Commission on Illumination. (See Appendix C.)

CIF - Common intermediate format. Video resolution of 352x288.

CIRC - Cross-interleaved Reed Solomon code. An error-correction coding method which overlaps small frames of data.

clamping area - The area near the inner hole of a disc where the drive grips the disc in order to spin it.

closed caption - Textual video overlays that are not normally visible, as opposed to open captions, which are a permanent part of the picture. Captions are usually a textual representation of the spoken audio. In the United States, the official NTSC Closed Caption standard requires that all TVs larger than 13 inches include circuitry to decode and display caption information stored on line 21 of the video signal. DVD-Video can provide closed caption data, but the subpicture format is preferred for its versatility.

CLUT - Color lookup table. An index that maps a limited range color values to a full range of values such as RGB or YUV.

CLV - Constant linear velocity. Refers to a rotating disc system in which the head moves over the disc surface at a constant velocity, requiring that the motor vary the rotation speed as the head travels in and out. The further the head is from the center of the disc, the slower the rotation. The advantage of CLV is that data density remains constant, optimizing use of the surface area. Contrast with CAV and ZCLV.

CMF - Cutting master format. Specification for storing information needed for full DVD mastering (including CSS protection) in the control area of a DVD-R(A) disc. See also DDP.

CMI - Content management information. General information about copy protection and allowed use of protected content. Includes CCI.

codec - Coder/decoder. Circuitry or computer software that encodes and decodes a signal.

color depth - The number of levels of color (usually including luma and chroma) that can be represented by a pixel. Generally expressed as a number of bits or a number of colors. The color depth of MPEG video in DVD is 24 bits, although the chroma component is shared across 4 pixels (averaging 12 actual bits per pixel).

color difference - A pair of video signals that contain the color components minus the brightness component, usually B-Y and R-Y (G-Y is not used, since it generally carries less information). The color-difference signals for a black-and-white picture are zero. The advantage of color-difference signals is that the color component can be reduced more than the brightness (luma) component without being visually perceptible.

colorburst - See burst.

colorist - The title used for someone who operates a telecine machine to transfer film to video. Part of the process involves correcting the video color to match the film.

combo drive - A DVD-ROM drive capable of reading and writing CD-R and CD-RW media. May also refer to a DVD-R or DVD-RW or DVD+RW drive with the same capability. (Also see RAMbo).

component video - A video system containing three separate color component signals, either red/green/blue (RGB) or chroma/color difference (YCbCr, YPbPr, YUV), in analog or digital form. The MPEG-2 encoding system used by DVD is based on color-difference component digital video. Very few televisions have component video inputs.

composite video - An analog video signal in which the luma and chroma components are combined (by frequency multiplexing), along with sync and burst. Also called CVBS. Most televisions and VCRs have composite video connectors, which are usually colored yellow.

compression - The process of removing redundancies in digital data to reduce the amount that must be stored or transmitted. Lossless compression removes only enough redundancy so that the original data can be recreated exactly as it was. Lossy compression sacrifices additional data to achieve greater compression.

constant data rate or constant bit rate - See CBR.

contrast - The range of brightness between the darkest and lightest elements of an image.

control area - A part of the lead-in area on a DVD containing one ECC block (16 sectors) repeated 192 times. The repeated ECC block holds information about the disc.

CPPM - Content Protection for Prerecorded Media. Copy protection for DVD-Audio.

CPRM - Content Protection for Recordable Media. Copy protection for writable DVD formats.

CPSA - Content Protection System Architecture. An overall copy protection design for DVD.

CPTWG - Copy Protection Technical Working Group. The industry body responsible for developing or approving DVD copy protection systems.

CPU - Central processing unit. The integrated circuit chip that forms the brain of a computer or other electronic device. DVD-Video players contain rudimentary CPUs to provide general control and interactive features.

crop - To trim and remove a section of the video picture in order to make it conform to a different shape. Cropping is used in the pan & scan process, but not in the letterbox process.

CVBS - Composite video baseband signal. Standard single-wire video, mixing luma and chroma signals together.

DAC - Digital-to-analog converter. Circuitry that converts digital data (such as audio or video) to analog data.

DAE - Digital audio extraction. Reading digital audio data directly from a CD audio disc.

DAT - Digital audio tape. A magnetic audio tape format that uses PCM to store digitized audio or digital data.

data area - The physical area of a DVD disc between the lead in and the lead out (or middle area) which contains the stored data content of the disc.

data rate - The volume of data measured over time; the rate at which digital information can be conveyed. Usually expressed as bits per second with notations of kbps (thousand/sec), Mbps (million/sec), and Gbps (billion/sec). Digital audio date rate is generally computed as the number of samples per second times the bit size of the sample. For example, the data rate of uncompressed 16-bit, 48-kHz, two-channel audio is 1536 kbps. Digital video bit rate is generally computed as the number of bits per pixel times the number of pixels per line times the number of lines per frame times the number of frames per second. For example, the data rate of a DVD movie before compression is usually 12 ´ 720 ´ 480 ´ 24 = 99.5 Mbps. Compression reduces the data rate. Digital data rate is sometimes inaccurately equated with bandwidth.

dB - See decibel.

DBS - Digital broadcast satellite. The general term for 18-inch digital satellite systems.

DC - Direct current. Electrical current flowing in one direction only. Adopted in the video world to refer to a signal with zero frequency. Compare to AC.

DCC - Digital compact cassette. A digital audio tape format based on the popular compact cassette. Abandoned by Philips in 1996.

DCT - Discrete cosine transform. An invertible, discrete, orthogonal transformation. Got that? A mathematical process used in MPEG video encoding to transform blocks of pixel values into blocks of spatial frequency values with lower-frequency components organized into the upper-left corner, allowing the high-frequency components in the lower-right corner to be discounted or discarded. Also digital component technology, a videotape format.

DDP - Disc description protocol. A specification for storing all the information needed to master a DVD (including CSS protection) on a DLT.

DDWG Digital Display Working Group - (see DVI).

decibel (dB) - A unit of measurement expressing ratios using logarithmic scales related to human aural or visual perception. Many different measurements are based on a reference point of 0 dB; for example a standard level of sound or power.

decimation - A form of subsampling which discards existing samples (pixels, in the case of spatial decimation, or pictures, in the case of temporal decimation). The resulting information is reduced in size but may suffer from aliasing.

decode - To reverse the transformation process of an encoding method. Decoding processes are usually deterministic.

decoder - 1) A circuit that decodes compressed audio or video, taking an encoded input stream and producing output such as audio or video. DVD players use the decoders to recreate information that was compressed by systems such as MPEG-2 and Dolby Digital; 2) a circuit that converts composite video to component video or matrixed audio to multiple channels.

delta picture (or delta frame)- A video picture based on the changes from the picture before (or after) it. MPEG P pictures and B pictures are examples. Contrast with key picture.

deterministic - A process or model whose outcome does not depend upon chance, and where a given input will always produce the same output. Audio and video decoding processes are mostly deterministic.

digital signal processor (DSP) - A digital circuit that can be programmed to perform digital data manipulation tasks such as decoding or audio effects.

digital video noise reduction (DVNR) - Digitally removing noise from video by comparing frames in sequence to spot temporal aberrations.

digital - Expressed in digits. A set of discrete numeric values, as used by a computer. Analog information can be digitized by sampling.

digitize - To convert analog information to digital information by sampling.

DIN - Deutsches Institut für Normung/German Institute for Standardization. (See Appendix C.)

directory - The part of a disc that indicates what files are stored on the disc and where they are located.

DirectShow - A software standard developed by Microsoft for playback of digital video and audio in the Windows operating system. Replaces the older MCI and Video for Windows software.

disc key - A value used to encrypt and decrypt (scramble) a title key on DVD-Video discs.

disc menu - The main menu of a DVD-Video disc, from which titles are selected. Also called the system menu or title selection menu. Sometimes confusingly called the title menu, which more accurately refers to the menu within a title from which audio, subpicture, chapters, and so forth can be selected.

discrete cosine transform (DCT) - An invertible, discrete, orthogonal transformation. A mathematical process used in MPEG video encoding to transform blocks of pixel values into blocks of spatial frequency values with lower-frequency components organized into the upper-left corner, allowing the high-frequency components in the lower-right corner to be discounted or discarded.

discrete surround sound - Audio in which each channel is stored and transmitted separate from and independent of other channels. Multiple independent channels directed to loudspeakers in front of and behind the listener allow precise control of the soundfield in order to generate localized sounds and simulate moving sound sources.

display rate - The number of times per second the image in a video system is refreshed. Progressive scan systems such as film or HDTV change the image once per frame. Interlace scan systems such as standard television change the image twice per frame, with two fields in each frame. Film has a frame rate of 24 fps, but each frame is shown twice by the projector for a display rate of 48 fps. 525/60 (NTSC) television has a rate of 29.97 frames per second (59.94 fields per second). 625/50 (PAL/SECAM) television has a rate of 25 frames per second (50 fields per second).

Divx - Digital Video Express. A short-lived pay-per-viewing-period variation of DVD.

DLT - Digital linear tape. A digital archive standard using half-inch tapes, commonly used for submitting a premastered DVD disc image to a replication service.

Dolby Digital - A perceptual coding system for audio, developed by Dolby Laboratories and accepted as an international standard. Dolby Digital is the most common means of encoding audio for DVD-Video and is the mandatory audio compression system for 525/60 (NTSC) discs.

Dolby Pro Logic - The technique (or the circuit which applies the technique) of extracting surround audio channels from a matrix-encoded audio signal. Dolby Pro Logic is a decoding technique only, but is often mistakenly used to refer to Dolby Surround audio encoding.

Dolby Surround - The standard for matrix encoding surround-sound channels in a stereo signal by applying a set of defined mathematical functions when combining center and surround channels with left and right channels. The center and surround channels can then be extracted by a decoder such as a Dolby Pro Logic circuit which applies the inverse of the mathematical functions. A Dolby Surround decoder extracts surround channels, while a Dolby Pro Logic decoder uses additional processing to create a center channel. The process is essentially independent of the recording or transmission format. Both Dolby Digital and MPEG audio compression systems are compatible with Dolby Surround audio.

downmix - To convert a multichannel audio track into a two-channel stereo track by combining the channels with the Dolby Surround process. All DVD players are required to provide downmixed audio output from Dolby Digital audio tracks.

downsampling - See subsampling.

DRC - See dynamic range compression.

driver - A software component that enables an application to communicate with a hardware device.

DSD - Direct Stream Digital. An uncompressed audio bitstream coding method developed by Sony. An alternative to PCM. Used by SACD.

DSI - Data search information. Navigation and search information contained in the DVD-Video data stream. DSI and PCI together make up an overhead of about 1 Mbps.

DSP - Digital signal processor (or processing).

DSVCD - Double Super Video Compact Disc. Long-playing (100-minute) variation of SVCD.

DTS - Digital Theater Sound. A perceptual audio-coding system developed for theaters. A competitor to Dolby Digital and an optional audio track format for DVD-Video and DVD-Audio.

DTS-ES - A version of DTS decoding that is compatible with 6.1-channel Dolby Surround EX. DTS-ES Discrete is a variation of DTS encoding and decoding that carries a discrete rear center channel instead of a matrixed channel.

DTV - Digital television. In general, any system that encodes video and audio in digital form. In specific, the Digital Television System proposed by the ATSC or the digital TV standard proposed by the Digital TV Team founded by Microsoft, Intel, and Compaq.

duplication - The reproduction of media. Generally refers to producing discs in small quantities, as opposed to large-scale replication.

DV - Digital Video. Usually refers to the digital videocassette standard developed by Sony and JVC.

DVB - Digital video broadcast. A European standard for broadcast, cable, and digital satellite video transmission.

DVC - Digital video cassette. Early name for DV.

DVCAM - Sony’s proprietary version of DV.

DVCD - Double Video Compact Disc. Long-playing (100-minute) variation of VCD.

DVCPro - Matsushita’s proprietary version of DV.

DVD - An acronym that officially stands for nothing, but is often expanded as Digital Video Disc or Digital Versatile Disc. The audio/video/data storage system based on 12- and 8-cm optical discs.

DVD-Audio (DVD-A) - The audio-only format of DVD. Primarily uses PCM audio with MLP encoding, along with an optional subset of DVD-Video features.

DVD-R - A version of DVD on which data can be recorded once. Uses dye sublimation recording technology.

DVD-RAM - A version of DVD on which data can be recorded more than once. Uses phase-change recording technology.

DVD-ROM - The base format of DVD. ROM stands for read-only memory, referring to the fact that standard DVD-ROM and DVD-Video discs can’t be recorded on. A DVD-ROM can store essentially any form of digital data.

DVD-Video (DVD-V) - A standard for storing and reproducing audio and video on DVD-ROM discs, based on MPEG video, Dolby Digital and MPEG audio, and other proprietary data formats.

DVI (Digital Visual Interface) - The digital video interface standard developed by the Digital Display Working Group (DDWG). A replacement for analog VGA monitor interface.

DVNR - (see digital video noise reduction)

DVS - Descriptive video services. Descriptive narration of video for blind or sight-impaired viewers.

dye polymer - The chemical used in DVD-R and CD-R media that darkens when heated by a high-power laser.

dye-sublimation - Optical disc recording technology that uses a high-powered laser to burn readable marks into a layer of organic dye. Other recording formats include magneto-optical and phase-change.

dynamic range compression - A technique of reducing the range between loud and soft sounds in order to make dialogue more audible, especially when listening at low volume levels. Used in the downmix process of multichannel Dolby Digital sound tracks.

dynamic range - The difference between the loudest and softest sound in an audio signal. The dynamic range of digital audio is determined by the sample size. Increasing the sample size does not allow louder sounds; it increases the resolution of the signal, thus allowing softer sounds to be separated from the noise floor (and allowing more amplification with less distortion). Dynamic range refers to the difference between the maximum level of distortion-free signal and the minimum limit reproducible by the equipment.