AV/IT Glossary—27 Days of #AVabc—D


 

 

Buzzword:
DSP-Digital Signal Processor—A specialized CPU or circuit designed to process signals such as audio and video which have been converted to digital form. DSP is used to process sound, video, and images in a variety of ways. DSP refers to various techniques for improving the accuracy and reliability of digital communications. The theory behind DSP is quite complex. Basically, DSP works by clarifying, or standardizing, the levels or states of a digital signal.

 

 

Delay—A basic DSP process in which the output of the input signal is delayed by a specified time (called the delay time).

Delay Correction—When an electronic signal travels through electronic circuitry or through a coaxial cable, delay problems may occur. The result of the delay in video is usually a blurred (ghostly, shadowed) image and special electronic circuitry is needed to correct it. Delay correction functions are found on all better video processing equipment. A common problem in analog video is the difference of delay between the luminance and the chrominance channels of the image, resulting in colors that look wrong or mis-registered.

Demultiplexer (demux)—An electronic device for separating several signals, which were combined by a device called a multiplexer*. In digital-signals, de-multiplexers separate digital video from digital audio, which were combined by time division multiplexing (TDM)*.

Dense Wavelength Division Multiplexing–DWDM—The multiplexing, or combining of several wavelengths into a single optical signal. DWDM is distinguished from Coarse Wavelength Division Multiplexing–CWDM in that the separation between wavelengths – 0.8 to 1.6 nm – is much smaller.

Depth—The impression of instruments, voices, or sounds existing behind one another in three dimensions, as in “soundstage depth.”

Detector—A device within fiber optic receivers that converts optical energy to electrical energy.

DHCP—Dynamic Host Configuration Protocol–A standardized client-server IP networking protocol that enables network administrators to centrally and automatically manage the assignment of IP addresses in an organization’s network.

Dialog Intelligibility—The ability to clearly hear and understand the dialog in a movie without strain. Dialog intelligibility is affected by the quality of components in a home-theater system, room acoustics, and how the system is set up.

Diaphragm—The surface of a loudspeaker driver that moves, creating sound.

Dichroic—A type of mirror, reflector, or filter that selectively reflects different wavelengths of light, permitting a projector to transmit more visible light with less heating of the film. Dichroic mirrors are also used for internal convergence of three-tube single lens video or computer projectors.

Dielectric—Insulating material in coaxial cables between center conductor and outer conductor.

Differential Gain—Unwanted variations in a chrominance subcarrier’s amplitude that result from changes in the signal’s DC level, usually specified between 10% and 90% of full scale .

Differential Mode Delay-DMD—A limiting factor in the performance of transmissions over multimode fiber, in which there is a differential in the arrival times at the receiver of various wavelengths, or modes along the fiber. This differential is caused by model dispersion which is inherent in multimode fiber.

Differential Phase—Unwanted variations in a subcarrier’s phase as a result of changes in the chrominance signal’s DC level, usually specified in degrees over a frequency range.

Diffraction—The bending of sound waves as they pass around an object. Also a re-radiation of sound caused by discontinuities in surfaces near the radiating device, such as the bolts securing drivers to a speaker cabinet. diffusion Scattering of sound.

Diffusion—Reduces the sense of direction of sounds, which benefits sound produced by surround loudspeakers.

Digital—A system of data or image values in the form of discrete, non-continuous codes, such as binary. When data is in a digital format, it can be processed, stored (recorded), and reproduced easily while maintaining its original integrity.

Digital Betacam®—A component digital videotape recording format that conforms to CCIR 601 standard, using 1/2" tape, 10 bits, 2:1 compressed. The primary manufacturer is Sony.

Digital Control—A method using discrete digital impulses to control individual functions within a system.

Digital Disk Recorder—A relatively new system, initially intended for post-production* purposes, for recording video and audio on a digital disk (such as a computer hard drive or a recordable DVD). The system was adapted to video camera capturing as well – as for ENG and production - using digital media for recording digital video. Solid state digital media is used for those purposes as well. The system was further developed for consumer use – as in set-top boxes for instant TV program recording and playback. The advantages of this system for editing purposes are extremely fast access to any point on the disk, elimination of dropout* and very fast back and forth shuttle speed. Several digital formats of data storage exist. Digital video editing using this media is sometimes called Non-Linear editing (non-analog). Some consumer electronic manufacturers have started to offer televisions with DDR hardware and software built in to the television itself.

Digital Light Processing (DLP)—A technology developed by Texas Instruments that reflects light from hundreds of thousands of tiny mirrors on a semiconductor chip to project an image. The chip itself is called a Digital Micromirror Device (DMD).

Digital Loudspeaker—Loudspeaker incorporating a digital crossover and power amplifiers. A digital loudspeaker takes in a digital bitstream, splits up the frequency spectrum with digital signal processing, converts each of those signals to analog, and amplifies them separately. The individual power amplifiers then power each of the loudspeaker’s drive units.

DigitalMedia™—A set of core technologies embedded in the DM product line. DM products meet all core requirements: uncompressed bit-for-bit 4K/60 distribution and scaling; streaming AV; an enterprise-class solution; and end-to-end scalable solutions for every room type.

Digital Power Amplifier—An amplifier that takes in digital signals and converts them to analog as part of the amplification process.

Digital S—A digital video format introduced by JVC™. This format is “back” compatible with the S-VHS* format so cassettes recorded in S-VHS can be used with a DIGITAL-S VCR. The technical specifications are very similar to the DVCPRO* format - 4:2:2 encoding, 3.3:1 DCT* compression and a 50 Mbits/sec data rate. The cassette lasts for 104 minutes and is 0.5 inches wide.

Digital Signal—An electrical signal which possesses two distinct states (on/off, positive/negative); typically represented by “0” or “1”.

Digital Technology—Digital technology is a base two process. Digitized information is recorded in binary code of combinations of the digits 0 and 1, also called bits, which represent words and images.

Digital Transmission Content Protection (DTCP)—An encryption technology that allows transmission of digital video and digital audio between components in a home-theater system, but prohibits those signals from being recorded. Used with FireWire (IEEE1394). Also called 5C to acknowledge the five companies that developed it.

Digital Video Recorder (DVR)—A device that stores digital video on a hard-disk drive. TiVo and ReplayTV devices are DVRs.

Digital Visual Interface (DVI)—A wideband digital video interface that can carry uncompressed high-definition video and control signals in the same cable.

Digitization—The transformation of an analog signal into digital information.

Digitizers—Video digitizers utilize video cameras to take pictures of photographs or live and still action. The information is decoded into RGB (digital form) and stored in the frame buffer.

D-ILA™-Direct Drive Image Light Amplifier—The D-ILA is a device based on the Image Light Amplifier or ILA developed by Hughes-JVC Technology Corporation. The D-ILA technology is a reflective liquid crystal modulator whereby electronic signals are addressed directly to the device. The D-ILA device has an X-Y matrix of pixels configured on a C-MOS single crystal silicon substrate mounted behind the liquid crystal layer using a planar process that is standard in Integrated Circuit technology.

DIN Connector—An acronym for Deutsche Industrie Norm. A round connector with notches, or keys, for alignment. They exist in several sizes: 4 pins, 5 pins, 8 pins, etc. A convenient way of combining all of the signal lines in one connector, 4-pin DIN connectors are often used for S-video.

Diode—An electronic device that allows current to flow in one direction only.

DIP-Dual In-line Package—A universal method of manufacturing integrated circuits (ICs) with the pins arranged in two parallel rows. Some DIP components are soldered in and some use DIP sockets.

DIP switches—Small switches that are used to change settings on printers, computers, interfaces, switchers, modems, etc. They are designed to fit in a DIP (Dual Inline Package) space on a circuit board.

Dipolar Speaker—A loudspeaker that produces sound from the rear as well as from the front, with the front and rear sounds out of phase with each other. Dipoles are most often used as surround speakers.

Direct Broadcast Satellite (DBS)—A method of delivering highquality digital video into consumers’ homes via an 18-inch roof-mounted dish. Previously known as digital satellite system (DSS).

Director’s Cut—A version of a film re-edited by the director for a premium consumer release.

Direct Stream Digital (DSD)—A method of digitally encoding music with a very fast sampling rate, but with only 1-bit quantization. Developed by Sony and Philips for Super Audio CD (SACD).

Direct-View—Another name for a conventional television set. Called direct-view because you view the image directly on the front of its picture tube.

Discrete—Separate. A discrete digital surround-sound format contains 5.1 channels of audio information that are completely separate from each other; contrasted with a matrixed surround format such as Dolby Surround, which mixes the channels together for transmission or storage.

Discrete Cosine Transform (DCT)—A Fourier-related transform which is used to convert an image from a spatial domain to a frequency domain. Video systems then process the information in the frequency domain. Typically, more signal energy is located in the lower frequencies than the higher frequencies. The DCT is used in many video compression codecs including JPEG, MPEG, MPEG-2, MPEG-4 and H.264.

Discrete Wavelet Transform (DWT)—A transform used to convert an image from a spatial domain a wavelet domain. Two filters are involved, the first a “wavelet filter” is a high pass filter, and the second a “scaling filter” a low pass filter. The DWT provides more efficient image compression than the DCT as it due to advantages analyzing signals with sharp discontinuities or spikes.

Dispersion—A limiting factor in optical fiber transmission performance, where a light pulse is broadened, or separated into modes or individual wavelengths. Dispersion limits transmission bandwidth and distance capability. The two major types of dispersion are modal dispersion and chromatic dispersion.

Dispersion Compensating Fiber-DCF—A special type of fiber designed to exhibit a large negative dispersion. DCF is typically used in long-haul telecommunication systems to compensate for dispersion in optical fiber.

Dispersion Shifted Fiber-DSF—A singlemode optical fiber with its optimal dispersion wavelength shifted, through the addition of dopants, to a wavelength that delivers optimal attenuation.

Display Device—Any output device for presenting information visually. Examples include: CRT (Cathode Ray Tube), LED (Light Emitting Diode), or LCD panel (Liquid Crystal Display). A general term for a projector or monitor.

DisplayID—Released in December 2007, this second-generation version of VESA EDID – Extended Display Identification Data is intended to replace all previous versions. DisplayID represents a 256-byte data structure that conveys display-related information to attached source devices. It is meant to encompass PC display devices, consumer televisions, and embedded displays such a LCD screens within a laptop without need for multiple extension blocks. Display ID is not directly backward compatible with previous EDID/E-EDID versions.

DisplayPort—The newest digital audio/video interconnect standard, designed primarily for use between a computer and display device. DisplayPort supports data rates up to 10.8 Gbps at a distance of 2 meters for full bandwidth transmissions, and up to 15 meters for reduced bandwidth signals such as 1080p/60, over copper cable. DisplayPort is not directly compatible with DVI or HDMI, but a DisplayPort connector can pass these signals, and the standard does provide an emulation mode for ease of integration with DVI or HDMI equipped products.

Dissolve—(1) An effect in which one scene or picture fades out as another fades in. In projection, the dissolve effect is achieved by varying the intensity of the lamps in the two projectors involved. Sometimes called lap dissolve or cross fade. (2) The hardware controlling the dissolve effect, which is properly called dissolve control or dissolve unit. A visual effect wherein one scene gradually fades away while slowly being replaced by another. Also see "Fade, Fade-to-black."

Distortion—In audio, this term implies undesirable changes in the waveform of a signal caused by the introduction of spurious elements. When a pure sine signal is fed into an amplifier and comes out harmonized, additional tones are created, naturally related to the original tone. This upsets the relationship between a specific tone and other tones related to it. In audio there are several distortion patterns - harmonic distortion, crossover distortion, transient distortion and intermodulation distortion. No matter what the type is, the result is unpleasant to the ear. Video distortion, like audio distortion, is the result of improper signal handling during video amplifying and processing. Video signal distortion affects the luminance* or chrominance* portions of the signal. It may distort the picture and produce improper contrast*, faulty luminance levels, twisted images, erroneous colors and snow*. The goal of a good video processor*, is, as in audio, to be a "wire with amplification" device which does not unnecessarily affect the brightness, contrast and tonal quality of the image.

Distribution Amplifier—A device that distributes multiple outputs from a single source input. Distribution Amplifiers (DAs) split signals, but also provide amplification and enhancement features to maintain the integrity of the signals.

Distribution Cable—Fiber optic cable comprising a bundle of jacketed fibers encased within an outside jacket.

Distribution Panel—For fiber optic applications, this is both a patch panel and splice panel, usually installed at a hub or entrance facility

Dither—(1) The process of filling a gap between two pixels with another pixel having an average value of the two to minimize the difference or add detail to smooth the result. (2) In audio, a process that deliberately adds a tiny amount of noise to a signal in order to mask unwanted sounds introduced when the signal’s original bit depth is reduced. Dithering is recommended when transferring audio to a device that uses a lower bit depth.

DLP™-Digital Light Processing—An imaging technology for video projection developed by Texas Instruments, based on the modulation of light reflected from mirror elements known as Micromirrors(tm). Each pixel is represented by its own Micromirror, which mechanically tilts in accordance to the extent of light reflected toward or away from the screen. A matrix of Micromirrors comprising the video image is situated on a microchip, or DMD(tm) (Digital Micromirror Device). DLP is implemented as a three-chip configuration (one DMD for each of the RGB colors), or as a one-chip configuration (R, G, and B are sequentially processed by a single DMD via a color wheel).

DMI™-Dynamic Motion Interpolation™—This Extron video processing technique is an advanced motion prediction and compensation method that treats motion content and still content with different algorithms to yield high fidelity images.

DMM-Digital Multimeter—A test and measurement device, typically handheld, that combines measurement tools for voltage, amperage, resistance, and other common electrical and electronic measurement needs.

DNS-Domain Name System—DNS is the way that an Internet domain name is located and translated into Internet Protocol (IP) addresses. A domain name is a meaningful and easy-to-remember “handle” for an Internet address.

DOC-Declaration of Conformity—A document that states the European Union directives and standards to which particular equipment should comply.

Dolby® Noise Reduction—A patented noise reduction technique from Dolby Labs that raises the volume of sound track elements most likely to be affected by inherent noise during recording and then lowers them again during playback so that the noise seems lower in relation to the wanted elements of the audio recording.

Dolby® Digital—A digital audio encoding and decoding technology utilized for DVDs, Blu-ray Discs, video games, and many cable and satellite television services. Also referred to as “AC-3.” Dolby Digital can transmit mono or standard two-channel stereo audio, as well as 5.1 channel surround sound (left front, center front, right front, left rear, right rear, and sub-woofer).

Dolby® Digital EX—A surroundsound format that matrix-encodes a “back-surround” channel into the left and right surround channels of a 5.1- channel Dolby Digital signal. This back-surround channel is reproduced by one or two loudspeakers located directly behind the listening position. Although Dolby Digital EX is the format’s official name, it’s often called THX Surround EX because THX was the exclusive licensor of the technology until late 2001. Jointly developed by Lucasfilm THX and Dolby Laboratories.

Dolby® Digital Format—Dolby Digital is the name for audio compression technologies developed by Dolby Laboratories. It was originally named Dolby Stereo Digital until 1994. Except for Dolby TrueHD, the audio compression is lossy. The first use of Dolby Digital was to provide digital sound in cinemas from 35mm film prints. It is now also used for other applications such as HDTV broadcast, DVDs, Blu-ray Discs and game consoles.

Dolby® Digital Plus—A digital audio compression technology designed as an optional codec for use with Blu-ray Disc. Dolby Digital Plus is an extension of the earlier Dolby Digital format and supports up to 13 audio channels, although Blu-ray Disc is limited to 8 discrete channels. The extra audio channels are often used to support multiple languages.

Dolby® Pro Logic—A type of Dolby Surround decoder with improved performance over standard Dolby Surround decoding. Specifically, Pro Logic decoding provides greater channel separation and a center-speaker output. A Dolby Pro Logic decoder takes in a 2-channel, Dolby Surround–encoded audio signal and splits those signals up into left, center, right, and surround channels. Nearly all A/V receivers and A/V controllers include Dolby Pro Logic decoders.

Dolby® Pro Logic II—Introduced in late 2001, Pro Logic II provides superior decoding of two-channel music and film sources compared with Pro Logic.

Dolby® Surround—An encoding format that combines four channels (left, center, right, surround) into two channels for transmission or storage. On playback, a Dolby Pro Logic decoder separates the two channels back into four channels.

Dolby® TrueHD—An advanced, lossless multi-channel audio encoder and decoder technology intended primarily for high-definition content and is optional for Blu-ray Disc; support for TrueHD is also optional in the HDMI 1.3 specification. TrueHD supports up to 8 discrete audio channels at 96 kHz sampling, or up to 6 channels at 192 kHz sampling. Since TrueHD is optional for Blu-ray Disc, discs encoded with a TrueHD audio track must also include a separate 2-channel digital audio track.

Domain—When referring to the Internet, a name that identifies a network. (i.e. yahoo.com)

Dome Diaphragm—The domeshaped paper, plastic, silk, or metal diaphragm of a loudspeaker that moves back and forth to create sound. Normally used in tweeters. Contrast with “cone diaphragm.”

Dot Clock—Also referred to as pixel clock. The timing device in a graphics card that determines the pixel resolution. The dot clock runs at a rate that produces the highest possible pixel resolution for that device. In a digital projector, the dot clock samples the analog video at a rate that produces the resultant pixel resolution. Also see "Pixel clock."

Dot Crawl—Sometimes called “zipper effect,” dot crawl refers to a specific image artifact that is a result of the composite video system. Dot crawl may be seen on TV news, for example, when a picture appears over the anchorperson’s shoulder, or when some text appears on top of the video clip. If you look closely, along the edges of the picture, or the text that has been overlaid, you’ll notice some jaggies rolling up or down.

Dot Pitch—The vertical distance (measured in millimeters) between the centers of like-colored phosphors that are in adjacent pixels on the monitor screen. The closer the spacing, the better the resolution. Dot pitch is specified in pixels/mm.

Downmix Converter—A circuit found in DVD players that converts the 5.1-channel discrete Dolby Digital soundtrack into a 2-channel Dolby Surround–encoded signal. A DVD player’s downmix converter lets you hear surround sound from DVD if you don’t have a Dolby Digital decoder.

Downstream Keying—One of the special effects* employed by a special effects generator*. A video picture is painted with natural or with artificial colors produced by the special effects generator as a function of its brightness. A washed-out sky can be painted a brilliant red, for example. Colors are streamed down from brightest to darkest and any level of brightness can be changed down to any darker level.

DPCP-DisplayPort Content Protection—DPCP is a content-protection scheme for DisplayPort developed by Advanced Micro Devices. Like HDCP 2.0, DPCP uses AES 128 encryption. To date, DPCP has not been implemented by any manufacturer of source or display devices equipped with DisplayPort. All devices currently on the market use HDCP for digital rights management.

Drain Wire—Non-insulated wire used in cable termination as a ground connection.

Driver—The actual speaker unit inside a loudspeaker cabinet.

DRM-Digital Rights Management—A generic term for technologies such as content scrambling in cable or satellite television transmission, HDCP, and DPCP that can be used to control the access to, or reproduction of, copyrighted, commercially-available content. DRM is used primarily to prevent piracy, the unauthorized duplication and distribution of copyrighted material. However, DRM often also governs how content can be used. Commercially-available DVDs and Blu-ray Discs, for example, are typically licensed for personal use in a residential environment. Use of such content in a public venue, such as a school or business setting, without express consent or licensing by the copyright holder, is typically in violation of the media’s license.

Dropout—Partial loss of a video picture, usually seen on the screen as white streaks, resulting in a poor quality playback. Flaws in magnetic tape coating resulting in loss of magnetic particles from the tape are the main cause of dropout. Special electronic equipment, usually digital, called dropout compensators, is needed to eliminate dropout effects. Normally, a dropout compensator replaces the missing information with data from adjacent pixels, lines or fields.

Drop Shadow—A special effect, which adds an artificial shadow or a three-dimensional, extruded shadow to a scene or an inserted object. This effect is used also in titling in order to emphasize the inserted titles.

Dry Contact Closure—A pair of electrical contacts that carry no live voltage.

DSL-Digital Subscriber Line—A generic name for a family of digital lines (also called xDSL) provided by telephone carriers to business and consumers.

DSP Room Correction—A technique of removing room-induced frequency-response peaks and dips with digital signal processing.

DSVP™-Digital Sync Validation Processing™—In critical environments or unmanned, remote locations, it is vital to know that sources are active and switching. Extron's exclusive DSVP technology confirms that input sources are active by scanning all sync inputs for active signals. DSVP provides instantaneous frequency feedback for composite sync or separate horizontal and vertical sync signals via the switcher's RS-232/422 port.

D-Theater—Copy-protection system proposed for the D-VHS digital videotape format.

DTS (Digital Theater Systems)—A discrete, digital surround-sound format used in movie theaters and home-theater systems. An alternative to Dolby Digital that uses a higher bit rate. Also called “DTS Digital Surround.”

DTS® Digital Surround—A digital audio encoding and decoding technology from DTS, Inc. that delivers 5.1 channels of surround sound. It is an optional surround sound format for DVDs but is mandatory for Blu-ray Disc. DTS Digital Surround has also been used in some LaserDisc releases as well as CDs, and is also featured in some video games.

DTS-ES Discrete—A 6.1-channel surround-sound format that includes a rear surround channel in addition to the conventional 5.1 channels. Called “discrete” because the rear surround channel is completely separate from the left and right surround channels, unlike DTS ES Matrix, which matrixencodes the third surround channel into the existing left and right surround channels of a 5.1-channel signal.

DTS-ES Matrix—A 5.1-channel surround-sound format that includes a rear surround channel that is matrixencoded into the left and right surround channels of a 5.1-channel signal. Unlike DTS ES Discrete, DTS ES Matrix is not a true 6.1-channel format because the soundtrack is carried in 5.1 channels.

DTS-HD High Resolution Audio—An extension to the DTS Digital Surround format that offers up to 7.1 channels at 24-bit resolution and 96 kHz sampling. DTS-HD High Resolution Audio is an optional surround sound format for Blu-ray Disc.

DTS-HD Master Audio—A lossless audio encoder/decoder technology from DTS, Inc. DTS-HD Master Audio allows a bit-for-bit representation of a movie’s original studio master soundtrack and supports up to 8 audio channels. Support for DTS-HD Master Audio is optional in the HDMI 1.3 specification released in 2006, and is also optional for Blu-ray Disc.

DTS Neo:6 Cinema—A DTS decoding technology for playing back 2-channel film-soundtrack sources (such as television broadcasts and the stereo audio channels from a VCR) through 5.1 or 7.1 loudspeakers.

DTS Neo:6 Music—A DTS decoding technology for playing back two-channel music sources (such as stereo CDs and FM radio) through 5.1 or 7.1 loudspeakers.

DTV-Digital Television—Often used to describe one of the many new forms of digital terrestrial transmission of video program material.

Dual-Link DVI—A dual-link DVI output has two TMDS links and twice the bandwidth of single-link DVI, and can therefore support much higher resolutions. With two TMDS links, the number of data channels is doubled, although there is still only one clock signal, so both links are clocked identically. Apples 30 Cinema Display with a native resolution of 2560x1600, is an example of a display requiring dual-link DVI. See also Single-Link DVI. Also see "Single-Link DVI."

Dual-Link HD-SDI—Is a method applying two HDSDI signals 1920x1080 video at 50 or 60Hz as progressive frames, at 12 bit depth or with 4:4:4 color quantization.

Duplex—Data transmission in both directions. Half duplex denotes transmission in one direction at a time, while full duplex refers to simultaneous transmission in both directions. In fiber optics, duplex also refers to a type of cable comprising two fibers for duplex transmission.

Dust Cap—A plastic cap that covers the connector ferrule, plug, or sleeve, and protects the connector endface.

DV-Digital Video—A serial digital video format. DV has the advantage over standard analog video of maintaining clear, crisp video without degradation from generation to generation.

DVB/ASI-Digital Video Broadcasting/Asynchronous Serial Interface—A standard for the broadcast of digital television signals. Terrestrial broadcast, primarily seen in Europe, is often stated as DVB-T. In the US, DVB-S is often used for compression and encoding of digital satellite transmission; for terrestrial applications, North America utilizes the ATSC standard.

DVC-Digital Video Cassette—A domestic and professional cassette format. DVC cassettes come in two sizes - mini or regular-sized for camera or desktop VCR use. The mini cassette (6.35mm) can be played directly from the desktop VCR without using adapters. Sometimes, the mini cassettes have a memory chip built-in. Resolutions of up to 500 lines are achievable.

DV Cam—A digital video format introduced by SONY™. This format uses DV*-like cassettes, has a 4:1:1 encoding scheme and outputs a 25Mbits/sec data rate. Cassettes come in two sizes- 46 minutes for field use and 180 minutes for desktop VCRs.

DVC Pro—A digital component video format introduced by Panasonic™ and Philips BTS™. The format uses two cassette sizes- 6.35mm and 0.5 inch. It provides a stream of digital information @ 25 Mbits/sec and has two uncompressed audio channels. It operated initially at 4:1:1 encoding and 5:1 DCT* compression, but was recently re-introduced at 4:2:2 encoding and a lower, 3:3:1 rate of compression. This has changed the amount of time that can be recorded on tape from 123 minutes for the desktop DVCPRO VCR operating at 4:1:1 to 61.5 minutes at 4:2:2.

DVD-Digital Versatile Disc—An optical disc similar in physical size to a CD-ROM, but capable of storing an entire movie. The technology uses MPEG-2 compression. Typical capacity for these discs is 4.5 GB, or about 133 minutes of digital video.

DVD-Audio—A digital format for delivering high-fidelity audio content on DVD – Digital Video Discs. DVD-Audio is a standalone format intended for audio only and is not used for the audio portion of DVD video content. DVD-Audio is similar in application to SACD, although to maintain compatibility with DVD players, the format is not capable of the very high sampling rates found in SACD. Support for DVD-Audio was added to the HDMI 1.1 specification in 2004.

DVD-R—A write-once recordable DVD format.

DVD-RAM—A re-writable DVD recording format that is incompatible with all other recordable DVD formats.

DVD-RW—A re-writable DVD recording format.

DVD+R—A write-once recordable DVD format that is incompatible with DVD-R and DVD-RW.

DVD+RW—A re-writable DVD format that is incompatible with DVD-R and DVD-RW.

DVE-Digital Video Effects—Special effects generators* which employ digital signal processing to create two or three dimensional digital wipe effects, where for example, the image can be rolled out of the screen, broken into tiny pieces or converted into a tube-like picture.

D-VHS-Digital-VHS—A new technology based on VHS, offering the features of conventional VHS with bit stream recording capability which allows the recording and playback of compressed digital data including digital television broadcasts and prerecorded high definition software.

DVI-Digital Visual Interface—The digital video connectivity standard that was developed by the DDWG – Digital Display Working Group. This connection standard offers two different connectors: one with 24 pins that handles digital video signals only and one with 29 pins that handles both digital and analog video. This standard uses TMDS – Transition Minimized Differential Signal from Silicon Image and DDC – display Data Channel from VESA – Video Electronics Standards Association.

DVI-D—DVI connector that supports digital signals only.

DVI-I—DVI connector that supports both digital and analog signals.

Dynamic IP address—An IP address that is automatically assigned to a client host in a TCP/IP network, typically by a DHCP server. Network devices that serve multiple users, such as servers and printers, are usually assigned static (unchanging) IP addresses.

Dynamic Range—The highest and lowest potential signal levels on a given device. Also applies to fiber optic applications in terms of the ratio between the most – or strongest – and least – or weakest – observable optical signals.

Dynamic-Range Compressor—A circuit found in some Dolby Digital¬-equipped receivers and controllers that reduces audio dynamic range. A dynamic range compressor can reduce the volume of peaks, or increase the volume of low-level sounds, or both. Useful for late-night listening when you don’t want explosions to disturb other family members, but still want to hear low-level sounds clearly.


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