D Connector
A connector with rounded corners and angles ends, taking on the shape of the letter "D." Commonly used in computers and video, most D connectors have two rows of pins. If they have more than two rows, they are usually called HD (High Density) connectors.
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D'Appolito Speaker Configuration
A vertical stacked three speaker arrangement with the tweeter sandwiched between two woofers and/or midrange units to control vertical dispersion and crossover lobbing for less ceiling and floor bounce. Used predominately to achieve THX® certification.
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D/A Converter
Digital-To-Analog. An electronic circuit which converts digital signals (binary codes) to the equivalent analog signals (voltages). D/A converters are found most commonly in LaserDisc, DVD and Compact Disc players, but are now becoming more popular as outboard units, where the circuitry and design are more specialized.
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D6500
6500 Kelvins, 6500°K. The SMPTE standard for the correct color temperature of NTSC white.
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DA
Display Adapter.
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DA
Distribution Amplifier.
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DAC
Digital to Analog Converter. A circuit that converts digital signals to analog (varying amplitude) signals.
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Damping
1) The loss of energy in a vibration system, usually through friction. 2) The physical or electrical control of resonance.
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DAT
Digital Audio Tape. A method developed by Sony and Hewlett-Packard for recording large amounts of information in digital form on a small cassette tape. It uses a rotating helical read/write head, similar to the technique used on a VCR.
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Data
(1) A representation of facts, concepts, or instructions in a formalized manner suitable for communication, interpretation, or processing by human or automatic means. (2) Any representations, such as characters or analog quantities, to which meaning is, or may be assigned.
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Data Grade Projector
A Data grade projector can usually handle signal rates up to, and including, the 1125 or 1250 line proposals for HDTV.
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Data Monitor
A monitor with horizontal scan capability between 15.75-36 (42) kHz. Data monitors and projectors are commonly associated with NTSC video, IBM CGA through VGA and Apple/Macintosh computer input sources.
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dB
Decibel. One-tenth of a Bel, a logarithmic unit of power, voltage, or sound pressure level ratio named after Alexander Graham Bell. The standard unit used to express gain or loss of power relative to a reference value. It indicates the logarithmic ratio of output power divided by input power. A power loss of 3 dB is an attenuation of half of the original value. The term "3 dB down" is used to describe the "half power point." In audio work, 0 dB is the threshold of hearing. 120 dB is the threshold of pain. A change of 3 dB halves or doubles the apparent loudness.
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dBm
Decibel Milliwatt. A ratio of decibel strength to 1 milliwatt.
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DBS
Direct Broadcast Satellite. A satellite distribution system whereby signals are transmitted directly from an operational satellite to standard receivers. Most effective distribution system for remote areas, though transmission may be affected by weather.
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DC
Direct Current. The flow of electrons or electrical current in one direction.
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DC Coupled
Circuit passes both AC and DC components of signal, so is sensitive to DC offsets.
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DC Restoration
The ability to hold video black at black in the display, independent of picture content. The correct blanking level for a video signal is zero volts DC. When a video signal is AC-Coupled between stages, it loses its DC reference. A DC restoration circuit clamps the blanking at a fixed level. If set properly, this level is zero volts. Some sets aren't good at holding black at black, independent of picture content or restoring the DC value of black in the video signal to a fixed DC voltage.
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De-Emphasis
A form of equalization used in CD players to reduce noise and distortion in program material that has received pre-emphasis boost of the high-frequency component of the signal. Discs recorded with pre-emphasis automatically engage de-emphasis circuits in the CD player. See Pre-Emphasis
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Dead
An acoustical condition in which reverberation is absent. A room whose surfaces are covered with heavily absorptive materials.
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Decay Time
The length of time taken for a signal to decay to a specific portion of its initial value. Decay time is often frequency dependent. The decay time of a room at a specific frequency is the time necessary for a sound of that frequency to decay 60 dB.
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Decibel
See dB.
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Decoder
1) In video, a device used to separate the RGBS (red, green, blue and sync) signals from a composite video signal. Also called NTSC Decoder. 2) The device in a synchronizer or programmer which reads the encoded signal and turns it into some form of control. 3) In audio, a device which takes a single encoded digital bitstream and breaks it into multiple datastreams, or restores four or more channels which were matrix encoded into two-channels.
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Decoding
Converting hue and saturation in the C signal to R, G, and B primary color signals.
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Decorrelation
A special type of DSP applied to the mono surround channel in THX(r) processors that divides the signal to the left and right rear speakers and then scrambles their relative phase. The objective is to create an ambient soundfield closer in spaciousness and depth to that in a cinema.
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Defeat
To bypass a signal processing feature, removing it entirely from the circuit.
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Definition
The fidelity with which a video picture is reproduced. The clearer the picture, the higher the definition seen in sharpness and detail. Definition is influenced by resolution.
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Deflection Yoke
The coils of wire surrounding the neck of a picture tube to focus and deflect electron beams.
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Degausser
A device used for eliminating ghosting in television monitors by demagnetizing the CRT and restoring color purity.
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Delay Line
A digital or analog device employed to delay one audio signal with respect to another.
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Delta Gun
Pertains to a direct view picture tube in which the electron guns are arranged in a triangle.
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Density
The ratio of weight to volume, measured in pounds per cubic foot, or grams per cubic centimeter of a material.
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Depth
Reproduction of the differing distances between the listener and the layers of instruments comprising an orchestra or group.
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Depth Of Field
See Front-To-Back Imaging.
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Descrambler
Device that decodes scrambled cable TV signals, usually combined with a converter as a converter/ descrambler. See Converter/Descrambler.
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Desktop Publishing
DTP. The use of a personal computer as a production system for generating typeset-quality text and graphics.
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Detail
An adjustment that enhances/improves image sharpness.
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Dichroic
A type of mirror, reflector or filter which 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 3-tube single lens video or computer projectors.
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Dichroic Lens
A special coating applied to the lens surface of the green gun of a big-screen television to filter out unwanted colors in the green spectrum.
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Differential Audio
See Balanced Audio.
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Differential Phase And Gain
Measure, respectively, how much a color shifts with changes in picture brightness and how much the picture brightness shifts with changes in color.
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Diffraction
The bending of a sound wave around an obstacle.
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Diffraction Interference
Frequency response aberrations caused by diffraction around the front surface of a loudspeaker or microphone.
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Diffuse Sound Field
The area in a room with multiple reflections equally probable in all directions.
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Diffuser
A device for the complex scattering of sound energy in all directions.
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Diffusion
See Diffuser.
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Digital
A system of recording data and images with discrete, non-continuous codes. The expression of information in terms of numbers or digits. Provides signal reproduction with little noise or distortion.
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Digital Audio Tape
See DAT.
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Digital Control
A method using discrete digital impulses to control individual functions within a system.
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Digital Light Processor
The Digital Light Processor is a micro mirror technology from Texas Instruments. It is also known as DMD or Digital Micromirror Device. A DLP chip is made up of an array of mirrors. One of the configurations currently being marketed has 848 elements per row and 600 rows. That's 508,800 mirrors per chip. DLP is efficient in light output both in active area of each element and reflectivity. The DLP imager requires a progressively scanned source to drive it. That means that all DLP projectors capable of accepting an NTSC input have line doublers as part of their processing electronics. The quality of the line doubler will effect the quality of the image. See DMD.
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Digital Linear Tape
DLT. The current standard media used as a DVD production master for delivery to the pressing plant. DLT is a tape format similiar to exabyte but with a much faster transfer rate and greater storage capacity.
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Digital Memory
Electronic circuit that allows a TV to recall a stored still picture and display it simultaneously with one or more additional pictures. Also applicable to LaserDisc player feature.
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Digital Micromirror Device
See Digital Light Processor and DMD.
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Digital Recording
A system of recording in which sound information is converted into a series of pulses that are translated into a binary code intelligible to computer circuits and stored on magnetic tape or magnetic discs. Also called PCM (Pulse Code Modulation).
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Digital Signal
Digital signals have two levels: high/low or on/off. AKA: TTL.
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Digital Signal Processing
DSP. Manipulation of signals for equalization, compression/expansion and reverberation in the digital domain. Resulting sound may replicate the acoustics of a club, concert hall, stadium, etc.
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Digital Special Effects
Digital circuitry that lets the user store and then manipulate the video image to achieve certain special effects.
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Digital Theater Systems
See DTS.
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Digital TV Memory
This feature allows the user to recall a stored still picture and display it simultaneously with one or more additional pictures.
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Digital-To-Analog Converter
See DAC.
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Digitization
The transformation of an analog signal into digital information.
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Digitizers
Video digitizers utilize video cameras to take pictures of photographs of live and still action. The information is decoded into RGB (digital form) and stored in the frame buffer.
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DIN Connector
An acronym for Deutsche Industrie Norm - a round connector with notches, or keyed that can be in several sizes: 4-pins, 5-pins, 8-pins, etc. A convenient way of combining all the signal lines in one connector, 4-pin DIN connectors are often used for S-Video.
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Diode
A two-electrode semiconductor device.
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DIP Switches
Tiny switches that are used to change settings on printers, computers, interfaces, switchers, modems, etc. They are designed to fit in a DIP (Dual In-Line Package) space on a circuit board.
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Dipole
A loudspeaker design, adopted by Lucasfilm THX®, for use to reproduce the home theatre surround channels. Two identical but opposing drivers radiate equal but 180 degrees out of phase sound energy from front and back. As such the loudspeaker has "dead spots" or "nulls" at the sides. A diapole turned with the “null” to the listener works well for ambience material reflected off room walls but not as well for direct source material in a discrete 5.1-channel or matrix split surround enhanced system whereby side and back wall phantom imaging is desired.
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Direct Radiator
A loudspeaker where the sound projects directly from the front of the cabinet, as in the vast majority of loudspeakers used for stereo reproduction.
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Direct Sound
Sound waves arriving at the listening location directly from the source. Differing from reflected sound, which arrives at the listening location after bouncing off the surrounding surfaces.
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Direct View
A type of video display in which the light from the phosphors is viewed directly on the tube face rather than projected onto a screen.
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Directivity
The polar response of an energy receiver or radiator, such as a microphone or loudspeaker.
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Director's Cut
A director-approved special version of a film re-edited from its original theatrical presentation.
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Disk Drive
A storage unit, used by a computer, made up of disks with a magnetic coating.
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Dispersion
The polar or radiation response of a loudspeaker. Expressed in degrees or in terms of frequency response at various angles off the forward radiating axis relative to the on-axis response.
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Display
Any output device for presenting legible information. May be any of the following: CRT (cathode ray tube), LED (light emitting diode), LCD (liquid crystal display), or gas plasma.
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Display Adapter
DA. A circuit board added to a computer to drive a monitor or other display device.
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Display Device
A general term for a projector or monitor that converts electronic signals carrying picture information into something that is intelligible to us as humans. The first job of a display device is the accurate reproduction of the incoming signal. The screen part should maintain the standards of the signal and exhibit neutrality and uniformity.
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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. Properly called dissolve control or dissolve unit.
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Distortion
The production of harmonics which do not exist in the original waveform. The undesired deviation of a signal from its source. Inexact reproduction of an audio signal.
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Distribution Amplifier
DA. A device that allows connection of one input source to multiple output sources such as monitors or projectors.
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DLP
Digital Light Processing. See Digital Light Processor.
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DLT
Digital Linear Tape. See Digital Linear Tape.
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DMD
Digital Micromirror Device. In 1977, it was originally called "Deformable Mirror Device." Texas Instruments has developed DMD microchips used in DLP (Digital Light Processing(tm)) projector subsystems that hope to replace the 100-year old CRT technology. DMD chips use an array of mirrors and memory cells. A digital image is stored in the memory, and then projected when light is reflected onto the mirrors.
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DMM
Digital Multimeter.
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DOC
Declaration of Conformity. A document stating the European Union Directives, and Standards to which particular equipment complies.
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Dolby Stereo®
The term used to indicate a Dolby-format matrix "stereo surround" theatrical release soundtrack. See Dolby Noise Reduction. Dolby Stereo first appeared in wide release with “Star Wars” in 1977. The format, which would become the industry standard for years to come, was an encoding/decoding scheme in which four channels (front L/C/R and Surround) were encoded into stereo (left total/right total) tracks on film. These were then decoded during playback to recover the original channels.
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Dolby Surround®
The home surround sound matrix format derived from Dolby Stereo film sound. The encoding method is the same as that for Dolby Stereo. Dolby Surround is a matrix encoding method that combines four discrete channels (Left, Center, Right, and a limited bandwidth Surround channel) into two channels. These two channels can be summed together for mono playback, or played back as normal stereo. When the two channels are fed into the active Dolby ProLogic decoder, the matrix is unfolded back into four channels again. The limited bandwidth Surround channel is reporduced through the Left Surround and Right Surround loudspeakers (though deep bass below 50Hz is often reproduced in this channel). If the matrix is fed into a passive decoder (with no sterring logic), then only the stereo signal plus the surround channel is unfolded. Dolby Surround tracks can be carried on home video or broadcast, and the decoders use a simple method of subtracting the left and right signals to obtain the surround channel. Thus, the speaker configuration is left, right, and two surround speakers reproducing a mono signal.
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Dolby®
Various processes used in recording and playback developed by Dolby Laboratories, Inc. and named after Ray Dolby, the company's founder and President.
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Dolby® AC-3®
The low bit rate multichannel coding technology developed by Dolby Laboratories that is used on Dolby Digital film soundtrack prints and on Dolby Digital encoded DVDs and LaserDiscs. Six channels (five full bandwidth and a low frequency effects or LFE channel) are allocated a data rate of just 384 kilobits per second as compared to the standard two-channel digital audio rate of 1,411,000 kilobits per second (1.411 megabits per second) due to the fact that aggressive data reduction and compression techniques are employed. Dolby Digital's algorithm scheme is the multichannel audio standard for the FCC-approved HDTV broadcast standard. The film version has a data rate of 328 kilobits per second, while the DVD, LaserDisc, and high definition television (HDTV) application is 384 kilobits per second. Dolby Digital is a standard option on the DVD format with a data rate up to 448 kilobits per second. The alternative to Dolby Digital on DVD is PCM audio (MPEG audio is the standard in non-NTSC countries or PCM audio). Dolby Digital also can be found in use in some cable and satellite applications.
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Dolby® Digital
The official Dolby Laboratories name for AC-3® encoding (see Dolby® AC-3®). The digital format used in cinemas and in consumer delivery systems such as home theatre LaserDiscs and DVDs, and high definition television (HDTV). The format uses Dolby's low bit rate AC-3 data reduced compression technology to derive the required digital audio bit stream. Perceptual coding is use to reduce the bit rate normally of the linear PCM signal by a factor of 10 to 1. Data rates are 448 kilobits per second for music-only and increasingly feature theatrical film soundtracks (stereo or 5.1-channels), nominallly 384 kilobits per second for 5.1-channels, 192 kilobits per second for two-channel stereo and 64 kilobits per second for monaural. The theatrical on-film application of Dolby Digital uses a data rate of 332 kilobits per second. On LaserDisc the Dolby Digital bitstream replaces one of the analog tracks and requires an outboard RF demodulator.
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Dolby® Noise Reduction
Complementary (record-play) signal processing systems developed by Dolby Laboratories to reduce the noise inherent in recording media without affecting the sound being recorded. Dolby A-type noise reduction is the original professional Dolby system and is used on Dolby movie soundtracks as is Dolby SR noise reduction (both identified as Dolby Stereo), while Dolby B-type, C-type and S-type systems are for consumer formats such as the audio cassette.
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Dolby® ProLogic®
The more advanced form of Dolby Surround matrix decoding that not only recovers the monaural surround information from encoded program material, but also adds a center channel to keep dialogue and center effects firmly positioned at the center focal point. ProLogic provides better channel separation and gives more accurate sonic perspectives, and is nearly identical to Dolby Stereo film sound through the use of steering-logic.
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Dolby® SR (Spectral Recording(r))
The most powerful analog Dolby system. Used for the analog soundtracks on all Dolby Digital prints and on many analog-only releases as well. It not only provides greater noise reduction than the original Dolby A-type system, but also permits recording a wider frequency range with lower distortion. The SR system is also used to record original analog printmasters of motion picture soundtracks used to source Dolby Digital, DTS® Digital Sound, and SDDS® sub-masters to create theatrical release prints.
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Dolby® SR-D
The term the motion picture industry uses to identify 35mm theatrical release prints containing both an analog Dolby Stereo SR ("SR") and Dolby Digital ("D") optical soundtracks. The term is sometimes misused to identify just the Dolby Digital format or presentation.
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Doppler Effect
The shift in apparent frequency when the source or the observer is in motion.
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Dot Clock
Also referred to as pixel clock. The highest rate that a graphics device can produce.
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Dot Crawl
A line of continually moving dots along the vertical edges of sharp color transitions. A form of chroma interference or residual subcarrier along color transitions caused by interaction between chrominance (color) and luminance (brightness) portions of signal. Also called Hanging Dots.
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Dot Pitch
The vertical distance (measured in millimeters) between the centers of like-colored phosphors (for color monitors) which are adjacent to each other on the monitor screen. A smaller dot pitch allows for more potential dots to be displayed, thus achieving better resolution. See Shadow Mask.
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Double System
The playback of sound and picture using separate systems. For example, in a DTS Digital Sound presentation the projector produces the image while a separate CD-ROM transport module reads the sound data.
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Doubler
See Line Doubler.
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Downmix
To automatically exract a stereo or mono mix from an encoded surround mix.
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Driver
Any sound-producing device such as an individual loudspeaker.
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Dropout
A momentary partial or complete loss of picture and/or sound.
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Drywall
A dense architectural wall construction material applied to wood or metal studs.
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DSP
Digital Signal Processing. The handling and modification of signals in the digital domain. Many Dolby ProLogic receivers today perform the decoding with DSP to improve the accuracy and reliability of logic-steering and channel separation. DSP is also used widely in other applications. See Digital Signal Processing.
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DSS
Digital Satellite System. A subscription based satellite TV service received by an 18-inch dish antenna.
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DTS®
Abbreviation for Digital Theater Systems, the company who developed DTS Digital Sound and DTS Digital Surround.
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DTS® Digital Sound
A high bit rate digital 5.1 channel (or 7.1 channel 70mm) sound system using perceptual coding. The digital data is stored and read from CD-ROM media. The CD-ROM reader plays in sync with a timecode printed on the film between the analog soundtracks and the picture frame. Similar to Dolby(r) Digital and SDDS(r) using lossy compression for multiple channels to be accommodated on a single digital data stream but at significantly higher bit rates. The first film to feature DTS Digital Sound was Jurassic Park in 1993. DTS also is available for 70mm and large-format systems such as IMAX in a 7.1 channel sound system format, which adds two additional channels behind the screen.
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DTS® Digital Stereo
A matrix encoding system (4 channels into 2) developed by DTS that is compatible with Dolby Stereo and other systems capable of matrix decoding. The format uses a novel method of optical recording which allows for 2 dB of extra headroom over Dolby Stereo.
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DTS® Digital Surround
The high performance consumer version of the high bit rate digital 5.1 channel sound concept. The DTS data compression method takes six channels of audio (5.1-6.0) and folds them into a single digital bitstream. The rate of data transfer (1.44 megabits per second) is much higher than for Dolby Digital (384 kilobits per second), resulting from less aggressive data reduction and compression measures. The DTS compression ratio is about 3 to 1. DTS Digital Surround offers up to 24-bit resolution per channel. Compact Discs as well as LaserDisc titles are available in the format. On Compact Disc and LaserDisc the DTS bitstream replaces the linear PCM digital stereo audio tracks. DTS Digital Surround is written into the DVD Forum standards and DVDs encoded with DTS Digital Surround began release in late 1998. DTS Digital Surround is what’s known as a “lossy” compression scheme. See Lossy Compression.
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DTV
Digital TeleVision. This is the umbrella term used to describe the new digital television system adopted by the FCC in December 1996. See HDTV, SDTV, and Grand Alliance
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Dual Antenna Inputs
This means that that a TV set can accommodate two antenna sources, for example, master antenna and cable-box, or master antenna/cable-box and DSS Decoder/Receiver. By having dual inputs, it allows one to switch easily between antenna sources as opposed to using switching devices.
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Dubbing
The process of copying from a recording. In film sound production, it has two further meanings; to substitute one's voice for another, and to create the final soundtrack mix.
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Dubbing Theatre
A special theatre equipped for mixing film soundtracks. The sound systems in dubbing theatres where Dolby Stereo analog and Dolby Digital, DTS Digital Sound and SDDS soundtracks are mixed and in Dolby-, DTS- and SDDS-equipped cinemas are calibrated to the same standards. This is intended to make it possible for audiences to hear the sound the director heard-and intended-when the soundtrack was mixed.
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DV
Digital Video. DV has the advantage over standard analog video of maintaining clear, crisp video without degradation from generation to generation.
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DVD
Digital Versatile Disc or Digital Video Disc. An optical disc system the same size as a CD/CD-ROM, but capable of storing an entire movie and six channels of discrete multichannel audio. This new, similiar to CD, format with greatly increased storage capacity and advanced interactivity and user features comes in 4.7, 8.5, 9.4 and 18 gigabyte capacities. The format is specified into five specification “books.” There are DVD-ROM (1998), DVD-Video (1997), DVD-Audio (1999), DVD-R write-once (1999) and DVD-RAM erasable (1999) The technology uses MPEG-2 compression. Typical capacity for these discs is 4.5 gigabytes (as opposed to the CD standard of 640 megabytes), or about 133 minutes of digital video. Additional capacity is achieved with dual layer and two sides for a maximum capacity of 18 gigabytes. The format allows for in addition to about two hours of digital video (MPEG-2 encoded), several tracks of audio, including Dolby® Digital, other 5.1 channel formats such as DTS® Digital Surround, and several channels for dialogue in different languages, plus supplemental material. The resolution of DVD has a potential of 480 lines of horizontal luminance or black and white detail, a complement to the maximum capability of vertical resolution of the 525 line signal. A 525 line DVD disc may, in fact, have 480 lines of vertical resolution available at all times, with proper processing in a high-end system. There are two additional, separate color channels, each of about 240 lines of horizontal resolution, significantly higher color resolution than is available in the NTSC composite video system, whose numbers for color resolution range from a low of 40 to a high of about 100 lines. Film-rate material is stored on DVD as progressive-scan frames rather than two half pictures. The potential of the format includes an ability to store a higher, video refresh rate progressively scanned as well.
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Dynamic Focus
Dynamic Focus helps retain sharp edges at the corners of the screen on a direct view display device. In a projector, Dynamic Focus helps to keep the beam in focus over the majority of the contrast range. As the beam current goes up, the beam size also tries to increase. There is a limit to how much this can be controlled, but it tends to reduce the appearance of blooming in the picture. The addition to maintaining focus at any point in the beam position on the CRT is usually associated with Electro-Magnetic focus. See Electro-Magnetic Focus.
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Dynamic Headroom
The amount by which an amplifier can exceed its rated continuous power in short bursts, expressed in decibels (dB).
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Dynamic Range
All audio systems are limited by inherent noise at low levels and by overload distortion at high levels. The usable region between these two extremes is the dynamic range of the system. Otherwise defined as the range between the loudest and softest sounds a sound format or system can reproduce with noise or distortion. Expressed in dB.
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