Glossary A-D

Index | 0-9 | A-D | E-H | I-L | M-P | Q-T | U-Z



Abbreviation for Advanced Audio Coding. An audio codec used increasingly for downloaded music files, streaming-media, and satellite-radio applications.


Abbreviation for Analog Analog Digital. A designation that indicates the recorded material was first recorded with analog equipment, then remixed on analog equipment and finally placed onto a digital recording medium.


The original name used for Dolby Digital. The name was later changed to feature the Dolby name.

Acoustic Suspension Speaker

A sealed-box speaker that uses the air behind the woofer to control cone movement.


An audio component that takes line level audio inputs and increases the gain or level and outputs the signal to speakers. Amplifiers are used with other separate components or can be integrated together to make an Integrated Amplifier. Amplifiers are also available for other signals besides audio.


A signal in which any level is represented by a directly proportional voltage; not digital.

Angle Of View

The maximum scene angle that can be seen through a lens.


The lens opening that controls the amount of light reaching the pickup device (imager).


Undesirable elements or defects in a digital video picture.

Aspect Ratio

This refers to a ratio between the width and height of a display or image. Typical aspect ratios include 4:3 (also called 1.33:1), 16:9 (also called 1.78:1), 1.85:1 and 2.4:1—essentially, the shape of the screen or image. It is the ratio of the width to the height. The standard square television screen is 4:3 or 1.33:1, while widescreen TV is 16:9 or 1.78:1. Most modern films are released in 1.85:1 or 2.35:1 aspects, which mean that even on a widescreen TV, the image will result in black bars at the top and bottom of the screen.


Advanced Television Systems Committee, an international organization that develops digital television standards. Also see "over-the-air HD".

ATSC HD antenna

An antenna that receives over-the-air high-definition television signals.

ATSC HD tuner

A tuner (internal or external) that receives over-the-air high-definition television signals.


A decrease or loss in a signal. Reduction of signal magnitude (loss) normally measured in decibels.

Automatic Frequency Control (AFC)

An electronic circuit used whereby the frequency of an oscillator is automatically maintained within specified limits.

Automatic Gain Control (AGC)

An electronic circuit used by which the gain of a signal is automatically adjusted as a function of its input or other specified parameter.

Automatic Iris Lens

A lens in which the aperture automatically opens or closes to maintain proper light levels on the cameras pickup device.

A/V Receiver

Also called a Home Theater receiver, sometimes the term "integrated" is also used. Receivers take audio signals from components such as a CD player, tape deck and phonograph, amplify it and output it to the speakers. An A/V receiver is designed to also accept video inputs, such as from a DVD player, cable box and VCR, and output the signal to a television. In most cases, the video signal is not processed but simply passed through to the TV. A/V receivers, in most cases, also have Dolby and DTS decoders to play multi-channel audio, or the “surround-sound” commonly known by most people.

A/V Inputs

The connections on any component, such as a TV, receiver or VCR that enable connection to other output devices. The inputs often take the form of RCA jacks.

Audio outputs

An audio output is a connection (most often an RCA jack) on a device, such as a TV, that can be connected to a stereo or home theater system. A fixed output means the stereo is used to control the volume. A variable output means that the TV and the stereo can each control the volume.



This is a device used to match or transform an unbalanced coaxial cable to a balanced twisted pair

BBE Viva

An audio technology that creates realistic 3-D sound while preserving high-definition sound. Makes subtle sounds clearly audible.


A method of connecting an amplifier or receiver to a speaker in which separate wires are run between the amp and the woofer and the amp and the tweeter.

Blu-ray disc (BD)

A next-generation optical disc format developed specifically for recording and rewriting high-definition video, with enhanced storage capacity (25GB single-layer or 50GB double-layer). Thus named because it uses a blue-violet laser rather than the standard red laser used by CDs and DVDs. Jointly developed by the Blu-ray Disc Association and several consumer electronics and PC companies, including HP.

B.L.C. (Back Light Compensation)

A feature of modern CCD cameras which electronically compensates for high background lighting to give detail which would normally be silhouetted.

Back Focus

The mechanical aligning of the imaging device with the focal point of the lens. Most important on zoom lenses to ensure the image stays in focus throughout the zoom range.

Band Width

The frequency range of a signal. The span that the information-bearing signal occupies or requires or the difference between the lowest and highest frequency of a band.

Black Level

The level of the video signal that corresponds to the maximum limits of the black areas of the picture.


The halation and defocusing effect that occurs around the bright areas of the picture (highlight) whenever there is an increase in the brightness intensity.


Video connector, the most commonly used in CCTV.


Combining two channels of an amplifier to make one channel that's more powerful. One channel amplifies the positive portion of an audio signal and the other channel amplifies the negative portion, which are then combined at the output.


C Mount / CS Mount

The two industry standards for mounting a lens on a camera. The C-Mount lens has a 17.5mm flange back distance. The CS-Mount lens has a 12.5mm flange back distance.


A device built into new-generation televisions that allows digital cable reception without a set-top cable box.


A device that translates light into a video image and transmits that image to a monitor for viewing. It contains the image sensor and other electronic circuitry to create a video signal.

Cathode Ray Tube (CRT)

The picture tube in a video monitor that can reproduce the picture image seen by the camera.


Short for Cable Access Television. The method for distributing RF signals via coaxial cable rather than radiated through the air.


The common abbreviation for Closed Circuit Television. A private or closed television system.

Center Channel

The center speaker in a home theater setup. Ideally placed within one or two feet above or below the horizontal plane of the left and right speakers and above or below the display device, unless placed behind a perforated screen. Placement is important, as voices and many effects in a multichannel mix come from this speaker.

Chrominance (C)

The part of the video signal corresponding to the color information.

Coaxial Cable

A type of shielded cable capable of carrying a wide range of frequencies with very low signal loss.

Color difference signal

A video color signal created by subtracting luminance and/or color information
from one of the primary color signals (red, green or blue). In the Beta cam color difference format, for example, the luminance (Y) and color difference components (R–Y and B–Y) are derived as follows:

Y = 0.3 Red + 0.59 Green + 0.11 Blue
R–Y = 0.7 Red – 0.59 Green – 0.11 Blue
B–Y = 0.89 Blue – 0.59 Green – 0.3 Red

The G-V color difference signal is not created because it can be reconstructed from the other three signals. Other color difference conventions include SMPTE, EBU-N1 0 and MII. Color difference signals should not be referred to as component video signals. That term is reserved for the RGB color components. In informal usage, the term “component video” is often used to mean color difference signals.

Color temperature

Indicates the hue of the color. It is derived from photography where the spectrum of
colors is based upon a comparison of the hues produced when a black body (as in Physics) is heated
from red through yellow to blue, which is the hottest. Color temperature measurements are expressed in

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. "Y" for luminance, "Cr" or "Pb for Chroma and red, and "Cb" or "Pb" for Chroma and blue. Component signals offer the maximum luminance and chrominance bandwidth. YCbCr is not compatible with progressive scanning and therefore not used for HDTV. YPbPr is used for analog standard and HDTV television signals.

Composite Video

Composite Video is the standard type of analog video signal utilized by most CCTV video cameras. This signal is plug and play compatible with most consumer television and VCR equipment. However, this type of video should not be confused with digital "component" inputs which may ALSO found on newer televisions and other home video equipment. A composite video signal has the correct phase rate, luminance, and chrominance information to be compatible with a particular video format such as NTSC, PAL, EIA, CCIR, etc.


The range of light and dark values in a picture or the ratio between the maximum and the minimum brightness values.


Db (Decibel)

A measure of the power ratio of two signals. It is equal to ten times the logarithm of the ratio of the two the iris.

DC Type Lens

An auto-iris lens with internal circuit which receives voltage and a video signal from the camera to adjust signals.


A feature that improves picture quality, producing a film-like richness. Sixty frames per second are shown as opposed to the standard 30 frames per second. (Also called "line doubling.")

Depth Of Field

The area in focus in front of and behind the subject.


The use of the binary numbers, one and zero, to represent a video, audio or data signal. Unlike analog signals which can degrade or have interference, digital signals maintain the quality of the original signal. Digital signals stored on computers, DVDs, CD, DVD's or other devices are exact duplicates of the original signal. When a digital signal falls below minimum thresholds, the signal is loss.

Digital Light Processing - DLP

A Texas Instruments display technology that uses a Digital Micromirror Device (DMD) to create and project vibrant, high-definition images either via television or a projector.

Digital Recording

This is the latest form of recording and is relatively new to the CCTV industry as a result is not the most economical method however it does have several advantages over the VCR analogue tape recorders. First of all it enables quick access to the desired

Digital Video Recorder (DVR)

This device is capable of accepting one or more video (and sometimes audio) input signals for recording onto digital storage media. A DVR is basically a computer specifically designed to gather and compress video into a digital video format for storage on a hard disk drive or other form of digital media.


Abbreviation for Direct Drive Image Light Amplifier. This Hughes/JVC technology uses a reflective LCD to create an image. A light source is then reflected off the reflective LCD and is directed through a lens to a screen.


Speakers with drivers on opposite faces that are wired electrically out of phase, creating an area of cancellation to the sides. Recommended by THX for use as surround speakers, with null directed at the listener to create a more ambient and non-localizable effect.

Direct-View Television

Display whose image is created on the surface from which it is viewed.


Abbreviation for Digital Light Processing. A Texas Instruments process of projecting video images using a light source reflecting off of an array of tens of thousands of microscopic mirrors. Each mirror represents a pixel and reflects light toward the lens for white and away from it for black, modulating in between for various shades of gray. Three-chip versions use separate arrays for the red, green, and blue colors. Single-chip arrays use a color-filter wheel that alternates each filter color in front of the mirror array at appropriate intervals.

Dolby B

A noise-reduction system that increases the level of high frequencies during recording and decreases them during playback.

Dolby C

An improvement on Dolby B that provides about twice as much noise reduction.

Dolby Digital

An encoding system that digitally compresses up to 5.1 discrete channels of audio (left front, center, right front, left surround, right surround, and LFE) into a single bitstream, which can be recorded onto a DVD, HDTV broadcast, or other form of digital media. When RF-modulated, it was included on some laser discs, which requires an RF-demodulator before the signal can be decoded. Five channels are full-range; the .1 channel is a band-limited LFE track. A Dolby Digital processor (found in most new receivers, preamps, and some DVD players) can decode this signal back into the 5.1 separate channels. Most films since 1992's Batman Returns have been recorded in a 5.1 digital format, though a number of films before that had 6-channel analog tracks that have been remastered into 5.1.

Dolby EX

An enhancement to Dolby Digital that adds a surround back channel to 5.1 soundtracks. The sixth channel is matrixed from the left and right surround channels. Often referred to as 6.1. Sometimes referred to as 7.1 if the system uses two surround back speakers, even though both speakers reproduce the same signal. Software is backwards-compatible with 5.1 systems, but requires an EX or 6.1 processor to obtain additional benefit.

Dolby Pro Logic

An enhancement of the Dolby Surround decoding process. Pro Logic decoders derive left, center, right, and a mono surround channel from two-channel Dolby Surround–encoded material via matrix techniques.

Dolby Pro Logic II

An enhanced version of Pro Logic. Adds improved decoding for two-channel, non-encoded soundtracks and music.

Dolby TrueHD

Dolby TrueHD is a high definition digital-based surround sound format that supports up to 8-channels of surround decoding and is bit-for-bit identical to a studio master recording. Dolby TrueHD is one of the several audio formats designed and employed by Blu-ray Disc and HD-DVD technologies. Dolby TrueHD is compatible with the audio portion of the HDMI interface. For more technical details, go to the official Dolby TrueHD page.


Officially known as the Digital Video Disc, though marketers unofficially refer to it as the Digital Versatile Disc. DVD uses a 5-inch disc with anywhere from 4.5 Gb (single layer, single-sided) to 17 Gb storage capacity (double-layer, double sided). It uses MPEG2 compression to encode 720:480p resolution, full-motion video and Dolby Digital to encode 5.1 channels of discrete audio. The disc can also contain PCM, DTS, and MPEG audio soundtracks and numerous other features. An audio-only version, DVD-A uses MLP to encode six channels of 24-bit/96-kHz audio.


A recordable DVD format that it is a write-once medium. Backed by Pioneer, Panasonic, Toshiba, and others.


DVD-R DL is a record-once format that is identical to DVD-R, except that it has two layers on the same side of the DVD. This allows twice the recording time capacity on a single side. This format is being incorporated slowly on some newer DVD Recorders.


A recordable DVD format that it is re-recordable medium. Backed by Pioneer, Panasonic, Toshiba, and others.


A recordable DVD format that it is a write-once medium. Backed by Sony, Philips, Yamaha, HP, and others.


A recordable DVD format that it is re-recordable medium. Backed by Sony, Philips, Yamaha, HP, and others.


A recordable DVD format similar to DVD-RW in that it is a re-writeable format. Unlike DVD-RW it is capable of being written to and erased over 100,000 times. Backed by Hitachi, Panasonic, Toshiba, and others.

DVI (Digital Video Interface)

A video standard which provides a digital video signal which maximizes the video quality of modern digital monitors such as LCD and Plasma flat panel displays. Unlike conventional analog monitors, each pixel (dot) comprising the display is addressed separately, which results in the maximum possible clarity and color accuracy.


Abbreviation for Digital Video Recorder. A DVR is a video recording device that records on a hard disk drive, rather than on video tape or disc. DVRs can be incorporated into cable and satellite boxes, as well as an addition to a standalone DVD recorder. DVR use may, or may not, be paired with a paid subscription requirement. A DVR is also sometimes referred to as a PVR (Personal Video Recorder).

Dynamic IP Address

A Dynamic IP address is a type of account from an ISP (internet service provider) where your computer or network is assigned an IP address that constantly changing and never remains the same. Also see IP Address and Static IP.

Dynamic Compression

Dynamic Compression is a term applied to a feature on many Home Theater Receivers, DVD players, and some televisions that enables the consumer to change the relationship between the loudest parts of the soundtrack and the quieter parts of the soundtrack when you are playing a DVD or TV program. In other words, if you find that the explosions or other loud parts are too loud and things such as dialog is too soft, by changing the dynamic compression setting, you can make it so the sounds of the explosions are not quite as loud and the dialog will sound louder. This makes the overall sound more even. This is especially useful when playing a DVD at low volume.

Dynamic Range

The difference between the lowest and the highest levels; in audio, it's often expressed in decibels. In video, it's listed as the contrast ratio.

Index | 0-9 | A-D | E-H | I-L | M-P | Q-T | U-Z