C
In S-Video, "C" is an abbreviation for chrominance, or the color information. ("Y" is for luminance, or the brightness.)
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C And C++
Computer programming languages. In video, "C" is an abbreviation for chrominance.
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Cable Equalization
The method of altering the frequency response of a video amplifier to compensate for high frequency losses in cables that it feeds. See Peaking.
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Cable Labs
Cable Television Laboratories. A research and development center funded by cable companies, active in ATV and other areas.
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Cable-Compatible
See Cable-Ready.
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Cable-Ready
A term used for a TV or VCR that can receive all cable channels-including midband and superband channels-without a cable converter box. But because such equipment cannot receive channels that are scrambled for security purposes, situations may require the cable company's descrambler/converter box.
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Cache
A small amount of relatively high-speed storage which is used as an intermediary between the data user and a larger, slower storage device (the backing store).
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CAD
Computer Aided Design. The use of the computer system for designing.
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Calibration
1) In video, the process of using test instruments and test signals to correctly adjust a video display device to NTSC and SMPTE specifications. 2) In audio, the process of adjusting the level of each channel in a surround sound system to a uniform level (typically 75 to 85 dB SPL).
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Cancellation
The destructive interference of two or more sound waves. Waves of similar frequencies and amplitude, but of opposite phase can produce mutual cancellation effects.
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Capacitance
The storing of an electrical charge. Capacitance is a condition that exists between conductors in a cable. At high frequencies this represents an impedance called capacitive reactance (Xc) which can cause signal loss or distortion.
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Capacitor
A device made of one or more pairs of conductors, separated by insulators, capable of storing an electrical charge. When there is a difference of potential between the conductors, and current cannot flow through the insulator, the potential is "stored" as an electrical charge. Cables are also conductors separated by insulators, therefore cables sometimes act as capacitors. A capacitor can store energy, block direct current and yet pass alternating current. For example, a capacitor used in a DC power supply, as a filter, stores energy as the voltage first rises. As the voltage either decreases in the source, or increases in the load, the capacitor discharges the stored energy back into the power line, smoothing out the changes. Another example would be in a multistage amplifier where a capacitor is used to couple the AC signal from one stage to the next, while leaving the DC voltage, that is required to power each stage, behind. It, essentially, blocks the direct current that amplifies the signal, while allowing the alternating current, the music, to pass. See Capacitance.
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Cathode Ray Tube
CRT. The video display tube used in monitors and receivers, radar displays and video computer displays. The CRT is a vacuum tube containing an electron gun. The gun directs a rapid succession of electron beams onto a phosphor-coated screen to produce the images seen on the external screen. See CRT Electron Gun.
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CATV
Community Antenna Television or Cable Television.
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CAV
1) Component Analog Video. Component video signals in which an analog voltage or current (rather than a set of numbers) represents the value of the pixel, the same as "analog components." Encoded video signals which can provide greater color resolution than composite video. An NTSC encoder must be used to convert the signals for a standard NTSC receiver. 2) Constant Angular Velocity (constant RPM or revolutions per minute). A LaserDisc format which is also known as Standard Play. A mode of playback in LaserDisc players in which the disc spins at a constant 1800 rpm. Each revolution traversed by the laser constitutes a single video frame, and there are 54,000 such frames per disc side resulting in 30 minutes of play. CAV LaserDiscs allow for video effects such as freeze-frame and multiple speed play. During playback the number of frames elapsed is shown.
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CCD
Computer Controlled Device.
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CCD Camera
Charge-Coupled Device Camera. A video camera which uses solid-state pickup devices rather than tubes. Sometimes called a chip camera.
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CCIR
International Radio Consultative Committee. A global organization responsible for establishing television standards.
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CCTV
Closed Circuit Television. A distribution system which limits reception of an image to those receivers which are directly connected to the origination point by coaxial cable or microwave link.
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CD
Compact Disc. A disc on which information or sound is recorded digitally and reproduced by digital reading.
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CD Player
A component designed to play compact disc (CD) recordings using a laser optical pickup.
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CD-G
Music CD plus graphics. In addition to digital audio, the disc has subcodes that carry text (such as liner notes, lyrics) and pixilated, computer-like graphics. A CD player with the proper adaptor is needed to access the subcode information.
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CD-I
Compact Disc-Interactive. A format that provides audio, digital data, still graphics and limited motion video.
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CD-R
Compact Disc Recordable. A compact disc format that permits data to be written onto a blank CD but not erased from it.
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CD-ROM
Compact Disc-Read Only Memory. A 4.75-inch laser-encoded optical memory storage medium with the same co
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CD-ROM XA
Compact Disc-Read Only Memory Extended Architecture. An extension of the CD-ROM standard billed as a hybrid of CD-ROM and CD-I, and promoted by Sony and Microsoft. The extension adds ADPCM audio to permit the interleaving of soun
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CD-V
The V stands for video. In the 5-inch format, typically used for music video and music, the gold-colored CD-V contains up to five minutes of LaserDisc-quality analog video with a 16-bit linear PCM digital soundtrack. The disc also many contain up to 20 minutes of digital audio. A conventional CD player can read the audio but a "combi" LaserDisc player is needed to reproduce audio and video. Five-inch CD-Vs are comparatively rare but CD-V nomenclature has been extended to 8- and 12-inch laser video discs.
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CDS
Cinema Digital Sound. The predecessor to today's digital sound formats. Developed by Kodak and Optical Radiation Corporation, it utilized six discrete digital channels but replaced the analog optical soundtracks on the film. The first film presented in CDS was Dick Tracy in 1990, but the format ceased to exist after only eight features. Playback reliability was a well-known problem.
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CE
Conformité Européenne. A label or mark on a product signifying ESD, EMI and safety compliance with all European Union (EU) Directives applicable to that product. Some interpret it to mean European Community or Compliance for Europe.
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CEBus(R)
Consumer Electronics Bus. The home automation standard developed by the Electronic Industries Association and allied associations representing the appliance, heating/ventilating/air conditioning, security, telecommunications, utilities and cable industries. See Home Automation.
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CEDIA
Custom Electronic Design And Installation Association.
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CEMA
Consumer Electronics Manufacturers Association. A division of the Electronics Industries Association (EIA), a national trade association.
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CENELEC
European Committee for Electrotechnical Standardization.
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Center Channel
In a cinema, the audio signal path directed to the center of the front three (or five) speakers behind the screen, or the speaker nearest the video monitor in a home theatre setup. The center channel is responsible for conveying the dialogue, as well as a substantial portion of the music and sound effects. In the home theatre it serves to maintain front channel imaging for off-center listeners.
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Center Channel Loudspeaker
A loudspeaker tonally matched to and positioned midway between the left and right stereo speakers to keep mid-front sounds (dialogue especially) centered on screen for off-center listeners. Placed above or below display device or behind perforated projection screen-"sound screen."
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Channel
A designated audio signal path, generally terminating at the loudspeaker.
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Channel Balance
The relative levels of the different channels in a home theatre system.
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Channel Separation
A measure (in dB) describing the ability of channels to be distinct from each other. For example, Dolby Surround, with only 3 dB separation exhibits noticeable crosstalk between channels. On the other hand, Dolby Digital or DTS Digital Surround, at >90 dB separation, is nearly perfect with resolving distinct channels.
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Channel-Block
A feature found on some TVs that allows users to affix security codes to certain channels. Typically used by parents to prevent children from viewing "adult" channels. Channels are blocked and unblocked using the TV set's wireless remote control. See Parental Lockout.
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Chapter
A subdivision of the data on a LaserDisc or DVD, similar to a track on a CD. Chapters on LaserDisc are given in numbers and can be accessed directly, randomly, or programmed. DVDs are often subdivided into scenes which can be accessed directly.
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Check Sum
A summation of digits, or bits, computed for the purpose of verifying the integrity of a block of data. For example, a check sum is computed on a block of data and sent with the data. At its destination, a new Check Sum is computed (using the same formula) and compared against the original Check Sum. If they don't agree, there is a data error.
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Chroma
The characteristics of color information, independent of luminance intensity. Hue and saturation are qualities of chroma. Black, gray, and white objects do not have chroma characteristics. The purity or intensity of color. Sometimes called "hue."
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Chroma Interference
Spurious rainbow patterns and color transition dots caused by interactions between the chrominance and luminance components of a composite video signal.
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Chroma Key
(1) An electronic matte where one image is matted on top of another without bleed-through. (2) A film and video process in which the subject is filmed in front of a blue or green screen. The colored screen is later replaced with another background, provided on film, tape or computer graphics. (Example: local TV weather report).
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Chroma Resolution
The amount of color detail available in a video system, separate from any brightness detail.
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Chromaticity
1) The hue of a color, as defined by the three coordinates on a CIE chromaticity diagram. 2) The information shown as a chromaticity diagram. 3) Color accuracy.
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Chrominance
Chroma. The signal (added to the luminance signal) that carries the color information needed to produce a color picture. The quality of a color without regard to brightness. Without the chrominance signal, the video picture would be in black and white.
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Chrominance Signal
Part of the 3.58 MHz color television signal containing the color amount or saturation information. Also called "chroma." Abbreviated by "C".
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CIE
Commission Internationale de l'Eclairage. ( The International Commission on Illumination) The organization responsible for the chroma diagram of 1939. A three dimensional diagram that defines light and color. Other systems have been developed by CIE more recently.
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CIE Chromaticity Diagram
A color chart defining the spectral limits of an additive color display and the quantities of red, green, and blue that must be mixed to produce any hue. The 1931 CIE diagram quantifies light, providing a means for defining it in mathematical terms, related to the way we see it. It's a graph of the human factors of vision.
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CinemaScope®
Developed by Twentieth-Century Fox to compete with Cinerama. Four magnetic audio tracks (allocated to the front L/C/R and surround) were printed on both sides of the sprocket holes on 35 mm film along with the anamorphic image. CinemaScope made its debut in 1953 with “The Robe.” Today's CinemaScope process is duplicated by Panavision and credited as "Filmed In Panavision."
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Cinerama®
One of the first film formats to feature multichannel surround sound in a seven-channel discrete format (far left 1, left 2, center 3, right 4, far right 5, left surround 6 and right surround 7) recorded on 35mm magnetic film. Premiering in 1952, it featured five speakers behind a large curved screen, plus discrete surrounds around the audience. Although an initial success, Cinerama suffered from technical problems and ultimately faded in the 1960's after CinemaScope®, Todd-AO® 70mm and other 70mm Panavision® formats achieved market success. Cinerama lives through the Cinerama Preservation Society with The New Neon Movies serving as its United States exhibition theatre located in Dayton, Ohio.
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Class A Amplifier
A design in which the output devices of the amplifier conduct current all of the time. Such amplifiers have very low distortion but consume more electricity and run hot.
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Class AB Amplifier
A design in which the output devices are set to conduct current only part of the time. Class AB amplifiers run cooler, produce more power and cost less than comparable Class A amplifiers
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Clipping
If a signal passing through an amplifier or other electronic circuit exceeds that circuits' voltage or current limits it will appear on an oscilloscope as if the tops of waveforms had been clipped off by a pair of scissors, hence the term. Clipped signals are generally distorted in a number of ways both audible and measurable.
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Clipping Circuit
A circuit that restricts the amplitude of the signal.
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Closed Captioning
Dialogue or other text appearing on a TV screen. This feature for the hearing-impaired is legally mandated on all TV sets 13 inches or larger. Programs and software that provide for this feature are indicated with a registered trademark logo.
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Closed Loop
A continuous loop of film or tape for repetitive playing, often enclosed in a cartridge.
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CLV
Constant Linear Velocity. Also known as extended-play. A mode of playback in LaserDisc players in which the disc rotates such that its linear velocity at the laser pickup is always constant. This means that at the start of playing the disc rotates quickest (1800 rpm, when the laser begins from the center) but then gradually slows as the laser approaches the edge (600 rpm). This allows for 60 minutes of playing time per side compared to 30 minutes for CAV standard play. See CAV. During operation the player shows the time elapsed. Effects such as freeze-frame and frame-by-frame are not possible though, so many units feature digital field storage for the CLV mode to enable such features.
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Coaxial
Refers to a type of digital audio connection for consumer audio components using an RCA type jack.
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Coaxial Cable
A standard round two-conductor wire in which one conductor completely wraps the other with the two separated by insulation. The inner conductor is surrounded by a braided conductor that acts as a shield. Constant impedance transmission cable. Example: 75 ohm, type RG-59 cable used for video signals. Abbreviated "coax."
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Collimation
The process by which divergent light rays from the projector are bent so that they are all parallel.
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Color
An adjustment that is used to control color intensit
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Color Analyzer
A sophisticated instrument which can precisely measure the color of light in terms of temperature (K or Kelvin). In video it is used to calibrate the color output of display devices. A Color Analyzer is necessary to set up the gray scale of a TV se
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Color Bars
SMPTE standard test bars used to match playback with original recording levels as a reference for color intensity, brightness, contrast and balance. Generated electronically, often accompanied by a 1000 Hz audio tone. A test pattern containing six basic colors: yellow, cyan, green, magenta, red, and blue used to check the chrominance functions of color TV systems.
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Color Burst
In color systems, a burst of sub-carrier frequency located on the back porch of the composite video signal. This serves as a color synchronizing signal to establish a frequency and phase reference for the chrominance signal. High frequency (3.5 MHz) pulses that determine the phase of a color signal.
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Color Control
This control sets the level of color saturation in the picture. A low setting should remove color from the picture and a high setting should produce lots of color.
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Color Decoding Matrix
The color decoding matrix is where the real work of decoding color occurs in the picture tube to provide the final solution for R, G, and B values. It's a manual device, meaning there is nothing in the NTSC signal that tells it how to calibrate itself. The color control calibrates how amplitude differences are decoded and the tint control calibrates how phase differences are decoded. Relating these adjustments to what is displayed on the screen, the color control adjusts the interpretation of the amount of color to be displayed while the tint or hue control sets the type of color to be displayed. The SMPTE Color Bars pattern allows for this manual adjustment of color and tint relative to the source signal output. Decoder calibration is accomplished by setting the amplitude of all of the blue bars to be equal using both color and tint controls and blue, red and green filters. Once this has been accomplished, all of the red bars will be equal in amplitude and all of the green bars will be equal in amplitude if the matrix is functioning properly. The adjustment of color and tint should be done while observing the blue only channel of the display device.
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Color Difference Signals
Two signals derived from the NTSC to RGB decoding equation, starting with Y = 0.3R + 0.59G + 0.11B, expression for the derived black and white signal. To solve for three unknowns, red, green, and blue, two more equations are required that contain information about R, G, and B. In video they are called the color difference signals. In math, they would be stated as A = R - Y and C = B - Y, where A and C are voltage values at any given instant in time, just as Y is a voltage value at any give instant in time. By adding A to Y, R is defined. By adding C to Y, B is defined. Now that the values of R and B are known, and the instantaneous value of Y is always known, real numbers for R and B can be plugged back into the Y equation to calculate the value of G. The NTSC to RGB decoder solves three equations for three unknowns every instant one is watching television.
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Color Encoder
A device which combines the separate red, green and blue signals into one composite video signal. Also called "colorplexer."
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Color Fringing
False colored outlines at the edges of a colored area that should be uniform in hue.
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Color Of Gray
In the video signal world, gray is defined as equal amounts of red, green, and blue. Gray exists from just above black all the way to white. Gray doesn't exist at black because black in a visual display is defined as an absence of light. There can't be color until there is light. At the other end of the gray scale, white is the 100 percent point of gray, the highest level of gray. The terms "color of gray" and "color of white" are used interchangeably as white is just the peak level of gray. The production standard for the color of gray is 6500° Kelvin in the majority of the world's TV systems. It is the proposed color of gray for most of the competing HDTV systems. A lower color temperature of 5500 Kelvin has been suggested in some circles for HDTV to make it compatible with the film and print industry. See Colors Of White
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Color Of Light
Color of light is defined in terms of x and y values on the 1931 CIE diagram used for the NTSC color system. Using this system, there are many specific colors of light within a general area of that color. The specific colors are defined by x and y values. The color red, as an example covers a rather large area of the diagram. Specific colors of red would have their own x and y values. The bell shape of the curve in the x, y plot represents an approximation of the human sensitivity to colors of light as it was known in 1931. See CIE Diagram.
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Color Phase
The timing relationship of the color video signal. The correct color phase will produce the correct color hues.
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Color Primary
See Additive Primary and Subtractive Primary.
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Color Purity
Quality of video's three primary colors-red, green, and blue-either separately or when mixed to produce other colors.
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Color Red, Green, Blue & Composite Sync Outputs
Provides analog red, green, blue level .7 Volt p-p video output signals and negative-going 4 volts p-p, non-terminated and 2.3 volts p-p terminated TTL level composite sync output, matching the input standards of most data monitors and projectors. On certain RGB interfaces, sync is automatically stripped from any input computer signal that has sync included on the green channel. With sync on the green channel, some large screen data monitors and projectors may display a greenish tint, as well as a pulling to the right at the top or bottom. Stripping sync from the green video and using the separate sync output on those interfaces solves these problems. Sync can be added to the green channel by setting the "sync on green" switch.
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Color Resolution
The number of colors available at once in an image, measured in terms of bits per pixel.
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Color Subcarrier
A 3.58 MHz signal interwoven with a standard NTSC monochrome signal that contains color information. The carrier frequency that contains the color signal information.
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Color Temperature
The color quality, expressed in degrees Kelvin (K), of a light source. The higher the color temperature, the bluer the light. The lower the temperature, the redder the light. On a correctly calibrated video monitor the color white will measure 6500°K.
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Color Triad
A single group of red, blue, and green phosphor dots
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Coloration
Audible deviation in the balance of sounds caused by the reproduction system. A response anomaly that alters the perceived sound.
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Coloration
A term used to indicate audible alterations to the sound arising from the response pattern of a microphone or loudspeaker. It is often used to describe the audible "signature" an audio system impresses on all signals passing through it. It can also describe sound alterations due to the environment. Coloration can be a result of standing waves or room resonances
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Colorplexer
Also called the multiplexer. Combines C signal and Y luminance signal to create a total colorplexed composite video signal which is transmitted to receiver as amplitude modulation of picture carrier.
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Colorplexer
See Color Encoder.
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Colors Of White
There is a line, and area around that line, inside the 1931 CIE diagram that defines the many colors we humans identify as white. They are identified in terms of color temperature. Traditional stage lighting, as an example, is somewhere between 2800° and 3200° Kelvin. Sunlight is in the area of 5400°K and overcast daylight is in the order of 6500°K. These are all different colors of white. If one were to look at a piece of white paper in any of these colors of light, it would be recognized as white, even though its color has changed a great deal. We, as human beings, are adaptable in our perception of color If an ideal object is heated to a particular temperature, indicated in degrees Kelvin, it will emit a particular "color" of white light. The complete range of colors of white forms the Black Body Curve on the CIE diagram. See CIE Diagram.
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Comb Filter
A filter, found in televisions, monitors and some LaserDisc players in which the luminance and chrominance signals are isolated from the composite video signal. So called because of the shape of its frequency response, the comb filter is an improvement over the "notch filter" and provides a better method of separating black and white "Y" from color "C." It preserves more detail in the black-and-white, resulting in a better quality picture with less chroma crawling or "zipper" artifacts. The comb filter will remove only the sidebands of the color information leaving the remaining luminance information to be properly reproduced as picture detail. The purpose of the comb filter is to improve resolution, picture quality, and reduce objectionable color patterns by more precisely separating color information from black and white information. Low (lumina)-to-mid (chroma)-line sets utilize a glass comb filter. High-end sets utilize a CCD or digital comb filter, which greatly enhances resolution. Top-of-the-line sets feature 3D Y/C Comb Filters for the best possible resolution.
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Combi Player
LaserDisc player that plays both video discs (12-, 8-, and 5-inch) and 5- and 3-inch audio-only compact discs. Latest generation LaserDisc Combi Players also play DVDs
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Complementary Color
Opposite hue and phase angle from its primary color. Cyan, magenta, and yellow are complements of red, green, and blue, respectively
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Component (Inputs/Outputs)
Component video is a three wire system. There are three channels of video information making up the picture. They could be red, green, and blue signals (RGB) or the intermediate stage of Y (black and white) plus the two channels of color difference signals (R-Y and B-Y). Delivery systems such as DSS and DVD are formatted in this latter system. It is also used in the professional video production world. Analog component video connections require three 75 ohm coax cables, which carry the Y, R-Y, and B-Y signals separately. Each of the three coax cables is terminated at both ends with RCA connectors. They may be color coded and bundled together in a single sheath, or three equal length composite cables may be used. In professional and industrial video equipment all of these signal formats are usually carried by coax cables that are terminated with the more rugged, impedance matched 75 ohm BNC connectors. Either component system has the potential to deliver a much sharper picture than the composite video system, or the S-Video system. It also has the advantage of not having to deal with the color carrier frequency, because it doesn't enter the picture.
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Component System
A stereo or home theatre system composed of separate elements, each with its own power supply. Usually selected individually by the purchaser.
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Component Video
The NTSC color television system starts with three channels of information; red, green, and blue (RGB). In the process of translating these channels to a single composite video signal they are often first converted to Y, R-Y, and B-Y. Both 3-channel systems, RGB and Y, R-Y, B-Y are component video signals. They are the components that eventually make up the composite video signal. Higher quality program production is possible if the elements are assembled in the component domain. Display devices such as televisions, monitors and projectors which receive component video bypass the necessary decoding steps for composite video and thus offer purer, higher quality performance.
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Composite NTSC
To encode start out with R, G, and B. Derive Y, the black and white signal. Generate two more signals, R-Y and B-Y, so that color can be obtained. Amplitude and band limit those signals to a point that they have to be renamed I and Q. Modulate the I and Q signals on two phase shifted 3.58 MHz subcarriers and add them both back into the Y signal. That's composite NTSC.
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Composite Sync
A signal combining horizontal and vertical sync pulses, and equalizing pulses, with no picture information and no signal reference level. Sometimes called "C", "S" (as in RGBS) or "HV."
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Composite Video
An all-in-one video signal comprised of the luminance (black and white), chrominance (color), blanking pulses, sync pulses (horizontal and vertical) and color burst. This is standard for broadcast NTSC TV and VHS and LaserDisc consumer video components. SVHS is a S-Video format with a separate luminance signal and the two color difference signal combined into one. DVD and DSS are component video formats. See Component Video and S-Video.
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Computer-Video Interface
A device which converts the "nonstandard" video output of computer systems to a "standard" RGB analog signal that can then be connected to a compatible data monitor or projector
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Connector
An electric or mechanical device consisting of a mating plug and receptacle. See Adapter.
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Constant Directivity
A loudspeaker device in which the produced sound does not become more directional as the frequency rise
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Constructive Interference
The addition of two waveforms of similar phase. Constructive interference is responsible for the production of standing waves in which a signal and its successive reflections are continually added to one another.
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Contact Closure
Bringing together two conductors so that an electrical current may flow through them.
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Contrast
The range of light and dark values in a picture, or the ratio between the maximum and the minimum brightness values. Also called Image Contrast. The differentiation between light and dark is the essence of contrast. The contrast of a picture is determined by the ratio of adjacent light and dark areas of the picture. It can be a more important parameter than actual light output when looking at absolute picture quality. It is calculated by dividing the amount of light in a bright area of the picture by the amount of light in the dark part of the picture. Contrast ratio = high light/low light. Low contrast is shown mainly as shades of gray, while high contrast is shown as blacks and whites with very little gray. When a value is put to what you will see, this type of contrast is Perceived Contrast. Another type is what is measured directly on the surface of the projection screen and is called Screen Contrast. Then there is yet another contrast value that is called Projector Contrast. The term also refers to a TV monitor adjustment which increases or decreases the level of contrast of a displayed picture. Also called "white level."
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Contrast Control
The Contrast control sets the level at which picture peak white is displayed. Also called the Picture Control. Where a Picture control substitutes for the Contrast control, color level may also be changed with the Picture adjustment.
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Contrast Range
The range of grays in a video image.
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Contrast Ratio
This is the ratio of the high light output level divided by the low light output level. In theory, the contrast ratio of the television system should be at least 100:1, if not 300:1. In reality there are several limitations. In the CRT, light from adjacent elements contaminate the area of each element. Room ambient light will contaminate the light emitted from the CRT. Well controlled viewing conditions should yield a practical contrast ratio of 30:1 to 50:1.
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Controller
Another term for an A/V preamplifier or processor.
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Convergence
The alignment of the red, green and blue scanning electron beams on a projected display; when the lines produced by the three color guns appear to form one clearly focused white line. The point at which the perimeters of multiple lenses align so that the perceived single image is clearly focused. Misaligned beams degrade the quality of the picture.
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Converter/Descrambler
In cable TV, a combination converter/descrambler box that selects a channel from the incoming cable feed, decodes it (if it is scrambled), and converts it to a prescribed channel (usually channel 3 or 4) on a TV set's channel selector.
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Copyguard
Several processes used to prevent illegal duplication of videocassettes and DVDs. Form most popular is Macrovision.
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Coverage Angle
The included angle between the points on either side of a loudspeaker axis at which the response is attenuated by 6 dB with respect to the on-axis level.
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CPS
1)- Characters per second. Used as a measurement of computer output. 2) In audio, cycles per second.
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CPU
Central processing unit. A computer's "brain"; the portion which reads and executes commands.
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Critical Band
In human hearing, only those frequency components within a narrow band, called the critic.
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Critical Distance
The distance from a sound source at which the direct energy (energy radiated directly from the source) is equal to the reverberant energy (radiated from walls, floor and ceiling).
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Cross-Color
A color interference problem descriptively termed "interleaved-color." A color (C) signal is separated from the composite video by using a bandpass filter centered at 3.58 MHz to obtain only the frequencies between about 3.0 MHz and 4.2 MHz. Unfortunately, this doesn't remove the luminance (Y) signal that overlaps the C signal in this same frequency range. The high frequency luminance signals contaminate the C signal and generate unwanted color patterns, or rainbows, in picture areas with fine details. They are particularly troublesome in images containing closely spaced lines. The technical term for this unwanted color interference is cross-color or cross-luminance. If the lower frequencies are not filtered out, then cross-color effects would occur everywhere in the picture, not just in areas where fine detail is present.
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Cross-Luminance
See Cross-Color.
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Crosshatch
A test pattern consisting of vertical and horizontal lines used for converging a color display device.
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Crossover
An electronic circuit device, used most commonly in loudspeaker systems, that divides an input sound spectrum into higher and lower bands about a specified frequency. Crossovers can either be passive or active. They are also found in many home theatre and cinema sound processors and are used to direct low frequency sounds to the subwoofer.
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Crossover Frequency
1) In a loudspeaker with multiple drivers, the crossover frequency is the -3dB point of the network dividing the signal energy between various transducers. 2) The frequency at which a crossover network divides the audible spectrum and sends it to a loudspeaker drive unit.
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Crossover Network
A component that separates the frequency band and routes each frequency range to the correct driver or amplifier.
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Crossover Slope
The steepness of a crossover filter expressed as xdB/octave. A subwoofer with a crossover frequency of 80Hz and a slope of 6dB/octave would allow audio frequencies at 160 Hz (an octave above 80 Hz) into the subwoofer, but signals at 160 Hz would be reduced in amplitude by 6dB. A slope of 12dB/octave would also allow 160 Hz into the subwoofer, but the amplitude would be reduced by 12dB. The most common crossover slopes are 12dB, 18dB and 24dB per octave. Crossover slopes are also referred to as "first order" (6dB/octave), "second order" (12dB/octave), "third order" (18dB/octave) and "fourth order" (24dB/octave). The steeper the slope the more the frequency spectrum is split more sharply, producing less overlap between the two frequency bands.
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Crosstalk
Interference, usually from an adjacent channel, which adds an undesirable signal to the desired signal.
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Crosstalk Isolation
Attenuation of an undesired signal introduced by crosstalk.
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CRT
Cathode Ray Tube. A vacuum tube that produces light when energized by the electron beam generated inside the tube. A CRT has a heater element, cathode, and grids in the neck of the tube, making up the "gun." An electron beam is produced by the gun and is accelerated toward the front display, or screen surface of the tube. The display surface contains phosphors that light up when hit by the electron beam. The CRT is commonly known as the picture tube and used in televisions and monitors. Some color CRTs have three guns for red, green and blue colors.
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CRT Electron Gun
The electron gun is the structure that produces three electron beams that strike the red, green, and blue screen phosphors. The phosphors emit light proportional to the electron beam current to create the displayed image. See Cathrode Ray Tube and CRT.
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CTS
Communications Technology Specialist. An A/V and video professional who, through practical experience and extensive industry training programs offered by the ICIA, has developed a high level of expertise. The CTS will use this expertise to help the end user select the A/V communications method that will best carry his message. Ongoing professional development assures that the CTS is prepared to analyze available options and decide how communications needs are best met.
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Cumulative Spectral Decay
The relationship between frequency and amplitude as a function of signal decay. See Waterfall Curve
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Current
The flow of electricity, and the rate at which it flows.
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Cursor
An indicator on a display that marks the currently active position.
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Cut-Off
The frequency at which a given effect ceases to operate. For example, a high-pass filter might have a low end cut-off frequency of 1000 Hz, so that all signals below 1000 Hz would be attenuated. Cut-offs are usually graduated or "rolled-off" in steps of several dB per octave (3, 6 or 12 for example) beginning at the cut-off frequency.
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CX Noise Reduction
A noise reduction system from CBS for the analog FM audio tracks on LaserDisc. It reduces the audible interference of the video carrier on the audio portion of the LaserDisc video signal.
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CYMK
Cyan, Yellow, Magenta and Black. See Subtractive Color.
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then "Add to Home Screen"