CAP set: Data passed between an MCS and a conferencing system that identifies the capabilities of the equipment, such as audio coding and transfer rate capabilities.

CCD: Charged-Couple Device used in some video cameras instead of an imagepickup tube. Light-sensitive microprocessor that converts an image into an electrical flow. CCDs are not prone to image smear or lag and make light weight cameras possible.

CCIR: Comite Consultatif International des Radiocommunications or International Radio Consultative Committee. This is a standards committee of the International Telecommunications Union, who have made the technical recommendation for European 625 line standard for video signals. The CCIR no longer exists-it has been absorbed into the parent body, the ITU. For a given "CCIR xxx" specification, This is covered under: "BT.xxx".

CELP: Codebook Excited Linear Prediction. A digital voice compression technique invented by AT&T, which provides good voice quality down to about 8kb/s and sometimes to 4kb/s. The voice is first digitized as PCM and then passed through CELP circuits. Like all source-coder systems, CELP transmits a “profile” of the voice characteristics, and then reconstructs a close synthesis of the voice at the other end.

CERN: Centre Europeen pour la Recherche Nuclaire (CERN) is a large particle-physics laboratory located in Geneva on the French-Swiss border. The World Wide Web originated at CERN

Chair-control video switching: A video-switching method using the ITU-T Recommendation H.243 standard in which a participant at a conference site selects the current broadcaster from the controls provided by the conferencing system. The conference must be using voice-activated video switching, and the H.243 Chair Control option must be installed at the site. Contrast with user-selected video switching.

Channel negotiation: In the ISDN Q.931 protocol, the process by which a stored-program control system enables the equipment at the customer premises to request a channel that is different from the one indicated in the setup message.

Checksum: An error-detecting scheme which is the sum of the data values transmitted. The receiver computes the sum of the received data values and compares it to the transmitted sum. If they are equal, the transmission was error-free.

Chroma Bandpass: In a NTSC or PAL video signal, the luma (black and white) and the chroma (color) information are combined together. If you want to decode an NTSC or PAL video signal, the luma and chroma must be separated. A chroma bandpass filter removes the luma from the video signal, leaving the chroma relatively intact. This works reasonably well except in images where the luma and chroma information overlap, meaning that we have luma and chroma stuff at the same frequency. The filter can't tell the difference between the two and passes everything. This can make for a funny-looking picture. Next time you're watching TV and someone is wearing a herringbone jacket or a shirt with thin, closely spaced stripes, take a good look. You may Check out: a rainbow color effect moving through that area. What's happening is that the video decoders thinks that the luma is chroma. Since the luma isn't chroma, the video decoder can't figure out what color it is and it shows up as a rainbow pattern. This problem can be overcome by using a comb filter.

Color Corrector A device used to correct problems related to the chroma of the video signal, as well as color balance and color noise. Composite video versions distort the image quality too much to be any value. Component video units work more transparently, as do SDI or digital video versions. Color correction in non-linear editing and compositing systems has been getting so fast as to make dedicated equipment nearly obsolete.

Chroma Demodulator After the NTSC or PAL video signal makes its way through the Y/C separator, the colors must be decoded. That's what a chroma demodulator does. It takes the chroma output of the Y/C separator and recovers two color difference signals (typically I and Q or U and V). Now, with the luma information and two color difference signals, the video system can figure out what colors to display.

Chroma Key: Electronically matting or inserting an image from one camera into the picture produced by another. Also called "keying." The subject to be inserted is shot against a solid primary color background. Signals from the two sources are merged through a special effects generator. The process of overlaying one video signal over another by replacing a range of colors with the second signal. Typically, the first (foreground) picture is photographed with a person or object against a special, single-color background (the key-color). The second picture is inserted in place of the key-color. The most common example is in broadcast weather segments where pictures of weather maps are inserted "behind" the talent. This is a method of combining two video images. An example of chroma keying in action is the nightly news person standing in front of a giant weather map. In actuality, the person is standing in front of a blue or green background and their image is mixed with a computer-generated weather map. This is how it works: a TV camera is pointed at the person and fed along with the image of the weather map into a box. Inside the box, a decision is made. Wherever it Check out: s the blue or green background, it displays the weather map. Otherwise, it shows the person. So, whenever the person moves around, the box figures out where he is, and displays the appropriate image.

Chroma: Short for chrominance. Chroma is the color component of the video signal. The NTSC, PAL, or SECAM video signal contains two parts that make up what you Check out: on the display: the intensity part, and the color part. Chroma is the color part. The color information in a video signal, consisting of hue (phase angle) and saturation (amplitude) of the color subcarrier signal.

Chroma Trap: In a NTSC or PAL video signal, the luma (black and white) and the chroma (color) information are combined together. If you want to decode the video signal, the luma and chroma must be separated. The chroma trap is one method for separating the chroma from the luma, leaving the luma relatively intact. How does it work? The NTSC or PAL signal is fed to a trap filter. For all practical purposes, a trap filter allows certain frequencies to pass through, but not others. The trap filter is designed with a response to remove the chroma so that the output of the filter only contains the luma. Since this trap stops chroma, it's called a chroma trap. The sad part about all of this is that not only does the filter remove chroma, it removes luma as well if it exists within the frequencies where the trap exists. The filter only knows ranges and, depending on the image, the luma information may overlap the chroma information. The filter can't tell the difference between the luma and chroma, so it traps both when they are in the same range. What's the big deal? Well, you lose luma and this means that the picture is degraded somewhat. Using a comb filter for a Y/C separator is better than a chroma trap or chroma bandpass.

Chrominance: In video, the terms chrominance and chroma are commonly (and incorrectly) interchanged. Check out: the definition of chroma. The color portion of a video signal separate from the luminance component, representing the saturation and tint at a particular point of the image. Black, gray and white have no chrominance, but any colored signal has both chrominance and luminance. The higher the chrominance level, the stronger the color (e.g., a strong signal produces red, and a weak signal, pink). Color saturation level can be changed using a proc amp.

CIF Common Interface Format or Common Image Format. The Common Interface Format was developed to support video conferencing. It has an active resolution of 352 x 288 and a refresh rate of 29.97 frames per second. The High-Definition Common Image Format (HD-CIF) is used for HDTV production and distribution, having an active resolution of 1920 x 1080 with a frame refresh rate of 23.976, 24, 29.97, 30, 50, 59.94, or 60 Hz. Common Intermediate Format, an optional part of the ITU-T's H.261 and H.263 standards. CIF specifies 288 non-interlaced luminance lines that contain 352 pixels. CIF is to be sent at frame rates of 7.5, 10, 15, or 30 per second. When operating with CIF, the number of bits that result cannot exceed 256 K bits (where K equals 1024)

CIR - Committed Information Rate: The rate at which a Frame Relay network agrees to transfer information under normal conditions, averaged over a minimum increment of time. CIR, measured in bits per second, is one of the key negotiated tariff metrics.

Circuit Switched: An ISDN bearer service that provides a 64 kbps (sometimes 56 kbps) path between two users for the duration of the call.

Clamp This is basically another name for the DC-restoration circuit. It can also refer to a switch used within the DC-restoration circuit. When it means DC restoration, then it's usually used as "clamping". When it's the switch, then it's just "clamp".

Clipping Logic A circuit used to prevent illegal conversion. Some colors can exist in one color space but not in another. Right after the conversion from one color space to another, a color space converter might check for illegal colors. If any appear, the clipping logic is used to limit, or clip, part of the information until a legal color can be represented. Since this circuit clips off some information and is built using logic, it's not too hard to Check out: how the name "clipping logic" was developed.

Clipping: An effect of distortion where the peaks of driven signals are chopped off. Clipping usually occurs in the amplifier when it is turned up too high, but it can occur in maladjusted circuits in a VCR or TV set. In video as opposed to audio, the electronic process of cutting off the peaks of either the white or black excursions of a video signal to limit the signal. Sometimes, clipping is performed prior to modulation, and sometimes to limit the signal, so it does not exceed the limits of the composite video signal (7.5 and 100 IRE units).

Closed Captioning A service which decodes text information transmitted with the video signal and displays it on the display. For NTSC, the caption signal may be present on lines 21 and 284. For PAL, the caption signal may be present on lines 22 and 334. Check out: the EIA-608 specification for (M) NTSC usage of closed captioning and the EIA-708 specification for DTV support. For MPEG-2 video, including ATSC and DVB, the closed caption data are multiplexed as a separate data stream within the MPEG-2 bitstream. It may use the picture layer user_data bits as specified by EIA-708, or in PES packets (private_stream_1) as specified by ETSI EN 301 775. For DVD, caption data may be 8-bit user_data in the group_of_pictures header (525/60 systems), a digitized caption signal (quantized to 16 levels) that is processed as normal video data (625/50 systems), or a subpicture that is simply decoded and mixed with the decoded video.

C-Mount: The standard screw mounting for 2/3" and 1" camera lenses. The distance from the flange surface to the focal point is 17.526mm. A C-Mount lens can be used on a camera with a CS-Mount by adding adapter ring to reduce the distance to 12.5mm.

CMYK This is a color space primarily used in color printing. CMYK is an acronym for Cyan, Magenta, Yellow, and blacK. The CMYK color space is subtractive, meaning that cyan, magenta, yellow and black pigments or inks are applied to a white surface to remove color information from the white surface to create the final color. The reason black is used is because even if a printer could print hues of cyan, magenta, and yellow inks perfectly enough to make black (which it can't for large areas), it would be too expensive since colored inks cost more than black inks. So, when black is used, instead of putting down a lot of CMY, they just use black.

Coaxil Cable: A standard cable consisting of a central inner conductor and a cylindrical outer conductor. Used for many video connections, especially the cable TV wire that comes into your home. Dozens of different variations are manufacturered for a variety of applications, bandwidth specifications and environments.

Codec (Codices is plural)- Sophisticated digital signal-processing unit or software algorithm that takes an analogue input and converts it to digital on the sending end. . Any technology for compressing and decompressing data. Codecs can be implemented in both software and hardware. Some examples of codecs are: Cinepak, MPEG, and QuickTime to convert analog video to digital form. At the receiving end, another codec reverses this by reconverting the digital signal back to analogue. Codec is a contraction of code/decode (or Compressor/decompressor or compress/decompress). A codec takes the form of a set of hardware or software components, or a combination of both.

COFDM is a multiplexing technique rather than a modulation technique. One of any of the common modulation methods, such as QPSK, 16-QAM or 64-QAM, is used to modulate the COFDM carriers.

Color Bars A standard video test pattern which includes samples of primary and secondary colors. Used to conform the colors in video monitors and other equipment.. There are several variations of test patterns used to check whether a video system is calibrated correctly. A video system is calibrated correctly if the colors are the correct brightness, hue, and saturation. This can be checked with a vectorscope.

Color Decoder : A device which divides a video signal into its basic color components. In TV and video, color decoding is used to derive signals required by a video monitor from the composite or Y/C signals.

Color Encoder: The color encoder does the exact opposite of the color decoder. It takes two color difference signals, such as I and Q or U and V, and combines them into a chroma signal.

Color Killer: A color killer is a circuit that shuts off the color decoding if the incoming video does not contain color information. How does this work? The color killer looks for the color burst and if it can't find it, it shuts off the color decoding. For example, let's say that a color TV is going to receive material recorded in black and white. Since the black and white signal does not contain a color burst, the color decoding is shut off. Why is a color killer used? Well, in the old days, the color decoder would still generate a tiny little bit of color if a black and white transmission was received, due to small errors in the color decoder, causing a black and white program to have faint color spots throughout the picture.

Color Phase: The phase of the chroma signal as compared to the color burst,is one of the factors that determines a video signal's color balance.

Color Purity: This term is used to describe how close a color is to the theoretical. For example, in the Y'UV color space, color purity is specified as a percentage of saturation and +/-q, where q is an angle in degrees, and both quantities are referenced to the color of interest. The smaller the numbers, the closer the actual color is to the color that it's really supposed to be. For a studio-grade device, the saturation is +/-2% and the hue is +/-2 degrees. On a vectorscope, if you're in that range, you're studio quality.

Color Space A color space is a mathematical representation for a color. No matter what color space is used -- RGB, Y'IQ, Y'UV, etc. -- orange is still orange. What changes is how you represent orange. For example, the RGB color space is based on a Cartesian coordinate system and the HSI color space is based on a polar coordinate system.

Color Subcarrier: The carrier frequency (3.58 MHz in NTSC and 4.43 MHz in PAL) on which the color information is impressed. Color TV sets use special circuits which decode the color component for accurate display. The color subcarrier is a signal used to control the color encoder or color decoder. For (M) NTSC the frequency of the color subcarrier is about 3.58 MHz and for (B, D, G, H, I) PAL it's about 4.43 MHz. In the color encoder, a portion of the color subcarrier is used to create the color burst, while in the color decoder, the color burst is used to reconstruct a color subcarrier.

Color Temperature Color temperature is measured in degrees Kelvin. If a TV has a color temperature of 8,000 degrees Kelvin, that means the whites have the same shade as a piece of pure carbon heated to that temperature. Low color temperatures have a shift towards red; high color temperatures have a shift towards blue. The standard for video is 6,500 degrees Kelvin. Thus, professional TV monitors use a 6,500-degree color temperature. However, most consumer TVs have a color temperature of 8,000 degrees Kelvin or higher, resulting in a bluish cast. By adjusting the color temperature of the TV, more accurate colors are produced, at the expense of picture brightness.

Color Temperature: A method for measuring the overall color of a light source, measured in degrees Kelvin (deg.K). Higher numbers indicate bluer light, lower numbers indicate a warmer light. The color temperature of the lighting must match the color temperature of the camera. In video this is accomplished by setting the white balance of the camera. Sunny Daylight is approximately 5500 deg.K. Overcast daylight is higher. Fluorescent Lights are approx. 4100 deg.K. Indoor incandescent lights are 2800 deg.K and professional Movie Lights are 3200 Deg. K

ColorStream, ColorStream Pro, ColorStream HD: The name Toshiba uses for the analog YPbPr video interface on their consumer equipment. If the interface supports progressive SDTV resolutions, it is called ColorStream Pro. If the interface supports HDTV resolutions, it is called ColorStream HD.

Comb Filter: This is another method of performing Y/C separation. A comb filter is used in place of a chroma bandpass or chroma trap. The comb filter provides better video quality since it does a better job of separating the luma from chroma. It reduces the amount of creepy-crawlies or zipper artifacts. It's called a comb filter because the frequency response looks like a comb. The important thing to remember is that the comb filter is a better method for Y/C separation than chroma bandpass or chroma trap.

Component Video: Video signal in which luminance and synch information are recorded separately from the color information. Formats such as Betacam, SVHS and Hi-8 use component signals to achieve maximum quality. Component video comes in several flavors: RGB (red, green, blue), YUV (luminance, sync, and red/blue) and Y/C (luminance and chrominance). Y/C is also called S-Video used in the S-VHS and Hi-8 formats.

Composite Video A single video signal that contains brightness, color, and timing information. If a video system is to receive video correctly, it must have several pieces of the puzzle in place. It must have the picture that is to be displayed on the screen, and it must be displayed with the correct colors. This piece is called the active video. The video system also needs information that tells it where to put each pixel. This is called sync. The display needs to know when to shut off the electron beam so the viewer can't Check out: the spot retrace across the CRT display. This piece of the video puzzle is called blanking. Now, each piece could be sent in parallel over three separate connections, and it would still be called video and would still look good on the screen. This is a waste, though, because all three pieces can be combined together so that only one connection is needed. Composite video is a video stream that combines all of the pieces required for displaying an image into one signal, thus requiring only one connection. NTSC and PAL are examples of composite video. Both are made up of active video, horizontal sync, horizontal blanking, vertical sync, vertical blanking, and color burst. RGB is not an example of composite video, even though each red, green, and blue signal may contain sync and blanking information, because all three signals are required to display the picture with the right colors.

Composite Video: A video signal in which the luminance and chrominance elements have been combined in formats such as VHS. A picture signal combined with synchronization and (possibly) color information. Usually called baseband video, or just video.

Compression: Reducing the representation of the information, but not the information itself. Reducing the bandwidth or number of bits needed to encode information or encode a signal, typically by eliminating long strings of identical bits or bits that do not change in successive sampling intervals. Compression saves transmission time or capacity. It also saves storage space on storage devices such as hard disks, tape drives, and floppy disks. For example, he process of electronically processing video signals so that it requires less storage on a computer hard drive. A 5:1 compression requires more storage space, but yields better quality than a 10:1 compression.

Conditional Access This is a technology by which service providers enable subscribers to decode and view content. It consists of key decryption (using a key obtained from changing coded keys periodically sent with the content) and descrambling. The decryption may be proprietary (such as Canal+, DigiCipher, Irdeto Access, Nagravision, NDS, Viaccess, etc.) or standardized, such as the DVB common scrambling algorithm and OpenCable. Conditional access may be thought of as a simple form of digital rights management. Two common DVB conditional access (CA) techniques are SimulCrypt and MultiCrypt. With SimulCrypt, a single transport stream can contain several CA systems. This enables receivers with different CA systems to receive and correctly decode the same video and audio streams. With MultiCrypt, a receiver permits the user to manually switch between CA systems. Thus, when the viewer is presented with a CA system which is not installed in his receiver, they simply switch CA cards.

Conforming: Online editing to create the final edit master. The offline edit master is used as a guide. technologically obsolete

Constant Bit Rate (CBR) means that a bitstream (compressed or uncompressed) has the same number of bits each second.

Continuity: Controlling the elements in a shot to insure that edits will flow smoothly and produce a coherent motion picture story without jarring the viewer.

Continuous Presence: An optional type of conference where all sites view four other sites arranged in a quadrant-screen display.

Contouring This is an image artifact caused by not having enough bits to represent the image. The reason the effect is called "contouring" is because the image develops vertical bands of brightness.

Contrast: The degree to which luminance values contain very dark and very light values. A high-contrast picture has more black and white values with fewer values in between. A low contrast picture has more middle tones without very dark or very light areas. A video term referring to how far the whitest whites are from the blackest blacks in a video waveform. If the peak white is far away from the peak black, the image is said to have high contrast. With high contrast, the image is very stark and very "contrasty", like a black-and-white tile floor. If the two are very close to each other, the image is said to have poor, or low, contrast. With poor contrast, an image may be referred to as being "washed out" -- you can't tell the difference between white and black, and the image looks gray.

Control Track: A linear track, consisting of 30- or 60-Hz pulses, placed on the bottom of videotape that aids in the proper playback of the video signal. Type of video editing that controls the in and out points of edits by counting pulses on a control track portion of the videotape. The pulses are counted by the edit controller to perform fairly accurate editing. Edit controllers which read time code make more accurate edits.

Control-L: This is a control protocol found on 8mm and some VHS decks that provides computer control of unit operation. Units are connected through a special cable. Sony's editing control protocol, also called LANC (Local Application Control), which allows two-way communication between a camcorder or VCR and an edit controller.

Control-S: Sony transport control protocol which duplicates a consumer VCR's infra-red remote transport control. Unlike Control-L, Control-S does not allow the controller to read tape counter information.

Convergence: Three colors-red, blue, and green-are used in television to produce all colors. These separate scanning beams (one for each color) must strike their targeted phosphors (screen's internal coating) with precise accuracy. If the beams are out of alignment, then the image and colors appear muddied.

CPE - Customer Provided Equipment: Equipment not part of the public (ISDN) network located and owned by the end user. This includes telephones, computers, etc…

Creepy Crawlies: Yes, this is a real video term! Creepy-crawlies refers to a specific image artifact that is a result of the NTSC system. When the nightly news is on, and a little box containing a picture appears over the anchorperson's shoulder, or when some computer-generated text shows up on top of the video clip being shown, get up close to the TV and check it out. Along the edges of the box, or along the edges of the text, you'll notice some jaggies "rolling" up (or down) the picture. That's the creepy-crawlies. Some people refer to this as zipper because it looks like one.

Cross Color: This occurs when the video decoder incorrectly interprets high-frequency luma information (brightness) to be chroma information (color), resulting in color being displayed where it shouldn't.

Cross Luma: This occurs when the video decoder incorrectly interprets chroma information (color) to be high-frequency luma information (brightness).

Crossfade: The audio equivalent of the video picture dissolve. The first sound track gradually fades out while the second sound track simultaneously replaces it.

Crosstalk: Interference from one signal that is detected on another. Usually refers to audio, but has applied to analog video as well. A signal from one stereo channel that bleeds into the other. Also, a signal from a video track on a tape bleeding into the signal on the adjacent track. The interference between two audio or two video signals. In audio crosstalk this signal leakage may occur between the left and right channels. It can be caused by poor grounding connections or improperly shielded cables. In video, crosstalk between channels can be luminance/sync crosstalk or chroma crosstalk. Video crosstalk can cause ghost images from one source appear over the other.

CSMA/CD: Carrier sense multiple access collision detect. Media-access mechanisms wherein devices ready to transmit data first check the channel for a carrier. If no carrier is sensed for a specific period of time, a device can transmit. If two devices transmit at once, a collision occurs and is detected by all colliding devices. This collision subsequently delays retransmissions from those devices for some random length of time. Ethernet and IEEE 802.3 use CSMA/CD access.

CS-Mount: A new generation of lenses designed for 2/3", 1/2" and 1/3" cameras incorporating CS-mounts. The distance from the flange surface to the focal point is 12.5mm. CS-mount lenses cannot be used on cameras with C-mount configuration. These lenses are smaller and cheaper than the C-mount equivalents.

CSU - channel service unit: A device that interfaces between a communication network and data terminal equipment. In T1 applications, referred to as a DSU (data service unit).

CSV/CSD: Alternate Circuit-Switched Voice/Circuit-Switched Data. A B-channel configuration that allows either circuit switch voice or data communication.

CSV: Circuit-Switched Voice. An ISDN circuit-switched call for voice where the transmission path between two users is assigned for the duration of a call ata constant rate.