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Dictionary of Technical Terms - C
chroma gain (chroma, color, saturation)
In video, the gain of an amplifier as it pertains to the intensity of colors in the active picture. A video key effect in which one video signal is inserted in place of areas of a particular color in another video signal. For example, a weatherman stands in front of a blue wall with a camera focused on him. The camera signal feeds a chroma keyer which detects the blue in the blue wall and replaces it with video from another camera, such as video of a weather map. Thus, the finished key makes the weatherman appear to be standing in front of the weather map. The range of colors accepted by a chroma keyer for use in creating a chroma key. The narrower the aperture, the more color selective the chroma key will be. See material dispersion. The color aspect of light including hue and saturation, but not intensity. The color perceived is determined by the relative proportions of the three primary colors. The chroma keying system used in some GVG digital video switchers. That portion of the video signal which contains the color information (hue and saturation). Video picture information contains two components: luminance (brightness and contrast) and chrominance (hue and saturation).chrominance/luminance inequality
A video specification that compares delay and gain differences between chrominance and luminance. An undesirable change in chrominance gain caused by a change in chrominance amplitude. Appears in a TV picture as incorrect color saturation. An undesirable change in chrominance phase caused by a change in chrominance amplitude. Appears in a TV picture as a shift in hue as the color saturation level increases.chrominance-to-luminance intermodulation (crosstalk, cross-modulation)
An undesirable change in luminance amplitude caused by superimposition of some chrominance information on the luminance signal. Appears in a TV picture as unwarranted brightness variations caused by changes in color saturation.CIE colors (Commission Internationale de l'Eclairage)
Colors specified by the International Commission on Illumination which sets standards for illumination including color. The interconnection of a number of devices to perform an electronic function. The material that encases the core of an optical fiber. May be either glass or plastic. Because the cladding has a lower index of refraction than the core, incident light is confined inside the core and transmitted. The circuit or process that restores the DC component of a signal. A video clamp circuit, usually triggered by horizontal synchronizing pulses, re-establishes a fixed dc reference level for the video signal. Some clamp circuits clamp sync tip to a fixed level, and others clamp back porch (blanking) to a fixed level. A major benefit of a clamp is the removal of low-frequency interference, especially power line hum. Optimum chroma and luminance transitions that define where one object ends and another begins. Edit transitions that are synchronized accurately in phase and in color frame. An output of a switcher consisting of Program video without any down- stream key.clear channel capability (CCC)
In telecommunications, DS1 data channels equipped to carry data containing all 0's. Normally done using B8ZS. 1. In keying, the trigger point or range of a key source signal at which the key or insert takes place. 2. The control which sets this action. To produce a key signal from a video signal, a clip control on the keyer control panel is used to set a threshold level to which the video signal is compared. 3. In digital picture manipulators, a menu selection that blanks portions of a manipulated image that leave one side of the screen and "wrap" around to enter the other side of the screen. 4. In desktop editing, a pointer to a piece of digitized video or audio that serves as source material for editing. An electronic limit to avoid overdriving the audio or video portion of the television signal. The master frequency of periodic pulses that are used to synchronize the operation of equipment. Undesirable random changes in clock phase. See clock skew. The reconstruction of timing information from digital data. A fixed deviation from proper clock phase that commonly appears in D1 digital video equipment. GVG digital distribution amplifiers handle improperly phased clocks by reclocking the output to fall within D1 specifications. A wipe that uses a circular pattern like the hand of a clock. In GVG editors, to create a new edit file which has parameters copied from an existing edit file.CMOS (complementary metal-oxide semiconductor)
A semiconductor device consisting of two complementary MOS Field Effect Transistors: a p-channel transistor and an n-channel transistor. Common mode rejection. Common mode rejection ratio. Central office. A cable which has a metallic noise shield surrounding a signal-carrying conductor. In television, the cable impedance is 75 ohms.
Y = 0.3Red + .59Green + .11Blue
R-Y = 0.7Red - 0.59Green - 0.11Blue
B-Y = 0.89Blue - 0.59 Green -0.3Red
In the NTSC system, the color subcarrier is phase-locked to the line sync so that on each consecutive line, subcarrier phase is changed 180 degrees with respect to the sync pulses. In the PAL system, color subcarrier phase moves 90 degrees every frame. In NTSC this creates four different field types; in PAL there are eight. In order to make clean edits, alignment of color field sequences from different sources is crucial. The sequence of color fields that make one complete color frame. In color television four (NTSC) or eight (PAL) properly sequenced color fields compose one color frame.color frame ID (identification)
An identification pulse that indicates the beginning of a complete color frame. A background color that graduates from light to dark or from one color to another. See also background wash. The synchronization of the burst phase of two or more video signals. Ensures that no color shifts occur in the picture when the signals are mixed in a switcher or other video device. An electrical filter circuit that passes a series of frequencies and rejects the frequencies in between, producing a frequency response similar to the teeth of a comb. Used on encoded video to select the chrominance signal and reject the luminance signal, thereby reducing cross chrominance artifacts, or conversely, to select the luminance signal and reject the chrominance signal, thereby reducing cross luminance artifacts. Comb filtering successfully reduces artifacts but may also cause a certain amount of resolution loss in the picture. In digital picture manipulators, a device that controls the way in which two or more channels work together. Under software control, it determines the priority of the channels (which picture appears in front and which ones in back) and the types of transitions that can take place between them. A point that acts as a reference for circuits, often equal to ground. In video switchers, for example, tally and GPI relays, when activated, often provide a closure to a common input, which may be ground or some other voltage, such as the voltage used to drive tally lamps. In telecommunications, a government regulated private company that furnishes the general public with telecommunications service facilities. Signals identical with respect to amplitude, frequency, and phase that are applied to both terminals of a conductor and/or both the input and reference of an amplifier. Typically, power line interference which appears on both terminals of a conductor with the same phase, amplitude and frequency. Amplitude of the common mode signal (signal of the same frequency, amplitude and phase) that can be applied to the two differential inputs of an amplifier and maintain its performance. See differential amplifier. A measure of how well a differential amplifier rejects a signal which appears simultaneously and in phase at both input terminals. As a specification, CMR is usually stated as a dB ratio at a given frequency. 1. For a differential amplifier, the ratio of differential gain to common mode gain. 2. Expressed in dB, the ratio of common mode input voltage to output voltage. 3. For an operational amplifier, the ratio of the change in input offset voltage to the change in common mode voltage. See component video. A digital representation of a component analog signal set, most often Y, B-Y, R-Y. The encoding parameters are specified by ITU-R BT.601-2 (CCIR 601). The parallel interface is specified by ITU-R BT.656 (CCIR 656) and SMPTE 125M.component digital post production
A method of post production which records and processes video completely in the component digital domain. Analog sources are converted only once to the component digital format and then remain in that format throughout the post production process. A group of component video equipment used within a larger non-component facility. The unencoded output of a camera, videotape recorder, etc., consisting of 3 primary color signals: red, green, and blue (RGB) that together convey all necessary picture information. In some component video formats, these three components have been translated into a luminance signal and two color difference signals, for example, Y, R-Y, B-Y. See also color difference signal. See composite video. A digitally encoded video signal, such as NTSC or PAL video, that includes horizontal and vertical synchronizing information. A video synchronizing signal that contains horizontal and vertical synchronizing information. Often referred to simply as sync. An encoded video signal, such as NTSC or PAL video, that includes horizontal and vertical synchronizing information. A digital picture manipulator effect where the picture is squeezed (made proportionally smaller). 1. Improper video signal level caused by non-linearity in a circuit transfer function. Results in lack of detail in either the black or white areas of the video picture. Can also be caused by pointing a video camera at a scene that has a total black-to-white range wider than a standard television signal can handle. 2. Reduction of the size of digital data files by removing redundant information (non-lossy) or removing non-critical data (lossy). Compacting of a digital signal, particularly when a high compression ratio is used, may result in small errors when the signal is decompressed. These errors are known as "artifacts," or unwanted defects. The artifacts may resemble noise (or edge "busyness") or may cause parts of the picture, particularly fast moving portions, to be displayed with the movement distorted or missing. Transferring edit decision list information gathered from an off-line edit to an on-line edit for final assembly. The addition of key frames to an existing key frame effect in such a way that the overall length of the effect does not change. In digital picture manipulators, the characteristic of location/positioning that determines whether the motion path continues smoothly, without interruption. Digital video picture defect caused quantizing at too coarse a level. The range of light-to-dark values of the image which are proportional to the voltage difference between the black and white voltage levels of the video signal. The contrast control is an adjustment of video gain (white bar, white reference). In routing switchers, the interconnecting communications path between control panels or devices and the routing matrices. A device used for entering operational commands to a device. Circuits used to generate or alter control signals. A room near a television studio where the director and production crew control the show. The control room contains the video switcher, graphics equipment, audio mixer, and banks of video monitors. A signal used to perform an alteration of or transition between video signals. The area on a videotape where frame pulses are recorded. A pulse laid down on videotape by a videotape recorder to identify the frame locations on the videotape. This enables the VTR to lock up correctly framed during playback. In fiber optic cable, the core is the light-transmitting material at the center of the fiber. A video noise gating operation in which pixels below a predetermined luminance threshold are replaced by ``clean'' black pixels. Useful in additive keying, where the additive mixer cuts a hole in the background video and adds the entire fill video, including the black matte surrounding the fill. Coring the fill video before keying substitutes a noise-free black around the fill. During keying, the black regions add nothing to the background and thereby eliminate noise surrounding the fill video that mightotherwise add to the background, causing noisy key edges. Relates to SMPTE 125M component digital video, in which the luminance component (Y) is sampled four times for every two samples of the two chrominance components (Cb and Cr). Cositing refers to delaying transmission of the Cr component to occur at the same time as the second sample of luminance data. This produces a sampling order as follows: Y1/Cb1, Y2/Cr1, Y3/Cr3, Y4/Cb3, and so on. Cositing reduces required bus width from 30 bits to 20 bits. Selection of either AC or DC coupling. See AC coupling. In telecommunications, an optical device used to interconnect optical fibers. The manner in which two circuits or systems are connected. Usually this involves either AC or DC coupling. In telecommunications, the optical power loss incurred in connecting optical fibers. Customer premises equipment. Central processing unit. Text or graphics moving horizontally across the screen. Cyclic redundant check. See Y, Cr, Cb. The amount of phase difference between two color difference signals as they travel through parallel circuit paths. See safe title/safe action area. In GVG digital picture manipulators, a function which defines the edges of the manipulated image, similar to cropping a photograph.cross chrominance (cross color)
Moire or rainbow artifacts in an encoded video picture caused when the video encoder or decoder misinterprets luminance detail as color information. Especially noticeable when the talent wears pin-striped clothing. A transition between two pictures where the first picture dissolves to black, and then black dissolves to the second picture. A video test signal containing a grid pattern used for convergence and linearity adjustments and on-screen alignment of graphics.cross luminance (dot crawl, chroma crawl)
A video artifact that occurs when the decoder in a monitor or receiver misinterprets areas of high color saturation as luminance information. This causes tiny colored dots to creep along the vertical or horizontal edges of objects. An electronic switch, usually part of an array of switches, that allows video or audio to pass when the switch is closed. 1. Undesired transmission of signals from one circuit into another circuit in the same system. Usually caused by unintentional capacitive (AC) coupling. 2. Signal interference from one part of a videotape to another. Video editing term meaning to position a videotape at a specific point. Video editing term meaning to fast forward or rewind a VTR to the next edit point in preparation for an edit. A digital picture manipulation term. The current effect in the register that was last recalled. A digital picture manipulation term. The current key frame for each channel is the key frame in the current effect at which the channel is presently positioned. A digital picture manipulation term. Memory used to retain the most recent source-related parameters for each source. A digital picture manipulator term. The current time is the current position in the current effect. This time is the "glue" which binds multichannel effects and is expressed in terms of seconds and frames from the start of the effect. Negative times indicate events before the start of the effect. A transition between two video pictures which is instantaneous, without any gradual change. On a video switcher, a large pushbutton that causes a cut between program and preview video when pressed.We've recently redesigned our website so your bookmarked links may no longer work. Please use either the search bar at the top right of this page or select an area from one of the tabs above to find what you are looking for.
