AV/IT Glossary—27 Days of #AVabc—V





Video Wall—A video wall is a special multi-monitor setup that consists of multiple computer monitors, video projectors, or television sets tiled together contiguously or overlapped in order to form one large screen. Typical display technologies include LCD panels, Direct View LED arrays, blended projection screens, Laser Phosphor Displays, and rear projection cubes.


V—(1) Vertical (as in RGBHV), or the vertical sync connector on a panel. This is used when the sync is separated into horizontal and vertical components. (2) In electrical specifications, “V” is the abbreviation for volts.

VAR-Value Added Reseller—A party who purchases a product, adds something to it, such as hardware or software, and then sells it as a package.

Variable Bit Rate (VBR)—Varies the amount of output data per time segment. VBR allows a higher bit rate or storage space to be allocated to more complex segments of video and a lower bit rate to be allocated to less complex segments.

Variable Level Control—This is a variable voltage level control similar to a contrast control on a data monitor. The level control increases or decreases the levels of red, green, and blue simultaneously, thus not affecting the adjusted grayscale of the monitor or projector.

Vault—A storage product that houses fiber optic cable slack and splice trays.

VCA-Voltage Control Amplifier—An amplifier whose output is controlled by varying its voltage rather than by direct resistance (as with a potentiometer). VCA’s are typically used in audio mixers; instead of the signal being directly manipulated by the fader (and being subject to inconsistencies in the fader itself), the fader controls a voltage that corresponds to a certain sound level.

VCO-Voltage Control Oscillator—Voltage-controlled oscillators are commonly found in wireless systems, frequency synthesizers, and other devices that must be able to tune across a band of frequencies.

VCR—Generally defined as Video Cassette Recorder. In Europe, however, VCR is a trademark for a particular video format developed by Philips.

VCSEL-Vertical Cavity Surface Emission Laser—A high speed, low cost laser diode that emits perpendicular to the surface of the chip, rather than from an edge.

Vectorscope—A special oscilloscope used in video systems to measure chroma.

VersaTools®—Extron product family of compact, affordable, and versatile solutions for common A/V system applications.

Vertical Blanking—Turning off the electron beam in a CRT during the time the beam returns from the bottom of the screen to the top after scanning each field of a picture. If vertical blanking does not occur, a diagonal retrace line will display from the lower right to the upper left of the screen.

Vertical Centering Control—Adjusting the vertical centering control one way shifts the displayed image toward the bottom of the screen and the other way shifts the displayed image to the top of the screen. Also called “vertical shift,” or “vertical position.”

Vertical Double Images—A video problem in which the display is split across the middle with two identical (squeezed) images on the top and bottom of the screen.

Vertical Filtering—This is a feature in some Extron scan converters that controls the number of lines to process, and the way they are processed. This affects the sharpness vs. flicker of the scan-converted picture.

Vertical Interval—The period of time between the end of one video field and the beginning of the next. During this time, the electron beam in a camera, monitor, or projector is turned off (blanked) while it returns from the bottom of the screen to the top. The portion of the video signal that represents this time period may also be called the vertical interval.

Vertical Resolution—Also known as “vertical definition.” The number of distinct horizontal lines, alternately black and white, that can be seen in a TV image. Vertical resolution is fixed by the number of horizontal lines used in scanning.

Vertical Temporal—A scaling process for video content that contains movement. This type of scaling process employs an averaging technique to merge the odd and even fields of video into a single frame. This type of processing treats the entire picture as if in motion and results in less motion artifacts. Disadvantages include blurring and loss of vertical resolution.

Vertical Tilt—A field-time distortion which changes the shape of a flat, low frequency video signal and is visible as dark or light bars at the beginning or end of the picture on the screen. Vertical tilt is usually caused by poor low frequency response, mainly of AC coupled circuitry. Vertical tilt in professional applications should not exceed 0.5%.

VESA-Video Electronics Standards Association—A nonprofit member organization dedicated to facilitating and promoting personal computer graphics through improved standards for the benefit of the end-user. www.vesa.org

VGA—Stands for "Video Graphics Array." It is the standard monitor or display interface used in most PCs. Therefore, if a montior is VGA-compatible, it should work with most new computers. The VGA standard was originally developed by IBM in 1987 and allowed for a display resolution of 640x480 pixels. Since then, many revisions of the standard have been introduced. The most common is Super VGA (SVGA), which allows for resolutions greater than 640x480, such as 800x600 or 1024x768. A standard VGA connection has 15 pins and is shaped like a trapezoid.

VHF-Very High Frequency—Television broadcast range between 30 and 300 MHz, on channels 2 through 13. The FM radio band is between channels 6 and 7 (88 to 108 MHz).

VHS-Video Home System—The half-inch videocassette format originated and developed by JVC and adopted by a number of different manufacturers.

VHS-C—A standard VHS system utilizing a compact cassette which, although it has less recording time, is very convenient for camcorders*. Special adapters allow these small cassettes to be used in regular VHS recorders.

Video—A format for transmitting and storing moving pictures. Video is transmitted and stored in various analog and digital physical formats.

Video Amplifier—A low-pass amplifier with a bandwidth of 2 to 10 MHz, used to strengthen the video signal for TV transmission and reception.

Video Bandwidth—The highest signal frequency that the video signal can reach. The higher the video bandwidth - the better the quality of the picture. A video recorder that can produce a very broad video bandwidth generates a very detailed, high quality picture on the screen. Video bandwidth requirements for studio work may vary from 5 and 200 MHz. Component video and graphics may reach bandwidths up to 500 MHz and higher.

Video Camera—A camera which contains an electronic image sensing CCD* (Charged Coupled Device) rather than photographic film. The CCD is scanned rapidly converting light rays to electric signals. A video camera has additional electronic circuitry which generates color* and sync* pulses. Some cameras are equipped with audio circuitry, e.g., microphone, audio amplifier and additional audio electronics. Professional cameras, in order to obtain a better picture, have a triple CCD system (three tubes in the past) - one for each basic color - red, green and blue. Most professional cameras have a genlocking* input, which allows the camera to be synchronized to an external source. Some cameras include additional electronic circuitry such as character generators for titling* and special effects*, Tally*, etc. CMOS type sensors are also used for some types of cameras. Those sensors are relatively inexpensive to manufacture.

Video Conference—A videoconference is a live connection between people in separate locations for the purpose of communication, usually involving audio and often text as well as video. At its simplest, videoconferencing provides transmission of static images and text between two locations. At its most sophisticated, it provides transmission of full-motion video images and high-quality audio between multiple locations.

Video Connector—The connector on the video card or computer’s graphics output that is connected to the video input on the local monitor.

Video Disc—An obsolete medium used for recording audio and video information on a disc the size of a regular LP record. There are several recording methods available. Video picture quality is quite high, but lack of re-recording capability limits the use of this system. It was replaced by the DVD.

Video Display—A device that converts a video signal into a visual image.

Video Editing—A procedure used for combining selected portions of several video footages, or of the same footage, in order to create a new, edited version. A variety of editing consoles are available which meet several standards, e.g., 1/2 inch, 3/4 inch, etc. During video editing, special effects* such as cross fading*, inserts, 3D effects, etc. can be added. Professional editing uses a special time code, which is printed on every frame of the magnetic or optical media. This allows for very accurate revision down to the level of a single frame. Very often, audio editing* is carried out simultaneously with video editing. The PAUSE control of a VCR can do simple cut-to-cut editing. In the digital domain NLE (Non Linear Editing) systems are used nowadays, which are fully digital, mainly computer based systems. The NLE system is hardware and software based, allowing for much more versatility and effects creation.

Video Enhancer—A general term used for a device which corrects problems on videotapes. A narrower definition is a machine which restores high frequency losses on videotapes by enhancing* the high frequency region of the video spectrum. A video enhancer often has controls such as Sharpness, Definition, Detail, etc., which are used for high frequency boosting. Unfortunately, there is a tendency for video enhancers to introduce Snow while adjusting the high frequency region of the spectrum. Only very advanced enhancers avoid this problem.

Video Gain—A nominal video signal level is usually 1 volt for Composite video, 0.7 Volts for component or RGB video or 0.3 Volts for the chrominance subsection, at which level a fully saturated picture is transmitted to the acceptor. However, for cases where the video signal is attenuated, a low-noise*, high-gain analog amplifier is built into quality video processing equipment. This amplifier provides video gain control whereby the video signal can be boosted or reduced. Dark pictures resulting from low level lighting are easily adjusted. An additional benefit of good video gain equipment is the ability to fade out pictures, for editing purposes.

Video Mixer—A device used to combine video signals from two or more sources. Synchronized inputs are mixed with each other and various special effects patterns and shapes are added in accordance with the proficiency of the video mixer being used. Two pictures can be superimposed; one on the other, while a third picture is cut into a “hole” in the scene. A video mixer usually generates sync* signals allowing genlocking* of additional video sources to the first source. Video mixing is done nowadays digitally with digitized analog or native digital sources.

Video Monitor—A video display with video input and output jacks but no television tuner.

Video Printer—The video printer is a special device that can grab and create a hard copy print of one video frame on photographic-like paper. A video printer is useful in industrial, medical and military applications. The quality of the print is limited by the quality of the picture on the screen, but for most applications it suffices.

Video Projector—A device that projects a video image onto a presentation surface.

Video Upconverter—Device or circuit within a device that converts a lower-resolution video signal to a high-resolution video signal.

Videoconferencing—Conducting a live conference between two or more locations using video cameras, microphones, and video monitors. The participants can be seen as well as heard. Referred to as a virtual conference room. Also see "Teleconferencing."

Video-Follow-Audio—In videoconferencing, when the video source switches automatically to show the person speaking, regardless of the location.

Viewing Angle—The viewing angle determines how far off the axis (screen centerline) a viewer can still sit and still see a quality image. This is no greater than 45 degrees off the projection axis.

Viewing Cone—The best viewing area for the audience. The term cone is used because there is width, height, and depth to the best viewing area, and this area emanates from the center of the screen.

Virtual Map—Used with the Extron virtualized matrix switchers (Matrix 3200/6400/12800 Series), a virtual map is made of tables stored in memory that relate physical connectors (on the back panel) to logical connections (as seen by the user). In printed form, this can show physical input/output connector numbers as they relate to virtual input/output numbers.

Virtual Memory—The process of increasing the apparent size of a computer’s random-access memory (RAM) by using a section of the hard disk storage as an extension of RAM.

Virtual Switching—A means of making real, physical input or output ports appear to have different numbers. For example, the Extron Matrix 6400 Switcher can be programmed to switch a set (group) of connectors as one.

Visible Light—The region of the electromagnetic spectrum that is visible to the human eye, from 380 to 770 nm.

Visually Lossless Compression—Allows the reproduced image to appear to human vision to be identical to the original image.

VITC-Vertical Interval Time Code—Timecode information that is stored on specific scan lines during the vertical blanking interval.

VLAN-Virtual LAN—A group of devices on a network with a common set of requirements that communicate as if they were attached to the same broadcast domain, regardless of their physical location. A VLAN is a Layer 3 network function. A group of network devices can be grouped together into a functionally separate logical network. VLAN and their network traffic will be segmented from other devices that may be connected to the same physical system.

VLB-Video Loopback—A feature in some switchers that allows a video signal to exit to another device, such as a decoder or scaler, and the output of that device is then used as another input to the same switcher. This allows any switcher input to use the decoder or scaler, saving the cost of buying separate units.

VOD-Video on Demand—Unicast streaming video offered by service providers that enables the reception of an isolated video session per user with rewind, pause, and similar VCR-like capabilities.

Voice Coil—Coil of wire inside a loudspeaker driver through which current from the power amplifier flows.

VOIP Systems—VOIP Systems or Voice over Internet Protocol are protocols & technology that allow the digital transmission of phone calls & multimedia over the Internet & other networks. VOIP is relayed over smartphones and other internet devices & requires equipment such as VOIP routers, phone adapters, telephone sets & more.

Volt—The electrical potential difference or electromotive force that will cause current of 1 ampere to flow through the resistance of 1 ohm. Symbolized by “V.”

Voltage—Analogous to electrical pressure. Voltage exists between two points when one point has an excess of electrons in relation to the other point. A battery is a good example: the negative terminal has an excess of electrons in relation to the positive terminal. If you connect a piece of wire between a battery’s positive and negative terminals, voltage pushes current through the wire. Current flow is the electron charge in motion through the conductor. One volt across 1 ohm of resistance produces a current of 1 ampere.

VPN-Virtual Private Network—A method of providing a private network connection via a secure communications tunnel over the Internet. VPNs maintain privacy applying tunneling protocol, encryption, and security procedures.

VS-VideoShift™—A technique used to move a video image around on the screen to prevent burn-in, or destruction of the phosphor. For example, burn-in can occur on flight schedule monitors in airport terminals, where the same image stays on the screen for a long period of time.

VSWR-Voltage Standing Wave Ratio—A term used to evaluate and measure impedance matching in high frequency electronic circuitry and transmission media (coax cables etc.), in order to achieve best signal transmission.

VTG-Video Test Generator—An Extron device that generates video test patterns at scan rates that simulate the most popular applications.

VU-Volume Unit—A unit that is designed to measure perceived loudness changes in audio. 100 VU is 100 percent of the audio that is supposed to be present. VU is measured on a VU meter.

VU meter - Volume Unit meter—For audio systems or recorders, a VU meter is a device that indicates the relative levels of the audio being recorded or played. It is usually calibrated to show a maximum recording level to avoid tape saturation and distortion.

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