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视音频专业术语表

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视音频专业术语表(22)

2017-02-13 09:15 admin 人关注

A B C D E F G H I  J K L M N O P Q R S T U V W X Y Z

V
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. Also see "Retrace."
Vertical Blanking Interval - VBI -
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 Frequency - See "Refresh rate."
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.
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 - Video Graphics Array. A widely used analog interface between a computer and monitor that uses a 15-pin plug and socket. The original VGA resolution was 640x480 pixels.
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.
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 connector - The connector on the video card or computer’s graphics output that is connected to the video input on the local monitor.
Video projector - A device that projects a video image onto a presentation surface.
Video standards - See "SECAM."
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.
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. Also see "Virtual map."
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.
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 - The electrical potential difference or electromotive force expressed in volts. Also see "Volt."
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.
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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