4:2:0 A chroma subsampling scheme. For every four samples of luminance taken, two are taken for each color difference signal, but only on every other scan line. (See 4:2:2.)
4:2:2 A chroma subsampling scheme. For every four samples of luminance taken, two are taken for each of the color difference signals on each scan line.
4:4:4 A chroma subsampling scheme. For every four samples of luminance taken, four are taken for each of the color difference signals on each scan line.
Active Video The portion of the video signal that contains program material.
Additive Color System The color system in which adding all colors together produces white. It is an active color system in that the object being viewed is generating the visible light as opposed to reflecting another light source. The television system is an additive color process.
AFM (Audio Frequency Modulation) A method, developed by Sony, for recording audio in the video track of a BetaSP recording. The AFM channels yield a higher quality audio signal than the standard longitudinal audio tracks. Unlike the longitudinal audio tracks, these tracks can only be recorded along with video.
Aliasing The distortion or artifact that results when the signal reconstructed from samples is different from the original continuous signal.
Amplitude Modulation (AM) A change or modulation in the height or amplitude imposed on a carrier signal. The changes in amplitude are analogous to voltage variations in the signal.
Analog In television, a signal that uses continuously varying voltage to represent the outputs from equipment for the purpose of recording, playing back, or transmitting.
Aperture The dot of electron illumination in a tube type camera that occurs where the beam intersects the face of the target. In analog video, the dot or beam aperture is the smallest size that an element of picture information can be.
Audio Over Ethernet Encoded audio signals using the standards and conventions of computer networking.
Artifacts Errors in the video, which might include chrominance smear, lag, blocking and chrominance crawl.
Aspect Ratio The mathematical relationship between the width and the height of an image. The standard NTSC, PAL, and SECAM analog aspect ratio for television is four units wide by three units high, shown as 4 ´ 3. The aspect ratio for High Definition television is 16 ´ 9.
ATSC (Advanced Television Systems Committee) The next generation of the NTSC, it is the group responsible for the creation of digital SDTV and HDTV standards in the United States.
B Frames The bi-directional frames indicated in an MPEG compression system. The data they contain is extracted from the previous and/or following frames and thus are referred to as bi-directional. These frames cannot stand alone, as they contain only portions of the video data from each frame.
Back Porch The period of time during horizontal blanking that follows the horizontal sync pulse and continues to the beginning of active video.
Bandwidth The amount of spectrum space allocated to each television channel for the transmission of television signals.
Base line Base line refers to the zero-units line of the video signal as seen on a waveform monitor.
Beam A stream of electrons, called the beam, comes from the back end of the tube and scans back and forth across the face of the target on the inside of the pickup tube.
Beam Splitter In a three chip camera, a beam splitter is an optical device that takes the light coming in through the lens and divides or splits it. It directs the light through filters that filter out all but one color for each of the camera chips.
Binary A system of numbers consisting only of zeros and ones. The language in which computers store and manipulate information.
Bit In digital or computer information, a zero or a one.
Bits Per Second (bps) Data communication speeds are measured as so many bits per second (bps).
Bit Rate The number of bits per second, expressed as bps, moving through a digital system.
Bit Stream An encoded compressed stream of video.
Black Burst An analog composite signal that combines the color subcarrier, horizontal sync, vertical sync, blanking, and a black video signal. It is also known as Color Black.
Black Level The measurement of the black portion of the video signal. In an analog television system, this should not go below 7.5 IRE units. In a digital video system, black may not go below 0 units.
Blu-ray Disc (BD) A type of DVD technology that employs a blue-violet laser beam with a wavelength of 405 nm.
Breezeway The part of the horizontal blanking period that goes from the end of the horizontal sync pulse to the beginning of the color burst cycle.
Burst (Color Burst) Eight to eleven cycles of pure subcarrier that appear on the back porch during horizontal blanking. The burst is used as a reference to synchronize analog color circuits in a receiver with the transmitted color signals. It is not modulated and does not have any of the other chroma information in it, such as hue and saturation.
Calibrate The process of standardizing a reference tool, such as a vectorscope or waveform monitor, so that any signal information that is displayed is measured accurately.
Cathode Ray Tube (CRT) The cathode ray tube (CRT) is a vacuum tube containing one or more electron guns, and a fluorescent screen used to view analog images.
Captioning/Closed Captioning Developed to aid the hearing impaired, the process of encoding and decoding typed text so that it may be displayed on a receiver or monitor. In the NTSC closed captioning system, the data is incorporated on line 21. Digital signals carry the data as part of the Ancillary data space.
Charge Coupled Device (CCD) A camera imaging chip consisting of multiple sites operating as capacitors that convert light energy to electrical charges.
Chroma Subsampling The sampling of the color or chroma information in an image. Chroma is sampled less often than the luminance to reduce the amount of data to be stored or transmitted.
Chrominance Pure color information without light or luminance references.
Codecs The many different algorithms used to compress video. The term was derived from the words compression and decompression.
Coherent Light Light that has a single, specific frequency.
Color Bars A test signal that provides the necessary elements for visual setup of video equipment. The basic display includes a white or video-level reference, black-level reference, chroma levels, and hue information. Additional elements also may be included.
Color Black An analog composite signal that combines the color subcarrier, horizontal sync, vertical sync, blanking, and a black video signal. It is also known as Black Burst.
Color Correction The process of correcting the mix of variable colors in any scene of video, generally handled by a software program, such as DaVinci Resolve, during post production.
Color Difference Signal The calculation of the quantity of chroma information in the signal minus the luminance (Y) information (i.e., R-Y, B-Y, and G-Y).
Color Encoding Translating the color video information from its original state to a condensed form for recording and transmitting.
Color Frame The phase or direction of the subcarrier signal with respect to the lines and fields that make up the color picture. In the NTSC system, the color frame is determined by the phase of the color subcarrier at the beginning of line 10 of the first field of each frame. In the NTSC system, there are four fields to the color frame cycle. In the PAL system, there are eight fields to the color frame cycle.
Color Gamut The allowable range, minimum and maximum, of the color difference signals. Within this range, colors will be reproduced accurately on a picture monitor or receiver. Outside this range, certain colors may be either distorted or not reproduced at all.
Color Subcarrier An additional carrier for the color information that is transmitted and recorded within the main carrier of the analog video signal.
Combing When interlaced material is presented on progressive displays, it can lead to a distracting artifact called combing. This leaves fine lines extending from areas of fast motion similar to the teeth of a comb.
Component A format of video that has three separate elements. In component video, these elements include either Y (luminance), R-Y, and B-Y (the color difference signals), or R, G, and B (the individual color signals).
Composite A complete analog video signal that includes all sync signals, blanking signals, and active video. Active video contains luminance and chrominance information encoded into one signal. Composite sync includes horizontal and vertical sync, blanking and color burst signals
Compression The process of reducing data in a digital signal by eliminating redundant information.
Constant or Variable Bit Rate Two different ways to control the flow of bits in a compressed signal. Constant bit rates can be used to compress images in real time, whereas variable bit rates cannot.
Control Track A recorded signal on videotape that allows the VTR scanner or head to align itself with the beginning of each video track. One control track pulse occurs for each revolution of the scanner.
Cross Pulse A monitor display that shows both the horizontal and vertical blanking periods. Also known as Pulse Cross.
Decibel A logarithmic relationship between two power values. In audio it is used to measure the intensity of sound, notated as dB. There are several variations of decibel measurements. For example, a sound 10 times more powerful than 0 dB is 10 dB, and a sound 100 times more powerful than 10 dB is 20 dB.
Decoding The process of reconstituting recorded or transmitted information that has been encoded back to its original state.
Demodulate To take a modulated signal that is imposed on a carrier and recreate the information it represents in its original form.
Diamond Display A display on a vectorscope for the RGB color component signals that indicates the valid limits for the color gamut.
Dichroic The filters inside a chip camera that filter out two of the three colors.
Digital A system that uses binary bits or digits (zeros and ones) to represent sine wave or analog information.
Dolby Developed by Ray Dolby and Dolby Laboratories, it was originally a technique for audio noise reduction. It is also a standardized system for 5.1 channel surround sound called Dolby Digital AC-3.
Downconverting Converting a video signal from a scanning standard with a higher pixel count to one with a lower pixel count.
Downlink A facility for receiving signals from a satellite.
Downsampling Reducing the size of a dataset by reducing the number of samples used to represent the signal. In digital imaging this will result in lost detail.
Drop Frame A type of timecode in which the timecode generator drops, or actually skips, two frame numbers, 00 and 01, every minute except the 10th minute. Drop-frame timecode is clock accurate.
Electron Beam A stream of electrons used to convert light energy to an electrical signal, as in a camera pickup tube, or to convert electrical energy to light, as in a monitor or cathode ray tube.
Electron Gun That part of the pickup tube or receiver that produces the electron beam.
Encoding The process of conforming audio or video to the form required for a specific process or device. In digital this usually refers to compressing to a specific codec.
Equalization The boosting or attenuating of certain frequencies when a signal is recorded or played back so as to more accurately represent or purposely alter the original signals.
Equalizing Pulses Pulses that assure continued synchronization of the video signals during vertical retrace as well as proper interlace of the odd and even fields of analog video.
External Sync A synchronizing reference that is coming from an external source.
FCC (Federal Communications Commission) The commission that regulates the practices and procedures of the communications industries in the United States.
Field One half of a scanned image formed by alternating scan lines. A field can be referred to as an odd field or an even field. In the NTSC system, each field is made up of 262½ lines. There are 2 fields per frame and 60 fields per second. In the PAL and SECAM standards, there are 312½ lines per field, 2 fields per frame, and 50 fields per second.
File Wrapper A delivery container that encapsulates audio, video and metadata.
Flash Designed by Adobe, this was originally an animation container but is now also used for video.
Flash Memory A solid-state recording media using EEPROM (Electrically Erasable Programmable Read-Only Memory).
Footprint The area of the earth that a satellite signal covers.
Frame The combination of the odd and even fields of a video signal. In each frame of NTSC video, there are 525 lines of information, and there are 30 frames in a second. In the PAL and SECAM standards, there are 25 frames per second, each frame containing 625 lines.
Frequency Modulation (FM) A change in the frequency of the signal imposed on a carrier. Frequency changes reflect voltage variations from the output of the originating source. In television, it is the method used for recording analog video information on tape and for the transmission of audio signals.
Front Porch In the analog video signal, that period of time during horizontal blanking that starts at the end of active video and continues to the leading edge of the horizontal sync pulse.
Full Raster The digital image contains the full number of horizontal pixels in an image. See Thin Raster.
GOP The defined Group of Pictures used in the MPEG compression process. The GOP will contain an I frame and may contain B frames and P frames. The group may consist of as few as 1 frame or as many as 30 or more.
Graticule A lined screen in front of a CRT on a waveform or vectorscope, which is used to measure and define the specifications of a signal.
Geosynchronous When satellites are placed in orbit, they are set in motion to move at the same speed as the rotation of the earth, making them stationary above the earth. The geosynchronous orbit is about 25,000 miles above the earth.
Gigabyte (GB) A thousand megabytes, or a thousand million, which is a billion.
Harmonics The multiplication of frequencies achieved by adding the initial frequency or fundamental to itself in an arithmetic progression.
HDTV (High Definition Television) The high-resolution standard for video. HDTV includes a high pixel count, increased line count, and a wide aspect ratio (16 ´ 9).
Hertz Anything measured in “cycles per second” or the number of changes that occur within one second.
Head Individual parts of a magnetic recording device that erase, record, or play back signals on a magnetic media.
Histogram Display A graph that plots the number of pixels in an image at each possible value. Often used in digital photographic systems to measure proper exposure.
Horizontal Blanking In analog video, the period of time in which the electron beam is turned off while it is repositioned to start scanning the next line.
Horizontal Resolution The amount of detail that can be achieved horizontally across an image. This is generally measured as the number of vertical lines that can be accurately recreated horizontally across the screen. In film it is measured in the number of lines per millimeter. In video it is measured by the frequency of the signal that can still be seen as individual black and white lines.
Horizontal Synchronizing Pulses That part of the analog video signal that ensures that all of the equipment used in the creation, transmission, and reception of the video signal is synchronized on a line-by-line basis.
HTML (Hyper Text Markup Language) One of the primary computer languages used on the Internet.
Hue A specific color or pigment. In television, one of the elements that makes up the composite color signal. Hue is represented by the direction of a vector on the vectorscope.
I Frame In the MPEG compression process, the I frame, or intra-frame, contains all the image data and needs no reference to the preceding or following frames. Used as the reference frame for the creation of the B and P frames.
Image Resolution The amount of detail contained in a video image based on the number of lines in the image and the number of pixels per line.
Incoherent Light Ordinary light, such as a light bulb.
Infrared Frequencies above 100 gigahertz and below 432 trillion hertz. Infrared is above the broadcast spectrum and below the visible spectrum. Infrared can be felt as heat.
Interframe Compression A compression scheme that reduces the amount of information required to describe a sequence of images by only preserving the information about what has changed between successive frames.
Interlace Scanning The process of combining two fields of video information. One field has the odd lines of the scanned image and the other field has the even lines. The two fields are interlaced together to form one complete image or frame of video.
Internal Sync The sync signal that is part of the composite video signal in analog video.
Intraframe Compression A compression scheme that reduces the amount of information that makes up an image without reference to any other frame before or after in time.
Intra Picture One frame that is a complete image sampled in detail so it can be used as a reference for the frames around it during the compression process. Also referred to as I frame.
IRE A measurement of units of video information on the waveform monitor graticule. One volt of video is divided into 140 IRE units. IRE is named after the Institute of Radio Engineers,
JPEG Named after the Joint Photographic Experts Group, a process of lossy image compression used for still images.
Kinescope An early process of capturing live television programs on film as a way to to archive them.
Line Frequency In the NTSC monochrome system, 15,750 lines per second, a multiple of 525 lines per frame at 30 frames per second. In the NTSC color system, approximately 15,734 lines per second, yielding 29.97 frames per second.
Linear Timecode (LTC) The original format for timecode recorded as an audio signal. It is also referred to as Longitudinal Time Code.
Logarithrms A mathematical calculation used to simplify large calculations.
Longitudinal Timecode (LTC) Timecode recorded and reproduced as an audio signal.
Lossless Compression In lossless compression, the restored image is an exact duplicate of the original with no loss of data.
Lossy Compression In lossy compression, the restored image is an approximation, not an exact duplicate, of the original.
Low Frequency Effects (LFE) The sixth channel in the 5.1 surround-sound audio system.
Low Pass A filter that allows luminance data to pass, but filters out the higher frequency color information.
Luminance The amount of white light in an image.
Macroblocks In compression, an I frame is divided into 8 ´ 8-pixel blocks and placed in groups of 16 ´ 16 pixel blocks called macroblocks.
Main Profile at Main Level (MP@ML) Main Profile means that I, B, and P frames can be used for compression, and Main Level means that the picture resolution is 720 ´ 480 in NTSC.
Media Exchange Format (MXF) A video wrapper defined by SMPTE to meet the needs of media production workflows.
Megabyte (MB) One thousand kilobytes.
Metadata Additional information that is added to the serial data stream that provides data about the picture and sound for display and other devices.
Mezzanine A moderate level of compression that is an intermediate format between uncompressed footage and highly compressed distribution codecs.
Modulated Carrier A specific frequency upon which changes have been made to carry or transmit information. There are many ways to modulate a carrier such as AM, FM, 8VSB and CODFM.
Motion Vectors During the compression process, the descriptions of distance and direction of macroblock movement within I, P or B frames are called motion vectors.
MPEG MPEG is the name of the standards group, Moving Picture Experts Group. The name is also used to describe a family of data compression schemes used in motion imaging.
MP3 (MPEG Audio Layer 3) An audio compression standard generally used to reduce the storage requirements for music.
Multicasting The transmission of more than one signal in the same spectrum space.
Non-Drop Frame A type of timecode used to label every video frame in numerically consecutive order. It is not altered to reflect the slower frame rate of color television, i.e., it is not clock accurate.
NTSC Named for the National Television System Committee, a method for creating composite analog monochrome television. Also, a method used to create color television based on color difference components modulated on one color subcarrier.
Octave In electronics, like music, a doubling of a frequency.
Oscilloscope A type of measuring tool that uses a video display to view and measure signal strength, frequency, and amplitude.
One Volt “Peak-to-Peak” The strength of a video signal measured from –40 IRE units to 100 IRE units in analog. In digital video, one volt is measured in millivolts, from –300 to 700 millivolts.
P Frames In the MPEG compression process, the P frames, or predictive frames, contain only data that is different from the I Frame. They are not complete images and cannot stand alone.
Packets In the data stream, after the data has been segmented to prepare for transmission, it is inserted in a packet. Packets are then contained in frames.
PAL Phase Alternate Line, a method for creating composite analog color video. The PAL system makes use of two color subcarriers simultaneously that are phase inverted from each other on alternate scan lines.
Pan and Scan The process of panning—or moving horizontally across an image—that can be applied during video transfer to reveal a particular portion of the widescreen image.
Parade Mode A display on a waveform monitor that simultaneously displays the luminance signal and the two color difference signals in sequential order.
Parity A function that provides a check on a set of binary data, for example by notating if it has an even or odd number of ones.
Pedestal The black level in the video signal. Also called Setup.
Persistence of Vision The period of time that the retina, or light-sensitive part of the eye, retains an image. The phenomenon that allows a sequence of individual images to be perceived as continuous motion.
Petabyte (PB) A thousand terabytes, which is a thousand trillion, or a quadrillion.
Pickup Tube The tube inside an analog camera that converts light into an electrical signal.
Pillar Box If the top and bottom of a 4 ´ 3 image is enlarged to touch the top and bottom of the 16 ´ 9 raster, an empty area will remain on the left and right of the image. This is referred to as Pillar Box.
Pixels Picture elements, the individual elements that make up a digital image.
Pixel Aspect Ratio How the width of a pixel compares to its height.
PLUGE (Picture Line Up Generating Equipment) The part of the SMPTE color bar display that may be used to correctly calibrate brightness on a picture monitor.
Primary Color In a defined color system, a color that cannot be created through a combination of any of the other primary colors.
Progressive Scan The recording and recreation of an image as a complete line-by-line frame from a single point in time.
Proxy A lower resolution substitute for large-scale video files.
PsF (Progressive Segmented Frame) A progressively scanned image that has been divided into two fields, each containing alternate lines from the frame. Unlike a true interlaced frame, both fields are from the same point in time.
Pulldown The process of duplicating video fields in order to map a 24 frame per second sequence into 30 frame per second video.
Pullup The process of removing the duplicate video fields introduced during the pulldown process that will restore a 30 frame per second video sequence to 24 frames per second.
Pulse Cross See Cross Pulse.
Quadrature Amplitude Modulation (QAM) A complex form of modulation that is capable of 64 or 256 levels rather than the 8 levels of 8VSB.
Quadrature Phase-Shift Keying (QPSK) Another form of modulation used in Satellite Broadcasting.
QuickTime A commonly used media container format created by Apple.
RAID (Redundant Array of Independent Disks) The recording of data redundantly over more than one hard drive disk to prevent catastrophic loss. There are several varieties of RAID providing various levels of protection.
Rasterizers A scope that takes an image in a vector graphics format (shapes) and converts it into a raster image (pixels or dots) for output on a video monitor.
Retrace During the scanning process, the return path of the electron beam.
Re-Wrapping The process of moving media between containers.
RF (Radio Frequency) That portion of the spectrum that lies between 3 kHz and 300 GHz.
Run-Length Encoding A type of lossless compression commonly used in graphics and computer-generated images (CGI).
Sampling Rate The rate at which analog data is read and the result converted to digital information.
SAP (Secondary Audio Program) In television recordings and transmission, a separate audio channel reserved for foreign languages or Descriptive Video Service.
Saturation The amount of color, or the ratio of luminance to chrominance information (e.g., the difference between red and pink).
Scan Lines The number of rows or lines of pixels that make up a television image. Common numbers are 480 for standard definition in the US, 720 or 1080 for High Definition, and 2160 for Ultra High Definition, or UHD (4K).
Scanner That portion of a VTR that houses the video heads. Also called the drum.
SDI (Serial Digital Interface) The SMPTE standard for the carriage of digital video signals on copper or fiber optic cable.
SDTV (Standard Definition Television) The name given to the original NTSC, PAL, and SECAM television standards.
SECAM (Sequential Colour Avec Memoire) A television standard using 625 scan lines per frame at 25 frames per second, developed by the French and used in several Eastern European countries. In the SECAM standard, there is no fixed color reference. All editing and image switching must be done as non-composite video with the synchronizing done after the fact.
Secondary Colors Those colors that are created by combining any two of the primary colors. In the NTSC system, the secondary colors are yellow, cyan, and magenta.
Server A computer-based storage device dedicated to housing and delivering data. In television systems, these devices may also decode the stored information to uncompressed audio and video signals for use by production equipment.
Setup The black level in the video signal. Also called pedestal.
Signal-to-Noise Ratio The relationship between the strength of the desired signal and the strength of the background noise or undesired information, expressed as a ratio S/N.
SMPTE The Society of Motion Picture and Television Engineers is an organization that sets the technical standards for television and motion pictures in the United States.
Spatial In digital image processing, a reference to where a pixel is on a two dimensional plane.
Spatial Density Resolution The combined pixel and line count in an image.
Spatial Redundancy The repetition of data within a frame that can be removed in the compression process.
Sprites A video object that is static and persistent.
Stereo An audio system consisting of discrete left and right channels.
Streaming Multimedia that is constantly received by an end-user over the Internet.
Sub-bands Images that are tiled into areas that are encoded separately.
Subtractive Color System The physical principle by which the eye perceives color in physical objects. In the subtractive system, an object absorbs all colors except that which the object is perceived to be. That color is reflected and stimulates the retina of the eye. In the subtractive color process, the addition of all colors will yield black, as all colors will be absorbed and none reflected. (See also Additive Color System.)
Surround Sound An audio system consisting of speakers located around the listener that creates a realistic audio environment in which the sound surrounds the listener.
Synchronizing Generator The piece of equipment that produces the synchronizing signals—such as horizontal and vertical blanking, horizontal and vertical sync, and color burst—that keeps all video equipment aligned in time.
Target The face of the pickup tube that is scanned by the electron beam.
Telecine The process that converts film to an electronic form. Telecine also refers to the machine used for the conversion.
Teletext Information that is sent along with the video signal that can be viewed separately from program material. Examples include a list of programs on a cable station or the local weather and news.
Temporal A type of compression that compares the changes between the images over time and stores the data that represents only the changes.
Temporal Resolution The frame rate, regardless of the pixel or line count, is the number of full frames scanned per second. This rate represents what is known as the temporal resolution of the image, or how fast or slow the image is scanned.
Terabyte (TB) A thousand gigabytes, or a thousand billion, which is a trillion bytes.
Test Signals Signals such as color bars, stairstep, multiburst, and cross hatch that are used in the setting up and checking of television equipment.
Thin Raster The digital image that subsamples the horizontal pixels in an image to reduce the amount of data stored and transmitted. See Full Raster.
Timecode A labeling system that is used to identify each frame of recorded video. There are several systems of time code in use worldwide.
Transcoding Converting a video signal with one encoding method into a signal with a different encoding method. In digital compression, converting from one codec to another.
Transform Coding Uses a complex conversion process to turn coded blocks of the image into a compressed image or video file for storage or transmission.
Transponders A channel of communication on a satellite.
Upconverting Converting a video signal from one scanning standard to another with a higher pixel count.
Uplink A facility for the transmission of signals to a satellite.
Ultraviolet Frequencies above 732 trillion hertz are called ultraviolet.
Vector A mathematical representation of a force in a particular direction. In television, it is used to measure color information where the angle represents the hue and the length represents the saturation.
Vectorscope A type of oscilloscope that is used to display the saturation and the hue of the video signal.
Vertical Blanking The period of time in which the electron beam is turned off while it moves from the bottom of the image to the top of the image to begin tracing or scanning the next field of video.
Vertical Interval That portion of the analog video signal that includes the vertical blanking, the vertical sync pulses, and the pre- and post-equalizing pulses. Also, the area where other information that is carried with the television signal—such as captioning, teletext, and satellite instructions—is inserted.
Vertical Interval Timecode A visual encoding of timecode inserted into the vertical interval of analog video signals. As the data is visual, the information may be read when the image is not moving.
Vertical Resolution The detail in an image dictated by the number of horizontal scan lines the image contains.
Vestigial A vestigial element is a part of something that has no useful value.
Video Object Plane (VOP) In compression, a video object plane consists of a sampling of the object over a number of frames.
Video Level A measurement of the luminance level of the video image. In NTSC, the analog video level should not exceed 100 IRE units nor go below 7½ IRE units. In digital images, black may be 0 millivolts and peak video may be 700 millivolts.
Voltage Voltage is measured in units and is the electric energy charge difference of electric potential energy transported between two points.
VU (Volume Units) Properly noted as dBVU, it is a measurement of the strength of an audio signal. Traditionally, 0 VU was the peak allowable transmission amplitude level of an audio signal.
WebM A video container used for the distribution of web files using HTML 5.
Windows Media A compression codec and video container designed by Microsoft.
WiFi (Wireless Fidelity) Referring to any IEEE (Institute of Electrical and Electronics Engineers) 801.11 network that is commonly used as a local area wireless network for laptop computing.
X Axis The line that goes from 0º to 180º is referred to as the X axis.
Y Axis The vertical up and down line that goes from 90º to 270º.