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Audio and Video Definitions Part 3 of 4

P&S -- Pan and Scan, q.v..
PAL -- Phase Alternate Line -- A 625 line 50 interlaced fields per second analog broadcast standard used in many parts of the world, primarily Europe, but not the U.S.A. So named because the chroma subsignal phase is different on each successive scan line to reduce picture artifacts. (NTSC uses such changing phase relationships also.) Programs are not interchangeable with NTSC even though they may occupy the same broadcast channels or be recorded on videocassettes of the same size and shape. Programs can be played back on SECAM equipment where they come out as black and white. There exist VCR's and TV sets that will play all three formats but they are not common in the U.S.A.
Pan and Scan -- Term used to describe a wide screen movie committed to video with a lesser aspect ratio. The picture is zoomed in on so that more or all of the TV screen is filled (to satisfy popular demand and improve vertical resolution), but both sides of the original picture obviously don't fit. A video technician "pans" the conversion machine (e.g. telecine) back and forth to capture what he considers or what he was told is the most important part of each scene while cropping the sides. Even film to film copies, notably 16mm and 8mm prints, have been made using the pan and scan technique. When you see the notice "... formatted to fit this screen ..." at the start of a movie broadcast on TV, that refers to the pan and scan transfer. In addition to losing "space" as the sides of the picture are cropped, movies as broadcast often lose "time" as they are "edited for (removal of possibly objectionable) content and to run in the time allotted".
Panamorph -- Trademark for an anamorphic lens that can be attached to many home theater or data grade video projectors to convert a 4:3 image to 16:9 or a 16:9 image to 2.35:1. The lens is advantageous when the best quality of image is achieved using the native lesser aspect ratio of the projector.
Passive Crossover, Filter, Switcher, etc. -- Refers to a circuit or group of electronic components that do not require any power other than the energy present in the input signal to perform the desired function.
Passive Radiator -- A woofer speaker cone that has no voice coil and whose vibration is caused by sound waves produced by another speaker in the same cabinet. It allows for some reinforcement of bass from the sound waves generated behind the powered speaker and also maintains the sealed cabinet needed for proper performance of acoustic suspension speakers.
Pay Per View -- Service offered by some cable TV or other program providers allowing a viewer to order a program by telephone (or nowadays sometimes directly through the cable TV tuner) and the system "unlocks" the tuner to permit viewing of the program. Generally applies to programs with predetermined fixed broadcast times; programs that are broadcast only when someone orders them are referred to as "video on demand".
Pb, Pr -- Refer to the two color component video signals that accompany luminance (Y) to make up analog component video. Specifically, Pb = 0.564 ( B-Y ) and Pr = 0.713 ( R-Y). The normalizing factors were chosen so that the signals have a maximum of 0.500 volts and a minimum of -0.500 volts while Y varies from 0 to 1.000 volts not counting the negative going sync.
Peak Music (or Momentary) Power Output (PMPO) -- Primarily an advertising gimmick. A measure of audio amplifier power output whose justification is that real life audio contains isolated short term peaks and can be faithfully reproduced by an amplifier that otherwise could not reproduce a continuous sine wave with such peak to peak voltages. There is no mathematical formula that relates a given stated PMPO with continuous sine wave output. Different equipment manufacturers compute PMPO using different methods that are often intended to yield the largest figure in watts for which measurements can prove. Amplifier power supplies contain capacitors that hold a charge that can act as a power reserve, and output sustained for but a a few milliseconds can sometimes be on the order of ten times the sustainable continuous power output.
Peek-A-Boo Scan Lines -- On what should be a non-interlaced display, usually an LCD panel, receiving a non-interlaced video signal, what appears to be every other row of pixels dark producing "gaps between scan lines" suggestive of interlaced video displayed on a CRT. It is more noticeable with eye movement following moving subjects. We believe it is intentional processing that darkens alternating rows of pixels on alternate approximately 1/60'th second intervals to prevent comet trails and/or uses temporal dithering to achieve certain intensity (gray scale) steps.
Persistence -- Measure of how long phosphors (such as in a CRT) continue to emit light after excitation (such as from an electron beam) ceases. Long erpersistence reduces the visibility of gaps between the odd scan lines as the even scan lines fade etc. but increases motion blur.
Perverse Telecine -- Situation in 2-2 pulldown (such as for film to PAL video conversion) where pairs of (interlaced) video fields are arbitrarily treated as complete video frames and where each such "frame" contains content-wise non-matching odd and even fields.
Phone Plug/Jack -- A plug (and matching jack) 1/4 inch in diameter, the plug is just over an inch long. Originally used in telephone switchboards, it is still used for audio applications. A single plug can be used for two channels (e.g. stereo) when it has a third contact (the ring) between the usual tip contact and the rest of the plug further back (the sleeve). Similar plugs (and jacks) also come in a 1/8 inch diameter (Mini) size for mono or stereo and a 3/32" diameter (Micro) for mono only.
Phono Plug/Jack -- An RCA plug/jack. Originally used with record players.
Picture Height, as in "lines per picture height" -- Reference distance measurement for resolution of TV screens, used for horizontal as well as vertical discussion. So chosen because much of the time the resolution of a particular TV and video system was the same for a variety of screen sizes. Also chosen because resolution was traditionally measured across the largest circle that fits in the area referred to and for a TV screen the diameter of such a circle equals "one picture height".
Picture In a Picture -- A feature on TV sets whereby a small picture for a second program can be displayed in or near one corner of the screen. The viewer can switch back and forth as to which program occupies the whole screen. In order for two broadcasts to be so seen simultaneously the TV set must have two tuners (channel selectors). More commonly there is only one tuner and the second program must come from a VCR or other local source. Also, Picture Outside Picture for the second picture being outside the boundaries of the first picture which does not fill the screen.
Pillarbox -- Video formatting, typically for pictures of a lesser aspect ratio than the screen shape, where the picture fills the height of the screen and unused screen area is at the sides. Also (rarely) used to ensure that material at the extreme sides is not cropped due to overscan. See, also, Letterbox, Windowbox.
Pinna -- What we refer to as (or the exposed part of) a person's (or animal's) ear. It helps gather more sound waves than would otherwise reach a person's eardrums and also has directional characteristics so the person can better tell what direction a sound is coming from.
PIP -- Picture in a Picture
Pits and Lands -- An actual description of how data is encoded on an optical disk such as a CD or DVD. The reflective layer is smooth and flat except where pits or holes all in a continuous spiral and representing one continuous stream of digital data have been pressed or burned into the reflective layer.
Pixel, or Pel -- Picture element; the smallest spot on the screen that can be resolved as having a different brightness or color from what is next to it. The "number of pixels vertically" is equal to the number of scan lines; for example if you block off all but a narrow vertical stripe on the screen, you will see a series of dots, one per scan line. For a computer screen or digital video, the screen is divided into several hundred "grid positions" horizontally as well; a pixel must be exactly one of the grid positions, not half of one and half of the next. For analog TV pictures, we can say that the number of pixels horizontally is equal to the maximum number of alternating black and white dots that can be reproduced all the way across the screen, which equals the aspect ratio times the number of "lines of resolution per picture height" horizontally.
Pixellation -- A checkerboard or quilt like coarse grainy effect of tiny or even medium sized squares over portions of a picture. It is used to disguise or censor part of the picture content or is encountered due to inability of the processing of digital video to keep up with subject motion and other frame to frame changes.
Plasma Display -- Directly viewed digital video display consisting of a transparent panel covered with fine juxtaposed vertical gas filled phosphor lined tubes or troughs and with related electronics including rows of fine juxtaposed horizontal elements behind. To form a video picture, minute portions of the gas in each tube can be excited and the phosphors at those places made to glow forming pixels.
PMPO -- Peak Music Power Output; Peak Momentary Power Output, q.v.
Posterization -- Visible steps , bands, or stripes of slightly different shades of color (or gray), or a contour map effect, in what should be a smooth gradation of color shading (or gray shading). Caused by inability of the system to represent a large number of different shades of each color.
Pot -- Potentiometer, a kind of variable resistor, namely one with a fixed resistance element and with a sliding "center" tap. Usually found behind volume and tone control knobs and graphic equalizer sliders, also commonly used as the screwdriver adjustments in back of a TV set to fine tune convergence, pincushion distortion, etc.
Power Bandwidth -- The frequency range over which an amplifier can deliver at least half (within 3 dB of) its rated output in watts. This is not the same as frequency response which describes uniformity of output at lesser power levels with respect to input, over a frequency range.
PPV -- Pay Per View.
PQ -- Picture Quality.
Preamplifier -- (1) Amplifier stage used to bring a minute signal such as from a phonograph cartridge or a microphone to the usual line level (typically about one volt) so the signal can be treated similarly to other signals being switched and fed into a main amplifier. Such a "preamp" can be a stand alone component or can be combined with a main amplifier or power amplifier. (2) An audio component with switching circuits for audio and/or video sources and likely to contain but may not necessarily contain a phonograph preamplifier and/or surround sound processing circuits and/or optical audio input processing and/or radio broadcast tuners. Not contained are amplifier stages which drive loudspeakers.
Pre-Pro -- Short for "pre-amplifier processor" which in turn is another term for a pre-amplifier that includes features such as audio/video switching and/or video conversion (composite to S-video, etc.).
Presence Control -- Control in a three way speaker system that varies the signal level applied to the mid-range speaker. (The woofer level is seldom controlled.)
Presets -- Means for programming a tuner to allow quick "one button" selection of specific desired stations (as frequencies or channels). This can be implemented mechanically using cams and levers, or electronically using memory and computer circuits.
Prime, as in Y', R', etc. -- The video signal or its components are correctly referred to by the various terms Y, R-Y, G, Cb, etc. without the apostrophe or "prime symbol" when the signal has not been modified to compensate for the gamma of the picture tube. The prime symbol is added, as in Y', Cb', etc. to refer to a video signal after gamma compensation. Prime Disclaimer -- To simplify things, all of the descriptions on this web site ignore the gamma compensation, and the terms Y, R-Y, etc. are used without the apostrophe throughout. This represents a slight dumbing down and departure from correctness of the material on this web site.
psf -- Segmented Frame, q.v. Unfortunately often confused with "fps" for simply "frames per second"
Pulldown -- (1) The general term used to describe committing motion picture film material to video. So named because a projector or telecine machine typically has a "pulldown claw" to advance the film one frame at a time past the gate, or window through which the projection beam or other light source passes. The most common pulldown procedure is called 3-2 (or 2-3) pulldown (q.v.) since for immediate broadcast, alternating film frames are scanned three times and twice respectively before the pulldown claw is activated. (2) The slight slowing of a motion picture, video, or audio program for synchronizing purposes, or to cause it to run in the time allotted without editing of material.
Pullup -- The slight speeding up of a motion picture, etc. for the purpose immediately preceding.
Push Pull Woofer System -- Speaker system with two woofers or subwoofers, one mounted normally, the other facing into the cabinet. The speakers are wired so both cones move in the same direction relative to the cabinet exterior, or in opposite directions relative to their respective frames and magnets. This configuration causes some even harmonic distortion caused by the speakers to cancel out.
PVR -- Personal Video Recorder; a digital video recorder.
Glossary Q
Q (Quadrature Color Component)-- Video subsignal representing yellowish green to purple color content, used in NTSC broadcasting. See I, Q.
QAM -- Quadrature (Amplitude) Modulation .
Quadrature Modulation -- A form of amplitude modulation where two signals can be modulated on the same carrier producing a single modulated signal with differing sidebands. The encoding of the two original signals involves phase relationships. It is not true that one signal is represented by the lower sideband and the other by the upper sideband, but both sidebands are needed to recover the original signals. A very common use is combining the two color components (Pb, Pr) of component video into a single color signal which in turn may be combined with luminance to form a single signal (composite video) that carries all of the essential video information. In video color practice a considerable amount of the higher frequency content and therefore horizontal resolution of the color components is lost so that the overall signal can be constrained to a certain bandwidth.
q.v. -- (quid videt; "which see") -- Means to go to or look up the description of the item immediately preceding. On this web site, sometimes we provide a link so if you click on the "q.v." the respective page or paragraph appears.
Glossary R
R-Y (approximately Pr for analog video or Cr for digital video or V for some applications including PAL)-- Video signal component consisting of the picture red content from which has been subtracted the overall luminance (Y). See B-Y and also see Prime Disclaimer.
Radio Frequency -- For video, refers to the antenna inputs to a TV set, or the overall video signal containing many channels modulated on carrier frequencies as input to the TV set's tuner. Also refers to audio channels encoded on video disks by being modulated onto carrier frequencies as if they were going to be broadcast.
Radio Frequency Interference -- (1) Interference to radio and TV programs imparted when the programs are still modulated on carrier waves, during broadcast or during transmission via a cable system. (2) Electromagnetic energy capable of causing interference to radio and TV programs being broadcast.
Rainbow Effects -- Red, green, or blue edges on moving subject matter caused by the sequential projection of red, green, and blue picture content from a video projector with a single image generating element and a color wheel, which projectors include all modestly priced DLP projectors. Although the better color wheel projectors produce sets of red, green, and blue sub-images that match in content and also more flashes per second, the viewer's eye movements may still result in the viewer's seeing the colored edges.
Rainbow Swirls -- See Cross Color.
RAM -- Random Access Memory.
Random Access Memory -- The memory chips in a computer (or memory cores in very old computers). More generally, data storage where desired material or empty storage space can be located computationally or by lookup, and then accessed directly, specifically without having to riffle through intervening material and without having to take hints from indexing along the way. By contrast, tape is a sequential access medium as opposed to a random access medium.
Raster -- The illuminated rectangle on the face of a picture tube produced by the scan lines whether showing a picture, a solid color, or snow (noise). "Underscan is when the raster does not fill the screen."
RBE -- Rainbow Effects, q.v..
RCA Plug and Jack -- A press-fit plug and jack connector with one conductor plus ground introduced (in the 1930's?) by Radio Corporation of America, now part of Thomson Electronics. The jack is a metal stud a little larger around than a pencil (about 3/8 inch) with a center hole that a small lollipop stick would fit (about 1/8 inch). The matching plug has one fat (1/8 inch) center pin that represents the live conductor, and a shell that presses onto the jack stud and that is almost always grounded. Normally the center pin is connected to the center conductor of a coaxial cable and the shell is connected to the shell or shield of the cable.
Reactance -- Resistance to the flow of alternating current within imposed by a coil of wire together with any metal about it, over and above the resistance to direct current the same coil of wire assembly imposes.The greater the frequency of the alternating current, or audio/video signal, the greater the reactance of a given coil.
Read Only Memory -- Data storage that may not be altered or modified during normal or routine use
Real Time Counter -- A display of elapsed hours, minutes, and seconds on a disk player or tape player, the information derived from video frames or from timing data encoded on a tape, contrasted with a counter that registers according to revolutions of a reel or spool or according to some other arbitrary method.
Rear Projection TV (set) -- A TV set in a "boxy" cabinet and having an optical system consisting of (for color TV, usually three) small CRTs or LCD panels or other picture forming elements, together with lenses and mirrors and perhaps a projection lamp used to project a picture against the back side of a translucent panel that serves as the viewing screen. RPTV's typically have screens ranging from 35 to 70 inches in size. The same concept is also used for small film and viewgraph viewers.
Receiver -- The best short definition of this term as it applies to electronics is "a device that captures an over the air broadcast (or satellite or cable or microwave transmission) and presents it for listening, data processing, or viewing". A "television receiver" is the complete TV set as we know it, which includes the cabinet, picture tube, loudspeaker, channel selector, usually a built in antenna, and all the related electronics. A "radio receiver" f.k.a. "radiotelephone receiver" is a "radio" as we know it, with built in antenna, tuning dial, loudspeaker, volume control, etc. But a "stereo receiver" generally does not include the antenna or loudspeakers, although it refers to the unit with everything else needed to receive FM stereo broadcasts, namely the case with built in radio tuner and tuning dial, amplifiers, volume and tone controls, sometimes pre-amplifiers for phonographs, etc. And an "audio visual receiver" generally includes a radio broadcast tuner, switching for video sources, audio amplifiers, but not a television broadcast tuner.
Red Push -- Accentuation of reds for the purpose of making flesh tones more attractive although not necessarily more correct. It is usually accomplished by designing of the color decoder to not conform strictly with the video standards and as a result it usually cannot be eliminated.
Regional Code-- Coding on a DVD intended to restrict playing of the DVD and therefore restrict release of the program content to specific geographic regions around the world. Roughly, Region 1 is the U.S.A. and Canada, Region 2 is most of Europe, Region 3 is most of Asia except China, Region 4 is the Australian continent, Mexico and South America, Region 5 is Russia, most of Africa, and India, and Region 6 is mainland China. A region code of zero means no restrictions.
Registration -- Convergence of the sub-images in each of the primary colors as it applies on the screen with respect to the three CRT's or LCD panels of a projection TV set, or on the printed page with respect to plates on printing presses, as opposed to with respect to electron beams that paint one spot at a time on a direct view CRT.
Repeater -- An amplifier (together with receiving and transmitting antennas if the signal is transmitted through the air) not at the beginning or end of a long transmission path and used to boost the strength of signals transmitted along/over that path. Applications could include the distribution of video within a building.
Resampling -- see Sampling
Resolution -- (1) Ability of a system to represent detail, expressed as pixels, lines or line pairs over some distance such as inches. For visual media, lines of resolution or line pairs of resolution is traditionally measured across the largest (perfect) circle that fits in the area being referred to. For a standard TV screen, such a circle would span 3/4 of the screen width. A lot of advertising deception involves mis-stating the lines of resolution to span the entire screen width. The number of lines of resolution horizontally need not equal the number of lines of resolution vertically (or diagonally). Because pixels can straddle and thereby lose detail in a digital system but not in an analog system, the number of pixels does not equal the number of lines of resolution (see Kell Factor). If resolution is expressed in pixels, both the horizontal pixel count and vertical pixel count spanning the entire screen should be specified. (2) Any one of a collection of formats for digital video in the sense that each "resolution" consists of a given number of pixels expressed as so many pixels horizontal by so many pixels vertically such as 640 x 480, together with other parameter specifications such as so many frames per second and/or so many microseconds for a horizontal retrace interval. So named because such a format can represent visual material with that many lines of resolution under ideal circumstances. Click here for more discussion on resolution.
Resolution Pumping -- The entire picture becomes slightly less sharp (typically when something starts moving) and sharpens up again a little later (typically when the scene becomes still). A common cause is less than sophisticated conversion from interlaced to progressive scanning (de-interlacing)..
RF -- Radio Frequency(ies). RFI -- Radio Frequency Interference.
RGB -- A video signal transmitted as three components (subsignals) using three wires and which subsignals are the respective picture color content of red, green, and blue, respectively. R, G, B -- The red, green, and blue components referred to separately. RGBHV -- The RGB signal where horizontal and vertical synchronization (sub)signals are carried on fourth and fifth wires, respectively. RGBS -- The RGB signal where horizontal and vertical sync. are combined (composite sync.) and carried on a fourth wire. RGsB -- The RGB signal with sync. combined with the green signal so that just three wires are needed. (There are no official designations for sync. on blue or sync. on red although these subsignals occasionally have sync. included as well.). RGBcvbS -- The RGB signal with sync. provided by an accompanying composite video signal with the same scan and frame rate on a fourth wire, often encountered with equipment using SCART jacks. Not all equipment that accepts RGBS will work with RGBcvbS although external devices exist that will strip off the (positive going) composite video from the (negative going) sync. pulses.
RIAA -- Recording Industry Association of America, a group that develops standards and policies for recordings. RIAA Curve -- A standardized frequency response curve (or contour) for recording of phonograph records, notably with attenuation of bass frequencies during recording to reduce the excursion of the cutting stylus, permit closer spacing of record grooves, and increase possible recording time, together with a compensating contour with bass boost for use at playback time.
Ringing -- In video, closely spaced repeated ghosts of a vertical or diagonal edge where dark changes to light or vice versa, going from left to right. The electron beam upon changing from dark to light or vice versa instead of changing quickly to the desired intensity and staying there, overshoots and undershoots a few times. This bouncing could occur anywhere in the electronics or cabling and is often caused by or accentuated by a too high setting of the sharpness control.
RMS -- Root Mean Square, q.v.
ROM -- Read Only Memory.
Root Mean Square -- The peak to peak voltage value of alternating current that is a square wave and that is otherwise equivalent to AC of said voltage that is a sine wave. The value is 0.707 times the sine wave peak to peak value. For amplifier power measurements, RMS is used to describe power output when the signal is a continuous sine wave.
RPTV -- Rear Projection Television (set)
Rumble -- Low frequency mechanical noise or vibration (such as from a motor) picked up by a phonograph needle and cartridge assembly and amplified, or picked up by a phonograph record cutting stylus assembly and recorded on the disk along with the audio.
Glossary S
S/N -- Signal to Noise Ratio.
S-VHS or SVHS -- Super VHS -- A variation of the VHS videotape format where the luminance resolution is about 400 TV lines. (The color resolution is the same as regular VHS, about 32 lines.) S-VHS VCR's will play regular VHS tapes and can record in regular VHS format as well, but regular VHS VCR's will not play S-VHS format tapes. Because S-video (separated Y and C) cabling is originally used for S-VHS VCR's, the term S-VHS is sometimes mistakenly used when "S-video" was intended.
S-Video -- Super video, also called Y/C -- A video signal transmitted as two subsignals requiring two separate wires: luminance (technically referred to as Y) and color ©. Although commonly found in S-VHS VCR's, this signal is not limited to such VCR's. Note: The C portion is already modulated on a subcarrier, 3.58 MHz (approx) for NTSC as if to be combined with the Y portion to become composite video, except not necessarily bandwidth limited to meet broadcast specs. Note: S-video can represent todays standard definition interlaced video signals only. Looking into the S-video cable plug, with the plastic pin in the 6 o'clock position, upper left (metal) pin is luminance, upper right pin is color, center metal pins are ground for the respective pins above them. Luminance and color are recorded as separate signals on all VCR's, using different subcarrier frequencies than S-video.
SACD -- Super Audio Compact Disk (made by Sony)
Safe Area -- The portion of the picture area, usually marked so in the camera's viewfinder, where important material, action, or text titles should be confined to. The purpose is to make sure that everything important can be seen even when the TV set has a lot of overscan, or to create movie and video programs that can be acceptably cropped into a choice of two or more picture aspect ratios. For video, the safe action area, where important subject matter is generally confined to, is the inner 81% of the picture area after discounting edge strips 5% of the respective screen dimension in width. The safe title area, used for positioning text such as credits, is the inner 64% of the picture area after discounting edge strips 10% of the respective screen dimension in width.
Sampling -- The process of converting an analog entity (such as a picture or a soundtrack) to digital form. In the case of a picture, a large number of evenly spaced spots (samples) are taken and each represented as one or more numbers for brightness (luminance) and color. These spots are referred to as picture elements or pixels. The more samples are taken, the more accurate (with higher resolution) an image can be reconstructed from the samples. For DVD, the image is 720 samples wide by 480 samples high for a total of 345,600 samples (may vary slightly). Even analog TV has sampling; each scan line is a discrete (as in digital) sample in the vertical direction although it is continuous (analog) in the horizontal direction. Resampling aka scaling -- The conversion of a set of samples to become a larger or smaller set of samples, for example a 720 by 480 pixel video frame to a 360 by 240 pixel video frame. Picture quality is lost irreversibly whenever resampling is done to yield a set of samples less than twice the original set both horizontally and vertically. Significant picture quality loss occurs when resampling is done to yield a set of samples less than about 140% (or reciprocal of the Kell factor) of the original set in each direction. This is because the only way to figure out what each new sample should be is to interpolate (guess based on the nearest old samples).
SAP -- Second Audio Program.
Satellite Speaker -- Speaker system with mid-range and tweeter speakers (or a single speaker for mid- and high frequency sounds), suitable for being mounted on a wall or ceiling and intended to be used together with a woofer in a separate cabinet. Many sound systems have several satellite speakers for surround sound and just one woofer or subwoofer given that listeners generally cannot tell from what direction low frequencies come.
Scaling -- The reformatting of video or digital pictures to occupy a different number of scan lines or a different number of discrete pixels horizontally or vertically. Scaling is also referred to as "resampling". See Sampling. Scaling is done to zoom an image on the screen without spreading out the existing scan lines, or to change the video from one format to another, for example HDTV to NTSC or NTSC to SECAM. Video Scaler -- Electronic device used to perform scaling, usually with a choice of scalings not necessarily an even multiple or fraction of the original scan line or pixel count.
(Horizontal) Scan Rate or Scan Frequency -- Number of scan lines per second, including scan lines representing the vertical retrace interval, usually expressed as kilohertz. In the U.S., for NTSC it is about 15.73 KHz, for 1080i HDTV it is about 33.75 KHz, for 720p HDTV it is about 45.0 KHz.
Scan Velocity Modulation -- An electronic means of automatically varying the speed of the electron beam as it sweeps across the screen, so as to make light to dark transitions representing edges of subject matter more sharply defined. Advanced videophiles tend to disfavor it, turning it off whenever possible.
SCART (Syndicat des Constructeurs d'Appareils Radiorecepteurs et Televiseurs)-- Refers to a 21 pin plug and jack combination often used in European video equipment. It carries both video and audio, offering a choice of carrying composite video and S-video, composite and component video, or composite and RGB. Also called a "Euro" or a "Perri" connector.
Screen Door Effect -- The fine grid of thin dark horizontal and vertical lines resulting from the gaps between illuminated spots (pixels) in a (usually projected) picture generated using digital displays such as LCD.
Screening Room -- A small private theater, typically used by movie producers, reviewers, and critics.
SDE -- Screen Door Effect.
SDI -- Serial Digital Interface -- A set of standards for digital transmission of video over 75 ohm coaxial cable preferably using BNC connectors.. For video it usually uses a 270 megabit per second data transmission rate and it supports the standard NTSC based video formats and ATSC video formats. It is suitable for transmission over 100 feet contrasted with DVI and HDMI which are limited to about 30 feet. The data formats are not the same as for DVI or HDMI which are also in widespread use today (2005).
SDTV -- Standard Definition Television.
SECAM (Sequential Couleur Avec Memoire)-- A 625 line 50 interlaced field per second analog broadcast standard used in Europe, primarily in France. Alternating scan lines carry R-Y and B-Y color difference signals respectively. The TV must contain delay (memory) circuits to make available both the R-Y and B-Y signals, which are then shared by (as common to) each pair of scan lines. Chroma resolution is half the luminance resolution vertically. Programs are not interchangeable with NTSC even though they may occupy the same broadcast channels or be recorded on videocassettes of the same size and shape. Programs can be played back on PAL equipment where they come out in black and white. There exist VCR's and TV sets that will play all three formats but they are not common in the U.S.A.
Second Audio Program -- An audio program or track other than used for stereophonic sound, such as the same program in a different language, or unrelated material such as weather forecasts, transmitted as the subordinate audio subchannel in a TV broadcast and receivable on TV sets with MTS (multichannel TV sound).
Segmented Frame -- One method of transmitting film source video, where each film frame's video is transmitted as two parts or segments, specifically odd scan lines and then even scan lines, that is, as if interlaced. Unlike traditional interlaced video with 3-2 pulldown, each field's worth of content is transmitted just once, and the overall frame rate is 24 (23.976 for NTSC) complete frames per second for U.S. films. It is still referred to as progressive scan since each pair of segments is (or should be) derived from the same film frame or source image. The notation often juxtaposes the letters P, S, and F, as in 480psf24 and this should not be confused with "fps" for simply "frames per second". (We use the notation [email protected] or [email protected] or [email protected] when including the frame rate.)
Selectavision -- Trademark of Thomson Electronics (which acquired Radio Corporation of America; RCA), refers to certain VCR's and a now obsolete playback only video disk system that RCA marketed. See, also, CED.
Set Top Box -- Currently refers to an external tuner for HDTV broadcasts, typically placed on top of the TV set.
sf -- See Segmented Frame.
7.1 -- Sound system with left, center, and right front speakers, left and right side speakers, left and right rear speakers, and a subwoofer. See Surround Sound.
75-Ohm -- Refers to TV antenna connections made using a round (coaxial) cable. Also refers to the impedance of all common video connections. For video cables, almost any cable will transmit an intelligible picture but the correct impedance is 75 ohm and also cables should have adequate bandwidth.
Shadow Mask or Aperture Grill -- A grill with holes or slots mounted about an inch behind the glass screen of the picture tube. It physically constrains the electron beam intended for the red phosphor dots (or stripes) from hitting anything but the red phosphor dots, and so on. Normally the exact shadow mask that will be installed in a picture tube is used to assist in printing the phosphor dots on the screen of that picture tube, as the optical process of printing the phosphor dots closely mimics the path of the electron beam. Mating a shadow mask with a screen panel early in the manufacturing process prevents slight variations from one mask to another from affecting the quality of the finished picture tubes.
Shimmering -- (1) Flickering halos or pinpoints of light caused by stray light rays from imperfect rear projection screen layers, which contain lens elements or from processing of the video signal by imperfect electronics. (2) Accentuated flicker of thin picture details moving up or down at certain speeds that interact with the scan rate.
Shrill -- Refers to sound with an abundance of content in the mid treble (1000 to 3000 Hz) range, often sounding obnoxious or even approaching the pain threshold due to this content.
60i as in 1080@60i-- 60 or 59.94 (interlaced) fields per second, each field with half as many scan lines as the number preceding the at sign (as the 1080 in the example). Also 48i, etc. for 48, etc. fields per second for example used in some film source transmission formats. Also 60p or 60, 30p or 30, etc. for that many (progressive scan; full) frames per second.
Skating -- Tendency of a phonograph tone arm to swing, usually towards the center of the record as the record rotates, which tendency puts an undesired greater stylus pressure on the groove inner wall compared with on the groove outer wall. Anti-Skating -- Mechanical compensation, usually involving springs, that counteracts skating. Calibration is typically done using a "record" with no grooves.
SKU -- Stock Keeping Unit.
SLP -- Super Long Play; Extended Play.
Slug, or Tuning Slug -- A movable ferrite core used to adjust a coil's behavior (inductance). May be the screwdriver (sometimes hex wrench) adjustments in back of a TV to adjust convergence, etc.
Small -- Setting on an amplifier that reduces the amount of low frequencies delivered to speakers other than a subwoofer. The purpose is to prevent overdriving the other speakers with the lower frequencies, and may be required with certain types of speakers. On some amplifiers the small setting is required to activate the subwoofer channel.
SMPTE -- Society of Motion Picture and Televison Engineers, also standards for video signal formats, video production and television set calibration said society has developed.
Soft Matte -- Refers to wide screen movies that were actually filmed wide-angle using the entire 4:3 aspect ratio film frame and where the projectionist adjusts mattes (aperture plates) to hide the top and bottom edges leaving the middle as a wide screen view. Sometimes what will become a wide screen film is shot in the 4:3 aspect ratio so that when committed to video, the entire width of the picture can be included and also the entire TV screen would be filled. Sometimes the top and bottom edges intended to be matted are not suitable for inclusion in a video edition because the special effects added later fell short of these areas or because extraneous things such as microphone booms were caught in those areas. This writer believes that when a wide screen movie that was shot soft matte is offered on video with extra material of interest such as director's notes, scenes from alternate scripts, or behind the scenes footage, the movie itself should be transferred to video unmatted if not anamorphic. The material at the top and bottom edges is behind the scenes material that can be given free of charge on a spherical transfer with no extra effort by the producer and no loss of picture quality.
Soft Telecine -- Encoding film source as 24 fps on a DVD or other digital media and the player duplicates frames or fields as needed (3-2 pulldown, etc.) to output the proper frame rate to the TV.
Solarization -- Above a certain level of brightness, what should be brighter content shows up as darker, giving a partial photographic negative effect. For a gray scale test pattern you might see: black, very dark gray, dark gray, medium gray, light gray, very light gray, light gray, medium gray instead of white where white belongs. Usually this indicates some malfunction in the video circuitry or display element. Solarization can occur when film is overexposed and the effect is sometimes used artistically for photographs.
Sonotube -- Trademark for a line of rigid cardboard (not corrugated) cylinders available in varying sizes and used as forms for poured concrete pillars and footings. Sometimes used for speaker enclosures.
Sound Pressure Level -- A measure of the intensity of sound or audio.
SP -- Standard Play.
SPDIF -- Sony - Phillips Digital Interface -- Format for transmitting audio digitally over coaxial cable.
Spatially Adjacent -- Refers to scan lines immediately juxtaposed on the screen. The term is needed when discussing interlaced video where juxtaposed lines are (for NTSC) 1/60 second apart in terms of when they were transmitted, received, and "drawn". See, also, Temporally Adjacent.
Spherical -- Opposite of "anamorphic"; refers to photography or cinematography where a picture is recorded in its actual horizontal to vertical proportions. That is, it is not "squished" to fit on a film frame with a lower (usually 4:3) aspect ratio and where a special lens would be needed to project it in the correct proportions. In the case of a wide screen movie, the image occupies the center portion of the film frame and the top and bottom edges of the frame are hidden by the projector aperture plates if they were not already covered and left blank by similar plates in the camera during filming. Also, having the curvature of the surface of a sphere or part thereof. At one time, color picture tube faces were spherical where the sphere radius was equal to the distance from screen to electron gun, so that it was easier to design the picture tube and supporting electronics to have little or no convergence or focusing errors.
Spider -- (1) The part of a speaker cone's suspension at the voice coil that keeps the voice coil centered within without rubbing against the magnet assembly while permitting axial (in and out) movement of the voice coil. (2) An insert that fits in the center hole of a 45 RPM record to allow the record to be played on a (multi-speed) phonograph with a smaller center spindle.
SPL -- Sound Pressure Level.
Spoke Time -- Time, usually expressed in percent, when a boundary between two color cellophanes in the color wheel of a single chip DLP projector or similar projector is crossing the light beam. During this time all pixels in the display element must represent black as the beam is in two colors and it is impossible to predict the proportions. The larger each cellophane is relative to the display element the lesser the spoke time is. A lesser spoke time means more overall light output from the projector, all other things being equal.
Square Wave -- Waveform which when drawn graphically consists of straight up, straight across, straight down, straight across, straight up, and so on. In terms of frequency content it consists of a fundamental and all of the odd harmonics in certain proportions. The significance of a square wave in amplifier testing is that frequency response and presence of certain distortions can be evaluated by examining on an oscillocope the reproduction of square waves of just a few different fundamental frequencies.
Squawker -- Mid-range speaker.
Squeeze Trick -- See Vertical Squeeze Trick.
Stairstepping -- The jagged appearance of sloped lines or edges inherent to the reproduction of a picture using pixels and/or horizontal scan lines.
Standard Definition -- Refers generally to NTSC and PAL, and to digital or analog TV signals and equipment that provides picture quality roughly the same as NTSC, that is, having about 500 scan lines and with the smallest picture details a little wider than 1/1000'th the screen width.
Standard Play -- The fastest (and first introduced) tape speed on a VCR or VTR, yielding the best recording quality although the least recording time for a given tape.
Stock Keeping Unit (SKU) -- -- A unique number associated with a manufacturer and model/style of merchandise to keep track of inventory in factories and stores. Usually pronounced "skew" rather than "escayoo" or as the entire phrase.
STB -- Set Top Box.
Studio Monitor -- Marketing term for a TV receiver, TV monitor, or sometimes just a speaker system intended for use in studios to permit monitoring of a program during production or prior to broadcast and which unit is supposedly of a higher quality than similar products marketed to consumers.
Stylus -- "Needle" for a phonograph. The term may refer to either just the pointed tip (nowadays usually a tiny diamond) that traces the record groove, or the entire replaceable assembly that includes the tip, a shank the tip is part of or attached to, and perhaps other components such as a small magnet (if the phonograph cartridge uses electromagnetic coils), mounting infrastructure, and/or protective blocks.
Subwoofer -- Speaker or speaker system for reproducing the lowest audio frequencies, typically not more than 100 Hz., such systems generally not also equipped with speakers to reproduce the higher frequencies. Reproducing low frequencies requires larger speakers and more amplifier power while low frequencies are less directional. This allows a sound system to have just one subwoofer system and the rest of the speakers and supporting audio components can be smaller, lighter, and less expensive.
Super Long Play -- Extended Play, q.v.
Surround Sound -- Generic term to describe a sound system with speakers both in front of and behind the audience. Examples: 4.0 -- System with left and right front speakers, and left and right rear speakers. 4.1 -- Same as 4.0 but with a subwoofer. 5.1 -- Has left, center, and right speakers in front, two speakers in the rear, and subwoofer. 6.1 -- Has left and right front speakers, left and right side speakers, left and right rear speakers, and subwoofer. 7.1 -- Has left, center, and right front speakers, left and right side speakers, left and right rear speakers, and subwoofer.
SVGA (Super VGA) -- 800x600 resolution. See VGA
SVM -- Scan Velocity Modulation.
SVOD -- Subscription Video On Demand. See VOD.
Sweet Spot -- (1) A relatively small area in a room, auditorium, or theater where the best quality of sound is heard or where monitoring is done for the best sound quality when a sound system is calibrated. "Sweet spot" can also describe viewing positions for live performances involving scenery although for movies the area where the view is close to its best is usually quite large. (2) The set of parameters such as number of scan lines and electron beam spot size where equipment such as a CRT TV set that accepts a continuous range of scan rates performs at its best. In the case of the preceding example the best picture quality is obtained when the scan lines barely overlap, with minimal blurring and without distinguishable gaps.
Swishing -- In analog tape playback on worn equipment, the fading in and out of higher audio frequencies due to changing of the azimuth of the tape head gap as the angle of the tape's passage across the head changes.
Glossary T
Tactile Transducer -- For audio/visual applications, a bass shaker q.v. More generally it is a device that converts audio or sub-audible frequencies as an electrical signal into vibrations intended to be felt rather than heard. Some, utilizing mid-range audio frequencies, are used for medical purposes.
Tape Monitor -- Control on an audio amplifier or preamplifier unit that selects the output from a tape recorder to be directed to the tone controls, power amplifiers, and speakers while at the same time a different audio source may have been selected and brought into the earlier amplifier stages and also sent out to the tape recorder. This permits the user to switch back and forth between listening to the source and to the tape recording (if the tape recorder has separate heads for simultaneous recording and playback). A similar control together with appropriate jacks may be present on A/V receivers for video recorders.
Telecine (Television from Cinema) -- Machine used to transcribe movie film content onto electronic media. The most common mechanism in professional equipment does not use a video camera but instead has a "one pixel" wide sensor that scans across an illuminated film frame for however many lines (480 for NTSC) are needed. Such a mechanism is called a flying spot scanner.
Telephonic -- Refers to sound with the quality of what would be heard over the telephone, namely pretty much lacking frequency content below 300 Hz and above 3000 Hz which is the typical frequency response of telephone audio circuits.
Television Line -- As a unit of measurement for resolution, "television lines" (in the plural), or TVL, refers to the maximum number of alternating black dots and intervening white spaces that can occur and be distinguished in a straight line whose length is equal to the diameter of the largest circle that fits in the screen or other area of reference. Photographers, when they refer to lines of resolution on film, count only the black lines or dots in a row in a test pattern, ignoring the intervening white spaces. The term TV Lines was introduced as an advertising gimmick to make TV, which has significantly less resolution than photographic film, seem to have more resolution than it does. In the singular, "television line" refers to the narrowest stripe where several of the same, alternating black and white, can be juxtaposed and still be distinguished.
Temporally Adjacent -- Refers to scan lines transmitted consecutively. The term is needed in discussing interlaced video where two temporally adjacent lines are both odd or both even. For progressive scanned video, lines that are temporally adjacent are also spatially adjacent.
Terrestrial -- Over the air, referring to broadcasts or broadcasting stations using antennas mounted on the ground or on ground based structures..
THD -- Total Harmonic Distortion.
THX -- Trademark for theater design guidelines including seating guidelines, and surround sound technology developed by George Lucas and named after one of his films, THX1138. The purpose was to ensure that a film "looks and sounds the same way" wherever presented. Complying theaters must choose equipment from an approved list of items and rent a specific electronic crossover network (bass/treble frequency divider) for the sound system. In video, THX refers to certain video and surround sound audio encoding on laser disks and DVD's. One video test pattern offered by THX has additional fine gray scales for near black shades including blacker than black and near white shades.
300 Ohm -- Refers to a usually flat TV antenna cable consisting of two conductors held parallel about 1/2 inch apart by insulating material, and related electronic components.
3-2 Pulldown (or 2-3 pulldown) -- One method of committing a 24 frame per second movie on film to 60 field per second or 60 frame per second video. Every other film frame is scanned three times and the intervening frames scanned twice to obtain the sequence of video fields or frames. If you single step through a VCR recording of a movie, you will often see the three-two-three-two pattern.
Three Way Speaker System -- Speaker system with separate speakers of appropriate types and sizes: (a woofer for) bass , mid range frequencies, and (a tweeter for) treble . If there are more than three speakers altogether, the speakers of each type are grouped together in three groups in terms of electrical connections.
Throw Distance (of a projector) -- The range of distances from projector to screen in which focus and also acceptable brightness can be achieved.
Throw Ratio (of a projector) -- The projector to screen distance divided by the picture width. This can be varied if the projector has a zoom lens.
Time Base Corrector -- Circuitry in a laserdisk player or VCR used to compensate for slight irregularities in disk rotation or tape movement which irregularities would otherwise result in scan lines' beginning at different horizontal positions on the screen and thereby cause vertical lines and edges as well as the entire picture to appear wavy.
Time Shifting -- The recording of a program for later viewing (or listening).
Tinny -- Refers to sound lacking in bass and also deficient in the lower mid-range (150 to 300 Hz). Characteristic of sound from small portable radios with speakers about two inches in size.
Tint Control aka Chroma Phase Control or Hue Control -- Correctly, the control that adjusts the phase relationships of the NTSC or PAL color decoder. The effect is to simultaneously change almost all colors in a manner analogous to rotating a color wheel (or painter's palette similarly arranged) and making color assignments (or picking up paint) based on the former position of the color wheel. The identical effect cannot be performed on video such as analog component video whose color content was not quadrature modulated onto a single AM signal although controls with a similar effect have been labeled tint controls.
TiVo -- (pronounced "tee-voh") Trademark for a video recorder that records on a magnetic disk similar to a computer hard drive, and which also requires a subscription to a commercial service that provides some of the programs that may be recorded.
Toe In -- The aiming of loudspeakers at the seating area as opposed to straight out from the wall they are against. Because the higher audio frequencies are "directional", if the speakers are not aimed at the seating area, higher frequencies rely on reflection off of another wall to reach the viewers' or listeners' ears. This reflection may be more desirable or less desirable depending on the room acoustics.
Tone Arm -- The mechanism on a phonograph that holds the stylus over the record, typically a bar or tube with a pivot at one end attached to the phonograph frame and the stylus assembly mounted at the other end. The term probably came about because on early phonographs the tone arm was a tube through which the actual sound was (acoustically) transmitted and amplified, the stylus attached to a diaphragm that immediately converted the stylus vibrations into sound waves with no electronic components involved.
Total Harmonic Distortion -- The amount of distortion consisting of spurious frequencies that are multiples of frequencies present in the source material, expressed as a percentage of the total output signal.
Transcoder -- As used in video, an electronic device to convert RGB to color difference video (Y, R-Y, B-Y) or vice versa.
Trimmer -- A kind of variable capacitor, often used to fine tune pushbutton TV and radio tuners, or sometimes used as the screwdriver adjustments behind a TV to adjust convergence, pincushion distortion, etc.
TTL Level -- Refers to digital signals where 5 volts stands for "one" and zero stands for "zero". Originally, Transistor-Transistor Logic, where the circuit main power supply was five volts DC and in many instances in modern equipment, still is.
Tubby (Boomy) -- Refers to sound with an abundance of content around 100 Hz (the mid-bass range).
Tuner -- The part of a radio, TV set, or stereo system that receives broadcast signals en-masse from an antenna and extracts, via a manually or remotely operated tuning dial or channel selector, the desired signal or program.
Twin Lead -- See 300 Ohm above.
2-3 Pulldown -- See 3-2 Pulldown
2x (referring to wheel speed) -- In a single chip DLP projector or similar projector, there are two red sub-images, two green sub-images, and two blue sub-images (alternating) projected for each video frame which in turn takes 1/50'th or 1/60'th of a second. If there are two cellophanes of each color in the color wheel, the actual wheel rotation speed would be equal to that for a projector with 1x wheel speed and one cellophane of each color in its wheel.
TV (Television) -- Should refer to a television receiver, specifically such a unit which also possesses channel selector and speaker and supporting electronics, although we use the term to also include such a unit that projects the picture onto a separate screen. (2) The concept of electronically capturing visual scenic information, transmitting such information, and reproducing such information as a motion picture "instantly" in another location.
TVL -- Television Line, q.v. Not necessarily a scan line.
TVCR -- A TV set with built in VCR.
TV/VCR Switch or Setting -- Every VCR has this, and DVD recorders with channel selectors have a similar switch or setting. With "TV" selected, whatever is fed in via the antenna in jack (typically all the channels) also comes out of the VCR's antenna out jack. With "VCR" selected, only the channel showing on the VCR's channel selector, or the taped program being played, comes out of the antenna out jack transposed to channel 3 or channel 4. The VCR's video out jack is unaffected, only the material on the channel showing on the VCR's channel selector, or the taped program being played, comes out here.
Glossary U
U-Matic -- A VCR format that uses 3/4 inch wide tape and is somewhat similar to the now obsolete Beta format.
U, V -- (1) The horizontal (greenish yellow to purplish blue) and vertical (purplish red to cyan) axes, respectively on a color wheel diagram used to describe most video. (2) The video signal components B-Y and R-Y, often considered synonymous with Pb and Pr but more correctly adjusted to different levels (proportions) relative to Y (luminance) compared with Pb and Pr. As stated in Wikipedia.org and Answers.com, U = 0.492(B-Y) and V=0.877(R-Y). To produce the picture, theY is also needed. U and V are also used for PAL video. Use of U and V in NTSC composite video is common but it does not quite optimize the color horizontal resolution to the maximum sensitivity of the human eye to reddish orange and greenish blue as the NTSC specifications call for. See, also, I, Q and Prime Disclaimer.
UHF -- Ultra High Frequency -- Comments: Channels 70-83 are no longer used for TV broadcast and TV sets are no longer required to receive them. Other services such as cellular telephones use this part of the UHF frequencies, which as a whole extend from about 316 MHz to 3.16 GHz. Currently most U.S. HDTV broadcasts use the existing UHF channel assignments.
UHP -- Ultra High Performance high intensity discharge, the lamp technology used in most consumer grade LCD, DLP, and LCoS RPTV's and front projectors. The lamp has a small (typically less than 1/2 inch diameter) bulb containing two electrodes with a gap of about a millimeter and produces a very intense near point source of light. Mercury vapor under high pressure is used to achieve the best spectral characteristics for the light.
Underscan -- Condition when the picture size is adjusted so that strips of unused screen area are along all borders. Computer users sometimes leave their monitors adjusted this way to guarantee that material such as the "start button" in the lower corner of the Microsoft Windows screen does not disappear beyond the edge. Also on some TV sets the edges of the picture suffer distortion when extended all the way to the picture tube edge. See, also, Overscan.
Uninterruptible Power Supply -- Power supply unit with connection to utility power and also a battery backup system which, in the event of utility power failure does not incur a power loss, even momentary, at the output.
Unity -- The number 1, when used as a multiplier. Unity Gain Amplifier -- An amplifier or amplifier stage that doesn't actually amplify, namely the output is the same as the input. It does have useful purposes, for example to prevent signals internal to a system from leaking out of an input jack or port, or to convert from a low voltage high current circuit to a high voltage low current circuit or vice versa. This writer has seen radios with several unity gain audio driver stages designed for the sole purpose of having the radio possess the number of transistors it was advertised to possess.
Universal Serial Bus -- One format, including plug and jack configurations, for data transmission between a computer and an external device, often used for digital cameras, scanners, and printers.
Upconversion -- (1) The reconstruction of a video frame or image to have a larger number of scan lines or pixels. See Sampling. (2) The transposition of a block of frequencies, for example one or more broadcast channels' program material, onto a block of higher frequencies. If, for example, a cable system were to carry two broadcasts originally on channel 5, and channel 6 was free, one might be upconverted to channel 6. (3) (Colloquial) The separation of composite video into S-video or the recovery of component video or RGB from S-video. Ed. note: We feel that the latter conversions are actually downconversions since composite video is a more complex format and component video is a more simple format and also the converting of the color material from S-video to component video involves going to lower frequencies.
Upconverting -- Refers to a DVD player that formats its video output into one of the HDTV formats (720p, 1080i, coming soon: 1080p) or (colloquially) refers to an A/V receiver that converts composite video into S-video, etc. cross feeding the result to the appropriate (S-video, component video) output. Just because the DVD player or A/V receiver upconverts does not guarantee that the picture quality will be superior to that obtained by feeding the original video signal to the TV as-is.
Upper Field -- The field of "even" scan lines is called the upper field because it usually begins with a half line of picture information at the upper right of the screen, above the first (full) scan line in the other field. If we use a numbering scheme where the first two full lines of the upper field ares labeled "2" and "4", then this half line would be part of scan line 525 for NTSC).
UPS -- Uninterruptible Power Supply.
USB -- Universal Serial Bus.
Glossary V
V -- Often used (not quite correctly) interchangeably with Pr. See, U, V.
V-Chip -- A licensed proprietary system built into a TV set to restrict viewing of programs such as for control a parent may wish to exercise over his children. Programs as broadcast contain encoded audience rating information that the V-Chip technology recognizes and may cause a program to be blacked out.
VB -- Vertical banding, q.v.
VCR -- Videocassette Recorder. Video tape recorder that uses tape contained in cassettes.

Cont. Part 4 of 4http://extratorrent.cc/forum/topic/7125/audio+and+video+definitions+part+4+of+4.html