Audio and Video Definitions Part 2 of 4
Wed Feb 09, 2011 09:05
Audio and Video Definitions Part 2 of 4
Dongle -- As used here, a small electronic gadget, typically the size of an audio cassette but which could be larger or smaller, that must be connected between two electronic components such as a DVD player and a TV for processing or converting the signal, where one might have expected just a cable with appropriate plugs to be sufficient. Examples: (1) The 300 to 75 ohm transformer needed between a twin lead antenna cable terminating in two spade lugs and a TV's coaxial antenna jack, (2) (stretching the definition) A transcoder needed to convert component video from a DVD player into RGB to go into a VGA jack of a video monitor.
Dot Crawl -- see Cross Luminance.
Dot Pitch -- The (center to center) spacing between phosphor dots or stripes of the same color on a TV screen. The smaller the better for picture sharpness, 0.28 mm is considered the minimum acceptable for a good computer display, while a typical 20" TV has an 0.81 mm dot pitch and large screen TV's have dot pitches a bit larger. Unfortunately, small (5 to 9 inch) TV sets have dot pitches well in excess of the now easily manufactured .28 mm which makes these products have unnecessarily coarse picture quality. Many TV screens use vertical stripes rather than dots in which case the dot pitch applies only in the horizontal direction.
Doubler -- See Line Doubler, or click here for a more detailed description.
Downconversion -- (1) The reconstruction of a video frame or image to have a smaller number of scan lines or pixels. This must be done to put an HDTV picture on a standard TV set. See Sampling. (2) Transposition of a block of frequencies, typically one or more programs modulated on carrier frequencies, onto a block of lower frequencies. For example a VCR does a downconversion when it tunes in, say, channel 56 and sends it to the TV as channel 4. (3) (Colloquial) The construction of S-video from RGB or component video or the construction of composite video from S-video.
Driver -- A "loudspeaker unit" (consisting of frame, cone or other shape diaphragm, and voice coil and magnet or electrostatic grid to convert an electrical signal into vibrating motion), or a similar voice coil and magnet and diaphragm assembly used for audio but requiring a horn or resonating chamber attached to it to deliver meaningful sound output. (2) A computer program that manages an input/output device such as a disk drive or a printer.
Dropout -- Momentary loss of audio or video most often encountered in magnetic tape or disk recording and playback. Causes include loss of contact between magenetic tape and the tape head, perhaps due to dirt or dust, and imperfections in the magnetic coating on the tape or disk.
DTV -- Digital Television; Digital TV, q.v.
DVB (as in DVB-c or DVB-t) -- A digital video encoding standard for (terrestrial) broadcasting (-t) or cable TV (-c) used a lot in the parts of the world that use PAL. Some of the compression techniques include combining (by weaving) odd and even interlaced fields and then performing video compression. The result sometimes resembles 24 fps (sped up to 25 fps) film source video with 2-2 pulldown. The significance is that de-interlacers that recognize 2-2 pulldown produce less than ideal picture quality when the small percentage of the picture material that differs from field to field is processed. Said correct differences often show up as areas of woven even and odd scan lines non-matching in terms of content, referred to as combing.
DVD (originally "Digital Video Disk", now "Digital Versatile Disk") -- A 5" plastic disk that looks like an audio compact disk or compact disk used for data, using the same concept of microscopic pits arranged in a spiral and read using a laser. Except for double sided DVD's (CD's come only single sided) the only way to tell the difference from a CD is to look at the label or markings engraved near the center. Today's DVD's can play a movie just over four hours in length without the need to stop the player and turn the disk over. The present standard (SDTV) DVD picture is usually 704 or 720 (occasionally 640) pixels across by 480 pixels high (576 pixels high for PAL). Live video is stored (recorded) as interlaced, up to 60 fields per second. Film source video may be stored as progressive, up to 30 frames per second. A CD player cannot play a DVD whereas most DVD players can play CD's. For computer use, the nominal capacity of a DVD is 4.7 gigabytes per layer. DVD's may have one or two layers per side, and double layer disks may also be double sided.
DVDO -- Trademark of Anchor Bay Technologies, which now produces the the iScan line of de-interlacers. The original DVDO, Inc. was acquired by Silicon Image Corp ca. 2001. In 2003 Silicon Image sold the DVDO and iScan names and the related stand alone de-interlacer business but not the chipset ownership to Anchor Bay Technologies. The latter was a new company some of whose founders founded the original DVDO, Inc. and have since developed new HDTV and SDTV de-interlacing technologies.
DVI (for Digital Video Interface) -- A set of digital video standards for transmitting video between components over wires such as between DVD player and TV set at distances generally up to about 30 feet. Its standards handle all of the common NTSC based SDTV formats and the U.S. ATSC formats and most of the common PC resolutions. HDCP copy protection is also supported. It uses a 24 conductor plug and jack set just over one inch by 1/4 inch in size. The transmission itself is over either a single 12 wire (single link) or two 12 wire (dual link) 165 MHz data channel(s).
DVR -- Digital Video Recorder.
Dynamic Range -- Ratio of the loudest and softest sounds that an audio system can reproduce or the ratio of the brightest and darkest shades (contrast ratio) that film or a video system can reproduce.
Easter Egg -- A special feature in a DVD video program which does not play in sequence with the main program and whose title or method of access is often obscurely located (quite hidden). Often the reference to it in an on-screen menu is a small icon that is selected using arrow keys on a remote control and which may be circular or oval shaped.
EDTV (Extended Definition Television) -- Marketing term for a standard definition TV set that displays a progressive scan (non-interlaced) picture and that usually has horizontal resolution near the high end (over 600 pixels across) for SDTV.
EIA -- Electronic Industries Association, whose members represent equipment manufacturers and establish standards. EIA Resolution -- Video resolution measured in the currently technically correct manner, as TV lines in a distance span equal to the picture height assuming a 4:3 aspect ratio.
Electronic Program Guide -- Feature on some cable TV tuners and other tuners that takes information for the purpose encoded in received program material and displays program schedules, program descriptions, etc. as provided. Interactive Program Guide -- A similar feature with communication back to the source, allowing viewer interaction such as requesting additional information or even selecting a program for video on demand or pay per view.
Electrostatic Loudspeaker -- A loudspeaker consisting of two metal grids (the holes or perforations let the sound out) with a diaphragm consisting of a membrane in between that vibrates in accordance with charges on the grids. It is quite often used for tweeters whereas it would have be quite large (many square feet) to move enough air for low frequency reproduction.
Enhanced Black -- Setting on some DVD players causing the source material official black to white range to be spread out over the the range 1 to 235 rather than the standard 16 to 235 using 8 bits, or over the analog range 0 to 100 (IRE units) rather than the U.S. NTSC standard 7.5 to 100 IRE. This setting is meant to match the DVD player to the TV's characteristics and may or may not bring out shadow detail and may even hide some shadow detail.
Enhanced for 16:9 -- For DVD, refers to a program where the entire 720 by 480 pixel video frame represents a 16:9 aspect ratio image. Whereas for a "standard wide screen" program, only the middle 720 by 360 pixels represent a 16:9 image with the topmost and bottommost pixels are unused (see "letterbox"). To show the full resolution, the enhanced program must be viewed on a TV or monitor with an adjustable image height control or a 16:9 aspect ratio screen. The exact number of pixels of picture height excluding letterbox bars will vary depending on the exact aspect ratio of the image, although the enhanced version will still have better resolution than a standard letterbox edition. All DVD players have a setting to reconstruct the picture with some loss of vertical resolution to be viewed on a standard 4:3 TV set without a height control. Enhanced wide screen programs may also be labeled "anamorphic" or "high resolution".
EP -- Extended Play.
EPG -- Electronic Program Guide
Equalization -- Non-flat frequency response curve or contour built into an amplifier to optimize the audio signal for the recording media or to correct for deficiencies that occur or that have occurred during recording or transmission. Often a record equalization curve and a complementary playback equalization curve to restore overall flat frequency response represent a standard. For example, the RIAA recording equalization attenuates bass frequencies so record grooves will have less excursion permitting groove spacing to be less, and playing time on a record can be greater.
Extended Kell Factor -- See Kell Factor
Extended Play -- (1) The slowest tape speed on a VHS VCR yielding six hours of recording on a "two hour" or "T-120" tape. (2) A 45 RPM phonograph record with ultra fine grooves and more than five minutes of playing time (enough for two typical popular musical selections) on each side.
Field -- Either just the odd lines of an interlaced video image, or just the even lines. A field is technically half of the picture.
Field Dominance -- A somewhat artificial but sometimes necessary way of treating pairs of (interlaced) fields as video frames. For (digital) storage of video on disk drives or video disks, it refers to the order in which the odd and even fields are stored .For video editing, when sections or scenes are cut and pasted ("spliced") , every cut must occur before an odd field (F1 dominance) or every cut must occur before an even field.(F2 dominance). The significance of field dominance includes the need to identify the proper temporal sequence for the stored video fields when further processing is done. Simply identifying the video as F2 (even) field dominant does not mean that the odd field in the frame should be located and processed first. There are certain telecine operations where from time to time the even field precedes the matching odd field temporally. Field dominance is not visible in original analog material and properly processed digital video as viewed.
Fill Ratio -- On a fixed pixel display such as an LCD panel, the ratio of the active areas of the pixels to the overall area of the display, which gives a measure of the obtrusiveness of the "gaps between pixels" which gaps show up as a dark grid on the screen.
Firewire (a.k.a. IEEE 1394) -- One format, used a lot by Apple Computer Corp., for transmitting digital information including video over wire between components such as between a computer and a monitor. Every analog to digital conversion results in some loss of quality, therefore it is advantageous to transmit video digitally to any component (such as a scaler) that processes video digitally. It is not very common in consumer video applications because it currently does not support HDCP copy protection.
First Surface Mirror -- Mirror with the reflective layer on the outer surface, used to avoid ghost images from additional reflections if light has to first pass through the mirror glass and then hit the reflective layer.
5.1 -- Sound system with left, center, and right front channels, left and right rear channels, and subwoofer. 5.0 -- The same system without the subwoofer. See, also, Surround Sound
Flutter -- (1) Repeated rapid increase and decrease of pitch of the reproduced audio, more than about two repetitions per second, due to non-uniform linear speed of analog tape. (A slow repetition is referred to as wow.) (2) Choppy rapid breakup and resynchronizing of a television picture from such causes as over the air signal reflection off of an airplane passing overhead.
Flying Spot Scanner -- See Telecine
Foldover -- (1) Defect where part of the top of the picture is superimposed upside down over the material just below, or a similar effect on the bottom or (less often seen) on a side. Quantitatively it could be something like (each instance may vary) scan line 20 being on top, scan lines 21 and 19 below it, scan lines 22 and 18 next, and on down to scan lines 39 and 1 superimposed. (2) Frequencies above a certain magic number in Hz (Nyquist frequency) showing up as spurious frequencies the same number of Hz below that number in Hz, for example if the magic number was 10000, a 11000 Hz frequency shows up as 9000 Hz, a 12000 frequency shows up as 8000 Hz. This is a defect; content above the magic number should be filtered out prior to processing. In audio, sour notes are produced.
Foley -- Machine used to generate sound effects for movies. The effects are nowadays usually prerecorded or electronically synthesized but originally they were created using mechanical noise making devices such as springs, flapping cards, beaters on wood blocks and cloth, etc. Named after Jack Donovan Foley (1891-1967) who was a pioneer in the art of adding sound effects to movie soundtracks.
Footprint -- (1) Roughly speaking, the physical size and shape of the portion of an object or building, nearest the floor or shelf or ground it is resting on. For a TV set on legs, the footprint would be the shape described by a string that encircled all of the legs. For a VCR with rubber feet but no legs, the footprint would be the shape of the entire body. (2) In an abstract sense, the irreversible consequences of a format or set of rules. For example, the 720 (or 704 depending on subject matter) pixel wide by 480 pixel high "grid" representing the DVD picture is a footprint, which in this context forever constrains the picture data to occupy discrete pixel positions implied by that grid and not occupy the spaces in between. Composite video is also a footprint whose manifestation in a video image is smeared color boundaries and rainbow effects amidst fine details, among other things. Color resolution is highly limited and it is almost impossible to get rid of all of the contamination from each other when the luminance and color information are finally and mandatorily separated for display of the picture.
Foot Lambert -- Measure of illumination level including light output off of video displays. One foot lambert stands for the level of illumination as seen on a uniformly lit panel where the sum total of light reflecting off of or emitted by one square foot of panel or screen area is approximately equal to the sum total of light (about 12-1/2 lumens) given off in all directions by a lit candle. Foot Candle -- Similar to foot lambert except the amount of light emitted or reflected is one lumen per square foot of surface area. See, also, Nit.
48i -- 48 interlaced fields per second. See, also @60i.
4.1 -- Sound system with left and right front channels, left and right rear channels, and subwoofer. See, also, Surround Sound
4:2:2 -- One method of specifying color (chrominance) resolution of digital video signals. The first number is the reference count of luminance pixels. The second number is the corresponding number of color pixels in the odd rows or scan lines. The third number is the corresponding number of color pixels in the even rows. DVD's rating is 4:2:0, the color resolution is half the (advertised; published) luminance resolution both horizontally and vertically, or each two by two block of luminance pixels has to be the same hue, or color in the sense of pink and red being the same color. In practice the color for a block of pixels may or may not be an interpolation such as the average taken from all of the relevant neighboring pixels. For analog video luminance and color resolution vary independently, and the color resolution may vary depending on which colors are juxtaposed, so this method cannot be easily applied. We could say that contemporary NTSC broadcasts have a rating of 4:0.5:0.5 or 8:1:1 (330 lines luminance, 40 lines color) although unlike digital video the "pixels" on each scan line don't have to line up vertically.
fps -- Frames per second. Also see Segmented Frame which may use the notation "psf". Often "i" (as in 60i, not 480i) is used to stand for fields per second.
FPTV -- Front Projection Television (set).
Frame -- All of the scan lines, both odd and even, that make up one complete "painting" of the video screen. Also any one exposed picture on a strip of movie film. Note that for interlaced video, one "frame" does not necessarily yield a single complete image subject-wise since subject motion may have occurred between capture of the odd field and capture of the even field.
Front Porch -- The few milliseconds of zero signal level at the end of the subject matter on a scan line and at the start of the Horizontal Retrace Interval.
Front Projection -- Video display technology consisting of a unit typically placed in the center of a room (usually on the ceiling) projecting a picture onto a movie screen or other surface. Front projection is used to provide a picture larger than other methods can achieve but requires a dark room for good shadow detail in the picture.
Full Frame -- Refers to a video program presented in the 4:3 aspect ratio whether or not it was originally created with that aspect ratio. If the original program was of a different aspect ratio the video presentation will use either or both of pan-and-scan (q.v.) techniques and soft matte (q.v.) source material without matting. Contrasted with Full as a setting on a wide screen TV set which refers to displaying the entire video frame content in a 16:9 shape, filling the screen.
Full Range Speaker -- A loudspeaker unit with a single voice coil (not woofer and tweeter in the same frame) that can give good reproduction of all types of music although it may be deficient in the lowest and highest one and one half octaves (below about 60 Hz and above about 8000 Hz.
Funhouse Effect -- Objects get wider or narrower or taller or squattier, or go through other geometric shape distortions, as they move across the screen, due to less than perfect "linearity" of circuits and/or "field uniformity" of lenses. The effect is suggestive of images seen in the curved mirrors found at amusement parks, carnivals, or circuses, often in a location called the funhouse. Nowadays one choice of viewing 4:3 aspect ratio programs on some wide screen TV sets is to have the center of the picture nearly correctly proportioned while the left and right sides are stretched out a little.
Gain -- (1) In a receiving antenna, the greater sensitivity to signals (coming from the favored direction if any) compared with a standard which is another antenna with certain characteristics. (2) in a movie screen, the greater amount of light reflected in desired directions (i.e. towards the viewing area) compared with a screen consisting of a surface painted with a certain standard flat white paint. Screen gain is achieved by reducing light reflected in non-favored directions such as upwards or downwards. (3) in an amplifier or amplifier stage, the amount of amplification.
Gamma -- The relationship between the brightness of a spot on the screen and the level of the video signal in volts or digital numeric values. It can be graphed as a curved line. If twice as many electrons are fired at a spot on a CRT screen, that spot does not look twice as bright to the human eye, Therefore for CRT's the gamma graph is not straight, or linear. In practice gamma also varies with the make and model of the TV set or monitor, the nature and quality of the electronics inside, and also the settings of the brightness and contrast controls. Gamma also applies to film where the intensity of light hitting the film results in the appropriate intensity of the color in the finished print or slide. Adjusting gamma is difficult especially considering that most people cannot tell what is correct unless they have a side by side comparison with the live subject, a supposedly correct photograph of the subject, or a TV that is adjusted correctly. Also personal preferences, comparable to preferences in adjusting stereo bass and treble controls, affect the settings. Typical test patterns for adjusting the gamma consist of dark and light patches, some of them using shades of gray, others using halftoning or dithering of black and white dots. The user is told to adjust controls on the monitor until some patches or stripes are distinguishable and others blend into each other. The instructions for using each gamma chart vary. Re-adjusting gamma may also be done to best show fine shading gradations both near black and near white. See, also, Prime Disclaimer.
Generation Loss -- The degradation experienced each time a recording or other information or data is copied. It can be zero, nil, for digital material.
Genlock (trademark?) -- Feature in a video processor that guarantees one interlaced field or progressively scanned frame of video output for each incoming interlaced field or progressively scanned frame of video. This feature reduces temporal judder caused by repeating or dropping of frames done by the processor but requires that the TV (or other display device) be able to stay in sync. with the video processor's output.
Ghosting -- Duplicate (i.e. not quite juxtaposed), copies of subject matter, often caused by ringing (electronic overshoot and bouncing) in the TV's circuits or by broadcast signals bouncing off a far away object (building, mountain) and coming back to your antenna time delayed.
Graphic Equalizer -- Group of amplifier tone controls each affecting a different range of audio frequencies and usually in the form of side by side vertical sliders arranged so that a curved line imagined to pass through each of the slider handles suggests a graph of the frequency response of the amplifier at the time.
Gray Scale -- A test pattern consisting of shades of gray, in order, starting with black and ending up with white. It may be a continuous sweep or a series of typically half a dozen to two dozen discrete steps. The gray scale step pattern is especially useful in identifying black crush (darkest shades of gray indistinguishable from black) and/or white crush.
Hard Matte -- Refers to wide screen movies that are filmed using a camera that blocks off the top and bottom edges of the 4:3 aspect ratio film frame, recording only that part of the image that will become the finished picture and leaving unused the top and bottom edges of each frame on the film. (This is how panoramic 35mm still cameras work.) Some producers use this technique so that the theater projectionist cannot err (or deliberately modify the presentation) by opening up the projector's aperture plates too much.
Harmonic Distortion -- Distortion in audio consisting of the addition of multiples (harmonics) of the frequencies originally present in the source material. Harmonic distortion in an amplifier occurs when the relationship between the input voltage and the output voltage (the transfer characteristic) is not uniform (linear).
HDCP (High-bandwidth Digital Content Protection) -- A data encrypting system developed by Intel, Inc. to inhibit the unauthorized distribution of digital video material through copying. It consists of "keys" (data) incorporated in the video data together with proprietary encryption (scrambling) circuitry and software in the various video components (tuner, TV, DVD player, etc.) that handle HDTV. Material that is protected may only be transmitted digitally and to components that decrypt the material prior to processing and re-encrypt the material before transmitting the material to another component using certain digital transmission formats including DVI that include the encryption.
HDMI (High Definition Multimedia Interface)-- A set of digital video standards for transmitting video and audio together and also component remote control signals over wires between components such as between DVD player and TV set at distances up to about 30 feet. The video data formats are the same as for DVI, including for ATSC HDTV transmission, but not all of the TV video formats and none of the "personal computer" video formats are included in the standard. The plug and jack assembly is about 3/4 inch by 3/8 inch.
HDTV -- High Definition Television.
HD Built-In -- Refers to a (full fledged) HDTV receiver, that is, a TV set with HDTV tuner, and with video circuits,and display elements to display all standard HDTV programs using at least one of the HDTV formats. Current marketing standards do not disqualify a set from having the HD Built-In label due to deficiencies in de-interlacing, video bandwidth, or optical resolution.
HD Capable -- HD Built-In.
HD Ready -- Refers to a TV set that accepts baseband video in one or more of the high definition formats, that displays a picture using one or more of the high definition video formats, but which does not have a tuner (channel selector) to receive HDTV signals off the air or from a cable system.
Head End -- The equipment that formats and combines the various source materials to occupy the channels of a cable or satellite TV system, or the location of said equipment.
High Definition Television -- A generic term describing TV signals, video formats, and equipment, providing either (1) pictures of approximately twice the horizontal resolution and twice the vertical resolution of common standard late 20'th century TV broadcasts extrapolated to a 16:9 aspect ratio, or (2) pictures made up of approximately a million pixels or more. 1280 x 720, or 0.92 megapixel, is generally regarded as the lower limit of picture detail content or resolution for HDTV. See, also, ATSC.
Home Theater -- (1) Place in the home where movies, skits, puppet shows, etc. may be presented and which is customarily used for those purposes, usually where the seats, fixtures and equipment are left in place when not in use. (2) The concept and art of presenting movies in the home with most of the ambience of a well run commercial movie theater, which includes showing the movie in its original aspect ratio and not edited or formatted for TV, and providing left, right, and rear sound channels. One standard calls for a screen at least 27 inches from corner to corner and at least five sound channels for movies.
Home Theater In A Box -- A (usually modestly priced) kit consisting of a DVD player, A/V receiver with several audio amplifier channels, cables, and several speakers usually including a subwoofer (but no TV or video monitor). So called because the kit is usually packaged in one, or nowadays usually two, cardboard box(es).Usually does not have enough amplifier power to produce sound levels comparable to a commercial theater in a large room.
Home Theater Personal Computer -- A computer used to process video in the home and equipped with specialized software, video cards and other equipment for that purpose.
Horizontal Retrace Interval; Horizontal Blanking Interval -- The time during which the electron beam is turned almost off (as if to draw black) and moved from right to left to get ready to draw the next scan line on the picture tube. Roughly, the horizontal retrace interval starts with a few milliseconds of zero level (the front porch) followed by a few milliseconds of negative signal level (the sync. pulse) followed by a few milliseconds of zero level (the back porch). In NTSC broadcast video, 10.9 microseconds are set aside for this purpose; the entire scan line, retrace interval and all, takes 63.5 microseconds. The time it takes to draw an entire line is adequate to allow the electron beam to draw at most 530 dots alternating black and white, given a 4.2 MHz bandwidth; the horizontal retrace interval takes away about 90 of these dots. Of the remaining 440 (give or take a few), 330 fit in the largest circle that in turn fits in the 4:3 screen, which leads to the 330 line horizontal resolution that is often mentioned when it comes to broadcast TV. The smallest dot achievable which determines the maximum number of dots into which a scan line may be subdivided depends on the program source and the quality of equipment. Also refers to the format data separating the data representing each row of pixels in digital video.
HTiB -- Home Theater in a Box.
HTPC -- Home Theater Personal Computer.
Hue -- A "single color" disregarding brightness or darkness (luminance). A simple somewhat vague way to describe hue is to say that pink and red are of the same hue and azure, blue, and navy are of the same hue. Hue Control -- Another name for Tint Control.
i (as in 50i, 60i, etc.) -- Fields per second. Much literature nowadays is describing interlaced video using written formats such as 480/60i, namely. with the "i" after the field rate.
I (In Phase Color Component) -- Video subsignal representing reddish orange to greenish blue color content, used for NTSC broadcasting. The term is not quite correct since the I component is actually about 33 degrees out of phase while in-phase demodulation of the color subcarrier yields the B-Y or Pb component. See I, Q.
I-Frame (Intra-Frame) -- In a video compression scheme, such as for picture information on a DVD, a frame that is complete. In order to begin playback, an I-frame must be located. Other frames (B-frames, P-frames, q.v.) are just the differences from adjacent frames. Thus frame 1 may be an I-frame. Frame 2 on the DVD might be a P-frame which when combined with frame 1, yields the complete frame 2 for display. Frame 3 on the DVD might be a B-frame which when combined with the complete frame 2 we just derived (or from complete frame 4 in backwards single stepping), yields the complete Frame 3, and so on. Usually there is an I-frame about every ten frames, so the player doesn't have to hunt too far when resuming playback in the middle of the program.
IEEE (Institute of Electrical and Electronics Engineers) -- A professional organization which has established some standards for radio and television electronics. Formerly Institute of Radio Engineers (IRE).
IM -- Intermodulation, usually used to describe distortion, as in IM distortion.
Image Stabilization -- Means of reducing shakiness in motion pictures (or blur in still pictures) recorded by hand held cameras. A typical optical method uses gyroscopes, which inhibit sudden or rapid rotational twisting or panning movements. Some newer methods for still cameras use moving lens elements. Electronic methods for video cameras attempt to shift field or frame subject content horizontally or vertically by a few pixels so as to match the content of a previous field or frame. Electronic image stabilization of interlaced video often results in reduced vertical resolution.
Integrated Amplifier -- Another term for an audio amplifier unit with preamplifier stages for microphones and/or phonograph cartridges, switching of multiple inputs, tone controls, and power amplifier stages to drive speakers.
Interlaced -- The drawing or transmission of all of the odd scan lines, then all of the even lines, for each video frame. Interlaced video was originally invented to reduce flicker given that video technology of the time could not draw video frames fast enough to keep the top of the picture from fading before the bottom of the picture was completed.
Interlace Factor -- The ratio of the number of psychologically perceived analog lines of vertical resolution in an interlaced video picture to that in a progressively scanned video picture, both pictures having the same number of scan lines and both pictures otherwise being equivalent. It is difficult to evaluate the interlace factor because it is difficult to produce interlaced and progressively scanned pictures with all other characteristics equal. See, also, Kell Factor.
Intermodulation Distortion -- Distortion, such as generated in an audio amplifier, consisting of spurious frequences that are sums or differences of frequencies in the original source material, as if amplitude modulation was taking place.
Interpolation -- Guessing what goes in between. A typical example in video is converting the video to have a different number of scan lines or pixels. If we imagine both a grid of the source pixels and a grid of the target pixels on the screen at the same time, a target pixel may be centered between two (or among four) source pixels. Sophisticated interpolation is not just taking the average of the nearest source pixels' content but may also vary from pixel to pixel and even be influenced by the content of pixels several removed from each target pixel. (Guessing what comes next or what goes beyond is called extrapolation.)
Invar -- Trademark for a metal alloy used for picture tube shadow masks, which alloy expands and contracts due to temperature changes less than most metals. Used so that more brightness can be obtained which requires stronger electron beams which in turn cause the shadow mask to heat up more and where expansion causes the holes to go out of alignment with the phosphor dots or stripes causing picture discoloration.
IPG -- Interactive Program Guide. See Electronic Program Guide.
I-Q -- Refers to one method of encoding of the color content of a video signal such that all colors could be depicted using a two dimensional diagram, more specifically a color wheel. There are two color signals one (I or In Phase) of which represents oranges and blues and the other (Q or Quadrature) represents greens and purples. (Both together are used to represent other colors.) This choice of colors permits giving the oranges and blues, which the human eye is more sensitive to, more frequency bandwidth (1.3 MHz standard) and thus greater color resolution in NTSC video. The remaining colors had to be limited to about 40 lines of resolution (0.5 MHz sideband width) since one of the sidebands of the modulated color signal is so limited and both the I and Q color components cannot be recovered from just the other sideband. Many TV sets today and all consumer VCR's limit color resolution to a theoretical maximum of 40 lines for all colors due to inexpensive circuitry. When it is not necessary to construct a composite video signal, the color signals U and V representing (approximately) blue-yellow and red-cyan respectively, are usually used instead of I and Q. We believe that all of the descriptions on this page can be understood quite well by persons without tremendously high intelligence quotients. Click here for more on video signal formats.
IR -- Infra-red.
IRE (Institute of Radio Engineers) -- Former name of the IEEE. The name IRE is still used with some electronic standards such as video signal brightness level e.g. 50 IRE.
iScan -- Trademark of Anchor Bay Technologies for its line of stand alone de-interlacers and scalers, which are also usable as NTSC to VGA converters.
ISF -- Imaging Science Foundation, a group of professionals that sets standards for calibrating of television and video equipment.
JPEG -- Joint Photographic Experts Group -- Organization which, among other things, developed standards for digital compression of material representing pictures, photographs, and motion pictures.
Judder -- Minute unnatural jerky movements in motion pictures, either in space or in time. It (in space) can be the result of consecutive film frames not pulled precisely to the same position in the projector gate. In terms of time, judder in video may be noticed because 24 frames per second for film source does not divide evenly into 60 fields or frames per second for NTSC video, and some film frames' content is shown on the screen for more time than other frames' content (3-2 pulldown, sometimes becoming 4-2 pulldown in certain situations).
Kell Factor -- The ratio of the number of psychologically perceived lines of resolution to the number of scan lines or pixels (spanning the same distance) taking into account all possible deficiences related to scan lines and pixels including gaps between the latter and including the fact that scan lines or pixels can straddle details in the original subject leading to in some cases a total blur, but not counting the effects of interlacing. The larger the better, 0.7 is considered very good. Deficiencies such as scan lines too thin or too thick, and flickering due to a low scan rate worsen the Kell factor. Click here for more on Kell factors. See, also, Interlace Factor.
Keystoning -- The trapezoidal or other departure from perfect rectangular shape of a projected picture because the projector from its sitting or hanging position has to be aimed at the screen at an angle that is not correct for it. The further from the lens the projector beam goes, the more stretched out will be the picture content at that place on the screen. Some video projectors have electronic keystone correction which electronically reshapes the picture on the display elements within to compensate for this projection distortion and cause the picture as projected on the screen to be in the proper shape. Some projectors have optical keystone correction achieved by adjusting lenses or mirrors inside.
Kinescope -- (originally a trademark) A CRT; picture tube, also a movie produced by capturing (cinematographing; filming or even videographing; videotaping) the picture from a TV screen.
Laser Disk -- The accepted terminology for 12 inch consumer playback only video disks recorded and read using a laser (and also 8 inch disks recorded using the same format). The video recording is of a composite video analog signal with about 5.3 MHz of luminance bandwidth which gives a maximum horizontal resolution of 425 lines per 4:3 picture height. There are two analog soundtracks and two digital soundtracks; not all players can play the digital soundtracks. All players can play both the CAV and CLV disk formats.
Laser Rot -- Tarnishing of the (metallic) reflective layer in a laserdisk or DVD or similar disk, making the disk unplayable; unreadable by the player's laser. Caused by a defect in manufacturing or deterioration of various materials in the disk that results in moisture reaching the reflective layer.
Layer -- A DVD is constructed of several layers of different materials. There are up to four data containing layers and the player can play two of these layers in sequence without the disk's being removed and turned over. Each layer can hold approximately two hours of NTSC video. To play "the other layer" the player's laser beam is refocused slightly. Layer Change -- The jitter or stutter that sometimes occurs as the DVD player reaches the end of the recorded material on one layer and switches to playing the other layer.
LCD -- Liquid Crystal Display.
LCoS -- Liquid Crystal on Silicon.
LD -- Laser disk.
Lens Shift -- Ability of a projector to optically shift the projected image up or down or from side to side relative to the projector to screen axis, that is, without repositioning or tilting of the projector, and also without electronic scaling, shrinking, or stretching of the image.
Letterbox -- The colloquial term used to describe a video program where the original scene has a larger (wider) aspect ratio than the TV screen and is zoomed out (shrunk) so that the entire width fits in the screen. An inescapable consequence is that there is unused screen area and wasted scan lines at the top and bottom. The term came about because viewers had the impression they were looking through a mail slot in a door or out of the slot of a gigantic mailbox. Not all movies are offered on video this way because the public continues to demand editions where the entire screen is filled. Also the vertical resolution of subject matter in letterbox editions is less compared with full screen pan and scan editions of movies. Although I have not seen any movies prepared in the following way it might have been interesting to gauge the public's reaction if instead of black bars, an image of a theater proscenium curtain appeared above and below the letterboxed picture.
LFE -- Low Frequency Effects.
Linear Audio Track, Linear Stereo Tracks -- The analog audio track(s) positioned at one edge of a video tape and recorded/played back by a separate stationary tape head. Due to the slow linear tape speed, the high frequency response of consumer VCR recording on these tracks is quite limited, extending to perhaps 8 KHz at most. Also, due to the precision of mechanical parts needed for accurate slow tape movement, wow and flutter is more likely to be greater.
Line Doubler (...Tripler, ...Quadrupler) -- A device whose purpose is to output video fields or frames with twice (or three times or four times) as many scan lines, which task is most simply accomplished by delivering each scan line's content to the the TV set twice (... three times, ... four times) and in quicker succession to keep up with the incoming field or frame rate. The original purpose of these devices was to reformat standard video for specialized video projectors and specialized large screen TV sets (then rarely seen outside professional environments) which use more scan lines to avoid showing noticeable gaps between scan lines. Today's de-interlacers are loosely also called line doublers because their output is video of the same format as that from a "plain" line doubler. High quality de-interlacers use techiques more complicated than just delivering each scan line twice. Click here for more detailed information.
Line Level -- The voltage level, usually around one volt, at which audio or video signals are transmitted from one component to another such as from a DVD player to a TV set, but not counting microphone connections (a much lower level) or speaker connections (a much higher level). Standards exist for the voltage levels so that most components from different manufacturers can be connected together easily, but occasionally a non-standard voltage level may be encountered for signal transmission between two specific components.
Line Pair -- On a test pattern consisting of closely spaced black parallel lines on a white background, a line pair is one black line together with the white space on one side of it. When photographers say "lines of resolution", they mean line pairs. In television and video, one line pair equals two TV lines or pixels, of resolution.
Line Pairing -- Superimposing of the respective scan lines of odd and even interlaced fields on the (CRT) screen, generally due to a defect or miscalibration of the TV set. The result is halving of the vertical resolution as well as (usually) more noticeable gaps between scan lines. The "540p mode" on most CRT HDTV sets is nothing more than intentional line pairing of what would otherwise be a 1080i display.
Lip Sync. Error -- Situation in motion pictures where picture and sound are not synchronized in time. So named because the error is particularly noticeable as subject lip movement that does not match the words spoken. For film and some videotape methods, the sound head is several inches away from the projector gate / video heads, and careful adjustment is needed. Video processing units, such as line doublers that accumulate several frames of video in order to do their processing, can introduce lip sync. error.
Liquid Cooled Tube -- A (vacuum) tube with a surrounding jacket or cavity filled with liquid for conducting away of heat. For projection TV the cooling liquid is typically contained in the lens assembly mounted against the faceplate of the tube where, incidentally, most of the heat is generated.
Liquid Crystal Display -- A panel on which tiny spots become transparent or quite opaque in response to electronic signals and which, given enough of such spots arranged as pixels in a grid pattern, can be used as a back lit directly viewed video display or used in a video projector. Generally the opacity depends on polarization. The crystals themselves change polarization and they together with a covering panel that imparts a fixed polarization combine effects to determine how much light is transmitted.
Liquid Crystal on Silicon -- A liquid crystal display element, for projection TV, with the crystals atop a mirror rather than on a transparent panel. Its advantage over regular LCD is a higher contrast video image in that the light must pass through the liquid crystals twice, (reflecting off the mirrored surface behind). Generally the fill ratio is better (the gaps between the active portions of each pixel position are smaller) than for regular LCD.
Lobing-- Fading due to cancellation of sound as one moves about the room when there are several speakers in use, including multiple speakers in the same cabinet. So named because a graph of sound intensity (loudness) versus angle off the speaker cluster center axis suggests multiple fingers or lobes or wings. The locations where cancellation is heard vary with the frequency being reproduced. Since sound bounces off the walls, it is almost impossible to predict where in a room the best sound quality will be heard.
Long Play -- The "middle" tape speed of a VHS VCR yielding four hours of recording/playback time on a "two hour T-120" tape and introduced shortly after VHS VCR's themselves were introduced (with a single faster speed). Not all VCR's will make recordings at the LP speed.
Lossy -- Refers to compression methods that discard some of the information or data to make a video or audio program occupy less storage space or less transmission bandwidth. This results in inability to perfectly reconstruct the original program. Lossless -- Refers to compression methods from which the exact original can be reconstructed.
Loudness Control -- Control on an audio amplifier that (switches in a circuit that) adds bass boost and some treble boost as the volume control is turned down, to counteract the human ear's lesser sensitivity to low and high frequencies at lower volumes.
Low Frequency Effects -- Bass, and the vibrations produced by bass shakers, if any.
Lower Field -- The field of "odd" scan lines is called the lower field because it usually possesses the lowermost scan line containing picture information. This scan line may contain only a half line's worth of picture information.
LP -- (1) Long Play, q.v.; "middle" tape speed on a VCR. (2) A 33-1/3 RPM phonograph record, long playing compared with the then (1950's) previously standard 78 RPM records.
Luminance, or Luma -- Brightness of a light emitting object, or the portion of a video signal that represents brightness. Used by itself, the luminance signal is sufficient to produce a full black and white image. It is said that the luminance signal is responsible for the picture detail. This is true because as the video standards (NTSC, etc.) were defined, the luminance signal was given a larger bandwidth to permit the carrying of all of the picture detail while the color signal was deliberately constrained to consume less bandwidth and consequently possess less detail. Those readers who know the difference between "luminance" and "luma" should refer to Prime Disclaimer. Except where otherwise noted, we use the two terms interchangeably throughout this web site which usage is not entirely correct.
Macro -- A group of commands, or signals, chosen from the repertoire of a remote control, which can be executed/sent in sequence with the touch of one button.
Macroblock -- In a video compression scheme, a group of spacially adjacent pixels, usually forming a rectangular block, processed more or less together and somewhat separately from other pixels.
Macroblocking -- Pixellation, q.v.
Macrovision -- Trademark for video encoding used to inhibit copying of video programs, particularly programs on DVD. A VCR has difficulty maintaining synchronization and black level when it encounters Macrovision encoding.
Maltese Cross -- An alternative mechanism to the pulldown claw for advancing film one frame at a time past the projector or camera gate. It consists of a square cam with inward bowed sides and with radial slots cut in the corners, alongside a continuously rotating disk with an eccentric pin that engages the square cam by sliding in and out of the latter's slots. One revolution of the disk produces a 90 degree rotation of the square cam. To keep the square cam (and the film held by sprockets linked to the square cam) still for most of the duty cycle, between pin engagements, the related disk has attached to it a concentric circular cam with a bite taken out of it, said circular cam contacting and matching the radius of the nearest bowed side of the square cam, except when the pin is engaging the square cam.
Matte -- A means of covering up part of an image. In motion picture photography and video it (as plural) generally refers to the aperture plates or other means of hiding from view the top and bottom edges, leaving what will ultimately be a wide screen movie picture. Whereas without the mattes the displayed image would be taller with extra material at the top and bottom that is really not part of the presentation.
MKV -- The Matroska Multimedia Container, is an open standard free container format, a file format that can hold an unlimited number of video, audio, picture or subtitle tracks inside a single file.
Memory or Memories (for video/audio) -- (1) Another word for "preset" q.v. (2) Ability of, or place in the mechanics or electronics of, a TV set or other electronic device to store (remember) custom settings made by the user, for example separate brightness and contrast adjustments for dark room versus lighted room viewing.
Moire Patterns -- Alternating and repeating blurred and clear areas of subject matter with uniform thin stripes or small polka dots, as seen on the screen. This occurs because the stripes or dots on the subject are spaced slightly differently from the scan lines or pixels on the screen and some of these features line up with the scan lines or pixels while others don't.
Monitor -- A person whose duty it is to observe, or equipment that makes it easier (or possible) for said person to make the desired observations. A "television monitor" can be simply a TV set without a tuner (channel selector) or more often these days it is a TV set that has additional video inputs to accept signals other than through its tuner. "Studio monitor" usually refers to an ordinary speaker system, that is, for monitoring audio. The term "television monitor" seems to suggest but really does not stand for better quality. (The full correct term for the standard TV set with tuner is "television receiver".)
Moth Eaten -- Loss of coloration in random places of what should be a more or less solid colored area, the most likely cause being deficiencies in video comb filtering. The effect is suggestive of (wool) cloth with holes in it due to attack by moth larvae.
Motion Adaptive -- Refers to de-interlacing line doublers and comb filters whose processing strategy or formula varies, where coincidentally the optimum processing depends on whether the subject matter depicted was stationary/steady or moving/changing. The best devices may vary their processing dozens of times within a single scan line. The device must digitize more than on video field, save (buffer) them on a rolling basis, and compare the content in small groups of pixels to determine whether subject matter was moving or not. More on line doublers. More on comb filters.
Motion Compensation -- An artifical intelligence interpolation procedure to construct an intermediate image for a new intervening frame for a motion picture, showing a "moving" subject in an intermediate position between the positions shown in two original consecutive frames. For some applications (de-interlacing) just the even scan lines or just the odd scan lines might be interpolated using motion compensation given the original odd lines and the original even lines as the content of two consecutive fields.
MPA, Maximum Pixels (picture elements, picture details) Across -- (new) My own term for labeling horizontal resolution in terms of the entire screen width. This is to establish a distinction from the traditional lines of resolution measurements across the largest circle that fits in the screen.
MPAA (Motion Picture Association of America) -- An organization, primarily of executives of the major movie making houses, which sets policies and standards for movies, including for movies' distribution and broadcast. MPAA also developed the audience suitability ratings: G (general) for all ages, PG for all ages but with parental guidance suggested for minors, PG- for parental guidance for viewers under the specified age [e.g. 13], R (restricted) for theaters to not admit minors not accompanied by an adult, X for theaters to not admit minors at all.
MPEG (Moving Pictures Experts Group) -- (1) An organization, or more correctly a large enough collection of groups that could be called an institution, which among other things developed various data encoding and compressing schemes so an full length movie could be recorded on a five inch disk (a DVD). (2) The standards and the various encoding and compressing schemes developed by MPEG; they have each been given different names such as MPEG-2.
MTS (Multi-channel Television Sound) -- A standard for providing a second audio channel, for such purposes as stereophonic sound or bilingual audio tracks, on a (n analog standard broadcast) TV channel.
Multicasting -- Transmission of more than one program on the same channel, using such techniques as subcarriers and the formats provided in ATSC digital broadcasting.
Multipath -- Copies of a broadcast signal arriving at the antenna delayed in time after bouncing off of other objects such as distant hills, the received result being ghosting on the screen.
Multiplex -- Theater building or complex with several theaters or auditoriums.
Multiplexer; Mux-- An electronic device used to transmit two signals or groups of signals on the same line where they would otherwise conflict with each other. If the frequency ranges of the signal groups overlap, a multiplexer must shift the frequency range of one signal, for example given two cable TV systems that each use channels 1 through 99, one system's signals could be transposed onto channels 101 through 199. A "de-multiplexer" aka "demux" separates the frequency groups, shifting the modified signal(s) back into its (their) original frequency ranges if needed.
NAB -- (1) National Association of Broadcasters. (2) Equalization standards for analog tape recording developed by the NAB.
NARTB -- National Association of Radio and Television Broadcasters, former name of the NAB.
Native -- Not counting, or prior to applying, any of: scaling, upconversion, downconversion, encoding, decodiing, modulation, demodulation, etc. For example the native resolution of "720p HDTV" is 720 pixels high by 1280 pixels wide but a particular TV set with a native 4:3 aspect ratio resolution of 640 by 480 on an LCD panel can convert a 720p 16:9 program to fit by displaying half the program's resolution horizontally and vertically, 640 by 360.
Negative Feedback -- The feeding of a small amount of an amplifier's output back to its input out of phase, the purpose is to cancel out some of the distortion (notably even harmonics) the amplifier may introduce.
Nit -- Measure of light output off of video displays, notably LCD panels. One nit stands for the level of illumination as seen on a uniformly lit panel where the sum total of light reflecting off of or emitted by one square meter (about 10-3/4 square feet) of panel or screen area is approximately equal to the sum total of light (about 12-1/2 lumens) given off by a lit candle (equal to the light output of a candle with certain standard characteristics). See, also, Foot Lambert.
Notch Filter -- An electronic filter that suppresses a small portion of a frequency range. A common use is as an inexpensive substitute for a video comb filter, where the frequencies used by the color information in a composite video signal are prevented from entering the luminance amplifier.
NTSC (National Television System Committee) -- U.S. government and industry committee which defined the 525-line 60 (59.94) interlaced fields per second analog broadcast TV standard over 50 years ago. (This format is referred to as NTSC.) Of the 525 scan lines, 480 (give or take a few) contain the picture and the rest contain synchronizing information, hold the encoded closed caption text, and provide a time delay to move the electron beam back to the top of the screen. NTSC is used mainly in North America and Japan. Originally 30 frames per second, the standard was changed slightly to 29.97 frames per second at the time color was introduced since that change made it easier to incorporate the color information into what is now a composite video signal. The change was so small that practically all older TV sets continued to receive the signal properly without loss of vertical hold.
Numbering Scheme (and disclaimer)-- There are several numbering schemes for NTSC scan lines as seen in textbooks. A few are described below. The scheme we use is (a).
(a) Odd numbers between 1 to 483 inclusive denote lines for the first field, then odd numbers from 485 to 525 denote a vertical retrace interval, then even numbers from 2 to 482 denote the second field, then even numbers from 484 to 524 inclusive make up a vertical retrace interval.
( A retrace interval comes first, using odd scan lines from 1 to 41 inclusive, then odd lines 43 to 525 inclusive make up the first field, then even lines 2 to 42 make up a retrace interval, then even lines 44 to 524 make up the second field.
© Scan lines numbered consecutively 1 to 21 make up a retrace interval, lines numbered 22 to 263 make up the odd field, the following retrace interval consists of lines numbered 264 to 284, the lines of the even field are numbered 285 to 525.
In these examples the picture may occupy up to 483 scan lines. If it does not occupy all 483 allowed scan lines, which extra lines are left black may vary depending on the make and model of equipment. There are other standards with slighly different numbers of active scan lines.
Nyquist Frequency -- In digital processing, half the sampling rate (where one sample equals one cycle). Its significance is that all content above it must be filtered out of the source material prior to the analog to digital conversion at the start of processing, otherwise artifacts will be produced.
OAR -- Original Aspect Ratio.
"Object" (on the screen) -- In the subject matter of a picture, a line or a patch of color. When quality of reproduced pictures is discussed technically, it is often necessary to think about small parts as hair, nose, arm, shirt, shoe, or even "iris of the eye" as opposed to "person". It is like having to deliberately not see the forest because of the trees.
Octave -- -- A frequency band consisting of any starting frequency extending up to a frequency twice the starting frequency. In an electronic context it is used to describe a filter's behavior such as attenuating three dB per octave.
Omnidirectional -- Having equal sensitivity to sounds or signals coming from any direction or, in the case of broadcasting antennas, radiating energy equally in all directions. May be understood to be or qualified as two dimensional (a circular pattern) or three dimensional (a spherical pattern).
Open Matte -- Video edition of a movie originally filmed soft-matte (q.v.) where more material above and below what should be shown in the theater is included to fill the TV screen.
Operating System -- The supervisory program such as Windows XP ™ that is always running in a computer that is turned on and ready for use. Contrasted with applications programs that are running only when someone wishes to use them, and "drivers" which are running only when another device such as a printer is in use.
Order of Magnitude -- A tenfold increase or 90% decrease; a decade, q.v. Frequency ranges: Medium frequency 316 to 1000 KHz (1 MHz) and 1.0 to 3.16 MHz; High frequency 3.16 to 10.0 MHz and 10.0 to 31.6 MHz; Very high frequency 31.6 MHz to 100 MHz and 100 to 316 MHz, etc. are in orders of magnitudes or as broken down here, pairs of one-half orders of magnitude. A one-half order of magnitude increase is an increase by a factor of the square root of ten, approximately 3.16, that is, if you multiply by the same number (the square root of ten) twice you get a one order of magnitude or tenfold increase.
Original Aspect Ratio -- The aspect ratio that the artistic director intended for a motion picture.
OS -- Operating System, a supervisory program such as Windows in a computer which program is running all the time and which program schedules and allocates resources for other programs that are started, executed, and stopped depending on what the user wishes to do.
OTA -- Over The Air.
Overscan -- The adjustment of a TV set so that all four edges of the video frame are slightly outside the screen. This was done by TV manufacturers decades ago when TV pictures shrank if the power line voltage dropped, the latter occurring often when everyone was using a lot of electricity. With overscan, there would still be enough picture to completely cover the screen when the picture shrank, and viewers stopped complaining that TV sets were defective.. However program material at the edges of the screen is lost. Today's TV sets don't suffer from picture shrinkage as much but overscan still occurs and too much of it is now regarded as a quality control deficiency. Still, TV producers keep important material away from the edges of the video frame, and many video cameras have marked in their viewfinders a "safe area". Sometimes the electronics in the TV set are deficient (rounded off horizontal and/or vertical sweep sawtooth waveforms) that the extreme edges of the picture are "squished" and overscan is deliberately used to hide this distorted material outside the screen borders.
Over the Air -- Broadcasting using a transmitter and antenna (not on a satellite) directly to the end users who use antennas to receive the signal.
p (as in 60p) -- Frames per second for non-interlaced video.
P-Frame -- In a video compression scheme, data representing the differences between the complete subject frame and its predecessor. This is the most compact amount of data needed to generate the subject frame given the complete frame preceding, but it does not allow backwards single step or playback. See, also, I-Frame.
Cont. Part 3 of 4