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A digital surround-sound system introduced by Dolby™ laboratories. The system is usually comprised of 5.1 channels (6.1 nowadays and counting)- five/six discrete channels - left, right, center/s, back left and back right. In addition one subwoofer covers the bass (low frequency signals, representing a limited spectrum of audio, hence the. 1 designation) that belongs to all channels. As the ear is not sensitive to the direction of the very low frequencies, the “lowbass” area, one subwoofer is sufficient.

In order to retrieve and decode AC-3 sound channels, a special amplifier/receiver is needed. The AC-3 system is also available on some digital video equipment for recording and playback, such as a DVD. Similar digital 3D sound schemes are also available such as THX®, DTS® and others, as well as Dolby surround, which is an analog scheme.

Automatic Chroma Correction. A system built into some VCRs and TV sets for automatic adjustment of color saturation levels. Most ACC systems measure the Color Burst* amplitude and use it as reference. As the system is automatic, erroneous color levels can appear in the video scene - an original grayish scene can become over colored, or a rich, saturated-color scene can become dull.

Active video

The part of a video signal visible on the screen.

Adaptive comb filter

A Comb Filter* that uses adaptation technology - changing its operation parameters by dynamically following changes in the picture.

Analog to Digital Converter. A device which converts an Analog* signal to a digital form. The process may be done with different levels of accuracy. The conversion fidelity is dependent on two factors - sampling rate and number of bits. The higher the rate and/or bits used during conversion, the more accurately the analog signal is reproduced. Until recently, the most common video sampling speed was four times the color subcarrier frequency (4xFsc - 17.7 Msps (million samples per second) for PAL 14.3 Msps for NTSC) Today, the standard (industrial and broadcast) tends to be 13.5 Msps for luminance signals. For color difference signals it is usually half for both PAL and NTSC. Industrial video signals are digitized at 8-bit accuracy (256 levels) while broadcast signals are digitized at 10-bit accuracy (1024 levels) or even at 12 bit. Hi-Fi audio signals are usually sampled at double the highest frequency audible to the human ear, i.e., 20 kHz (or more - sampling at 44 kHz or even higher frequencies) with an accuracy of 16 bits or more.

Advance definition Television. The “HDTV” standard which was used in Japan. “True” HDTV is now replacing this format worldwide.

A digital audio standard established by the Audio Engineering Society and the European Broadcasting Union. The signal is serial digital, comprising two channels. The basic sampling resolution is from 16 to 24 bit, sampled at frequencies between 32 kHz and 192 kHz (44.1 kHz is the most common). Two sets of 4 bits of information are included for other data transmission (one set can be added to the 20 bit of audio, for a 24 bit system). Additional bits are transmitted as well, and the transmitted frames of the interwoven audio channels are grouped to frame blocks.

Automatic Gain Control. Electronic circuitry that assures a fixed predefined output level, automatically compensating for varying input levels. Used in audio, video and RF equipment to ensure that output signals are maintained at constant levels in the face of wide variations in the signal-input levels. Low level signals are boosted and high level signals are attenuated to an average level. Automatic gain control has a tendency to introduce audio noise* and hiss* into the audio channel of a videotape. In sophisticated equipment, automatic gain control is often superfluous, and the user can select the option of manual control.

An electronic device, mainly used in security installations, where several video cameras positioned in different locations on the premises, scan automatically, and are viewed one after the other on one monitor. When an intrusion occurs in the field-of-view of one of the cameras, a special alarm signal is sent to the scanner instantly activating the particular camera in question. It usually triggers an additional alarm device drawing attention to the event. Sophisticated scanners have internal microprocessor control, allowing them to skip or analyze every scanned source, as well as activating, when necessary, a special device, which relays a suspicious camera image to a remote location for monitoring via a telephone line.

An artifact created when an ADC* converts an analog signal to digital form and the sampling rate of the converter is less than double the highest frequency component within the analog signal.

The Alpha channel is a separate channel of data, transmitted alongside the original color or video information - whether it is video or computer based. It is used to specify an Alpha value for each color pixel in order to control pixel based image blending and mixing. Values of the Alpha channel range between 0 and 1. (In SDI applications the Alpha channel uses 256 different levels from 0 to 1)

Image blending and mixing based and controlled by the Alpha Channel data stream.

An obsolete LCD* display system, suffering from many technical flaws, replaced by polysilicone-type and other active displays.

Amplitude Modulation, AM, is used when a signal, (usually an RF* signal) is transmitted carrying low frequency information. The low frequency signal modulates -(changes) the amplitude of the RF signal, and is recovered (detected) at the receiver’s end.

Video information that is transmitted on the air as TV transmission employs this system. Some radio stations use it also (AM Broadcast), although the superior FM* system dominates radio transmissions.

A video monitor which accepts analog level signals. Several types of inputs are accepted by analog monitors making them very flexible: composite* video, RGBS, YC, YUV* and any combination of these standards. The signals transmitted to an analog monitor are usually between 0 and 1 Volt and use 75-ohm coaxial cables.

Signal in which the output varies as a continuous function of the input, while the values of the transmitted information are within defined limits. Any variation in an analog video signal may represent a specific video parameter, e.g., when the luminance* signal is high (0.7 V above black level) the picture is very bright. When the signal is low (0.1 V), the picture is very dark; at 0 V the picture is totally black. TTL* digital signals, in contrast, are predefined as only 0 or 5 V or other fixed logic levels, and do not vary.

The anamorphic horizontal compression system used in the cinema industry, optically compresses the wide-screen movie frames by a special lens, to fit on a standard film (35 mm or similar). When displayed on the screen, the opposite effect is used – stretching the frames to the original wide-screen format. In the DVD format, a similar process takes place, where the frames are digitally compressed horizontally on the disc. When played on a standard, 4:3 aspect TV, a letterbox image is shown, but when set to 16:9, a full wide-screen image is shown on a Plasma screen or video projector which is capable of 16:9 image reproduction.

Data added to a digital video data stream including information such as embedded digital audio, control signals, etc.

American National Standards Institute.

Antialiasing is a procedure which, by smoothing and filtering, eliminates or reduces, aliasing noise*. The procedure usually involves low pass filtering of the processed signal prior to digitizing in order to eliminate signals, having frequencies close to and greater than half of the sampling frequency.

Originally, creation of the appearance of movement, such as in a cartoon by flipping a series of gradually varying drawings in rapid sequence. Today, creating animation and cartoons is done more effectively using computers with appropriate graphics software and genlocking* hardware. The final product of computerized animation can be integrated into videotapes or a video production using encoding* equipment.

A device (a PC card or a standalone machine) that bridges the wireless network to the wired one.

An adjustable opening that effects the amount of light entering a camera. The aperture (sometimes referred to as the Iris) is measured in F-stops. Smaller F-stop numbers mean that more light reaches the optical sensing device of the camera.

The screen structure element of Sony Trinitron-™ monitors.

Average Picture Level. A measure of average video luminance level expressed as percent of maximal white level. When the APL is low, the picture is dark, when the APL is high the picture is bright.

The ratio between the width and height of the TV picture on the screen. In a normal TV set or monitor the aspect ratio is 4 to 3 (4:3). The new aspect ratio in HDTV* and IDTV/EDTV* is 16:9 which resembles the aspect ratio in a movie theatre (Widescreen).

New TV systems support both 4:3 and 16:9 aspect ratios (PAL PLUS*) and can automatically switch between them.

Advanced Television. A digital television system comprising standard, enhanced and high-definition versions.

Pertaining to frequencies of a normally audible sound wave (15 to 20 kHz). Audio has been, until recently, a very neglected side of video recording and processing. Very often, during videotape duplication and enhancement, the quality of the soundtrack is detrimentally affected. Several special soundtrack enhancement devices and integrated audio and video enhancers* have recently appeared on the market (see Audio Equalization and Audio Exciter). New VCRs and TV systems employ Hi-Fi quality sound tracks, and are sometimes equipped with decoders for DOLBY SURROUND, AC-3 or other three-dimensional sound encoding devices.

The range of audio frequencies over which an amplifier or receiver will respond and provide useful output. The higher the audio bandwidth the better the sound quality. The highest practical frequency for the human ear is 20 kHz. An audio amplifier delivering a flat response of up to 20 kHz will faithfully reproduce the audio soundtrack of a video recording.

A feature used in video editing* to add, replace, or mix audio signals with the original sound track without affecting the picture (video portion). Special controls and connectors are available for this purpose on some quality video recorders. When dubbing is not available on, or is limited by, the video recorder, audio dubbing can be performed externally using audio/video processors.

Combining audio material of different origin into one continuous piece. For example, when a sound track is added to a videotape, various background sounds, music and speech may be supplemented in order to highlight particular scenes in a movie. Audio correction can also be done during video editing. Audio equalization, audio noise reduction, Dolby* encoding, etc. are functions available on many quality editors.

An audio process, hardware or software based, which breaks down the audio spectrum into several frequency bands to compensate for changes in audio frequency-dependent levels, allowing the user to control (boost or cut) each frequency segment individually. The main use of audio equalizers is to compensate for inadequate acoustics in the room where the sound is being played. Another very important use for audio equalization is to revitalize the playback* characteristics of low quality tapes and poor recordings in order to recreate the original sound.

An audio circuit available in high quality audio equipment, designed to recreate the harmonic content of an audio signal which was lost during video or audio tape duplication. Using the audio exciter to recreate the lost harmonic content, generates a sparkling audio sound. This effect is different from normal high frequency boosting which generates noise* and hiss* while improving the frequency response of the audio signal. Audio exciting is available only on special sound correction devices.

During video production, the video signal is normally accompanied by an audio signal. Sometimes, during the switching or processing of signals, the audio signal is separated from the video signal. In such a case, a complex situation arises whereby each signal must be processed, mixed and enhanced separately. Audio-follow-video is a process which overcomes this difficulty and both signals, audio and video, are switched from an audio-video source to an audio-video acceptor simultaneously (not in separate passes).

The mixing or blending of two or more audio signals to generate a new signal, which is often used for audio dubbing. Audio mixing requires that all audio channels involved are amplified and equalized to the same level. To mix a line level input with a microphone signal, the microphone signal must be pre-amplified to bring it up to a level similar to that of the line signal. In video processing, audio mixing is used for the insertion of background music behind the dialogue. It is also employed in the creation of cross fading between two audio sources. It produces a drift in the level of the received signals until one fades out and the second becomes dominant.

A hiss* (random high frequency noise) or a hum (low frequency noise from the power-line frequency and its harmonics or ground loops) heard on audio or video equipment. It is the result of poor signal handling or of discrepancies between audio pickup devices and media. Audio noise reduction* circuitry eliminates or reduces audio noise.

A term which was often used when discussing a channel on a TV receiver or on video equipment, which has been especially designed to accept VCR audio-video signals. This channel automatically activates special circuitry within the TV set or monitor to prevent picture distortion* and skewing*. It is also used for audiovideo processors, which handle both types of signals. The AV definition (Audio- Video) has broadened since then and now describes anything that handles both signals simultaneously.

A device which combines audio and video signals. In the analog world it describes a machine, which modulates the audio signal on a high frequency carrier and mixes it with the video signal for transmission on a single cable. In the digital world it describes a device which embeds digital audio signals within a digital video signal.

A unique feature, available only on Kramer equipment, which provides optimal automatic suppression of snow* (signal noise level) during any stage of video enhancement* (See Noise Gate.)

Audio Video Interleaved. A computer video/graphics format. This format interleaves digitized video frames (or computer-generated frames) and synchronized audio in one file. The clips generated in the AVI format may be played back in a Windows® equipped PC, usually independent of screen resolution and color palette. This also denotes a practically uncompressed file format obtained for example in a PC, when digital or analog video and audio are captured from an external source. As it is uncompressed, it can occupy up to 200 MB of disk space for every minute of captured video.

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A part of the composite video signal which is between the trailing edge of the horizontal sync and the beginning of the corresponding active video line (end of horizontal blanking).

A signal that is divided into two antiphase signals, traveling on two wires (and sometimes with a third - a ground reference wire). Transmitting a balanced signal achieves better signal to noise ratio, and the signal is more immune to noise and interference. The receiving end requires a differential amplifier, which amplifies only the differences between the antiphase signals, thus canceling noise picked up on the way.

The balanced system is used either when very low signals are to be transmitted over long distances (such as those generated from high quality microphones) or at broadcast audio studios for highest quality signal recreation. The balanced signal system is used in TP* (Twisted Pair) wire setups when it is essential to use non-coaxial wires for data, video, audio or graphics transmissions.

See Video Bandwidth.

A process that reduces digital signal bandwidth in order to allow its transmission as a DTV* signal. A 6 MHz transmission bandwidth requires signal bandwidth compression down to about 20 Mbps.

Normally refers to a non-modulated composite video signal, with the frequency spectrum extending from a few Hertz (or from DC) up to several megahertz, and covering the full bandwidth of the video signal.

Bit Error Rate. A term used in digital circuits for measuring the fidelity of a transmitted and received digital signal by measuring the error probability (or number of bits received incorrectly.)

A video recording and playback* standard on 1/2” tapes distributed mainly by Sony™. From its inception BETAMAX competed with the VHS* system developed by JVC™. Both were intended for home use and there was no substantial difference between the two formats. Today, the Betamax system for home video is practically non-existent as that market is completely dominated by the VHS system.

BETACAM and BETACAM SP are wide-spread professional video recording and playback formats. BETACAM uses 1/2 inch tapes, employing the component video* system for highest professional quality outputs. Many editing systems* and controllers are designed around this format.

A digital video format introduced by SONY™. This format uses MPEG* compression with a data rate of 18 Mbps. The compression ratio is high - approaching 10:1. Output quality is very good despite the high compression ratio because it uses an MPEG-2 4:2:2 profile. Cassettes use metal particle technology and come in two sizes - 60 minutes for fieldwork and 184 minutes for studios. These VCRs also play analog Beta tapes, for backward compatibility.

A video signal comprising sync* and color burst* signals which produces a black image on the screen. It is used to genlock* other video sources to the same sync and color information.

Black burst generators are used in video studios to genlock an entire studio to the same signal for easier switching and mixing between sources.

See SPG.

That level of the DC voltage of a particular part of the video signal which corresponds to the black areas in a video scene. The black level is used as a reference for comparison with other tones in the picture and other video signals.

An electronic process which establishes a fixed DC level for a picture signal at the beginning of each scanning line. The black level* of a video signal is set to a specific, predefined DC voltage. This process is used, for example, when two video signals are to be mixed and the black levels must therefore be equal.

Designation of a video signal, part of which (spikes or the sync tip) goes below black level transition. Usually, such signals (besides the sync), are undesirable within the video signal. They appear, however, due to image enhancement or poor transition response of the video amplifier or processor. If the signal excursions below black level are small, they can be ignored. If they are too large, approaching sync tip level, image instability might occur, as the blacker than black spikes may be interpreted as sync pulses. Sometimes those excursions are deliberately created for image enhancement and special effects and copy protection purposes. Digital processing can handle some blacker than black signals.

The period when the screen is darkened, which occurs when the electron ray in a monitor or a TV set retraces to start a new line or a new field. The instantaneous amplitude of that signal is such that it makes the return trace invisible.

The blanking period is used to eliminate the appearance of the CRT retrace beam so it will not be visible on the monitor. Switching done during the retrace period results in “clean switching”. (See Vertical Interval Switching.)

A disturbing phenomena apparent when a part of the video picture becomes “brighter than white” due to wrong exposure or due to a very strong light source shining directly into the camera lens. The blooming effect distorts the colors and the fine details of the area affected by the strong light. This effect can also be seen when a color decoder chip within a TV set or monitor is badly tuned or malfunctions. In order to check whether the blooming effect is a result of a badly illuminated scene or a malfunctioning monitor, the signal should be fed to another good monitor. If the effect persists, it shows that the video source is defective.

Blue key generation is a process, which inserts of one video picture into a predetermined area in another one, through the use of special hardware.

The primary picture is shot with the subject against a special blue tinted background. The blue content of this signal is then removed and the second picture is inserted in that area where the blue background was located.

Blue keying is a very important special effect, which is often used in news broadcasting where pictures of the news being discussed are viewed on a screen behind the anchorman. An extension of the Blue Key is the Chroma Key*.

A technology used for wireless transfer of data over a short distance. The technology uses a 2.4 GHz carrier, and is suitable for short distances up to 10 meters (30 feet). It allows for low speed data transmission, up to 720 Kbps. The technology can be used to transfer control data in a video studio, replacing RS-232 wires, as it can work through walls. It can also be used for access control and short-range user ID.

Blu-ray Disc (also known as Blu-ray or BD) is an optical disk storage media format introduced by Sony™. Its main uses are HDTV and data storage. The disc has the same dimensions as a standard DVD or CD. The name Blu-ray Disc is derived from the blue-violet laser used to read and write this type of disc. Blue-ray disk can store 25 GB on one layer or 50 GB on dual layers disks.

A simple graphics Bit Map format created by Microsoft™ for the Windows™ program. Many graphics programs running under Windows, which support formats from monochrome up to 24-bit color, use the BMP format. The BMP format does not support image file compression, so 24-bit, high-resolution color images occupy a large amount of disk space.

A type of connector used for high frequency signals in VCRs, general video equipment and RF* equipment.

The Bi-directional control of audio and video signals to permit raising and lowering of signal levels.

The boundary between two merged video pictures, such as in blue keying* or wiping. Bordering is a special effect which can be used in video processing to alter the border from a sharply defined line to a fuzzy ill-defined blend of the two pictures. The width of the border, its color and its texture are easily changed.

Color identification signals in the vertical interval period used in the older SECAM system which look like bottles on the oscilloscope.

A special, artificially generated video signal for testing, where the APL* is changed at a low rate, testing the low frequency response of a video device as well as black level clamping*.

A part of the video signal which belongs to the blanking period, extending from the rising edge of the horizontal sync signal and the beginning of the color burst* signal.

See Color Burst*.

The signal generated in many video processors starting at the outset of the color burst signal* and ending at the end of that signal. This burst gate signal is mainly used for black level clamping * and DC restoration.

Monitoring an unprocessed video signal. For example, when using a screen splitter, special effects generation is often previewed on a screen before actual recording. The processed signal is observed on half the screen and on the other half, the unprocessed, bypassed signal is viewed for comparison.

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An electronic process compensating for high frequency losses incurring in long cables due to various cable shortcomings. Equalization is usually performed by special controls or trimmers mounted on the amplifier or switcher which allow variable operation to equalize different cable lengths and qualities. Equalization is best done at the source amplifier, at the beginning of the long cable, to preserve optimal signal-to-noise ratio. Cable equalization (EQ) is also important for fast digital signals. For digital signals, cable EQ is done at the end of the cable. In this case the equalization is usually automatic and no trimming is required.

An interfering artifact that appears when a signal which is transmitted via a cable to an acceptor is unable to transfer its’ energy in full to the load, due to cable shortcomings or improper loading at the remote acceptor. Some of the energy is reflected back to the source (as if coming from a mirror) and is irregularly remixed with the transmitted signal. The result is “ghosting”, artifacts and signal noise.

A TV system that uses cables rather than antennas for the transmission of TV programs and commercials. In many countries the cable TV network transmits side by side with the regular TV network (MATV)*. Many commercial stations use cable TV, because it is easier to control and the picture quality is superior to that received from an antenna. Hundreds of channels can be transmitted simultaneously with CATV, which is almost impossible with MATV.

The combination of a camera and a video recorder in one device. It permits easy and rapid simultaneous photography and recording. It is available in most video formats, VHS, VHS-C, Beta, 8-mm video, Hi-8, Super-VHS, DV, etc.

See VIDEO CAMERA.

A single camera cable handling the following signals: video, audio, DC power supply, remote control line, tally* control and others. A camera breakout setup allows various signals, which are transmitted on the main camera cable, to be separated and made available externally. On many better video processing devices there are breakout systems. A connector outlet is provided, to which the multi-pin camera plug is attached.

A camera power supply. Some professional video cameras* can use an external 12 VDC voltage supply which is derived either from a battery belt worn by the cameraman, from a battery within the video recorder itself, from the mains power supply (after down-conversion) or some other DC source.

The required 12 VDC supply must be highly regulated. Many problems in camera recording such as black-outs, distorted images, faulty colors and other interference showing on the screen can be the result of a poor power supply.

A type of microphone with a sound pick-up characteristic and which resembles a heart-shaped sphere. The cardioid microphone is used in applications where a specific pick-up characteristic is needed.

Category 5, an unshielded cabling system consisting of four twisted pairs of wires used for communication and networking. At the end of the CAT 5 cable there is a RJ-45 connector. This was initially used in computer network environments in 10/100 Mbps systems. There are newer, higher bandwidth systems such as CAT 6 and others. The four twisted pair system can be used to transfer VGA, video, audio and other signals as well, using the appropriate transmitters and receivers.

A microelectronics chip which stores minute electric charges on a matrix of micro-capacitors. These voltages are bucketed (in the sense of a bucket brigade) from one address to another according to an external-clocking signal. This permits storage of analog memory on the chip.

CCD technology was once used in audio to store a signal, which could be retrieved later to create an echo effect via retrieval delay. CCDs are at the heart of video cameras and digital still cameras. Lenses cast a beam of light on the CCD, which acts as a sensor and temporarily stores the visual image. CCDs were used to store a video signal, which was later retrieved for time base correction*. Digitally storing video information is performed using digital video tapes (mini DV for example) recordable DVDs, hard disks and large flash memory chips. There are also other types of semiconductor optical sensor devices such as CMOS sensors – which differ in their characteristics, light sensitivity and noise levels.

Comite Consultatif International des Radiocommunications. A European committee which was situated in Paris and created and approved standards related to Audio and Video. The committee is no longer active and has been replaced by the International Telecommunication Union (ITU.)

Specifications and parameters for application of Component Video* signals (Y, Cr, Cb) in a 4:2:2* system, recommended by the CCIR, now known as ITU-R BT.601-2.

The definitions of the parallel connector pinouts, multiplexing schemes, syncs, blanking periods, etc. for parallel and serial interfaces with CCIR 601, now known as ITU-R BT.656.

A surveillance system - commonly used in security applications - where the video signals are not publicly distributed. Cameras are connected to television monitors in a limited area such as a bank, a museum, a store, or a parking lot. CCTV video is often of very low quality - usually black and white – and more sophisticated systems in sensitive installations may be connected to frame grabbers recording at very low frame-rates (typically, around one frame per second, or even slower).

Compact Disk. A digital, optical-based audio, video and computer data storage medium. Audio CDs have taken over from vinyl records in the consumer field, because CD audio quality is very high and unaffected by mechanical problems.

In video, CD-ROM and erasable CDs are fast penetrating into Multimedia, video editing and video recording, as digital image quality is high, suffering no generation loss. The DVD will ultimately replace the CD. Video can be recorded on a CD in several formats- low quality VCD, VCR quality SVCD and mini-DVD. The latter can store around 15 minutes of DVD quality video on a standard 700 MB CD.

In the computer field, the CD ROM (Read Only Memory) system (player and disk) is used to retrieve enormous amounts of data - text and graphics - up to several hundred megabytes from one disk. Re-writable CDs (CDRW) became very popular for data storage and retrieval but the recordable DVDs with their enormous 4.7 GB storage space (and double that capacity) at an affordable price are pushing CDs into history’s dustbin.

Compact Disk Interactive. A machine designed for consumer use, like audio CDs, with special dedicated compression hardware. It allows storing and replaying a much larger quantity of data, and supports JPEG and MPEG* standards.

Compressed Time Division Multiplex. A color component time compression system used by BETACAM* VTRs. The two-chrominance signals (R-Y and B-Y) are compressed, multiplexed and recorded at the same time as the luminance signal.

An obsolete color standard developed by IBM for personal computers which permits the display of only four colors out of a menu of a total of 16 colors at any given moment, and at a resolution of 320 x 200 lines (on a TTL* digital monitor).

With special electronic processing hardware, CGA output provided a video image, computer generated, that was used for special effects, animation, titling*, etc.

A machine used in video production to produce captions or titles. The character generator is similar to a PC word processor, allowing the user to change fonts, character attributes, font colors, background colors and so on.

Several electronic chips designed to perform a specific task together are called one chip-set. Manufacturers of VGA* cards, computer main boards, multimedia hardware and other video hardware use chip-sets to perform specific tasks which are integrated into the work of the entire board.

A device used to correct problems related to the chroma subsection of the video signal, including chroma saturation, hue, color balance and color noise.

Noise which manifests itself in a video picture as colored snow. It may be the product of one or more of the following factors:
1.The chrominance in the video signal is weak.
2.There is excessive color information, which creates over-saturation.
3.A poorly manufactured video device.
4.Low quality videotapes.
5.Poor color decoding.
Good color processors reduce or eliminate chroma noise.

A process available on better quality special-effects generators and mixers which allows superimposition or replacement of one video picture in a predetermined area of another one. The first picture is photographed with an object or person against a special, single-color background. The complete color content of this particular signal is removed and the second picture is inserted in that area where the background was (See Blue Key).

The level of color in a video picture as manifested by the strength and saturation of the tones. The higher the chrominance level the stronger the color (e.g., a strong signal produces red, and a weak signal, pink). A strong signal produces a high saturation level and a weak signal, a weak saturation level. Color saturation level can be changed using a color processor*. Thus colors can be made stronger or paler. A quality color processor can also change the tint, - red can be changed to green and green to blue.

An electronic process, which corrects, line-by-line, the video blanking level or sync tips by clamping it to a predefined DC level. The process reduces the DC level changes when switching between different sources, eliminates picture jumps on the screen and the accumulation of low frequency noise and instability. Clamping also increases the dynamic range of video amplifiers by limiting the average picture changes, which stress the video amplifiers.

Analog signal quality gradually degrades with cable length. Digital signals behave differently. Up to a certain distance, depending on equipment and cables used, the signal is perfect. Extending the cable length by only a few meters beyond that distance may cause a total signal crash which is known as the Cliff Effect.

An electronic process for limiting the amplitude of video or audio signals. Sometimes, clipping is performed prior to Modulation* and sometimes to limit signal level, so that it will not exceed a predetermined, allowed level. In video, the term SOFT clipping is used when the luminance signal is limited, and HARD clipping is used when both luminance and chrominance signals are limited. Clipping a signal can distort it, resulting in additional, unwanted harmonics.

An operation for decoding text information transmitted alongside video and audio information. The decoded text is displayed at the bottom of the screen.

An artificial video signal, electronically generated by a signal generator. It produces color bars on the video screen which are used to establish a proper color reference before recording and playback* and for adjustment purposes.

A reference color subcarrier signal transmitted at the beginning of each scanning line (during the blanking period) of a composite video signal or the “C” component of a Y/C signal. It is used for color synchronization and to establish a reference for the color information following it. The color burst is an amplitude and phase reference for both color hue* and color intensity. It is transmitted at the DC voltage level which is practically the black level* of the signal. The luminance signal, which follows the color burst, should not fall below the color burst level. Black level clamping* is usually performed in the color burst area.

The sample accuracy in digital video systems is measured by the length (amount of bits) of the digital word. Color depth describes how long (how many bits) is the digital word. DVI uses up to 24 bpp while HDMI1.3 can use up to 48 bpp.

A device which breaks down the video signal to its color components – Red, Green and Blue, or color difference components. A color decoder chip set is used in TV receivers, for example, and the recovered color signals are used to drive the CRT.

Component video uses Y (luminance) and two color difference signals: R-Y and B-Y representing - in a formula - the red and the blue contents of the signals. The color difference signals are derived from a calculated subtraction of the luminance part from each of the signals representing the red and blue parts of the video signal. YIQ* and YUV* are derived from similar formulas.

The number of a specific field in a color frame* sequence (1 to 8 in PAL, 1 to 4 in NTSC.)

A set of video frames which is different in each broadcast standard (PAL, NTSC, SECAM) and which is made of a certain number of sequential frames with different SCH phases until the first frame SCH or color difference signal repeats. In PAL the sequence consists of 4 frames or 8 fields, in NTSC and SECAM it is 2 frames or 4 fields. In SECAM the structure is different from PAL or NTSC.

See BOTTLES*.

Circuitry, which disables the color decoding* process in TV sets when a black and white transmission is received. The color killer circuitry looks for a color burst signal, and when it detects that the color burst is absent (as in black and white transmissions) color decoding circuitry is disabled. The circuitry was added to TV sets in order to improve the quality of black and white images, because the attempts of the TV to detect color information in a B&W signal result in artificial, disturbing color fringes and noise.

The timing relationship in a color video signal which keeps the hue* of a color signal correct, measured in degrees. Color information is encoded in the video signal as the difference in phase between the sine peaks of the chrominance signal and the color burst* subcarrier signal. If the two signals overlap exactly, then the phase difference is designated as zero degrees. If the sine signals do not overlap, the color phase can vary from 0 to 360 degrees. Each shift in the color phase represents a specific tint on the screen. If two sine waves are shifted one from the other by 180 degrees, then the colors are totally inverted.

A way to alter the colors of a video signal. At the first stage, the video signal is separated into its black/white and color constituents. Further separation usually strips down the color information to its basic components, red, green and blue.

After color correction, the signals are recombined into a normal video signal by the processor with improved or changed colors.

See CHROMA Corrector.

Indicates the hue* of the color. The term is derived from photography where the spectrum of colors are based upon a comparison with the hues produced when a special metal body is heated from red through yellow to blue, which is the hottest. Color temperature measurements are expressed in degrees Kelvin.

A mathematical way to describe color information. In different color space schemes all the different formulas used describe essentially the same colors.

A standard monochrome video signal has additional modulation frequency bands (sidebands) added in order to convey color information. These are the color subcarrier components.

Using the color burst as a reference, the ratio of the color subcarrier of the video signal to the burst indicates the intensity of the colors (in PAL* and NTSC). Thus, when there are relatively limited color subcarrier components inthe video signal, the colors are weak or pale. The system is, in fact, a little more complicated than this since in PAL and NTSC the color subcarrier contains red and blue information simultaneously which must be further processed to RGB by a color decoder* in the monitor.

The color subcarrier frequency in PAL* is about 4.43 MHz and in NTSC* it is about 3.58 MHz. Since it resides outside the highest luminance frequency, the relevant usable luminance* frequency is limited to about 4 MHz in PAL and to about 3 MHz in NTSC (when using simple analog filters.) The luminance frequency response after separating chrominance from luminance may be much higher when using a digital Comb Filter*.

A process which allows painting a black/white or even a color video image with artificial colors.

Circuitry designed for best separation of Y and C from a composite video signal. Standard circuitry uses analog bandpass and bandstop filters, which result in unclean separation of Luma from Chroma, possible phase shifts (hue changes), signal delays and a host of other undesirable effects.

Comb filtering is a digital process, separating Y from C, based on “combing” out the chrominance signal from the luminance. It is called comb filtering because chroma resides in specific bands along the frequency axis which resemble a comb. The drawbacks of digital comb filtering are some undesirable effects due to digitization of the video signal, higher cost than analog filters and sometimes the need for time base correction* prior to “combing” in order to obtain the best results.

Software based protocol or language, linking several devices to enable them to communicate one with one another. Communication protocols are used between computers DVRs and VCRs or editing controllers allowing bi-directional conversation between the units. The linked units use specific hardware connections in addition to the software and protocol. See also RS-232/RS- 422*.

A simple composite video signal comprises luminance* information, color* information (chrominance) and sync information in one transmission channel.

When performing video image improvement operations and special effect* generation on a composite video signal, a trade-off between color quality and picture resolution is unavoidable. To achieve maximum video quality, professional equipment therefore uses one of several component systems which split the signal into several channels: RGB* splits the video signal into its red, green, blue, and sync* components. The YUV* system uses a different set of components: luminance + sync, and red/blue color difference. The Super-video (Y/C - Super-VHS* and Hi-8*) system, separates the luminance andchrominance components.

Different types of equipment are required for each format and each component system has its own advantages and disadvantages. In a video studio, it is not uncommon to find a composite or Y/C video recorder, an RGB camera and a component YUV mixer. Special interface units are needed to bridge between the various formats of video.

A digital form of Component Analog signals usually related to CCIR 601* (ITU-R BT. 601-2.)

Contrast is a function of differences in intensity between the darkest and the brightest areas of a picture. When contrast is high the picture contains sharp blacks and whites. When low, the picture shows only variations in gray tones. Excessive contrast can result from improper illumination or photographing in harsh sunlight. In such a case, it can be corrected using a video processor*. In the same fashion, a low contrast image, which is the result of insufficient illumination, can be enhanced. Very few video processors on the market today offer real contrast control.

A way of mixing two video images using a special effects generator* or video mixer. While maintaining a fully contrasted image, this process does not allow the mixed image to exceed the maximum permitted amplitude (which would cause degradation in picture quality). Using a quality video mixer, contrast is consistently maintained without the introduction of distortion.

An accentuated edge defining a video or a computer generated image.

A way to interface between two machines or signals. In video and audio, coupling can be direct – called DC coupling; through capacitors – called AC coupling; using transformers – called inductive coupling; by opto devices - using optocouplers or using RF (radio frequency) transmitters and receivers. DC coupling preserves the original DC levels of the signals and insures maximum signal flatness. However, erroneous DC levels, if they exist, are transferred between the machines and may cause damage.

AC coupling practically isolates the two machines or signals from their respective DC components, but has the problem of poor low frequency response and signal breathing effect. For example, video switchers and DAs may have AC or DC coupling either at the inputs, outputs or both. A smart system allows the user to decide which way the signals should be coupled to and from the DA or switcher.

Transformer coupling is problematic in the video field, mainly because of bandwidth considerations, as the transformer should perform equally in all relevant frequencies, and magnetic core transformers hardly ever do so, especially when a true flat response is needed. Transformer coupling is used in the audio field mainly for maintaining proper balanced* signals, for impedance matching and for ground isolation - as ground loops may be quite harmful in audio. It is used in video as well for similar reasons. Opto-coupling in video is mainly used to link devices in remote locations, by using fiber optics technology instead of coaxial connections, thus extending substantially the range of operation.

RF connection is mainly used in radio, TV and cable transmissions, in microwave links - node to node for ENG* and in satellite transmissions. RF modulators* and demodulators are needed to maintain the link. RF offers the longest connection range of all systems, crossing continents, oceans and even outer space.

Digital red and blue color difference signals.

A term used in video and audio editing* to describe a procedure whereby one signal is gradually faded out while a second signal is faded in until it fully replaces the first signal.

A digital video effect showing several images that appear to be riding on different planes. The planes may be parallel to each other, intersecting, perpendicular or in any other geometric form and relationship.

The interference of one signal by an adjacent one caused by stray electromagnetic or electrostatic energy. For example audio crosstalk results from leakage, - between the left and the right channels or between different inputs. In video, crosstalk between input channels can be classified into two basic categories: luminance/sync crosstalk and color* (chroma*) crosstalk.

When crosstalk in video is too high, images from one source appear as ghosts on the other. Low crosstalk is an essential feature for any audio and video device and is based on accurate design and proper signal handling. Crosstalk risk gets higher with higher signal frequencies.

Cathode Ray Tube. A vacuum tube which produces light when an electron beam hits its internal surface. A “gun” which creates electrons and a high voltage source that accelerates them generate the electron beam. The CRT is used as a picture displaying tube in video monitors, TV sets, computer monitors and others. It is assumed that the CRT will be replaced in the future by flat displays – such as LCD/TFT, Plasma or other modern types.

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D

A recording format utilizing a 19 mm-wide (3/4”) video tape and digital component video signals conforming to the ITU-R BT.601-2 (CCIR 601*) standard.

A recording format utilizing a 19 mm-wide (3/4”) video tape and digital composite video signals conforming to the SMPTE 244M* standard.

A recording format utilizing a 1/2”-wide video tape and digital composite video signals conforming to the SMPTE 244M* standard.

A recording format utilizing a 1/2”-wide video tape and digital component video signals.

Another name for Digital-S, the digital s-Video (YC) format.

Digital Audio Broadcasting. A system which allows broadcasting of CD quality audio.

Digital to Analog Converter. A device doing the opposite of an ADC*, converting a digital logic signal to an analog (linear) signal. The ADC and DAC are widely used for conversion between analog and digital video and audio signals.

Digital Audio Tape. A system developed for recording and playback of digitized audio signals, while maintaining signal quality as good as with a CD. DV, DVCAM* and others are digital video formats. A similar format is used in the computer industry for storage and retrieval of data, mainly for backup purposes.

A process developed for reducing the number of transmitted or stored bits of information with minimal effect on data or signal quality. Several algorithms (software formulas) as well as specific hardware devices are used for data compression, each with its own drawbacks and advantages. The right system should be selected to suit the specific needs of the user.

Use of computer generated red, green and blue data in video applications. Data superimposition over a video signal is carried out by high quality color decoders* which convert analog* or digital video signals to RGB* signals. The computer generated data is genlocked* to the video source and superimposed on the decoded RGB signal by using a special key or strobe input. The signal can then be re-encoded to re-establish the original video signal format, now including the computer data (graphics, text, etc.)

Decibel. A logarithmic ratio measuring signal amplitude and power, allowing easy evaluation of very large or very small ratios.

Direct Broadcast Satellite. It is also known as DTH - Direct To Home. A satellite transmission system received directly at the consumer’s home.

Discrete Cosine Transform. One of the algorithms (software formulas) used in data compression. This algorithm is widely used in image and movie compression (JPEG and MPEG*).

Display Data Channel. A bi-directional communication standard between a graphics source (a PC) and a monitor.

Digital Display Working Group. A group developing digital display standards such as the DVI*.

A digital method for “eliminating” redundant pixels in an image. The process is widely used for image scaling and for over-sampled ADC’s*. If every second pixel is stored in a digital image storage apparatus, the decimation factor is 2, and the image size occupies only one quarter of the original size. Decimation of a high order deteriorates the signal and unwanted artifacts are added to the picture, whether it is a video or a still picture.

A filter built in decimation* circuitry designed to reduce or eliminate the unwanted effects of the decimation process.

See Color Decoder.

The aggregate of fine details available on the screen. The higher the definition of the picture, the greater the number of fine details that can be recognized on the screen. The fine details of a picture appear in the highest frequency region of the signal.

As a result of the limited frequency response* of magnetic tapes, of connecting cables and of the electronic circuitry employed in the recording process, the high frequency part of the video spectrum is often attenuated. Therefore, during analog video recording, picture definition is frequently impaired. This creates a loss of fine details and blurs the picture. Each additional generation* of a copy of an analog videotape results in fewer and fewer fine details as losses are accumulated. Digital videotapes, due to the nature of digital storage technique, are far less sensitive to this problem.

To overcome definition loss, the use of video enhancers* is recommended. However, low quality video enhancing,* while trying to cure the definition loss problem, generates excessive noise* (snow* on the screen) and the advantages of enhancing are lost. A high quality image enhancer uses a noise gate* to limit the snow and noise* and produces a sharp image with minimal snow.

An electronic or software procedure that converts two interlaced video fields to a single progressive field. De-interlacing changes the sync rates and the progressive image can be displayed on an appropriate progressive-scan monitor, Plasma or LCD TV. The de-interlaced image resembles the image of a computer screen, without the interlacing flicker. This is one of the steps used in Scaling*.

When an electronic signal travels through electronic circuitry or through a coaxial cable, delay problems may occur. The result of the delay in video is usually a blurred (ghostly, shadowed) image and special electronic circuitry is needed to correct it.

Delay correction functions are found on all better video processing equipment. A common problem in analog video is the difference of delay between the luminance and the chrominance channels of the image, resulting in colors that look wrong or mis-registered.

An electronic device for separating several signals, which were combined by a device called a multiplexer. In digital-signals, de-multiplexers separate digital video from digital audio, which were combined by time division multiplexing (TDM).

A measure of non-linearity related to a composite video amplifier/processor. It is measured by comparing two chrominance signals of initially equal amplitudes riding on two different luminance levels. The inaccuracy is measured as a percentage.

A measure of non-linearity related to a composite video amplifier/processor. It is measured by comparing two chrominance signals of initially equal phases riding on two different luminance levels. The inaccuracy is measured in degrees.

A relatively new system, initially intended for post-production* purposes, for recording video and audio on a digital disk (such as a computer hard drive or a recordable DVD). The system was adapted to video camera capturing as well – as for ENG and production - using digital media for recording digital video. Solid state digital media is used for those purposes as well. The system was further developed for consumer use – as in set-top boxes for instant TV program recording and playback. The advantages of this system for editing purposes are extremely fast access to any point on the disk, elimination of dropout* and very fast back and forth shuttle speed. Several digital formats of data storage exist. Digital video editing using this media is sometimes called Non-Linear editing (non-analog). Some consumer electronic manufacturers have started to offer televisions with DDR hardware and software built in to the television itself.

A digital video format introduced by JVC™. This format is “back” compatible with the S-VHS* format so cassettes recorded in S-VHS can be used with a DIGITAL-S VCR. The technical specifications are very similar to the DVCPRO* format - 4:2:2 encoding, 3.3:1 DCT* compression and a 50 Mbps data rate. The cassette lasts for 104 minutes and is 0.5 inches wide.

Digital Direct Drive Image Light Amplifier. A CMOS chip technology developed by JVC , with 2048X1536 pixels (3.2 megapixels) on a 1.3” chip, used for display devices. The system easily allows HDTV* resolutions – up to 1920x1080 to be comfortably displayed. Combining high-speed response and a vertical alignment liquid crystal, this technology enables reproducing clean, smooth and sharp HDTV images.

Deutsche Industrie Norme. A German based standardization system, adopted by other countries as well. The DIN standard connectors for example, are very popular on video and audio equipment.

DisplayPort is a digital display interface standard introduced by VESA. It is a license-free and royalty-free, digital audio/video connection system, intended to be used primarily between a computer and its monitor, or a computer and a home theater system. It supports nowadays up to 2560 x1600 pixel resolution (WQXGA) and 10.8 Gbps data rate. It directly competes with the HDMI* standard.

In audio, this term implies undesirable changes in the waveform of a signal caused by the introduction of spurious elements. When a pure sine signal is fed into an amplifier and comes out harmonized, additional tones are created, naturally related to the original tone. This upsets the relationship between a specific tone and other tones related to it. In audio there are several distortion patterns - harmonic distortion, crossover distortion, transient distortion and intermodulation distortion. No matter what the type is, the result is unpleasant to the ear.

Video distortion, like audio distortion, is the result of improper signal handling during video amplifying and processing. Video signal distortion affects the luminance* or chrominance* portions of the signal. It may distort the picture and produce improper contrast, faulty luminance levels, twisted images, erroneous colors and snow. The goal of a good video processor*, is, as in audio, to be a “wire with amplification” device which does not unnecessarily affect the brightness, contrast and tonal quality of the image.

A device which distributes one video, audio, graphics or digital signal source to several acceptors for simultaneous recording, monitoring or processing. A good quality distribution amplifier amplifies the incoming signal, pre-compensates the signal for potential losses (resulting from the use of long cables, for example) and generates several identical buffered and amplified outputs. Video distribution amplifiers are mainly used in duplication studios where many copies of a tape must be simultaneously generated from one source. Often, a video processor* is inserted between the source and the distribution amplifier for correction and fine-tuning of the source signal before multiplication, so that all copies are corrected in the same way.

Digital Light Processing. A graphics/video projector part, based on DMD (Digital Micromirror Device) - a chip developed by Texas Instruments. The microchip has thousands of micromirrors on its face, reflecting light emitted on it. The mirror’s angle dictates the amount of the reflected light. Projectors using this technology output a high contrast image.

A technique developed by Dolby™ Laboratories which improves the signal-tonoise ratio* of a recording by raising the level of specific frequencies in quiet passages before recording, and lowering them to their original levels during playback* (a compression- expansion process). This automatically reduces any noise* that was introduced as a result of the recording or playback process. There are several schemes related to DOLBY noise reduction, using different frequency bands of operation.

An analog/digital transmitted audio system developed by Dolby™ Laboratories for encoding audio surround channels within a videocassette/DVD/TV transmission mainly for home or cinema theatre use. The analog system adds three additional channels - center and delayed back right and left. The digital AC-3 system have the surround channels separated and digitally encoded. In both cases a special decoder is needed to retrieve the additional audio channels.

Dolby® TrueHD is Dolby’s next-generation lossless technology developed for high-definition disc-based media. Dolby TrueHD delivers tantalizing sound that is bit-for-bit identical to the studio master, unlocking the true high-definition entertainment experience on next-generation discs. It supports up to eight fullrange channels of 24-bit/96 kHz audio.

The distance between the pixels on a monitor, measured in millimeters. The smaller the pitch, the higher is the apparent screen resolution.

See Enhancing.

One of the special effects* employed by a special effects generator*. A video picture is painted with natural or with artificial colors produced by the special effects generator as a function of its brightness. A washed-out sky can be painted a brilliant red, for example. Colors are streamed down from brightest to darkest and any level of brightness can be changed down to any darker level.

Color difference related signals for the SECAM system color modulation.

Partial loss of a video picture, usually seen on the screen as white streaks, resulting in a poor quality playback. Flaws in magnetic tape coating resulting in loss of magnetic particles from the tape are the main cause of dropout. Special electronic equipment, usually digital, called dropout compensators, is needed to eliminate dropout effects. Normally, a dropout compensator replaces the missing information with data from adjacent pixels, lines or fields.

A special effect, which adds an artificial shadow or a three-dimensional, extruded shadow to a scene or an inserted object. This effect is used also in titling in order to emphasize the inserted titles.

Digital Television. The proposed standard for digital video broadcasting in the US and Canada. The system is based on MPEG-2* and is similar to the DVB* system in most respects.

See Audio Dub.

Digital Video. A format initially used by SONY™ for the output of a digital camera or VCR. The DV format uses a special communication protocol: IEEE1394* (a.k.a. Firewire, iLink). The format is basically a digital component video format (YUV). In PAL it is based on 50 fields/sec and 625 lines per frame and the encoding system is 4:2:0. In NTSC there are 60 fields/sec and 525 lines and the encoding system is 4:1:1. These field and line rates are similar to those used in the analog formats. The audio part of the DV format is digitally encoded but uncompressed, with sampling rates that can be selected by the user: 44.1 kHz at 16 bits for two sound channels (similar to an audio CD) or at 12 bit and 32 kHz sampling rate, for four audio channels.

The compression rate is about 5:1 and this standard provides a 25 Mbps data rate. Every compressed frame is fed in parallel to ten channels during recording (NTSC) or to 12 channels (PAL), therefore, dropout effects become almost obsolete. There are two cassette sizes for this format: a mini cassette for up to 60 minutes of recording and a regular cassette for up to 240 minutes of recording.

Digital Video Broadcast. The system proposed for digital video broadcast in Europe and is similar to analog TV broadcast. The system is based on satellite transmission, ground-based receivers and the video signal is MPEG-2* encoded.

Digital Video Cassette. A domestic and professional cassette format. DVC cassettes come in two sizes - mini or regular-sized for camera or desktop VCR use. The mini cassette (6.35 mm) can be played directly from the desktop VCR without using adapters. Sometimes, the mini cassettes have a memory chip built-in. Resolutions of up to 500 lines are achievable.

A digital video format introduced by SONY™. This format uses DV*-like cassettes, has a 4:1:1 encoding scheme and outputs a 25 Mbps data rate. Cassettes come in two sizes- 46 minutes for field use and 180 minutes for desktop VCRs.

A digital component video format introduced by Panasonic™ and Philips BTS™. The format uses two cassette sizes- 6.35 mm and 0.5 inch. It provides a stream of digital information at 25 Mbps and has two uncompressed audio channels. It operated initially at 4:1:1 encoding and 5:1 DCT* compression, but was recently re-introduced at 4:2:2 encoding and a lower, 3:3:1 rate of compression. This has changed the amount of time that can be recorded on tape from 123 minutes for the desktop DVCPRO VCR operating at 4:1:1 to 61.5 minutes at 4:2:2.

Digital Versatile Disk (formerly: Digital Video Disk). A data or video media, allowing storage of data or playback of video and audio from a digitally recorded disk which resembles a CD. The video disk allows playback of a full feature movie of more than 2 hours. MPEG compression is used for recording. The audio section is digitally recorded as well, with various surround sound schemes, such as Dolby AC3*. The world was divided into several “zones” incompatible with each other. Several different standards exist, similar to PAL and NTSC and some manufacturers have released Multi-standard / Multi-zone players. Copy protection schemes are built into the DVD player in order to avoid piracy. The single layer DVD capacity is about 4.7 gigabytes and the double layer capacity is 8.5 gigabytes.

DVD players are available for the PC as well, which also allow playback of regular data CD-ROMs as well as music CDs.

Recordable DVD (named DVD RAM or DVD R) has recently been introduced. There are currently 5 leading standards for recordable DVDs. The old one which was recently upgraded, is the DVD RAM, and then there are DVD+R, DVD+RW (Rewritable) DVD-R and DVD-RW (Rewritable). It will take several years until one standard prevails, if at all. In a DVD, as the signals are recorded digitally, quality is expected to be very high, and fast, random access to any part of a movie will allow fast and easy editing. There are already stand-alone DVD recorders in the market with analog or digital inputs, allowing the recording of up to 2 hours of high quality video or TV programs, or several hours of lower video quality. The recordable DVD probably marks the end of the classic VCR.

Digital Video Effects. Special effects generators* which employ digital signal processing to create two or three dimensional digital wipe effects, where for example, the image can be rolled out of the screen, broken into tiny pieces or converted into a tube-like picture.

Digital Visual Interface. A digital graphics interface standard, using a large type of graphics connector. The RGB signals are transferred differentially and digitally, differing from the VGA analog standard. This standard is used for interfacing between graphics sources such as a PC, grabber card, set top box etc; and a graphics acceptors such as a digital monitor, Plasma screen, video/ data projector and similar devices. Control data is also transferred via the DVI interface. The DVI-D connector (24 pins) uses only the digital format, while the DVI-I connector (29 pins) transfers digital and “old” analog VGA type signals on additional pins. The DVI signals - due to their high-speed digital contents - are sensitive to cable length, and are prone to digital problems like the Cliff-effect* and jitter, similar to the DV* or SDI* signals.

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End of Active Video. A digital code used with digital component video signals, marking the end of a video line.

European Broadcasting Union. A European organization of broadcasters which among other activities, defines recommendations and statements for the 625/50 line television system.

See Enhancing.

A process used to combine images from two projectors or more for creating a large, combined image. The Scaler / Processor involved allows for overlapping edges on the projected images to be “blended” with no sign of “stitching”. The advantage of this process is that it creates large detailed images combining the pixel count of all projectors involved.

The Extended Display Identification Data (EDID) is a data-structure, provided by a display monitor, to describe its capabilities to a graphics card connected to it. The EDID enables the DVI/HDMI source to “know” what type of monitor is connected to the output. The EDID includes the manufacturer’s name, the product type, the timing data supported by the display, the display size, luminance data and (for digital displays only) pixel mapping and other data.

A process

Error Detecting and Handling. A system employing codes inserted in a digital video signal to detect possible errors and error rates.

A system to control and synchronize several VTRs, disk recorders, audio tape recorders and other accessories during postproduction*. An editing controller uses a dedicated computer, which is built into the controller.

An obsolete digital color standard developed by IBM™ for personal computers which was able to display 16 out of a menu of 64 colors, at resolutions of up to 640 x 350 lines. EGA was used on personal computers for desktop publishing applications, high-resolution CAD programs or other programs where high-resolution, multicolored graphics were required. Several years later this standard was replaced by VGA, Super-VGA, XGA and higher resolutions.

Electronic Industries Association. An association of manufacturers in the electronic industry having common interests.

A test color bar signal similar to the SMPTE bars.

Circuitry used in video processing which imitates the colored glass filters used in photography. Various color signals are generated and then mixed in different proportions with the video signal. This permits color changes in the video scene for color correction or special effects generation.

A process which translates several signals of information simultaneously from an analog* or digital form to a coded form, without any apparent loss of image quality. An encoder usually accepts RGB* or YUV* inputs from either an analog or a digital source and converts these signals to a full-colored composite or Y/C video signal. This device performs the opposite of a color decoder.

Improving a video image by boosting high frequency or other signals which are usually lost during recording. There are several types of enhancing. Luminance enhancing takes place mainly in the border areas between light and dark images. The transitions (edges) between the light and dark areas are extenuated. When there is a light area on the screen located on a dark background, the edge of the left part of the area becomes lighter and the right side becomes darker. In double-edge enhancing, all the edges surrounding the area become enhanced and the enhanced area itself appears, in effect, three-dimensional. Chrominance enhancing improves color saturation and restores normal hue.

Electronic News Gathering. A process of recording news events by using electronic cameras and recorders (non-film).

Equalization. A special kind of amplification, focused on a specific part of a signal’s spectrum for compensating losses and distortions usually created by long cables.

Synchronization pulses of double frequency and of short period leading and following the vertical sync. Proper equalizing pulses are needed for picture stability on the screen, for proper vertical deflection, interlacing* and for PAL* switch generation. Missing or distorted equalizing pulses can cause misalignment of the video image on the screen, skewing* effect, color distortion and loss.

Encapsulated PostScript. The PostScript format and language is a trademark of Adobe Systems Inc™. It is a page description and typesetting language, widely used in typesetting and desktop publishing systems. The EPS format is a postscript description file format, easily transferable between various graphics programs.

A European technological developments project, which defined the HDTV standard.

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F

In video, fading deliberately diminishes the video picture until it becomes totally black. Fading a video image is often used as an artistic tool in video productions. For example, gradually replacing one scene with another by cross fading*.

In audio, fading decreases the level of the signal until it is no longer heard. Audio fading is often used together with video fading resulting in the sound and image disappearing simultaneously.

Federal Communications Commission. An American governmental authority, which sets rules, related to communication, electrical interference, etc.

A medium made of translucent fibers with appropriate interfaces for transmitting analog and digital signals. Light is used to represent the signals. The original signals are recovered to recreate the electronic signals at the far end of the fiber. The optical fiber system provides high electrical isolation between transmitter and receiver, as well as immunity to electromagnetic and static interference. The signal loss in a fiber optics system is usually smaller than in coax cables, and so optic fibers are often used to carry signals over very long distances (tens and hundreds of kilometers.)

See IEEE 1394*.

Annoying visual phenomena mainly related to the interlacing of video fields, which show up as small vibrations on the screen. Flicker also appears when static images are displayed on the screen, as in computer generated text when transferred to video. Poor digital image treatment, as in low priced standard converters (going between PAL and NTSC), will create an annoying flicker on the screen. There are several electronic techniques to minimize flicker, such as line averaging and filtering.

Animation flick files created by Autodesk™ software, such as Animator™ or Animator Pro. The FLI/FLC file system contains a series of consecutive compressed frames or images that can be replayed as an animation sequence using a special program. This format is widely used in computer generated animations and in clips used for video.

An almost obsolete magnetic storage device used in computers. Floppy disks store mainly digital data, text and graphics, and computer programs. Floppy disks came in two major sizes: 5.25 inch and 3.5 inch.

The 3.5 inch disks are more rigid than the 5.25 inch version. Both were subdivided into low density (double density) and high-density types, storing 360 KB and 1.2 MB on the 5.25 inch format, and 720 KB and 1.44 MB on the 3.5 inch format. Some developments in this field have extended storage on a 3.5 inch disk to 2.8 MB and above. In comparison to hard disks, the advantages of floppy disks are low price and portability, while the disadvantages are slow access time and limited storage. New media formats - magnetic and optic based - are replacing the floppy disks, having much larger storage capacities (from hundreds of megabytes up to several gigabytes), faster access times and ever lower prices.

There is an enormous variety of video formats. They vary in tape width - 4mm, 8mm, 0.5 inch, 0.75 inch, 1 inch, etc.; in signal formats - composite, YC and component video; and in operation - analog or digital. In addition, digital formats themselves take various forms - no single standard prevails. Also, all formats exist in PAL, NTSC and SECAM and their sub-standards, which implies that any video production studio requires an extensive range of interface devices to enable equipment designed for a specific format to work with devices designed for other formats.

An electronic device that captures a video frame or field and stores it on a digital storage device, e.g., hard disk, memory card, floppy disk etc.

An electronic device utilizing digital technology, with several video inputs. The frame synchronizer synchronizes and genlocks* sync and color of one input to those of another. After frame synchronization, the two video images can be blended, wiped and processed as they use the same sync and color subcarrier frequencies and the same phase. See also TBC*.

A process which catches and freezes one TV/video frame on the screen. Freeze frame can be done in an electromechanical way, by stopping the VCR’s tape advance and re-scanning the same frame over and over again, or by electronic means by storing the whole frame in digital-chip memories. Digital freeze-frame is one of special effects* that are performed by a special effects generator* or a TBC*.

When a low frequency signal modulates (changes) the frequency of an RF signal of a much higher frequency (causing it to move around the basic carrier frequency) - the process is called frequency modulation or FM. This system is extensively used in broadcast radio transmission, as it retains high signal quality. FM is used in video to record signals on videotape. The FM system is less prone to interference and is therefore used in higher quality equipment.

The maximum signal bandwidth handled by an electronic device, which is a measure of the quality of reproduction of various or extreme frequencies within the band. If the frequency response of a video processor, for example, is adequate, there is no discernable deterioration in picture quality at the edges of the spectrum and no fine details or color are lost. In Hi-Fi audio reproduction, frequency response should extend up to 20 kHz, the practical limit of human hearing. The frequency response plot not only measures the extreme edges of the frequencies handled but also linearity and fidelity throughout the whole spectrum.

A term used in radio frequency transmissions for the generation of a stabilized high frequency signal. The frequency steps are derived from a crystal-stabilized frequency. Using a chain of switches, a wide range of high frequency signals can be generated from the same low frequency crystal oscillator. This process is mainly used in complex broadcast equipment for RF* modulation and transmission.

A part of the composite video signal which resides in the blanking period, between the end of the active line (the leading edge of the horizontal blanking period) and the leading edge of the horizontal sync.

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The light emitted from a CRT* is not linearly proportionate to the electric signal levels driving it, thus a distortion is created in the image shown on the screen, where contrast loses its linearity. This non-linearity is expressed by an exponential function called Gamma.

A process used in video and computer graphics images to correct internal microcontrast within the image and brightness. For example, Gamma correction can change the ratio in an image between the brightest, specific color component, and the weakest.

When two signals, such as audio and video signals, are concurrently processed, simultaneous fading* is required. This technique is known as ganged fading.

A graphics metafile format, vector based, which was developed by Digital Research™ and is used in DTP and graphics applications.

The number of duplication steps between a master recording of videotape and a given copy of that master. A second-generation duplication is a copy of a copy of the original master.

When master analog videotape is duplicated, the second-generation copy is usually inferior in quality to the master. This depreciation, known as generation loss, appears as distortion, lack of details, improper colors, etc. The limited frequency response of video and audio magnetic tapes and the imperfections in electronic circuitry are the main causes of generation loss. Video enhancing* equipment is intended to eliminate or reduce generation loss. High quality video processors pre-enhance the video signal to overcome generation loss. Digital video recording and editing are essentially immune to high frequency generation loss, but are prone to instability and other synchronization-related problems.

A system for synchronizing two video signals to the same timing and color phase in order to coordinate their colors and syncs. Genlocking permits mixing, cross fading, keying and special effects* generation between the two signals. A video camera* can be genlocked to a second camera through the genlock connector on the camera. All professional cameras have genlocking capabilities. Genlocking two VCRs is more difficult and requires the intervention of a sophisticated device called a time base corrector* (TBC) or a framer synchronizer*.

A special, dedicated microprocessor installed in a computer graphics card, which takes over most of the graphics work from the main computer microprocessor. As the graphics co-processor deals only with graphics work, the speed of graphics operation is substantially accelerated, which is necessary for computer generated animation* and fast computer graphics display. Nowadays, “3D” graphics processors with many-megabyte graphics RAM (memory) exist on almost every graphics card, enhancing and accelerating 3D PC games as well as any other PC graphics work.

Graphic images, whether computer generated or video generated can be stored on a disk for further use employing one of the standard storage formats. There are several formats, each with its advantages and disadvantages. The user should decide which format is best for his purposes by comparing the features of the formats available. Some popular formats used are – JPEG, TIFF, GIF, TARGA, PCX* and EPS*.

A computer program than can create and display symbols, drawing and text on a computer monitor. Special hardware can convert the computer graphic files from such a program to video signals. This permits the graphic material to be added to a video presentation for special effects* generation, editing, etc.

Interference that in video may show on the screen as “crawling” vertical bars. A ground loop is created when two elements in a circuit - or two different machines connected together - receive their ground reference signal from different places. A different ground potential (voltage) creates this loop, interfering with the signal. Special ground-isolation devices are needed to cure the problem. Ground loops are also a problem in audio, where their most disturbing effect is a low frequency oscillation known as “hum” or “motorcycling”. Some audio related ground loop problems can be cured by properly reconnecting the ground leading cables to a single point, usually at the most sensitive input area, or at the power supply. Such problems emerge mainly when high amplification is needed, such as when microphones or other sensitive pick-ups are connected to the system.

A phenomenon occurring in poorly designed electronic equipment where there is a variable delay in the transmission of information through the circuit. In video, when several signals are transmitted together and some arrive before others as a result of group delay, the video picture is distorted. For example, in low quality video processors, there may be a substantial delay between the transmission of color and black and white information. The color part does not overlap on the black and white part and a double image or shadows occur, as well as image blur. Good quality video processors automatically compensate for group delay. Group delay may also be invoked in long connecting cables or RF* transmission.

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A mass storage media for digital information used in computers, video and audio and recently also used for digital image/video storage in digital cameras and camcorders. In contrast to a floppy disk*, the hard disk is usually non-removable (though there are already some removable and transportable hard disks). The access time of a Hard disk is much shorter than that of a floppy disk, and the amount of data (images or full video-scenes, for example) that can be stored on a large disk can reach several gigabytes. The name hard disk comes from its internal construction of metal (mainly aluminum) platters, which are very stiff, and not floppy.

High-bandwidth Digital Content Protection (HDCP) technologies protect high value digital motion pictures, television programs and audio against unauthorized interception and copying between a digital set top box or digital video recorder and a digital TV or PC. HDCP is a specification developed by Intel Corporation to protect digital entertainment across the DVI/HDMI interface and is made of three different sub systems of protection. The HDCP specification provides a robust, cost-effective and transparent method for transmitting and receiving digital entertainment content to DVI/HDMI-compliant digital displays. Implementation of HDCP requires a license.

The High-Definition Multimedia Interface (HDMI) is a compact audio/video connector interface for transmitting uncompressed digital streams and represents a digital alternative to consumer analog standards.

HDMI supports, on a single cable, any TV or PC video format including standard, enhanced, and high-definition video along with up to eight channels of digital audio.

High Definition TV. Several standards were introduced for HDTV broadcast, with much higher resolution on a special TV screen. HDTV or the like - IDTV* or EDTV – is becoming the predominant system in broadcast and home. There are two basic standards of HDTV - analog and digital. The analog system was used mainly in Japan but is being phased out; while the digital system was adopted by the US, Australia and Europe, and later also adapted in Japan. Several broadcast stations already transmit HDTV signals, but the price of the receivers is still quite high, thus limiting the penetration of HDTV to the home market. The chosen display format for HDTV is 16:9 vs. the classic 4:3 aspect ratio*.

High Definition Serial Digital Interface. A format of digital video in serial form, digitized at 4:2:2 ratio. The stream of data is very fast - from 1.485 Gbps up to 2.97 Gbps (also called 3G HD-SDI). Other information such as multi channel digital audio signals, time code* and control can be embedded in this stream of information.

A method of recording video information on VCR tapes. The tape is scanned in a helical (slanted) way rather than horizontally or vertically. The helical scan method packs much more information on a given length of magnetic tape than all other methods. For this reason this method is used in the digital world as well - in DAT* and in digital video recording systems.

A Y/C video format similar to Super-VHS, introduced by SONY™, using 8 mm wide videotapes. Picture quality is very high and camcorders using this format are very small and handy, making them a very good choice for amateur and semi-pro video photographers.

A computer graphics format, beyond VGA* and Super-VGA*, which displays 32,000 or 64,000 simultaneous colors on the screen at 640x480 pixels resolution and above. This number of shades of color, simultaneously displayed on the screen, exceeds the color resolution of the human eye, which can resolve about 4,000 different shades of color. True color displays 16.7 million shades of color (24-bit color information).

The primary background noise* in audio recording, stemming from circuit noise in the amplifiers of the playback* recorder or from residual magnetism on the tape. Several noise reduction* methods are available, such as Dolby™, DNR (Dynamic Noise Reduction), DNL (Dynamic Noise Limiter), etc., to reduce the hiss while still retaining full signal bandwidth. In video transmission, “hiss” or high frequency noise, may show as snow* on the screen.

The horizontal sync* signal is a short pulse at the beginning of each video line which keeps the horizontal scanning of the monitor exactly in step with the transmission of each new line. The vertical sync signal is a pulse transmitted at the beginning of each field and frame. Its purpose is to maintain the monitor in field-by-field synchronization with transmission of the next frame pulse. Sync signals reside in a part of the video signal in which no visual picture information is transmitted. During that particular part of the transmission (the blanking retrace period* or vertical interval*), the electronic beam is blanked and retraces back to the other side of the screen to start a new line or a new frame. Both horizontal and vertical sync are needed to create a fully stable picture.

A line-time distortion, tilting the edge of a white bar. The phenomenon shows on the screen as white or black streaks, bleeding away from the original position, creating a muddy, fuzzy image on the screen. It is a result of the poor low frequency response of an amplifier, (see Vertical tilt.) Horizontal Tilt should not be greater than 0.5% in professional applications.

A feature built into an electronic device, allowing connecting or disconnecting cards, power supply elements or external devices while the original device is powered.

Hue, Saturation and Intensity. This is a color space* (a way to represent color) that describes an image. This measure uses polar coordinates. RGB color space is based on a Cartesian coordinate system.

Hue, Saturation and Lightness. A measure similar to HSI.

Hue, Saturation and Value. A measure similar to HSI.

Often used synonymously with the term tint. It is the dominant wavelength, which distinguishes a color or tint as red or yellow, etc. Video hue is influenced by several factors: Adjustment of the white balance* of the camera, quality of the electronic equipment which is being used and lighting of the scene. In the NTSC* standard, hue errors are more common than in the PAL* standard due to a different color encoding system. The PAL system compensates for color problems and it corrects wrong hues during operation. Video color processors* are the main tools used to adjust and correct hue problems. For example, when videotape is shot in a green park there is a tendency for a greenish tint to dominate the whole scene, which should be removed in order to restore natural skin tones.

An interfering visual or aural signal resulting from poor coupling or connection between machines, ground loops, transformer or other electric noise or a bad electronic design.

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The name of a port and protocol used in industrial and consumer electronic devices. I2C ports are relatively slow, and therefore are most suitable for generation of the control signal effecting a large system. The advantage of this port system is simplicity and that only a small number of interface lines are needed.

A computer and a connected monitor identify each other by the ID BITs, which are specific pins of the connectors and cables linking them. Those pins, when connected to a signal common ground (terminated) indicate which monitor is connected, and what signal the computers’ graphics card should output to this specific monitor. A PC VGA system uses pins 4, 11 and 12 as the signaling bits, while a MAC computer uses pins 4, 7 and 10. Some PC notebooks output the VGA signal to an external VGA monitor only when shorting ID BIT pin 4 to ground. In this case, the notebook PC should sense the ID BIT at pin 4 connected to ground at boot-up.

Improved Definition Television (Enhanced Definition TV). This standard resembles HDTV* in output quality without the complexity of the HDTV system. The improved picture quality is achieved by extensive processing carried out in the receiver. No different transmission system is needed.

Institute of Electrical and Electronic Engineers. An organization that sets many communication, broadcast and other standards.

A recommendation for a fast universal interface and protocol developed by Apple™ and published by the Institute of the Electrical and Electronics Engineers, also called Firewire (iLINK)*. This standard allows fast interfacing between digital cameras, VCRs, CD-ROMs, hard disks, scanners, graphics cards and editing systems. Data rates of up to 400 Mbps are easily obtained by this standard as well as fast and accurate audio/video synchronization. This standard allows “hot swapping” inputs and outputs, adding to its versatility. Firewire is catching on rapidly in the professional and consumer video market due to its simplicity, versatility and the ability to easily interconnect video and computer hardware. New definitions raise the standard to 800 Mbps and higher.

Interchange File Format. A graphics file format for Amiga computers, created by Electronic Art and Commodore.

Intermodulation - distortion or noise. An undesired form of distortion generated by a non-linear amplifier carrying several different signals simultaneously.

Video signals should be treated with care and accuracy, as proper RF* signals, since they occupy a very large spectrum of frequencies - from almost DC (0 Hz) up to several Megahertz. Video generally uses 75-ohm cable and lines. Input and output impedance (a form of resistance) must be matched to 75 ohms. If the output impedance of the video source, or the input impedance of the receiver, or the cable carrying the signal, are not properly matched to 75 ohms, a series of problem may arise. Signal level will not be kept to standard, high frequencies will get lost and fine detail and color information will be lost. In addition, instability, oscillations apparent as snow, component heat-up and ghost images may also appear. In the digital domain, cable mismatch may create an instant signal breakdown (see Cliff Effect*).

International Communication Satellite Organization.

A TV system which uses the TV/Cable-network for bi-directional communication. Via TV a user may order groceries, watch a selected movie (VOD- Video On Demand) or get the weather forecast.

A system developed for television to carry more channels in the broadcast band. This system reduces transmitted bandwidth to half by displaying each video frame by two interlacing (interwoven) fields. One field carries the even video lines and the other the odd lines. Interlacing causes a certain amount of visible flicker, but in live video it is hardly noticeable.

Flicker is more disturbing in PAL, where the vertical line frequency is 50 Hz, and two 25 Hz fields are displayed one after the other, than in the 60 Hz NTSC system.

Interlacing is sometimes used in the computer graphics field as well, where higher resolutions can be displayed on an inexpensive monitor by interlacing the image. However, with static images, such as computer-generated text and graphics converted to video, interlacing causes more annoying flicker. Many manufacturers try to eliminate or minimize the flicker effect related to interlacing by raising the allowable vertical frame frequency in PC monitors to 70 Hz and even higher. The trend nowadays is to eliminate interlacing wherever possible, even in the video domain, by line-doubling, scaling or using 100 Hz vertical scan rate TVs and monitors.

A frequency to which a signal wave is shifted locally as an intermediate step in transmission or conversion from one frequency to another. In TV transmissions, a video signal is modulated onto a high RF* signal via IF as a temporary stage.

A term used in digital video for creation of new pixels by mathematical comparison to the adjacent pixels. It is the opposite of the Decimation* process. This system is often used for DACs* for easing the analog filtering requirements.

The input and output of the IF circuitry provided by RF* modulator when IF* is being converted (modulated) to RF. The IF loop generated by the RF modulator is accessible externally and can be supplied to other RF modulators. They can also accept IF from another modulator in order to convert it back to RF.

A function related to the NTSC color difference signals, where I is one function involving different relationships or sums of R-Y and B-Y, and Q is another function.

Infrared. An invisible light, below human eyes’ perceivable spectrum, used for communication between electronic devices and their remote control units. This method is short ranged, effective only at the line of sight. The IR signal may be converted to an electronic signal carried by a wire to a different location where it is reconverted to IR for controlling a remote device.

The term is also used as a video level measurement unit. In the American NTSC system “0” IRE reference is the blanking level, the sync tip is at -40 IRE and the peak white is at 100 IRE. Therefore, a standard 1-Volt peak to peak video level is equal to 140 IRE units.

International Telecommunications Union.

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A term describing instability on the time axis. In video, jitter appears as image vibration and breakdown. Special, mainly digital equipment, is used to correct jitter (see TBC). Jitter is far more important for digital video signals – SDI signals for example. Digital clock jitter that accumulates along a video transmission line can create an abrupt signal loss (Cliff Effect) and special electronic circuitry is needed to restore stability (see Reclocking).

A control available on high quality VCRs to view individual fields or frames of a tape.

Joint Picture Experts Group/Motion Picture Experts Group. Standards of storage and retrieval of compressed still and moving video scenes, as used in multimedia* video and computer graphics applications. The standards are based on specific hardware and software algorithms. The JPEG compression system is able to compress graphics files at a 75:1 compression ratio or even more, and can greatly reduce a 24-bit color image for easy storage and transfer.

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A measure of distortion in a processed video signal, which shows on the screen or on the oscilloscope as overshoots and “ringing”. Test equipment generates a special signal - a 2T-pulse - in order to measure this distortion. The distortion level is given as a percentage.

A control signal that identifies and creates the border of a cutout in a background video image into which another video image is inserted. The key signal can be created and derived from many sources and should be genlocked time-wise to the main and inserted video signals.

When an image is projected on a screen at an angle, it takes a trapezoidal form. This distorted image can be electronically corrected, creating a perfect rectangular image. Most video projectors have this feature built-in, correcting even severe angle-projection distortions. Usually some image degradation takes place during processing, but it is hardly apparent if the original distortion was not exaggerated.

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A subset of the Audio part in the MPEG-1 and MPEG-2 standards. Some of its definitions are - 32-384 kbps, sampling rates of 16-48 kHz etc.

Liquid Crystal Display. A screen for displaying text and graphics based on liquid crystal technology, where minute currents change the transparency of the screen.

The advantages of LCD screens are very low power consumption (can easily be battery driven) and the low price of mass-produced units. The LCD system first became wide spread in digital wristwatches which can operate for a very long time on small batteries. The disadvantages of LCD were narrow-viewing angles, slow response (the first ones were too slow to be used for video), invisibility in the dark unless the display is backlit, and difficulties in displaying true colors on color LCD displays. With the introduction of new technology and especially TFT* driven LCD displays, picture quality began resembling the quality of a CRT (the Cathode Ray Tube used in televisions and monitors). Brightness has improved dramatically and the price is dropping constantly. New large active LCD (TFT* driven) displays are replacing TV tubes, but are still quite pricy. When the prices of large LCD screens start approaching the prices of CRTs, they will inevitably replace most home TV sets, and will provide, at a reasonable cost, a TV which can be hung on the wall like a picture.

A test signal recorded at the beginning of a tape, comprising an audio and a video signal, which is used as a reference for future recording and playback.

Use of a video line amplifier/compensator (equalizer, EQ.) to pre-compensate for high frequency loss resulting from transmission of video signals over long cable distances (several hundred meters). Deterioration in the picture takes the form of loss of fine details and color distortion. Sometimes the entire video signal, including sync information, is severely attenuated. The analog line amplifier is usually installed at the beginning of the line. In the digital domain, a similar process is used – also called EQ., which employs high digital amplification stages and sometimes another process called reclocking, which is similar to analog TBC* operation.

In its simple form, a device which converts a video signal to a high frequency computer DATA type signal. It is intended primarily for displaying video on a VGA monitor or on a DATA wide screen projector. An ADC is applied to the video signal, reading it into RAM* (Random Access Memory), adding lines and shifting the data to use high frequency scan rates as used by computers, and then passing the signal through a DAC* in order to obtain an analog signal. Those devices are sometimes also called de-interlacers as they convert an interlaced video signal to a non-interlaced signal. See also Scaler*.

Lip sync is a technical term for matching lip movements with voice. This technique is often used for compensating video processing delays in television programs or during scaling processes.

When lips are out of sync from the video, a video or audio delay is needed to match these movements.

Low Noise Amplifier/Low Noise Block down-converter. Amplification equipment used near a satellite-receiving dish, for low noise amplification and frequency shifting, before the signal enters the satellite receiver.

The resistance impedance that a properly terminated cable places on the signal transmitted through it. In the case of a high frequency signal, signal-to-cable matching is essential to prevent signal deterioration.

A specific load resistance (which is equal to the cable’s characteristic impedance) should terminate the cable, which in video is usually 75 ohms. Improper cable loading results in signal distortion*, ghost images, color loss and other adverse phenomena. The source resistance should be equal to that of the cable’s impedance and the load resistance.

A machine used in broadcast and video production studios for generating a logo, to be displayed on the screen, usually in a specified corner. The logo, which is a graphic symbol, is usually stored on a ROM (Read Only Memory) or a flash memory chip and is keyed into the video picture upon request.

Today, the classic generated logo has been replaced by a PC generated logo, encrypted into the video image using Genlock* equipment.

The computerized PC logo generator allows more flexibility in logo generation providing more graphic and eye-catching tools and is easier to use. Most logo generators/inserters contain more than one logo in their memory. Logos maybe uploaded to the machine from a PC directly (RS-232, USB, Firewire) or via a floppy disk reader which is built-in the inserter. Logos may be generated using graphic images, short animations or resized video files.

A term used to describe the cascading or chaining of a video signal to several video machines (distribution amplifiers*, VCRs, monitors, etc.). For example, a VCR is hooked up to a distribution amplifier, which has a video-input connector, and a loop output connector. When a signal is transmitted to the first machine through the input socket, it is fed, as an unprocessed signal, through the loop output connector (parallel connection) to the second machine. In turn, exactly the same signal is fed to a third device which is attached to the second one, and so on. Thus a very large number of VCRs or other video devices can be looped together for multiple processing. Proper signal terminations should be noted. In a large cascaded setup, signal termination is normally applied at the last machine in the chain.

Longitudinal Timecode. Another system for encrypting Timecode on a tape (see Timecode, VITC). This system uses an audio track for Timecode recording.

Noise which manifests itself in a video picture as white snow. It is the product of one or more of the following factors: low signal level due to poor lighting conditions, a poorly-manufactured video device, low quality video tapes, excessively long video cables used without pre-compensation, dirt on the video recorder heads which interferes with reading and writing, and over-enhancement of the video signal. Good quality video processors do not generate Luma noise. They maintain an excellent enhancement level, without sacrificing picture quality, by using noise gates. Snow* can easily be reduced or eliminated in poorly recorded tapes and a clean copy can be created. In the digital domain, Luma noise may be a result of poor digitization processes, signal jitter (digital clock related problems), logic level incompatibility and similar voltage-related reasons.

A measure of light intensity. Approximately one-foot candle dispersed on a square foot.

A video signal includes luminance, chrominance* (color information), and sync*. Luminance is the photometric measure of the brightness in a video picture. If luminance is high, the picture is bright and if it is low the picture is dark. Thus, luminance is the black and white part of the picture. Changing the chrominance level will not affect the brightness of the picture.

A method used in photography for measuring the energy density of light, and for comparing sensitivities of cameras. (1 Foot-candle =10.76 Lux or one Lux=1 Lumen*/square meter).

Low Voltage Differential Signal. A signal format used for connection, for example between a notebook and an LCD monitor.

Lempel, Ziv and Welch. Compression and encoding method named after the inventors, which analyzes a file - even a color file, and reduces its size by checking redundancy of patterns.

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A professional video format, utilizing a 1/2-inch metal particle videotape, using component video for recording and playback. The system is being further upgraded to use digital video signals.

Multiplexed Analog Component video. This system uses a single coax cable or any other single link for transmission of component video*. Digital time-compression is usually needed to perform this operation.

An audio-video-graphics matrix switcher is a device which resembles a telephone switchboard. It is an array of electronic switches which routes a number of signals to one or more outputs. A matrix switcher usually has several inputs which can be directed by the user, in any combination, to various output devices connected to the switchers. Monitors, Plasma screens, projectors, VCRs and other output devices can be connected. The user can direct source number 1 to acceptor number 2 while simultaneously connecting source number 8 to acceptors number 1, 3 and 4. The possibilities are almost endless.

Master Antenna TV. The classic TV broadcasting system where antennas are used for transmitting and receiving TV programs.

In the recording process, audio* level is a critical factor. If is too high, audio distortion* occurs. If it is too low, the signal-to-noise ratio* deteriorates. Thus precise measurement of audio level is essential during recording. A mechanical VU-meter or an electronic LED bar graph meter measures audio level. One of the most effective and fastest methods employs LEDs which change color according to signal level. When the audio level is too high or too low the lamp changes from green to red signaling that a problem has arisen.

Middle East SECAM. A modified SECAM standard (B, G, D, and K) used in several countries in the Middle East.

A microphone is a device which converts sound waves to electrical impulses. High-quality microphones usually generate a very low signal level. Low noise, high fidelity pre-amplification is required to boost the output of a microphone before the signal reaches the main audio amplifier where it is processed as a regular audio signal. Pre-amplifying low level microphone signals may be achieved by precise matching of microphone impedance and use of low noise electronic amplifying devices. Some microphones (mainly condenser type) need DC power in order to operate (phantom voltage) even before connecting to the amplification circuitry.

In order to obtain the highest quality output signal from a microphone, its internal impedance should be matched to that of a pre-amplifier with exactly the same input impedance. Microphone impedance may vary from a few ohms to several megaohms.

Motion JPEG*. Each frame/field is compressed to JPEG standards, and the sequence is displayed by sequencing through the JPEG frames. This system provides the best video quality, with little or no artifacts, but needs very fast processing.

A video artifact appearing on the screen as close, jittering color lines. This effect is created in the analog video world where high frequency luminance information creates color beats due to insufficient luminance filtering and shortcomings of the monitor. The TV color decoder mistakenly interprets the high frequency signals as chrominance information and creates unwanted color fringes. In the digital world this effect arises due to incorrect sampling rate.

A digital special effect carried out between two or more images, where the images are merged and transformed, one into the other. The images may be human faces or any other objects. The effect is widely used in video and in the movies, and requires much processing power.

A system for coding moving pictures and sound developed by the Motion Picture Experts Group. The data rates are 1.5 Mbps. Layer II audio is a subset of this system. MPEG-1 is used for CD audio and video.

A collection of definitions for digital audio and video compression used in digital video and audio transmission and play back. Definitions of this standard are used for the DTV* and DVD* formats, and were developed by the Motion Picture Experts Group.

Content-based standard developed by the Motion Picture Experts Group, aimed at multimedia applications. The compression algorithms for MPEG-4 are more efficient than those used in MPEG-2.

A content representation standard developed by the Motion Picture Experts Group for visual and scene motion recognition, for information search purposes.

Mean Time Between Failures. A term used to measure long time reliability of a machine or media. The higher the number (usually measured in hours of operation), the smaller the chance of failure in a given time period.

A video test signal composed of sinusoidal bursts of increasing frequencies, mainly used for frequency response testing and alignment of video equipment.

Simultaneous duplication of one signal source to many tapes. In the analog video world - during multi-distribution - a video processor* can be connected between the video source and the distribution amplifier* to enhance the copies or the monitor images.

Hardware and software that merge video, computer graphics and multi-channel sound in one interactive session. Multimedia can simultaneously display several live video scenes in small windows on one computer screen, and control the position and shape of the windows using a computer mouse and keyboard. Retrieval of music and other audio signals and of video scenes recorded on a computer hard disk, for educational, presentation and production purposes are only some of the applications made possible by multimedia, which creates a single computer-video-audio entertainment center. Nowadays the name is linked to everything related to graphics/video and audio production and entertainment.

A device for combining several signals into a single composite signal, used extensively nowadays in the digital video/audio environment.

A monitor (mainly for computer use) which synchronizes on different sync frequencies, allowing the use of different graphics formats on a single monitor, provided the graphics card used is able to do so. Multiscan monitors (sometimes called Multisync or Multifrequency monitors) are able to cope with many different graphics formats, and thus became the preferred choice of most PC users. Digital LCD monitors, can operate in many different sync frequencies, but the best image is obtained at a specific resolution and scan rate, known as its “native resolution”.

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The conversion of a video picture to a negative image. Black and white are reversed and colors are inverted. Red becomes a bluish tint and green becomes purple, etc. This is a typical special effect* integrated into the some special effects generators* or video cameras. Negative effect is also used to generate electronic color slides from color negatives. An electronic color filter* is used for the fine adjustment of the hues.

Nicam (728) stands for Near Instantaneous Companded Audio Multiplex, and is a system initially developed and adopted by the British BBC for Stereo TV transmissions. The system is being used now in most countries in Europe, and may become the standard in stereo TV transmissions. Audio information is digitally coded and transmitted alongside the video information, allowing mono sound reception in receivers not equipped with the NICAM system (down compatibility). A NICAM TV receiver is equipped with a decoder which converts the coded digital information into two stereo, analog sound channels.

Noise Figure. A term used to measure and evaluate noise in various electronic systems such as amplifiers and processors. NF is the ratio between the input noise power and the output noise power of an amplifier, or an amplification stage in a more complex system.

A general term used in electronics to indicate any unwanted electrical disturbance or random signal, unrelated to the signal being processed and tending to modify it. Electronic noise may be the result of several factors: electrical currents and voltages randomly triggered in an electronic device by temperature and voltage applied to the device, avalanches of voltages in an imperfect chip, noise induced by external interfering sources such as the national power-line grid, electric motors, fluorescent lamps, etc. In the digital domain, noise is related to improper digitization processes, poor signal handling, exaggerated signal compression and incompatible signal logic levels.

Sophisticated circuitry, for discrimination between unwanted low energy noise signals and the “real” signal being processed. Noise gates and automatic noise gates are integrated into high quality processing devices.

An electronic process used to reduce noise* level in audio and video. It can be performed either before or after recording. An encoding/decoding system, such as the Dolby* noise reduction system, is used before recording. Noise reduction can be performed on an existing tape using DNR (dynamic noise reduction). In professional video production, the most effective means of noise reduction is by digitizing the video image and carrying out a computerized pixel by pixel analysis of the data. In this way most of the noise elements can be discarded.

The amount by which the video output signal, when subjected to any load within its capacity, differs from an ideally linear output. The greater the deviance, the greater the distortion* of the video signal, resulting in both black and white and color problems. All good amplifiers /processing devices are designed to contend with nonlinearity.

Non Return to Zero (NRZ) is a digital coding system used in RS-232 serial data links. This coding system is polarity sensitive. Non Return to Zero Inverse (NRZI) is a coding system which is insensitive to signal polarity. In this system, low signal levels mean no change in logical levels, and high signal levels represent a logic change from “0” to “1” or vice versa. The NRZI system is more immune to interference and is widely used in digital systems, like SDI*.

Standard of color telecasting used in the United States and Japan, which takes its name from the American committee, which formulated it. The NTSC standard has the advantage of simplicity but there are several major drawbacks to its use such as limited video bandwidth which affects picture sharpness* and faithfulness of colors.

The minimum frequency at which a signal may be digitally sampled, in order to allow for faithful reproduction. The Niquist criteria stipulates that sampling must be done at least at double the highest frequency available in the sampled signal. In practice, slightly higher than the Nyquist sampling frequency - or even oversampling* - is usually used.

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A cost-effective preliminary stage of video editing, using low-grade copies of the edited material mainly for control and edit-design purposes.

An obsolete eastern European broadcasters’ union, which merged with the EBU in 1993. The name was also used to describe the broadcasting system in the Eastern Block - a modified SECAM system.

Actual video editing, using high quality materials usually based on decisions made during the Off-Line stage.

Keyed insertion of one image into another. Overlay is used, for example, to super-impose computer generated text on a video image for titling purposes. The overlay procedure requires genlocked* sources for proper operation. In the computer field, overlay files are accessory files containing mainly graphics information, following or within computer programs.

When a signal is digitally sampled at frequencies much higher than the NYQUIST* frequency. When this method is used, filtering the signals is easier and less expensive, although sampling at higher frequencies is more problematic.

Displaying a video or computer generated image in a size exceeding the physical screen, therefore showing only part of the information. Overscan normally stretches the image in both directions, and is used to fill up a screen with an image initially smaller than the screen, like some computer generated graphics images in formats smaller than video (CGA* or EGA* images.)

A distortion in a signal due to imperfections in the processing in the signal path. For example, when a square wave has sharp spikes at its edges. The overshoot level is measured as the percentage of the spikes relative to the original signal. Sometimes overshoot is done on purpose, emphasizing the edges of a video signal to create a sharpness effect.

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P

The European color TV broadcasting standard featuring 625 lines per frame and 50 frames per second. It has a more complex color encoding* system than NTSC*, but provides better color fidelity and better resolution.

A widescreen TV standard (16:9 format) used mainly in Europe for creating a “better-looking” image on the screen. It employs special technology for color and luminance image enhancement and resembles the HDTV format. It shows as a letterbox on a regular TV.

A connector panel facilitating wired cross connection of signals (eg. video, audio, CAT 5).

A graphics file format developed by Zsoft Corp. This format, which is raster based, supports graphics from monochrome up to 24-bit color (16 million colors).

Similar to EQ./Equalization*. An electronic compensation process for high frequency signal losses in long cables. Peaking restores image crispness, and different cable lengths require different peaking.

A small DC step (sometimes called setup), within the video signal separating active video* from the blanking level, which indicates the picture’s black-level*. It is used as a reference in a standard video signal for the white level and all the gray levels in between. Only NTSC uses a pedestal - usually a 7.5 IRE step.

An electrical voltage supplied to a condenser type microphone to power its built-in circuitry. The voltages applied can be up to 48 volts DC, depending on the microphone characteristics. If a phantom voltage is applied erroneously, damage may be caused to the system or the microphone.

A change in the color subcarrier* signal whereby its timing is moved out of phase, i.e., occurring at a different instant relative to the original signal. Since color information is encoded in a video signal as a ratio between the modulated color signal and the color burst* phase, a deviation in the color subcarrier phase results in a change in the hue* of the picture. In NTSC* video transmission, phase error results in a substantial change in the hue. In PAL, small changes in hue are automatically corrected, and only a minor reduction in color saturation* occurs. The hue remains consistent.

The most popular Macintosh graphics file format, bitmap based, supporting from monochrome up to 24-bit color images.

A border created while one video image is inserted into a designated area in another (in a circle, rectangle or almost any other shape) by using a special effects generator* or another keyer. This border* between the two images can vary from a sharp line to a vague blending of images between the two pictures. One of the features in special effects generators is picture border (edge) control. It allows the user to control both the color and the sharpness or fuzziness (softness) of the border between the two images.

The smallest “dot” on the TV or monitor screen usually comprised of tri-color dots: red, green and blue. The PIXEL size is a measure of the screens’ maximal apparent resolution.

The quantity of fine details in a video picture. A picture appears sharp when it contains fine details, extended micro-contrast (the distinction between fine details and the surrounding background) and sharp, thin edges. Picture sharpness is easily lost during the recording process and, to a lesser extent, during playback*. Advanced video enhancement equipment is used to improve picture sharpness, especially micro-contrast. Potential losses, which might damage an image during video processing, are automatically pre-compensated.

Although picture sharpness is a subjective factor, it is technically measurable as the ratio between high frequency signals (about 2 MHz) and low frequency signals. In the digital domain, the apparent picture sharpness corresponds exactly to that of the source signal, and if affected, it is usually due to the monitor’s ability to resolve picture details.

Picture-In-Picture. A digitally based method of inserting one video image into another for special effects purposes and for monitoring several video images simultaneously on one screen (several PIP units can be used together each compressing an image into the main screen in a different location).

See Picture Element*.

The process whereby a videotape on some other video source (DVD*, etc.) is displayed on the monitor. During playback, analog or digital video enhancement, carried out on a video processor, can be incorporated into the signal to alter, correct or restore it.

A cable with a fire-resistant covering, meeting UL specs.

A short period of time, of several microseconds, before and after the sync pulse that is a part of the blanking period, riding on blanking signal level. The porch can be used for clamping purposes, as it does not carry visible picture information.

All the editing work done with crude video material in the studio after filming. Editing, special effects insertion, image enhancement, and other processes enriching and fine-tuning the production are done in a studio during postproduction.

The conversion of a standard video image into a picture which consists of a few large single-colored areas. Graduations of fine color and brightness are totally removed. The result is a crude, harsh image. This is a typical special effect* available on special effects generators*.

A color difference signal representing a scaling formula for B-Y and R-Y signals. By using the appropriate formula, 700 mVpp of Pr and Pb represent a 100% saturation level in component video.

In many cases, through acquaintance with video equipment, tapes and cables, a user anticipates video losses. Therefore, he can introduce video enhancement into the video signal in advance to compensate and restore the original unattenuated and undistorted signal (See also Line Compensation*).

A standard function on video special effects generators* which allows the operator to select any of the video sources attached to the device and preview all special effects before he begins video processing. The preview bus is operated through a series of switches on the special effects generator, each of which is assigned to a specific input. Each input signal can be previewed on its own monitor by pressing the relevant switch. This is a rapid and effective method to check work before going on the air.

The basic colors used in TV and video systems – Red, Green and Blue.

Similar to the preview bus. It is also operated through a series of switches, each of which is assigned to a specific input device (special effects generator, routing switcher*, etc.) One or more input signals can be chosen to be mixed or simultaneously processed in another fashion. The processed output of the program bus is the final product, which goes on the air or to the final edit cut.

An electronic device which is designed to change parameters in a video or audio signal. A video ProcAmp, for example, has color saturation, hue, brightness, contrast and/or definition control.

A non-interlaced scan, providing all the video/graphics lines in a frame consisting of one field instead of two fields – odd and even, thus reducing the flicker in the visible image.

While a film is converted to video using a Telecine* machine for example, it is necessary to match the film frame rates and the video frame rates. The process used for NTSC is called 3:2 Pull-down, and for PAL it is called a 2:2 Pull-down. Due to the complexity of the process, digital artifacts are often generated. A good quality Scaler* automatically detects the Pull-down process and corrects the flaws to generate a clean, jagged-free image.

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Q

A process resulting in four full video images on one screen, each occupying one quarter of the screen. Quad splitting allows the use of one monitor for four video sources simultaneously, useful for video editing, duplication and studio control, as well as for security applications.

The conversion of an analog signal to a digital signal. The analog signal is sampled at a specific frequency and at a predefined sampling resolution, expressed in bits (8 bits, 10 bits, etc.)

Interfering artifacts caused by quantization, resulting in signal impurity and distortion.

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R

A term used to describe radio signals incoming to a receiver or outgoing from a radio transmitter (above 150 kHz). Even though they are not really radio signals, TV signals are also included in this category.

A process for projecting video and data from the rear side of the screen in order to keep a clear line of view for the audience. The projected image is inverted, and is projected on a special translucent screen.

A large TV set with a big screen, with sizes varying between 32 to 60 inches allowing a big TV or video image to be displayed for a large audience. A powerful internal projector projects an inverted image on the rear side of the screen via a set of mirrors. When projection TVs were first introduced, the image was dim and was viewable at a narrow viewing angle only. As technology progresses, images are becoming clearer and brighter and can be viewed at almost any angle.

A process used in Serial Digital communication to reduce signal jitter (usually a result of long cable runs) on the signal. By Reclocking at adequate intervals, and rebuilding the stable, original signal clock, jitter can be completely overcome. In the analog world, Time Base Correction using a TBC* performs a similar task.

A process or instrument for controlling an electronic device from a remote location. The remote control unit can be wired to the controlled device by cable, or it can control the device by transmission – either infrared or RF based.

A small socket on a VCR or video camera* which permits remote control from any unit which is connected to it. Through the remote socket on a VCR, commands such as Play, Pause and Record can be initiated.

When energy is reflected in a cable, between a signal source and an acceptor (see Cable reflection*), the amount of energy reflected is called the return loss and is measured in decibels. Return loss depends on frequency, load and cable length.

Amplification of a signal by a receiver before processing or transmission. An RF* signal is frequently attenuated during processing due to hostile environments (high capacitance, improper loading, etc.). To avoid such losses, RF amplification is performed before the signal is transmitted. RF amplification is also needed when an RF signal, coming from an RF modulator, is distributed to several acceptors simultaneously.

A process which takes low frequency signals such as audio and video and, via an RF modulator, converts them to higher (broadcast) frequencies suitable for radio or TV reception.

The process of supplying an RF* signal to several acceptors simultaneously. During RF distribution, RF amplification* and proper input and output matching should be performed in order to avoid signal losses.

Radio Frequency Interference. An electrical interference generated by some electronic or electric devices appearing in the radio frequency range. The RFI should be controlled and suppressed in order be approved by the authorities.

See RF Conversion.

The basic constituents of a color video signal. By using a color encoder, in conjunction with sync* information, a complete composite video signal comprising luminance, chrominance and sync can be generated. Professional processing equipment always employs RGB signals for editing and processing. The use of component video*, of which RGB is one form, results in superior quality output.

A parameter indicating the speed and frequency response of an amplifier or of a processing stage in an electronic circuit. Rise Time is the time it takes a signal to change its level from 10% to 90% of the maximum amplitude. The shorter this time, the faster the amplifier. Shorter Rise Time indicates better high frequency response.

Registered Jack 45. A connector type which can handle up to 8 wires (or 4 twisted pair wires), mainly used for Ethernet / PC network applications.

RS-170 is the American standard used for black and white TV that defines video signal parameters - Sync, Blanking and signal levels. RS-170A is a revision of RS-170, allowing color transmissions and video use.

Communication methods between computers and video equipment that are hardware based and software controlled. In the computers, RS-232 is carried through the serial port* to another serial port, where the data streams serially between the computer and its peripherals - mouse, plotter, printer, etc.

In the computer field there is usually a handshake protocol* between the ports that operate bi-directionally. Video equipment can be controlled by either RS- 232 or by RS-422 system, and as the RS-422 method connects several devices on the same line in parallel in a simple way, it is more popular in the video market.

Computer controlled VCRs, editing controllers, switchers and other studio equipment are found in most video studios. In order to successfully link two pieces of hardware, they must use the same communication protocol*.

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S

Start of Active Video. A term used in digital component video to indicate the onset of the active line.

A hermetically sealed device, employing SAW (Surface Acoustic Wave) technology, which responds only to a very specific bandwidth. It permits a narrow frequency band to pass through while rejecting all other signals.

A SAW filter has very steep shoulders cutting out everything that is outside its band of transmission. SAW filters have excellent out-of-band signal rejection quality eliminating, to a great extent, all unnecessary, spurious signals.

With the aid of SAW* technology special modulation used in TV transmission is easily achieved and a number of transmitting bands can be compressed into close broadcast ranges. An RF* modulator utilizing SAW* technology, produces a very clean and accurate signal on the screen.

Converts from one video/graphics format to another, changing the scan rates and the way the image is built. A video Scaler has analog video - composite, YC or Component inputs, in PAL, SECAM or NTSC. The signals are digitized, de-interlaced* and scaled to the required RGB format signals, then they may be outputted as analog RGB signals (VGA through UXGA for example) after conversion back to analog. Other possible outputs may be an HDTV component signal or a digital format such as DVI*. A graphics Scaler converts one graphics format to another (SVGA to SXGA or UXGA to VGA, for example).

Changing the scan rates and signal structure; and conversion of an input signal to another format - analog or digital. A Scaler* does this.

A machine that changes the scan rates (sync frequencies and data) of a signal to transform it to another format. If, for example, a VGA signal is to be converted to video, a Scan Converter is needed. The operation is done by converting the analog VGA signal to a digital form using an ADC, reading the information into a RAM memory, rescaling the signals and sync information and converting them back to an analog form using a DAC*.

Scan converters convert both the sync frequencies and the DATA information simultaneously in order to shift all into another format.

Scan Converters are also used in order to match specific monitors to signals of other formats. A good example is in the medical field, where data emerging from medical equipment at non-standard rates (like from ultrasound scanners or CT scanners) is to be converted to VGA or video formats for processing or recording.

Scan Converters are usually confined to limited formats in order to keep the price low, but there are expensive Scan Converters that convert between a large number of different formats.

A European video-audio connector widely used in consumer equipment. The SCART connector has 21 pins, carrying two audio channels - in and out, video channels - in and out, RGB signals, ground and some additional control pins. In order to connect two VCRs or a VCR to a monitor only one SCART-to-SCART cable is needed, avoiding the cable jungle of video and audio inputs and outputs, which may confuse the home user.

Simplicity of connections is the main advantage of the SCART system, however, it is not recommended for professional use as the physical connection is quite weak and signal leakage is too high.

An electronic process, which allows the video screen to be split horizontally or vertically showing the signal before processing on one part of the screen and the processed signal on the other.

Full screen splitting provides precise fingertip control of the video enhancement process. Screen splitting is a proprietary process developed by Kramer Electronics. It has been adapted at the consumer level in video processing equipment and is now used worldwide.

Serial Digital Interface. A format of digital video in serial form, evolving from parallel digital component video, digitized at 4:2:2 ratio. The stream of data is very fast - from 270 Mbps up to 360 Mbps. Other information such as digital AES/EBU audio signals can be embedded in this stream of information.

One of the digital test signals used for testing SDI PLL (Phase Locked Loop) and equalizer circuitry.

Standard Definition Television (or sometimes also known as Standard Digital Television). A digital broadcast format based on digital component video and MPEG2 compression. Usually refers to 480i.

A process that allows replacing one image on a screen with one from another source seamlessly, ie. without creating visual interference or image breakdown. It can be done in the video world using frame synchronized sources and vertical interval switching, and in the presentation world by pre-synchronizing video and data sources and switching them during the vertical interval. Another effective technology is performing the switch via a short black period (Fade-To-Black Switching).

Sequential Couleur a Memorie. The TV and video standard used in France, Eastern Europe and some Arab countries. The system resembles PAL; however, due to limitations and the complexity of its color encoding, serious video production is almost impossible within the framework of the SECAM system. In countries using the SECAM standard most video production is done using the PAL standard and, prior to transmission, the video is converted to SECAM.

A computer IO (Input-Output) port through which the computer communicates with the external world. The standard serial port is RS-232 based and allows bi-directional communication on a relatively simple wire connection as data flows serially. It is being replaced with the much faster USB (Universal Serial Bus) standard.

A Deserializer which converts between Serial Digital Video and parallel Digital Video, and is mainly used for interfacing the two digital formats.

Serrations are short, positive pulses within the vertical sync which are needed for proper synchronization of the video image on a screen. Loss of serration pulses can result in a loss of picture stability, and frequently leads to skewing* and color loss in the PAL system.

A very accurate electromechanical or motor control system found in video and audio tape recorders.

A process used in photography to generate a brownish tone in pictures providing an antique appearance. The same idea has been electronically adapted in video special effects* generation.

A color picture can be converted to sepia tones or a black and white picture can be colored in sepia.

A provision available on some VCRs for fast search of frames while playing a video tape.

The ratio, in decibels, of the maximum peak-to-peak voltage of a relevant signal in relation to the voltage of all interfering non-relevant noise* signals. In audio, the higher the signal-to-noise ratio, the clearer the sound; in video, the better the ratio, the less snow* resides in the picture.

A video test signal for testing frequency response.

Due to loss or distortion of equalizing pulses* and serrations, mainly in high generation videotapes, the upper third of the video picture may flag sidewise or skew. To overcome the problem at the consumer level the TV is equipped with an AV channel, which, when selected for VCR viewing, changes some time constants in the sync regeneration circuits and allows viewing without skewing.

In professional studios this problem is solved using a TBC.

Society of Motion Picture and Television Engineers.

An organization which recommends standards for the film and television industry.

A standard which defines the interface for system M (525/60) digital television and which is based on CCIR 601. This standard is defined for use in television studios for up to 300 m distance. It is a Bit-Parallel digital interface for component video signals at 4:2:2 digitization format.

A standard which defines the interface for system M/NTSC (525/60) digital television and which is based on CCIR 601*. This standard is defined for use in television studios for up to 300 m distance. It is a Bit-Parallel digital interface for composite video signals at 4xFsc sampling frequency. This standard defines the sampling parameters, the relationship between sampling phase and color subcarrier and the digital levels of the video signal.

A standard which describes the serial digital interface for 525/60 and 625/50 digital television equipment, operating at either 4:2:2* component video signal or 4Fsc composite video signal. The standard proposed by the SMPTE is intended for 10-bit digitization schemes.

A standard which expands the SMPTE 259M standard and defines a bitserial digital interface for HDTV component signals operating at data rates of 1.485 Gbps and 1.485/1.001 Gbps. The standard uses a 20-bit word size. The standard proposed by the SMPTE is defined for 720p, 1080i and 1080p resolutions.

A standard which defines a bit-serial digital signals operating at data rates of 2.97 Gbps and 2.97/1.001 Gbps running on two wires. The standard is also called Dual Link HD-SDI.

A standard which defines a bit-serial digital interface for HDTV component signals operating at data rates of 2.97 Gbps. The standard proposed by the SMPTE is defined for 1080p resolution at refresh rates of 50-60 Hz and 50- 60/1.001 Hz.

A general term used to describe interference on a TV or video image. Snow in video is synonymous with chroma and Luma noise. It often manifests itself in a video picture as colored or black and white dots.

Snow can result when the chrominance in the video signal is weak or oversaturated, when the signal is over-enhanced, when the video head is dirty or due to a host of other reasons. Good video processors reduce or eliminate snow.

A method of inserting a sound channel into an analog video signal. The sound channel is modulated and inserted into the line sync signal. A special device is needed in order to retrieve the audio information. It is a good way to add a sound channel to a video signal (adding a second channel for stereo, for example).

Artistic effects added to a video production in order to enhance the viewing of a tape.

Special effects may vary from the limited addition of patterns, the mixing of several video images together, completely changing color and texture of the image, to sophisticated digital effects such as shrinking the picture, page flipping, three-dimensional effects, etc. Special effects generators are usually used to create special effects*.

Devices designed to generate special effects. The simplest devices can process a single video signal - changing its color, generating sepia tones, inverting the picture to a negative form, posterizing* the image and fading* or breaking up the image into various patterns. More sophisticated equipment utilizes several video sources, computer-generated graphics and sophisticated animation* with digital effects. Many special effects generators have a built-in color generator for adding color or border lines to the video image.

Sync Pulse Generator, sometimes called Black Burst Generator. A device, which generates sync, burst, subcarrier and other signals and is used as a reference source for video and television studios. Some SPGs generate Color Bars* as well, that may be recorded as reference signals at the beginning of a video tape or used for equipment alignment.

A video test signal which generates several signal stairs at different levels (amplitudes) for measuring and evaluating non-linearity.

An electronic process by which a mono audio signal is broken down into two signals, creating a three-dimensional stereophonic effect from a monophonic signal.

In many instances, especially in old recordings, it is impossible to re-record the original signal in stereo. In such cases, high quality stereo stimulating circuitry can generate a three-dimensional effect covering the whole audio spectrum in both channels.

True stereo simulation is achieved by manipulating the monophonic audio signal on the basis of frequencies and phases, taking into consideration the physical aspects of hearing (distance between the human ears, human frequency hearing response and the psychological perception of sound).

An electronic device for digital capture and playback of TV and video pictures, using a storage device such as a Hard Disk* or RAM (Random Access Memory).

Simultaneous mixing and processing of both left and right audio signals.

Shielded Twisted Pair. When a twisted pair cable system is used for transmitting signals from one point to the other, the cable pair(s) may be shielded. The shield quite effectively protects the signals from interference, but often has an adverse effect on the transmitted signal bandwidth, reducing it due to the distributed capacitance resulting from the use of the shield. In critical high bandwidth applications, sometimes UTP* cables are used.

A video system which differs from standard Composite video in several crucial ways. The bandwidth is considerably wider as luminance* and chrominance are separated in the signal. This format, named also Y/C, is widely used for production in semi-professional as well as in many broadcast studios. When used with 8-mm video tapes it is called Hi-8.

vA computer graphics format beyond VGA*. Super-VGA displays 16 colors at resolutions of 800x600 and 1024x768 pixels, as well as 256 colors at 640x480 and 800x600 pixels resolution. The 640x480 at 256 colors is the most suitable for video use (after conversion to video) with almost natural colors. The format was extended up to 1280X1024 pixels resolution and 16.7 million colors.

A video test signal comprised of sine waves of equal amplitudes and linearly changing frequencies used to measure the frequency response of a video device.

General term for a device used to route different signals (audio, video, graphics or RF) from various sources to various acceptors. For example, a classic video switcher switches between the pictures from a number of video cameras to one monitor.

Super eXtended Graphics Array. A graphics standard, with a 1280X1024 pixels resolution, using a 5:4 aspect ratio.

A term used in electronics to describe the precise matching of two waves or functions. In television and video, sync is an essential element in the video signal to keep the scanning processes in phase. The sync signal instructs the monitor as to the exact moments at which a frame or line starts and ends. This information is critical for the proper positioning of the image on the screen. When a sync signal is distorted or missing, the picture may lose stability. It may become garbled to the point of total image breakdown. Electronic circuitry in many video processing devices provides sync restoration* and correction. Sometimes a TBC* is required to recover or restore sync. (See Horizontal and Vertical Sync).

A process which adds the synchronization signals to the graphics “green” signal, allowing transfer of graphics information over three cables (Red, Green+Sync and Blue), instead of four (RGBS) or five (RGBHV).

A process which replaces distorted and missing sync* information with good synchronization pulses generated by the restoring device. In many instances, during video editing* or multiple generation copying, sync pulses are lost or distorted. Sync restorers check the incoming syncs, analyze the frequencies involved and generate new, fully restored syncs, which replace the faulty source syncs.

Sync stripping is an electronic process, done either with discrete components or with special electronic chips, whereby the sync information is separated from the rest of the video information for timing correction, clamping and other purposes.

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T

A signal lamp on professional video and TV cameras to inform performers and crewmembers which particular camera is on the air. In large studios the lamp arrangement is duplicated on mixing tables for the convenience of the director.

A device used to rectify the results of distorted sync* pulses which are due to mechanical faults (tape transport, tape stretch, etc.). TBCs are also used to synchronize two video sources to allow mixing.

In the past, CCD* technology was used to move or alter a video signal in an analog* memory chip which was suitable for simple analog synchronization. However, CCDs had very limited memory capabilities. Therefore, digital TBCs are now common. They usually break down the video signal into its components. This is extremely flexible as it permits storage of a full frame or more in a digital memory device (RAM type chips). They operate in full bandwidth with 8 or more bit conversion schemes and are suitable for professional applications. In the digital domain a similar process is used, named reclocking, which restores stability of a digital signal by restoring the original clock signals and fixing the jittering signal with a stable time base.

Transmission Control Protocol/Internet Protocol. A communication protocol commonly used for Ethernet and Internet communication. The system relies on data sent in packets of certain sizes, suitable for the medium used.

A system intended to combine several signals on one channel by alternately sending packets of each signal in predefined segments of time.

Telecine is a device that converts film movies to video. The main problem in filmto- video conversion is the frame rate. In film movies it is 18 or 24 frames per second, which does not match the video frame rate of PAL or NTSC. For good conversion, interpolation and other techniques are used in the telecine device.

In advanced telecine machines, film movie is sampled digitally and converted to video, frame after frame, in real-time. One of the most popular digital systems used in professional telecine machines is called flying-spot, which allows almost transparent conversion to video. The digital process is called pull down*.

A device used in news casting for displaying large text on a partially transparent screen where the reader can look at the camera and read the text from the screen placed in front of the camera. In old systems, one person read the news, while the other rolled a transparent, long message banner in front of the camera. In modern Tele-prompter devices, the user does it with a mirrored computer screen that, in most cases, he controls himself.

A service provided by some TV broadcasting stations, which transmits latent data information alongside the video signal. In order to retrieve the teletext information and display it on the screen, the TV receiver is equipped with a teletext decoder. The data information is usually encoded and inserted in the vertical-blanking interval. Corrupted teletext information often causes image instability and picture roll because it effects the video syncs.

A load device, usually a 75-ohm resistor, connected by a switch to a video transmission line to terminate the line. For a video signal be correctly transmitted without losses, proper impedance is essential at the end of the line. In many video-processing devices, a termination switch is therefore included as a standard feature. When the termination switch is in the Hi-Z position, the video signal is not terminated but looped to the next station. The signal can thus be transmitted in parallel through a number of devices. The termination switch terminates the final device.

TFT stands for Thin-Film-Transistor. This technology is mainly used for manufacturing flat computer and video screens, which are superior to classic LCD* screens. Color quality, fast response and resolutions are excellent for video and graphics, and therefore TFT screens are replacing tube-based Wide Screen projectors* as well. In the beginning there were some price and technical problems with TFT screens. The price was high, mainly due to low yield in the wafer production process, the brightness of the screen was quite low and the resolution, although fine for composite video, was not sufficient for highresolution computer graphics. As technology advanced, most of the problems were solved and now, bright, high-resolution TFT screens are available at very reasonable prices.

A graphics file format initially developed for use with Truevision Targa/Vista graphics boards. This file format, with its variations, supports up to 32-bit formats. The images in the file can be either uncompressed or compressed with RLE (Run Length Encoding) compression format, and the file structure is very simple, reliable and suitable for file transfer and exchange between various computers.

A widely used graphics file format for PC and Macintosh computers. This file format supports from monochrome up to 24-bit color and supports RGB through CMYK formats. Despite its popularity, the format is quite complex, and Tiff files created by one computer may be unreadable by another.

A digital code or number inserted into a videotape or stream, unseen on the screen, for editing purposes. The time code identifies every frame of the videotape/stream and displays hours, minutes, seconds and frames. For editing purposes it is a must, as each video frame can be addressed individually. There are several methods of inserting and reading time codes such as VITC*, LTC and others.

The superimposition of text on video footage. Titles are added to a video scene during or after the production. Sophisticated titling devices allow the user to prepare text and graphics in various sizes, fonts and colors which are later inserted, one-by-one, at the appropriate times and places. An entire feature film can be titled in this fashion. Many video cameras* either include built-in titlers or permit externally-produced titles to be mixed with the image produced by the camera while shooting.

Transition Minimized Differential Signaling (TMDS) is a technology for transmitting high-speed serial data and is used by the DVI and HDMI video interfaces, as well as other digital communication interfaces.

This technology is similar in a way to LVDS* but uses a Current source rather than Voltage source used in LVDS.

Twisted Pair. A system for transferring high-frequency signals on a twisted pair of wires instead of a coax cable. The TP system is used in video, audio, graphics and in the computer world as one of the network interconnecting standards.

The twisted pair system is essentially a balanced* system, where antiphase signals are transmitted on the two wires. Some sophisticated TP systems allow the transfer of several signals simultaneously on the wires, such as video and two audio channels.

A method of controlling the mechanical position of the video head over the recorded material on video tape. Due to small differences in alignment of headto- tape position in different VCRs, it is sometimes necessary to re-adjust the tracking control on one VCR when playing a tape that was recorded on another. Nowadays, most VCRs have an automatic, digital tracking system and no user intervention is required.

A term used to describe Standards Conversion between PAL, NTSC and SECAM.

A combination of a transmitter and a receiver on a satellite. Geostationary satellites that are used for TV program transmissions worldwide have several transponders, each operating independently. The transponder allows bi-directional communication with earth stations. DTV uses satellite transponders.

A special sync signal used in HDTV* which improves immunity to noise and interference.

A graphics format of various resolution schemes which displays 24-bit (16.7 million colors) or even 32-bit color information. This format, perfectly suitable for video, displays “true color” on computer and video screens (after appropriate conversion). In order to display “true color”, the graphics card of the computer must have enough RAM installed (at least 1-2 MB - depending on the required resolution).

A term used in digital electronics describing the ability of a device or circuit to be connected directly to the input or output of digital equipment. Such compatibility eliminates the need for interfacing circuitry. TTL signals are usually limited to two states, low and high, and are thus more immune to interference than analog* signals.

A term used for a monitor which accepts TTL* level signals (such as those generated by a computer). TTL monitors differ from analog monitors, which accept composite or component video signals bearing color, black and white, and sync information as well as analog graphic signals such as VGA through UXGA. TTL monitors offered high resolution on the screen but were very limited in the number of colors available at any one time. (See CGA, and EGA). Nowadays, digital monitors with DVI inputs are taking over, providing the best of both worlds – high resolution and color rich images.

Television Receive Only. A term describing a local or home antenna system.

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U

The opposite of Overscan. A video or computer image is shrunk on the screen, leaving black borders around it. Underscan is used to scale large images to the screen size and to show on the screen what is happening in the blanking period - at the beginning and end of the lines and the frames. By underscanning, some latent problems in the image can be seen and identified for correction.

The transmission of a signal to a satellite, or the primary link in a microwave system.

Universal Serial Bus. An advanced PC I/O system, much faster than the legacy serial and parallel connections. The system allows for Plug-and-Play operation, connecting up to 127 external devices via an appropriate hub to the PC. The newer system, USB 2.0, allows up to 480 Mbps communication speed.

Unshielded Twisted Pair. A twisted pair system for signal transmission, using unshielded pairs of wires. Data, video, audio and other signals may be transmitted over long distances using a twisted pair transmitter-receiver system. When blocking of adjacent interference is required, an STP* system is used.

Ultra eXtended Graphics Array. A graphics format with a 1600X1200 pixels resolution.

Color difference signals for PAL chrominance scaling. They represent a formula related to B-Y and R-Y levels.

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V

An electronic test machine for color video systems, for color problem tracing and correction in a TV or video studio. The vectorscope, which is similar in appearance to an oscilloscope, displays color vectors and components, as well as the relative position of the Color Burst. See also Waveform Monitor.

When one video signal replaces another, the switching process causes a random interruption in the first video signal (in the midst of a frame) and a random entrance into the second video signal (also in the middle of a frame).

The result is a visible jump in the edited or viewed image. This situation is amplified when the tape is copied, and the disturbance on playback* is much more serious.

To avoid this phenomenon, switching is performed at a very specific point during the vertical blanking retrace period* which is also known as the vertical interval. This allows very smooth replacement of a whole frame by a second whole frame provided that the video sources are Genlocked* to each other. VIS is used also in the presentation and graphics worlds, where sources are switched during the black period of the vertical interval, thus allowing glitch-free transitions.

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

Vertical Interval Time Code is the most popular method for inserting and reading time codes* on a videotape or disk. The time code is inserted in the vertical interval (the screen blanking period) of the video signal, where it is not apparent on the screen, and a time code reader easily retrieves it. The system consists of a time code generator to insert the information, and a time code reader to retrieve it. In most cases, both units - the generator and reader - are built into one machine. The VITC system is very reliable, as each and every frame of the video signal has its individual time code and mark.

A color graphic standard introduced by IBM for personal computers, which displays either high resolution graphics (640 x 480) or 256 colors simultaneously, albeit at low resolution. Due to excellent aspect ratio, which resembles the standard video aspect ratio, VGA is suitable for video recording (after scan conversion* and encoding*).

Video Home System. A format developed by JVC™ utilizing half-inch tape, which is the most widely used analog video format.

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

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

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

CMOS type sensors are also used for some types of cameras. Those sensors are relatively inexpensive to manufacture.

A “virtual” conference of a group of people at different locations, using video cameras, monitors, microphones and loudspeaker systems. The popular linking methods between the sites are multiple ISDN lines, DSL or some other fast internet/network system.

In digital video applications, sometime a heavy video processing is needed, for example, in virtual studio applications. In these cases, since the background is being processed, the foreground should be delayed. A Video delay device can delay the foreground, by using internal memory components, with the amount of fields needed and synchronize between the foreground and the background.

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

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

A general term used for a device which corrects problems on a video or a graphic image. A narrower definition is a machine which restores high-frequency losses by enhancing* the high frequency region of the video/graphics spectrum. An enhancer often has controls such as Sharpness, Definition, Detail, etc., which are used for high frequency boosting. Unfortunately, there is sometimes a tendency for analog enhancers to introduce snow* while adjusting the highfrequency region of the spectrum. Image enhancing is done in the digital and graphics domains as well, usually using different technologies, albeit with the same purpose and uses as the analog video enhancer.

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

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

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

A video wall is large screen made up of several monitors, placed close to one another, which, when viewed from some distance look like a large video screen or wall. A digital processor breaks down the original video or graphic image into several pieces, by converting the analog video signal to digital, rescanning and resampling it, and generating individual analog video outputs for each monitor. The unit is relatively expensive, and is used, as are wide screen projectors, mainly for public viewing.

Video On Demand. A system which allows a user to select a video movie to be displayed on his TV at any selected time. The requests are transmitted to the center either by an Interactive TV* system via a standard or cable modem, or via a PC and a telephone link. More limited systems are called Near VOD where freedom of choice is more limited. VOD requires a bi-directional CATV (upstream/downstream) system.

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

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W

A test machine similar to an oscilloscope designed to show composite or component video waveforms. Every video line may be selected for display and analysis. The waveform monitor helps fine-tune equipment in a video or TV studio and is very useful in locating problems encountered using complex video equipment. It is sometimes integrated into a Vectorscope*.

The ratio of signal to noise level after mathematical manipulation. The mathematical calculation for audio takes into account the frequency response of human hearing, and for video the limitations of the human eye and the TV/ monitor characteristics. This number is usually higher by a few decibels than the standard S/N ratio (shows better results).

An electronic process used in video or digital still cameras* to retain true colors. White balancing is performed prior to shooting a specific scene. The camera is pointed at a white object (a wall, for example) and controls on the camera are adjusted until a hairline in the viewfinder is brought to a particular point. This ensures that the tints* in the recorded images will be natural. White balance, as simple as it seems, can be problematic. Unnatural colors are the result of incorrect white balance. To correct this situation post production, an analog or digital chroma corrector* is used to restore white balance and normal tints*. Most modern cameras nowadays perform automatic white balance control which eliminates many color aberration problems.

A device which electronically limits the maximum “white” level of a video signal, in order to avoid “over-burned” images on the screen.

Audio noise with randomly variable amplitude and frequency. It is made up of uniform sounds of the entire audio spectrum, hence the term “white”, like white light which is a mixture of all the different colors (frequencies) of light.

A display device that projects a video or computer image on a large screen, mainly for public viewing. The first wide screen projectors had very poor quality and brightness, but today, quality and brightness is very good. The classic wide screen projector has three color tubes - red green and blue, and the image is created on the screen by blending the three colors. One of the most common problems encountered with wide screen projectors was poor alignment of the three tubes. In most high quality projectors, the alignment required to get a good superimposition of the three images on the screen is almost automatic and is much easier than in the past.

LCD* (Liquid Crystal Display) TFT* driven screens, which eliminate alignment problems completely, became the heart of a new series of wide screen projectors. The TFT* based projectors offer better price/performance ratios than three tube projectors. Another new generation of projectors is based on DLP/DMD (Digital Micromirrors Device) technology in which a semiconductor chip is covered with hundreds of thousands of micro mirrors that change their angle to a beam of light shining on them. This system creates an image that is much more saturated and has more contrast.

Wireless Fidelity. A certification that approves 802.11 devices which are interoperable and therefore allowed to use the Wi-Fi logo.

A process in which one picture is electronically wiped off the screen and replaced by another. In special effects generators* there are numerous wipe patterns varying from simple horizontal and vertical wipes to multi-shaped, multi-colored arrangements.

Windows Metafile Format. A graphics vector file format developed for Microsoft Windows®, useful in DTP and graphics application.

Wide (Super) eXtended Graphics Array. Wider than XGA* formats, with 16:9 aspect ratio. WXGA varies between 1366X768 pixels resolution to 1280X720 pixels and WSXGA varies between 1920X1080 pixels to 1600X900. Used in some home theater video projectors for outputting a wide image on the screen.

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X

A graphics file format, bitmap based, developed for X Windows, which is a Graphics User Interface for the UNIX operating system.

eXtended Graphics Array. A very popular graphics format with 1024x768 pixels resolution. Recently it was extended to higher resolutions as well.

A type of connector, usually of 3 pins (4 and 5 pins are also available), used in professional studio applications. The most familiar use of an XLR connector is in audio - where a balanced* audio signal uses two of the three pins, and the third carries the common ground.

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Y

A complex division of the video signal used in systems such as S-VHS* or Hi-8. Due to the intricacy of YC, special processors, switchers, amplifiers, etc., are needed for video editing.

A video component system employing luminance* and two color components directly related to the red and blue components. Y, Pb, Pr and Y, Cb, Cr are subsets of this format, widely used in presentation, multimedia and professional video applications. The SDI* format is based on component video, but in a digital serial stream. Professional component video* systems are used in studios and require special equipment to simultaneously handle the three signals. Interface devices are used to link the various system components - RGB, YC, YUV, SDI* and YIQ (a system similar to YUV used for NTSC).