A Video Dictionary

Video Dictionary

1

1080i: 1080i is ATSC high definition 1920 x 1080 interlaced video format where a frame of video is delivered in two fields. The first field contains the odd lines of the image and the second field contains the even lines. Each field is updated every 1/60th of a second resulting in 30 frames of video per second.

1080p: 1080p is ATSC high definition 1920 x 1080 progressive scan video format where a complete frame of video is delivered at either 30 or 24 frames per second.

16:9: Aspect ratio of an HDTV signal which is 16 units by 9 units, whatever size those units may be. In the film trade aspect ratios are described in relation to one, which means this aspect ratio is described as 16/9 or 1.78:1.

2

2:2 pull-down: Method for transferring 24 frame-per-second film to PAL/SECAM video running at 25 frames per second.

2:3 Pull-Down: 2:3 pull-down, commonly called 3:2 pull-down, converts film footage to NTSC video. Film footage is shot at 24 frames per second (FPS) and NTSC video is shot at 30 FPS. 3:2 pull-down refers to the electronics needed to convert 24 FPS to 30 FPS so that it can be viewed on a NTSC video device. To accomplish this, 4 frames of film are converted to 5 frames of video by inserting an extra field of film frame every other frame:

Video Frame 1 2 3 4 5
Video Field a b a b a b a b a b
Film Frame 1 2 3 4

3  

3LCD: Common 3 color system for projecting images via LCD or liquid crystal display. Uses dichroic mirrors to separate the RGB components of white light coming from a projection lamp. Each color is feed to separate LCD panels which control the about of colored light that passes through. The light from each LCD is recombined using a dichroic prism before going out the lens and on to a screen.

4

480i: 480i is ATSC Standard Definition Television (SDTV) 702 x 480 or 640 x 480 interlaced video format where a frame of video is delivered in two fields. The first field contains the odd lines of the image and the second field contains the even lines. Each field is updated every 1/60th of a second resulting in 30 frames of video per second.

480p: 480p is ATSC Enhanced Definition Television (EDTV) 1280 x 720 progressive scan video format where a complete frame of video is delivered at either 60, 30 or 24 frames per second.

7

720p: 720p is an ATSC high definition 1280 x 720 progressive scan video format where a complete frame of video is delivered at either 60, 30 or 24 frames per second.

8  

802.11a: An IEEE specification for wireless networking that operates in the 5 GHz frequency range (5.725 GHz to 5.850 GHz) with a maximum 54 Mbps data transfer rate. The 5 GHz frequency band is not as crowded as the 2.4 GHz frequency, because the 802.11a specification offers more radio channels than the 802.11b. These additional channels can help avoid radio and microwave interference.

802.11b: International standard for wireless networking that operates in the 2.4 GHz frequency range (2.4 GHz to 2.4835 GHz) and provides a throughput of up to 11 Mbps. This is a very commonly used frequency. Microwave ovens, cordless phones, medical and scientific equipment, as well as Bluetooth devices, all work within the 2.4 GHz frequency band.

802.11g: Like the earlier 802.11b standard, it operates in the 2.4 GHz frequency range (2.4 GHz to 2.4835 GHz) but provides a throughput of up to 54 Mbps. Compatible with 802.11b devices at the 802.11b data speeds. Many other devices operate in the 2.4 GHz range where there is greater risk of interference. This can affect data throughput adversely.

8VSB: 8 level Vestigial Side Band. Amplitude Modulated (AM) broadcast system developed to carry the MPEG 2 transport stream(s) of DTV at 19.2 Mbs. Uses the same 6MHz bandwidth as a normal channel does today but more efficiently.

A

a-Si: "Amorphous Silicon"

Aberration: Imperfections in the focusing characteristics of a lens or lens system. Spherical aberration -- Light rays from the center of the lens would come to a focus at a different distance compared with light rays from the periphery of the lens, making the overall focus less precise.  Chromatic aberration -- Light rays of different colors would come to a focus at different distances  from a lens (red is "bent" or refracted least), giving a rainbow fringe around objects and also making the overall focus less precise.

AC-3: Adaptive transform Coder 3, the bitstream designation of Dolby Digital. A variable, lossy audio compression method using perceptual coding to drop sound data you cannot hear. It can be used to deliver from 1 to 5.1 tracks of audio along with metadata on how best to play back a particular recording on a particular system. The '.1' track is a low frequency effects (LFE) track limited to 120 Hz. Metadata can offer control information on down-mixing, dynamic range and level normalization as well as informational data such as artist, copyright etc. The proper ATSC designation is presently A/52A. Encodes audio sampled at 32KHz, 44.1KHz and 48KHz into 32Kbps to 640Kbps data streams. Compression varies with quality with an average of 12:1.

Academy Ratio -- Loosely, the 4:3 aka 1.33:1 aspect ratio (more correctly 1.37:1), which aspect ratio was the standard for shooting movies up until the 1950's.

Active Matrix: A common type of LCD used in laptops, cameras, and LCD projection panels that were produced in the late 1980s to early 1990s. Another name for it is thin-film transistor (TFT). A typical active matrix TFT display is a single panel of LCD glass that controls all three primary colors. TFT displays are noted for their quick response time and their ability to display full motion video and animations without image ghosting.

A/D:  Analog to Digital.

AES/EBU: Audio Engineering Society/European Broadcasting Union. Three pin XLR type connector used to send digital audio.

AGC: Auto Gain Control. A feature typically for VCRs that adjust incoming video levels to reasonable levels. Video copy protection routines fool this component into thinking the incoming video is too 'hot' which therefore causes the video to be extremely dim, sometimes to the point where you can’t see anything.

Amplitude Modulation: Amplitude Modulation (AM) is a method of transmitting information using varying signal levels on a non-varying carrier signal. The waveform of the information being sent exists in the difference of signal level between the peak of the first carrier wave to the peak of the next carrier wave and so on.

Analog Hole: A movie industry term for the potential to create high quality copies of copy protected digital content by digitizing the analog output that is unprotected. Digital streams can be copy protected using encryption whereas analog signals cannot.

Anamorphic: A technique for changing aspect ratios by optically or digitally stretching or compressing an image to or from a format with a different native aspect ratio. Movie studios used this technique to put the first widescreen movies on standard 35mm film and then used an anamorphic lens to recreate the image in the widescreen format in which it was originally shot.

Anamorphic Lens: An anamorphic lens is a lens that has different optical magnification along mutually perpendicular radii. This provides the ability to project a source image of one aspect ratio, such as 4:3, into a different aspect ratio, such as 16:9, by using different magnifications for the horizontal and the vertical dimensions of the projected im

ANSI: American National Standards Institute. A private organization that coordinates and administers various voluntary consensus standards such as ANSI lumens. The first ANSI standard was for pipe threading in 1919 when it was called the American Engineering Standards Committee.

ANSI Contrast: Contrast is the ratio between white and black. The larger the contrast ratio the greater the ability of a projector to show subtle color details and tolerate extraneous room light. There are two methods used by the projection industry: 1) Full On/Off contrast measures the ratio of the light output of an all white image (full on) and the light output of an all black (full off) image. 2) ANSI contrast is measured with a pattern of 16 alternating black and white rectangles. The average light output from the white rectangles is divided by the average light output of the black rectangles to determine the ANSI contrast ratio. When comparing the contrast ratio of projectors make sure you are comparing the same type of contrast. Full On/Off contrast will always be a larger number than ANSI contrast for the same projector.

ANSI Lumens: ANSI lumens is a measurement of the overall brightness of a projector. Because the center of a projected image is brighter than the corners, ANSI lumens is the most accurate representation of the image brightness. ANSI lumens are calculated by dividing a square meter image into 9 equal rectangles, measuring the lux (or brightness) reading at the center of each rectangle, and averaging these nine points.

Aperture: A device that controls amount of light admitted.

Aperture Correction: Compensation for the loss in sharpness of detail because of the finite dimensions of the image elements or the dot-pitch of the monitor.

Aperture Grill: A set of vertical wires to mask the electron guns in a CRT to ensure the beams hit their respective color phosphors. One or two horizontal stabilizing wires are used for spacing, which can be usually seen on the monitor. Monitors using this technique are usually flatter than their shadow mask counterparts. This technique was originally patented by Sony and marketed under the Trinitron name, which has since expired.

Artifacts: Stray pixels and other aberrations that don’t belong in an image.

Aspect Ratio: The ratio of image width to image height. Standard television is 4:3 or 1.33:1. Panavision or Cinemascope is 2.35:1 with 1.85:1 being quite common as well. Widescreen displays are 1.78:1 or 16:9.times the height. For example, if you want an image 40 inches high then you need a screen that is at least 40 * 1.78 inches wide or 71 inches. Other relatively common aspect ratios are 3:2, 4:3 and 5:4.

ATA Rated Case: A case rated strong enough to be shipped by common carrier; freight lines, UPS, FedEx, etc. Most cases of this type are easily recognized by their metal reinforced corners and handles. These cases are often referred to as 'Anvil cases'.

ATRC: Advanced Television Research Consortium. An industry group composed of RCA, Sarnoff Labs, Philips and NBC, banded together in 1990 to develop digital HDTV technologies. Sarnoff designed the transport layer for the presently used MPEG 2 bitstream, which is a way to reduce errors, and Philips designed the HDTV decoders for the present ATSC standard.

ATSC: Advanced Television Systems Committee. Formed in 1982, this international committee develops voluntary standards for terrestrial digital television. Countries adhering to its standards include Canada, Argentina, Mexico, South Korea and the U.S.A. ATSC Digital TV Standards include HDTV, SDTV, data broadcasting, multichannel surround audio, and interactive television.

Attenuate: To reduce. Turning the volume down on your television set is attenuating it.

Auto Balance: A system for detecting errors in color balance in white and black areas of the picture and automatically adjusting the white and black levels of both the red and blue signals as needed for correction.

AVI: Audio/Video Interleave. The file format for Video for Windows (VfW). Used in conjunction with a codec to play back video. Format dictates how video and audio are stored in relation to each other but not the particular compression scheme used, which is handled by the codec.

Azimuth: The direction to point a satellite dish when coupled with altitude. Due north has an azimuth of 0 degrees and due east, 90 degrees and so on.
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B

Balanced Input: Three conductor input with two signal conductors that are directly out of phase with each other. This cancels each other out when they pick up electromagnetic interference along the path but doesn’t affect the signal. The third conductor is ground.

Banana Connector: A type of speaker wire plug with a expanded single shaft that looks like a banana. Inserts in 5-way binding posts and offers a large contact area, which helps performance.

Bandwidth: The number of cycles per second (Hertz) expressed as the difference between the lower and upper limits of a frequency band; also, the width of a band of frequencies. Practically speaking, bandwidth is the amount of data that can pass through a given connection per unit of time.

Barrel Distortion: Distortion where screen image expands outward towards edges of the screen. Instead of being square, edges are curved outward like the edge of a barrel. Opposite of pincushion.

Betamax: Sony’s competing home recording standard to VHS in the 1970s. It produced etter quality than VHS, but at a higher price.

Bezel: The frame or face of a device, such as, a projector grill, or CRT or LCD display frame.

Binding Post: Type of amplifier or speaker connection.

Black Level: The darkest part of a picture. This can vary between display devices and viewing environments. NTSC black is set at 7.5 IRE, which is very slightly gray. The white level divided by the black level gives a contrast ratio for a particular display device.

Blanking: The period of time that an electron gun is turned off to reposition itself to paint the next part of the video onto the CRT screen.

Bleeding: Video distortion where color “bleeds” from an object onto other parts of the image which are not supposed to be that color.

Blooming: Video distortion where an overly bright screen object causes phosphors near it to excite therefore enlarging the object and softening its edges.

Blue Laser: Color of the laser used with Blu-ray high definition DVDs. Blue laser light has a shorter wavelength than red, which is why blue lasers can retrieve and store more data in a given physical area.

BNC: Bayonet Nut Connector or British Naval Connector. A high quality, locking cable plug which is used extensively in professional video.

Bowing: Video distortion where lines which should be straight are curved. See barrel distortion and pincushioning.

Brightness: Overall light output from an image. While a brightness control can make an image brighter, it is best used to better define the black level of the image.

Broadcast Flag: A set of status bits or flags that are included with a television program that dictates whether or not the program can be recorded. It may also indicate other restrictions on the recorded content such as prohibiting the viewing of the content on an analog display.

Burn-in: Image distortion where phosphors are discolored at a differing rates in a display device such as a plasma, CRT or SED TV. Usually caused by displaying a static image for extended periods. Screensavers are used to prevent burn-in on CRTs and plasma displays use a periodic dynamic single pixel shift of the image to avoid burn-it.

C  

CableCARDTM: An alternative to a cable TV set-top box which allows the consumer to choose which type of set-top box they want as opposed to only the ones a particular cable company offers. Many display devices offer a direct connection for a CableCARD which is a PMCIA type card that handles decryption. A new standard of CableCARD has been proposed which offers interactive features such as pay-per-view and interactive program guides.

Calibrate: To adjust with reference to a standard.

Cathode Ray Tube (CRT): Analog display device that generates an image on a layer of phosphors that are driven by an electron gun.

CATV: Community Antenna TeleVision or cable television. Method of delivering television broadcasts via coaxial cable, which is less susceptible to interference that via antenna. CATV cable is another term for coaxial.

CBR: Constant Bit Rate. Refers to an unchanging encoding rate for MPEG where quality gets downgraded on compression demanding scenes such as ones with a high amount of movement. Variable bit rate (VBR) encoding keeps quality at a standard level and is considered more efficient.

CCD: Charged Coupled Device. Electronic sensors used in video cameras that convert light energy into electrical.

CD-R: Compact Disc - Recordable. See CD.

CD-RW: Compact Disc – Re-Writable. See CD.

CEA: Consumer Electronics Association. An industry association of some 2000 electronics manufacturers. Produces the Consumer Electronics Show or CES.

CEDIA: Custom Electronic Design and Installation Association. International industry association for home electronics installation and design related businesses. It also certifies members with professional designations.

Center Channel: Center designated signal of a 5.1 audio system. Typically for home theater, the corresponding speaker should be as close as possible to the video image associated with the sound.

Channel: A separate signal or signal path.

Chroma: (C) The color part of a video signal.

Chromatic Aberration: An optical defect of a lens which causes different colors or wavelengths of light to be focused at different distances from the lens. It is seen as color fringes or halos along edges and around every point in the image.

Chromaticity: The color quality of light that is defined by the wavelength (hue) and saturation. Chromaticity defines all the qualities of color except its brightness.

Chrominance: (C) Color portion of a video signal.

Chrominance-to-luminance delay: State where color signal lags behind the brightness signal, which shows as color smearing or bleeding at the edge of objects.

Closed Caption: Closed caption (CC) superimposes a transcript of the audio portion of a video program over the program image. Its primary use is to provide people that are deaf or hard of hearing the opportunity to read a transcript of the audio as it is being played. Closed Caption is also helpful for people learning to read or learning a foreign language. Closed Caption can also be used to display text unrelated to the program being viewed, such as weather or news.

Coated Optics: A variety of materials put on high quality lenses to minimize the amount of light reflected back to the lamp and the amount of ambient light that mingles with the focused light leaving the lens. Generally good coatings can add 15% or more to the lenses brightness. Other coatings are used for filtering colors.

Coaxial: An audio or video cable with a single internal wire with an outer shield that is ground. In audio, a speaker type where one speaker is positioned within another larger speaker’s cone.

Codec: Stands for COmpression/DECompression. Generic term for an algorithm for compressing and decompressing data, audio, or video files. Lossless codecs such as LZW are used for data files where every bit must be preserved, while lossy codecs such as MPEG and WMA are used for video and audio files where losing information is tolerable.

COFDM: Coded Orthogonal Frequency Division Multiplexing. An HDTV broadcast method adopted predominantly in Europe as opposed to 8VSB being adopted in the U.S.A. Sends a digital signal over a thousand or so carrier signals from multiple antennas. Resistant to multipath where the same signal gets reflected off objects to create ghosting or faint duplicate signals arriving later.

Color Analyzer: A device for measuring the color accuracy of a display device relative to the standard of D65 or 6500 degrees Kelvin.

Color Bars: Calibration pattern used to adjust the brightness, saturation and hue of video displays.

Color Break-up: Image anomaly which looks like a rainbow at the edge of bright objects on screen. Also called rainbow effect where sequential color systems, such as single chip DLP projectors or some LCoS RPTVs, update color information at different locations on the screen because of quick movement of screen objects or a viewer’s gaze. For instance, the red component of a white object will show at a different location on the screen than blue when an object moves quickly across because color is being displayed sequentially. This also occurs with quick relative movement such as moving your gaze from point to point across the screen. Most noticeable in bright objects.

Color Decoder: Circuit in a display device that separates the color part of the signal from the luminance. Can effect picture quality if set by manufacturer to compensate for higher color temperature of overdriven displays or other color variations.

Color Dynamics: The whitest whites, reddest reds, bluest blues and greenest greens. High color dynamics are a result of dynamic range/contrast ratios. Having excellent color dynamics implies rich colors, excellent definition, high contrast.

Color Saturation: Measure of color purity. Highly saturated colors emit a very narrow band of wavelengths of light instead of the broader spectrum of frequencies emitted from mixed colors. A display with good saturation capability will look vibrant.

Color Temperature: Color balance of white light which goes from red to blue as the temperature rises. Measured in degrees Kelvin, which starts at absolute 0 or –273 degrees Celsius, color temperature matches the reference standard of the light being emitted from a carbon block heated to the stated degrees. For instance, the early morning sun is around 2500K, which is the same warm light that a carbon block heated to 2227° Celsius would emit. Heating the block further to ~10000° Celsius would emit the same bluish light of a blue-sky mid-day sun. Common color temperatures are 5500 Kelvin (black and white movies) and 6500 Kelvin (standard color films).

Color Wheel: Rotating wheel with 3 or more translucent color filters used to display sequential color on single imager light valve based projection devices. The imager reflects or transmits the color component of a given image when the wheel’s corresponding color filter is affecting the light passing through to the lens. A 1X wheel cycles through all colors in 1/60th of a second.

Comb Filter: Reduces interference between color and luminance signals carried in composite video. Better than a notch filter and in order from worst to best quality, 2-line, 3-line and 3D.

Combing: A motion artifact caused by interlace where an object has moved appreciably within a frame and its new position is displayed in a different position in one field over the other. Looks like the teeth of a comb.

Component Video: Component Video is a method of delivering quality video (RGB) in a format that contains all the components of the original image. These components are referred to as luma and chroma and are defined as Y'Pb'Pr' for analog component and Y'Cb'Cr' for digital component. . It is comprised of luminance (Y) and two chrominance channels of blue minus luminance and red minus luminance.

Composite Video Signal: Single signal version of video where both chroma and luma are carried with chroma on a 3.58MHz sideband of the luminance signal, usually through a 75 Ohm cable. Poorest quality signal type.

Compressed Resolution: Most projectors and displays automatically accept images that are of greater resolution than the native (true) resolution of the video device. The resulting image is scaled to fit the native resolution of the video device using a variety of scaling algorithms. Not all video devices use the same compression algorithms; therefore, the quality of compression can vary. The nature of compression in a digital device means that some image content is lost.

Contrast: Contrast increases as the white point increases. Increasing the white point creates a greater difference between white and black.

Contrast Ratio: The ratio between white and black. The larger the contrast ratio the greater the ability of a video device to show subtle color details and tolerate ambient room light. There are two industry methods used: 1) Full On/Off contrast measures the ratio of the light output of an all white image (full on) and the light output of an all black (full off) image. 2) ANSI contrast is measured with a pattern of 16 alternating black and white rectangles. The average light output from the white rectangles is divided by the average light output of the black rectangles to determine the ANSI contrast ratio. When comparing the contrast ratio of video devices make sure you are comparing the same type of contrast. Full On/Off contrast will always be a larger number than ANSI contrast for the same video device.

Convergence: An issue for CRT displays, projectors, and RPTVs. Convergence is the alignment of the component colors of a display where the respective electron beams or pixels must sit at the precisely correct position for the proper color to be rendered.

Convergence Error: Colors of a color component display such as a CRT or projector do not line up correctly to create a proper image and create color halos or incorrect color.

Crosstalk: Interference of an electrical signal by another electrical signal in close proximity caused by its electromagnetism.

CRT: Cathode Ray Tube.

D  

D-ILA: Direct Drive Image Light Amplifier. Proprietary JVC version of LCoS light valve technology.

D-VHS: Digital tape standard with backward compatibility to SVHS and VHS. First device offering HDTV recording and playback at up to 28Mbs data rates. D-Theater capable D-VHS VCRs are capable of playing back copy protected pre-recorded HD movies.

DAC: Digital to Analog Converter. Electronic component that converts a digital signal to an analog.

dB: dB or decibel is a measure of relative loudness. 0 dB is the threshold of hearing. 60 dB is equivalent to normal conversation. 120 to 140 dB is the threshold of pain such as a jackhammer or gun shot. 10 db of change will double the loudness.

DBS: Direct Broadcast Satellite. Also called Direct To Home, a small dish digital broadcast system that gets sent via satellite between 12GHz and 18GHz frequencies. Subject to attenuation by rain.

DCDi: Directional Correlation Deinterlacing (DCDi)was developed by Faroudja and is a video algorithm designed to eliminate jagged edges that are generated by interlaced video.

Deflection Yoke: Electric coil used to deflect the electron beams in a CRT display.

Degauss: Method to get rid of magnetic fields that build up in CRT monitors and distort the video signal causing discoloration.

Deinterlacer: Electronic component that converts an interlace video signal to progressive scan.

Deinterlacing: Act of converting an interlace video signal to progressive scan.

Delay: Commonly used in sound engineering where a sound is played back later at different speakers in order to maintain directionality of original sound. Uses the psychoacoustical phenomenon of precedence effect where a sound is first heard is where it is perceived to come from even when coming from multiple places.

DFP: An all-digital monitor connection using TDMS designed by the Digital Flat Panel Group. Limited to 1280x1024 resolution and a cable length of 10 meters. Uses an MDR20 connector.

Diagonal: The diagonal of a screen or flat panel can be computed by using the Pythagorean theorem: squaring the width, squaring the height, adding them together and taking the square root. A 100" diagonal 16:9 screen measures 49" high by 87" wide; a 100" diagonal 4:3 screen measures 60" high by 80" wide. Use the Projection Calculator to get screen dimensions on all common aspect ratios.

Dichroic: A mirror or lens that reflects or refracts selective wavelengths of light. Typically used in projector light engines to separate the lamps "white" light into red, green, and blue light.

Digital Cliff: Description of how a digital signal deteriorates with interference and attenuation. Either the signal is completely functional or not at all with no slight quality degradation that exists with analog.

Digital Closed Caption: Digital closed caption is available on digital TV programs at the election of the service provider. Unlike the Closed Caption sytem, Digital Closed Caption allows the setting of the size, color, style and opacity of captioned text. When Digital Closed Caption is in use, it will be indicated by the appearance of a 3-letter abbreviation that indentifies the language of the displayed text.

Direct-View Television: Display device where the imager is viewed directly as opposed to a projection surface.

Discrete: As it relates to surround sound systems, discrete sound is a separate recorded track for each channel. Other systems may amalgamate tracks into one and then separate them out electronically.

Distortion: A usually undesirable variation from an intended output caused by the characteristics of a particular device.

Distribution Amplifier: An amplifier used to maintain a clean noise free signal to a projector or flat panel device over significant distances. Even with good heavily shielded cables, range of video and computer signals is limited to a few dozen feet before noticeable degradation. In ceiling mount situations, where the wiring may pass along side or across electrical conduits, a distribution amp may be needed with shorter distances. Many distribution amps can also split the signal into 2 or more amplified signals for driving multiple projectors or flat panels.

Dithering: Method of displaying intermediate colors that don’t exist in a limited palette by using a pattern of small dots out of that palette.

DivX: Video format based on the MPEG 4 standard. Commonly used for downloadable video files.

DLP: DLP (Digital Light Processing) is a commercial name for a display technology from Texas Instruments (TI). The technology inside is often referred to as DMD (Digital Micro-Mirrors). It consists of an array of mirrors where each mirror represents a pixel element. For example, a high-definition DLP projector or rear projector with 1920 x 1080 pixel resolution would have and over 2 million tiny mirrors. Each mirror is attached to an electronically driven hinge that controls the amount of colored light that is reflected from the mirror into the projection lens and onto a screen. Projection systems using DLP technology use 1 to 3 DMD devices.

DMD: Digital Micromirror Device. Name of the actual imaging chip used in a Texas Instruments DLP projection systems.

DNR: Digital Noise Reduction. A system that reduces picture noise by comparing previous frames to the present and smoothing out what appears to be noise to the algorithm. Helps reduce flickering in still parts of a video image.

Dolby Digital: A lossy compression system to deliver sound on DVDs, ATSC and DBS broadcasts in up to 5.1 channels. Also called AC-3. See AC-3.

Dolby EX: Backwards compatible system to add a sixth channel used for the middle rear playback to Dolby Digital (AC-3) making it 6.1 or 7.1 sound. 7.1 sound uses an additional center rear speaker playing back a duplicate track. Needs a Dolby EX decoder. See AC-3.

Dolby Pro Logic: An analog 4 channel surround sound system with left, right, center channels and a mono rear channel, typically duplicated across 2 speakers. Rear channel is limited to 7KHz and system stores all channels in a matrix recording on 2 discrete analog channels. Has difficulty playing back non-encoded material at full fidelity.

Dolby Pro Logic II: Updated version of Pro Logic. Offers better performance with playing back non-encoded sources over a surround sound system with full spatial cues and fidelity.

Dot Crawl: Video artifact where little dots crawl along the borders of differing colors, particularly noticeable on graphics. Effect of composite encoding and easily removed by using s-video or component cabling. Will not disappear if the source was recorded using composite video and the artifact has been recorded.

Dot Pitch: The distance between side-by-side phosphor color groups (RGB) on a direct view display that uses phosphors. The smaller the better.

Downconvert: To convert a higher resolution signal to a lower resolution. For example, 720p to 480p.

Dropout: Missing information from a broadcast or recorded media and typically show up as white specks in an analog environment. Dropout is more pronounced with interframe compression techniques such as MPEG because the error displays until the next complete frame is drawn, otherwise known as an I-frame. This can take up to ½ a second.

DSP: Digital Signal Processing. A digital method of manipulating incoming and outgoing signals on an ongoing basis. Often used in audio to create reverb among other effects.

DSS: Digital Satellite System and now called DBS. A system for sending and receiving digital satellite broadcast signals using small receiver dishes.

DTCP: Digital Transport Copy Protection. A digital rights management technology standard issued by the DTLA (Digital Transmission Licensing Administrator) to prevent the unauthorized copying of copyright material.

DTLA: Digital Transmission Licensing Administrator. Controls the licensing of the DTCP copy-protection technology.

DTS: Digital Theater Systems. An alternate method of encoding multitrack audio used on DVDs and other sources like D-VHS. Offers less compression compared to Dolby’s more common AC3 system and, arguably, better fidelity.

DTS 96/24: Digital Theater Systems. A version of DTS that plays back a 96kHz sampling rate, 24-bit resolution recording at full fidelity.

DTS ES: Digital Theater Systems Extended Surround. Backward compatible system to DTS with a center rear channel added.

DTS Neo:6: Sound process that separates stereo audio into 5 or 6 channels. Also decodes Pro Logic encoded analog sources. It offers two modes, music and cinema. Music mode allows the left and right channels of a stereo signal to pass through without processing, retaining fidelity, but still adds signals for the remaining speakers. This gives up some imaging for fidelity.

DTV: Digital Television. A system that uses digital signals instead of analog including the ATSC standards, DBS and digital cable.

DVD: Digital Versatile Disc. Same physical size as a compact disc but has a capacity to hold a minimum of 4.7GB of data, 9.4GB if dual layer and/or dual sided. DVD-Video discs can hold about 4 hours of video on a dual layer disc depending upon the amount of compression applied. It uses MPEG-2 compression at a maximum rate of 9.2 Mbps with most video compressed at about 4Mbps at 720x480 pixels. All players support AC-3 (Dolby Digital), PCM, and MPEG-2 audio with up to 8 separate tracks. DTS is usually supported but isn’t mandatory to the format. DVD-Audio supports up to 6 channels of 24 bit, 192KHz sampled PCM audio.

DVD+R: Digital Versatile Disc + Recordable. A write-once recordable DVD format with 4.7GB capacity supported by the DVD+RW Alliance. More robust that DVD-R.

DVD+RW: Digital Versatile Disc + Read Write. A rewriteable DVD format with 4.7GB capacity supported by the DVD+RW Alliance. Can be rewritten up to 1000 times.

DVD-A: Digital Versatile Disc-Audio. Allows for very high quality audio with up to 6 channels. Sample rates can be up to 192KHz at 24 bits of resolution. It allows for video as well as asynchronous slide shows of up to 99 still pictures per track. MLP (Meridian Lossless Packing) is supported as a lossless compression alternative to PCM.

DVD-R: Digital Versatile Disc - Recordable. A recordable write-once DVD format with 4.7GB capacity supported by the DVD Forum. Not as robust as DVD+R.

DVD-RAM: Digital Versatile Disc Random Access Memory. More robust as a rewritable format for computers than DVD±RW, it is housed in a cartridge and is incompatible with DVD-ROM drives and video players. Can be rewritten up to 100,000 times.

DVD-RW: Digital Versatile Disc - Read Write. A rewriteable DVD format with 4.7GB capacity supported by the DVD Forum. Can be rewritten up to 1000 times.

DVI: Digital Visual Interface. DVI is a standard that defines the digital interface between digital devices such as projectors, flatscreens and personal computers. For devices that support DVI, a digital-to-digital connection can be made that eliminates the conversion to analog and thereby delivers an unblemished image.  It can also carry an analog signal and comes as DVI-I (integrated - analog and digital), DVI-D (digital only) and DVI-A (analog only).   Dual link DVI connections add additional resolution capabilities. Digital cable lengths should not exceed 15 feet. Specifications on DVI are available at www.ddwg.org. Click for more details on DVI.

DVR: Digital Video Recorder. Also known as a PVR or Personal Video Recorder. A hard disk based video recorder, which usually offers long recording times and the capability to pause incoming broadcasts. When the unit has access to electronic programming guides, it can record shows on an ongoing basis as well as do keyword and genre searches.

Dynamic Range: The ratio between the highest and lowest levels a device can perform. For a video device it is a measure of contrast ratio. For an audio device it is usually stated in dB.

E

EBU European Broadcasting Union: A Geneva based organization of private and public European broadcasters. Started in 1950, it assists members with broadcast rights and does technical development of broadcast standards.

Edge Enhancement: A techniques used to increase apparent resolution by increasing contrast around object edges. Usually counterproductive with already high-resolution sources and can become a source of image distortion.

EDTV: Extended Definition TeleVision. EDTV is a class of digital television (DTV) that refers to the 480p format. 480p is a progressive scan video format that produces a full frame of 480 lines of video.

Electron Gun: A device used in a CRT to shoot electrons at screen phosphors, which then excite and light up creating an image. There are three guns in a color CRT, one for each primary color (RGB), and one in a black and white.

Electronic Whiteboard: Looks like a regular conference-room whiteboard except that it captures notes and drawings made on it electronically that can be sent remotely for teleconferencing or stored digitally for future reference.

EMI: Electro-Magnetic Interference.

F  

False Contouring: Also known as solarization or posterization. False contouring occurs when color shows as distinct contours or edges where there shouldn’t be any. This occurs when colors that should flow naturally between shades or brightnesses do so discretely in clearly defined bands. The visual effect is the look of a topographical map instead of a video image.

FCC: Federal Communications Commission. U.S. government agency responsible to Congress that regulates interstate and international communications via radio, television, wire, satellite and cable. Commenced operations in 1934.

Feedback: Feedback occurs when the output of a device returns as the input of the same device. A microphone recording the sound from a speaker which is playing back the same microphone as a source is an instance where this can occur. Signals get replicated multiple times and if they are amplified, the amplification gets repeated as well. This is how room noise turns into a loud screech if microphones aren’t placed properly; however, this can occur to any electrical signal.

Fiber Optic Cable: Sends signals as light pulses instead of electrical energy. Made of glass or plastic, these cables are not susceptible to electromagnetic interference.

Field: One half of a video frame consisting of either all of the even-numbered scan lines or all of the odd-numbered scan lines in a frame.

Fill Rate: Given as a percentage, this characteristic indicates how smooth an image will look viewing a particular display. An imaging system with a low fill rate will exhibit a screen door pattern in its images.

FireWire: High speed serial bus with a speed up to 400Mbps. See IEEE 1394.

Fixed-Pixel Display: Any device that has a 'native' pixel resolution. CRTs are the only non-fixed-pixel displays where resolution is determined by bandwidth.

Flat Response: A state where no frequency of an electronic device is emphasized over another when output. In audio, a device with a flat response is able to transmit all frequencies fully, with equal capability. No device can actually do this perfectly.

FM: Frequency Modulation. Method for sending information by adding the frequencies of the information to be sent to a carrier versus modulating a carrier’s wave amplitude. The carrier is filtered out.

FM Based Remote: A remote control that broadcasts its instructions with an FM transmitter, normally required in large rooms and no line of site requirement.

Focal Length: The distance from the surface of a lens to its focal point.

Foot-Lambert (fL): Measurement of luminance (brightness) emitted from a surface. One foot-Lambert is equal to one lumen per square foot. The metric equivalent of one foot-Lambert is 3.426259 nits or cd/m2. The SMPTE standard for theater cinema is 16 fL.

Form Factor: A general description of a projector or flat panel's size and shape. For example, a light projector with a small case can be said to have a small form factor, and would be good for mobile presentation. Similarly, a flat panel that is slim and wall mountable would be considered to have a small form factor.

FPS: Frames Per Second.

Frame: A frame is one complete video image. When all lines of the video image are delivered sequentially, it is called progressive video. When the odd lines and even lines are delivered as separate fields, it is called interlace video.
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Frequency Response: Measures the frequencies a component is capable of reproducing and how well it does it. Usually stated as a set of frequencies with a variance measured in decibels (dB). The ideal is to have no variance or flat response, along with a wide range of frequencies.
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Front Projection: A system where the projector sits in front of the screen with the image getting reflected back to the audience.

Front Room Projector: A projector that sits close to the screen and is capable of throwing a large image.

Full On/Off Contrast: Contrast is the ratio between white and black. The larger the contrast ratio the greater the ability of a projector or flat panel to show subtle color details and tolerate extraneous room light. There are two methods used: 1) Full On/Off contrast measures the ratio of the light output of an all white image (full on) and the light output of an all black (full off) image. 2) ANSI contrast is measured with a pattern of 16 alternating black and white rectangles. The average light output from the white rectangles is divided by the average light output of the black rectangles to determine the ANSI contrast ratio. When comparing contrast ratio, make sure you are comparing the same type of contrast. Full On/Off contrast will always be a larger number than ANSI contrast for a given product.

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G

Gamma: Relationship between input video voltage and output brightness. Determines how mid-tones appear as eye sensitivity is non-linear and display devices use different methods to account for this as well as their own display characteristics.

Gamma Correction: Adjustment to gamma or how gray levels between black and white are displayed as the eye is sensitive to these in a logarithmic manner. For example, good gamma correction allows subtle shadow detail in a dark image to be easily perceived.

Gauge: Wire thickness measure. The lower the gauge, the larger the wire.

Geometry: Characteristic of a display to accurately show an image without distorting it. When a display’s geometry is good, it represents square objects as a square, etc. See pincushioning and barrel distortion.

Ghosting: A faint duplicate image, usually offset from primary image. Can be caused by multipath, which is a delayed, attenuated duplicate signal bounced off an object to an antenna or other interference.

Gray Scale: A table of shading devoid of color, progressing from black to white. The number of discernible gray levels defines the color resolution of the display device and is used to evaluate color acuity and contrast.

H  

Hanging Dots: Artifact of composite video where stationary dots exist where two colors meet. Caused by interference between main video signal and color carrier. See dot crawl.

HD-DVD: High-Definition Digital Versatile Disc. Two formats have been proposed for these high-capacity DVDs, including Blu-ray and the generically named HD-DVD. Blu-ray is backed by Sony and Panasonic among others through the Blu-ray Disc Association and HD-DVD is backed by NEC and Toshiba through the DVD Forum. Blu-ray uses a higher resolution blue laser allowing for more disk capacity than HD-DVD, 25GB compared 15GB per layer. At present Blu-ray is more expensive and cannot be replicated on existing manufacturing lines.

HDCD: High Definition Compatible Digital commonly known as High Definition Compact Disc. Codec for traditional audio CDs with audio resolution of 20 bits for more accurate replication of the original sound.

HDCP: HDCP (High-bandwidth Digital Content Protection) is a method for protecting copyrighted digital content that uses the DVI (Digital Visual Interface) or HDMI (High-Definition Multimedia Interface, previously known as DVI-CE) by encrypting its transmission between the video source such as a set-top box, DVD player, or computer and the digital display device such as a projector, monitor or television. To view digital HDCP protected content, both the sending and receiving device must support HDCP.

HDMI: HDMI (High Definition Multimedia Interface) is an uncompressed, all-digital audio/video interface that supports audio/video sources such as a set-top box, DVD player, A/V receiver, and video monitors such as a digital projector or digital television (DTV). HDMI is backward compatiable with DVI 1.0 specification and supports HDCP.   HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio, and interactive controls on a single cable. It transmits all ATSC (Advanced Television Systems Committe) HDTV standards and supports 8-channel digital audio. First product releases using HDMI occurred in 2003.

HDTV: High-Definition Television. Generic term that indicates a higher resolution format than previous standards. At present, denotes anything higher than a 480p signal. Most common formats are 720p, 1080i and 1080p.   HDTV capable: A television that supports 720p or 1080i or higher resolutions and has a built-in HDTV tuner for off-air reception of HD signals from a special antenna. To view cable and satellite HDTV programming, a cable set-top-box or satellite receiver is required.

HDTV ready: A television that supports 720p or 1080i or higher resolutions and does not have a built-in HDTV tuner for off-air reception of HD signals from a special antenna. To view cable and satellite HDTV programming, a cable set-top-box or satellite receiver is required.

High Gain Screen: A screen that uses one of many methods to collect light and reflect it back to the audience, which dramatically increases the brightness of the image over a white wall or semi-matte screen. Technologies used include curved screens, special metal foil screens (some polarized), and certain glass bead screens. High gain screens achieve higher brightness by directing more of the reflected light towards the center of the screen.

Horizontal Resolution: Amount of pixels across an image, from left to right. A 1920 x 1080 HDTV has a horizontal resolution of 1920 pixels.

Horizontal Scan Rate: Period of time it takes to refresh an image on a screen, usually measured in Hertz (cycles per second). Computer monitors typically have scan rates starting at 60Hz going to 85Hz.

HTPS: High Temperature Poly-Silicon. An active matrix transmissive LCD technology used in 3LCD projectors.

Hue: Hue or tint is the parameter of color that allows us to distinguish between colors. 

Hz: Hertz. Also called cycles per second and in video displays is the rate at which an image is refreshed.

I

ID1 detection: Detection of widescreen signalling (WSS) from a broadcaster. Allows broadcaster to configure television to proper aspect ratio.

IDTV: Improved Definition TeleVision. Television transmitters and receivers that (a) are built to satisfy performance requirements over and above those required by the NTSC standard and (b) remain within the general parameters of NTSC standard emissions. Note 1: IDTV improvements may be made at the TV transmitter or the receiver. Note 2: Examples of improvements include enhancements in encoding, digital filtering, scan interpolation, interlaced line scanning, and ghost cancellation. Note 3: IDTV allows the TV signal to be transmitted and received in the standard 4:3 aspect ratio. Synonym enhanced-quality television.

IEEE: Institute of Electrical and Electronics Engineers. An international, non-profit, technical organization based in the U.S. that develops standards.

IEEE 1394: Also called FireWire or iLink. A serial bus which can address up to 63 devices, communicating at up to 400Mbps but is limited to a cable length of 4.5 meters. Its content copy protection scheme is called DTCP or 5C. Most DV camcorders have a IEEE 1394 port as well as D-VHS VCRs and some set-top boxes for cable and satellite.

iLink: High speed serial bus with a speed up to 400Mbps. See IEEE 1394.

Imaging: In audio, a particular system’s ability to reproduce sound so that it seems to be coming from a particular location.

Impedance: Total inductance, resistance or reactance to a signal flow. Reactance is like inertia where acceleration takes time to get going and time to stop but there isn’t a net loss in energy. Resistance on the other hand, translates electricity into acceleration or heat. Impedance is measured the same as resistance, in Ohms.

Infra-red Remote: An infra-red (IR) remote control transmits in the spectrum of infra-red light, such as a television remote. Unlike RF remotes, IR remotes must point at the receiver (line of sight). Typical range is limited to 30 feet including the distance to and from reflected surfaces. For example, if you are controlling a projector and you point the remote at the screen which is 12 feet from you and the projector is 10 feet, the total distance is 22 feet. Most projectors have a IR sensor in both the front and rear of the projector, whereas, flatscreens generally have a single IR sensor in the front of the unit. When working at or near the maximum distance, pointing right at the receiver is necessary. IR remotes must have clear path or reflected path to the receiver to operate.

Interlaced: A process where a video image is delivered in two fields each containing half the video image rather than a single frame that contains the entire image. The first field contains all the odd lines and the second field contains all the even lines. For example, each 480i frame is made up of two fields of 263 and 262 lines of resolution and updated at 60Hz. 480 denotes the active picture area; however, the total frame size is actually 525 lines. 480i and 1080i are interlaced signals whereas 720p is a progressive signal where each video image is delivered in a single frame. Interlaced video was introduced with the first televisions because of bandwidth limitations.

International Power Supply: A unit that can operate under a international selection of power requirements. The specs of units vary widely, but the minimum is 105-230 volts, and 50-60 cycles AC (alternating current). If you see a specification like 110v, 220v instead of a range, those ratings are usually +/- a given percent such as 10%. Most units are "self-switching" they will automatically switch to whatever power source you plug it into. Others will have to be switched (internally or externally to accommodate a difference voltage or cycle range.

Invert Image: Invert image flips the image from top to bottom, to compensate for ceiling mounting a projector upside down. Projectors typically ceiling-mount upside down, because most have a built-in offset that allows you to mount the screen at a comfortable height, yet still project an image without tilting the projector and causing keystone distortion.

ISF: Imaging Science Foundation. Organization that trains and accredits display calibration technicians as well as certifies display hardware. Designs standard testing and calibration procedures and tools.

J

Jaggy: The stair-step or sawtooth effect seen on lines that are not horizontal or vertical or the edge of objects in digital displays. Also known as aliasing. Smoothing and antialiasing techniques can reduce the effect of aliasing.

Jitter: Abrupt variations in signal amplitude or timing that cause reproduction instability in audio, video and data. Usually caused by bandwidth limitations or impedance termination issues that can sometimes be caused by the cable and/or connections you are using. Power supplies can also be a source of this problem.

JPEG: Joint Photographic Experts Group. Name of association that created the image file standard of the same name. A lossy compression scheme for storing high quality, full-color images. Also used as a video format under the guise M-JPEG of which a variant is used for DV video.

Judder: Apparent stutter of on-screen movement. Commonly caused by 3:2 pulldown where movie frames are on screen for differing times due to frame rate translations. Also occurs on PAL to NTSC conversions. Solved by 3:3 pulldown.

K

Kelvin: A temperature measurement scale where 0° Kelvin (0°K) is equal to absolute zero, the temperature at which all molecular movement ceases. One degree of Kelvin is equal to 1 degree of Celsius. The color temperature of large image devices is measured in Kelvin. The higher the temperature, the bluer the light.

Keystone: Keystoning occurs when the projector is not perpendicular to the screen, thereby creating an image that is not rectangular.

Keystone Correction: Keystone correction makes a projected image rectangular. This can be accomplished by positioning the projector to be perpendicular to the screen. Since this is not always possible, most projectors are equipped with keystone correction that allows the image to be keystone corrected (made rectangular) by adjusting optics, making mechanical adjustments, or applying digital scaling to the image. Keystone correction can be one or two dimensional and manual or automatic depending on the projector and the manufacturer. Be aware that digital scaling will introduce some artifacts that are more evident when viewing small text and less evident in presentation type material or video.