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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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, while 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 60 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 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 | ||||||
3D Ready
A projector that is 3D Ready can accept a 120Hz frame-sequential 3D signal from a computer via either NVIDIA's 3D Vision system or one of several educational software suites. These projectors are not compatible with the HDMI 1.4 3D specification used on 3D Blu-ray players and set-top boxes. We also refer to this type of 3D as PC 3D Ready.
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.
480i
480i is ATSC Standard Definition Television (SDTV) 720 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) 720 x 480 progressive scan video format where a complete frame of video is delivered at either 30 or 24 frames per second. 480p also refers to a display format comprised of 854 x 480 pixels, 16:9 widescreen.
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.
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-Si
"Amorphous Silicon"
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.
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.
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 image.
Anamorphic Ready
A projector that supports anamorphic projection using an optional anamorphic lens.
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
Flaws and aberrations in a video image that derive from technical limitations in the capture, encoding/decoding, transmission, and display of a video signal.
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.
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.
Blackboard Mode
Blackboard mode is a projector feature that allows the projector to detect the color of the display surface such as a chalkboard of painted wall and automatically adjust its output to optimize accurate color reproduction.
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.
Brightness (Perceived)
The brightness of a projection system can be precisely measured with a light meter. For example, a typical movie theater is setup to deliver 16 foot-Lamberts. The higher the foot-Lamberts, the brighter the image. A common misconception is that a projector with twice the foot-Lamberts of another projector will be twice as bright. While it is true that a light meter will detect it as twice as bright, your eye will not. The perceived brightness will increase by about 50%. It will not double because the human eye has a logarithmic respond to light.
Brilliant ColorTM
Brilliant Color - a technology developed by Texas Instruments for its DLP projectors that produces six channels of color including red, green, blue, cyan, magenta, and yellow; thereby, allowing an increase in the color gamut.
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-in.
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.
Some projector models are only sold through authorized CEDIA dealer networks and might not be sold online.
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.
CLO
In 2012, the Society for Information Display (SID), introduced the Color Light Output (CLO) specification as an alternative to the ANSI lumen measurement of brightness in projection systems. The essential difference is that the ANSI lumen specification provides for the measurement of maximum white brightness based on white light output alone, whereas CLO represents the sum total brightness of the three independent color channels, red, green, and blue. While all projector manufacturers continue to publish the ANSI lumen brightness specification, some publish the CLO specification as well.
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.
Crestron RoomView
Crestron RoomView Connected is built into projectors enabling direct network connectivity for remote management of AV networks.
Crestron RoomView® Express software provides enterprise help desk management, remote monitoring and control of global AV networks without any special wiring, hardware or programming. Once connected to the network, classroom teachers and presenters can instantly control any installed RoomView Connected™ projector. With no programming required, AV and IT managers can globally monitor and control networked projectors throughout a school, campus, or corporate enterprise.
Adding a Crestron control processor enables control of all AV devices, lighting and environmental systems on the network from any Crestron touch screen, Web browser and Apple® and Android® mobile devices including iPad™ and iPhone®.
By leveraging the Ethernet port on RoomView Connected projectors and accessing RoomView, AV managers and support staff can remotely take control of classroom technology, troubleshoot and perform remote system diagnostics, track projector usage and lamp life, log network activity and much more. Remote capabilities allow efficient scheduling of projector power-off at preset times, routine maintenance, faster response times to support calls, alert notifications if projectors are disconnected, and broadcast messaging of emergency alerts to all projectors.
Crosstalk
Interference of an electrical signal by another electrical signal in close proximity caused by its electromagnetism.
CRT
Cathode Ray Tube.
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.
DICOM
A DICOM projector (Digital Imaging and Communications in Medicine) provides the medical profession with the ability to simulate 21 different levels of grayscale in the rendering of X-rays, CAT scans, MRIs and other medical imaging applications.
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.
DisplayPort
DisplayPort is a digital display interface developed by the VESA. The interface is primarily used to connect a video source to a display device such as a computer monitor, though it can also be used to transmit audio, USB, and other forms of data. Displayport can be used to transmit audio and video simultaneously. The DisplayPort signal is not directly compatible with DVI or HDMI but passive adapters can be used to adjust the signal levels and convert the connector style.
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. 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.
Document Camera
A document camera can be attached to any projector; however, there are projectors that integrate these features either as a camera on an arm that is attached to the projector or a document scanner that is built into the body of the projector.
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.
Dual Lamp
A Dual Lamp projector has two lamps where one lamp either serves as an automatic backup to the other lamp or is preprogrammed to switch at specific intervals. The benefit of this type of lamp system is it significantly reduces the probability of lamp failure during use.
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 Player Projector
A projector with an integrated DVD player.
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.
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.
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 Blending
When more then one projector is used side by side to project wider content into a seamless wide image, Edge Blending technology can be used. Edge blending can be done in the projector or with an external video processor. Edge blending works to remove the bright visible band that occurs when two images overlap. Edge blending will gradually fade out one of the images in the banded zone while the adjacent image is gradually faded up.
Edge Enhancement
A technique 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.
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.
Frame Interpolation
Frame interpolation, also called motion interpolation, is a video processing technique in which two sequential frames of video are analyzed for motion shifts that occur between Frame A and Frame B. Intermediate frames are then created and inserted between A and B to estimate incremental steps in the movement. The objective is to reduce motion blur and judder in order to achieve a cleaner and more stable video image.
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.
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 HD 3D
A projector that is Full HD 3D compatible can use any of the 3D formats enabled in the HDMI 1.4 3D specification: frame packing, top/bottom, or side-by-side. These projectors are compatible with the 1080p 3D signal from a Blu-ray player, set-top box, or other HDMI 1.4 device, but may not be compatible with 120Hz frame sequential 3D from a computer.
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.
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.
Geometry Correction
Geometry Correction (sometimes referred to as Image Warping) is the process of digitally distorting a projected image so that it precisely matches a specific projection surface or shape. Image geometry correction compensates for the distortion created by off-axis projector or screen placement or non-flat screen surface, by applying a pre-compensating inverse distortion to that image in the digital domain.
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.
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.
HD-SDI
Serial Digital Interface (SDI) is a standard for digital video transmission over coaxial cable. The most common data speed is 270 megabits per second (Mbps). However, speeds of up to 540 Mbps are theoretically possible. A related standard, known as high-definition serial digital interface (HD-SDI) provides a nominal data rate of 1.485 Gbit/s Standard 75-ohm cable is used.
HDBaseT
HDBaseT is an international standard for the transmission of ultra-high-definition video & audio, Ethernet, controls, USB and up to 100W of power over a single cable, for up to 100 meters. HDBaseT eliminates cable clutter without compromising performance and high quality. The connector is typically a RJ48 8 pin Ethernet jack.
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 compatible 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 Committee) HDTV standards and supports 8-channel digital audio. First product releases using HDMI occurred in 2003.
HDR
High Dynamic Range (HDR) yields higher overall contrast than Standard Dynamic Range (SDR). Deeper blacks and brighter highlights result in a longer tonal scale that can render detail in shadows and highlights that tends to get lost in SDR. HDR systems generally come with wider color gamuts for greater potential color accuracy.
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 Lens Shift
The purpose of Lens Shift is to eliminate keystoning and provide greater flexibility in the placement of the projector relative to the screen. Lens shift may be a manual adjustment or motorized.
Horizontal lens shift typically allows the projector to be placed anywhere between right and left edge of the projection screen and may also be used to geometrically align images when stacking projectors. Vertical lens shift is also available on some projectors.
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.
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.
IMAX Enhanced
IMAX Enhanced is a new licensing and certification home entertainment program established in 2018. To qualify and carry the IMAX Enhanced logo, the highest-end TVs, projectors, sound bars, and A/V receivers must meet stringent performance standards established by IMAX, DTS and Hollywood's leading colorists in order to create a consistent and higher bar for image and sound performance on premium devices.
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.
Input Lag
Input lag is the delay between your video source sending a frame to your projector and the projector actually displaying that frame. This is a very important aspect of gaming, where an input lag of 40ms or less is preferred.
Interactive Projector
Interactive projectors became popular in 2010 and come in many variations. This technology encompasses any solution that enables active participation by the user with the projected content, rather than just the passive viewing of content. Typically the presenter is allowed to interact with either the projected image, the projector, or in some cases another device, using either an electronic pen, a mechanical pen or even a finger. These Interactive Projectors essentially create an electronic whiteboard on any surface where the image is projected allowing the presenter to interact with the projected image using a stylus that may be electronic or mechanical. Some interactive projectors allow user generated information to be captured and replayed, printed, or copied with or without the original projected image.
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.
Interpixel Gap
The non-picture area between pixels in a fixed-pixel display. Commonly called screen door effect when noticeable. Also relates to fill rate, a measurement that describes this characteristic. For example, a D-ILA projection system has a fill rate of 93%, which indicates a smooth image and has a small interpixel gap.
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.
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. Motion judder in film is due to the fact that the 24 frame/second sampling rate is too slow to resolve camera panning motion. Judder is also 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.
Kelvin
Zero degrees of Kelvin, otherwise known as absolute zero, is equal to -273.15 degrees of Celsius, the temperature at which all molecular movement ceases. A temperature difference of 1 degree Kelvin is equivalent to a difference of 1 degree Celsius. The color temperature of large image devices is measured in Kelvin. The higher the temperature, the bluer the light.
Kensington Lock
A security device found on projectors and other electronic equipment that allows the equipment to be secured by key or combination to another object using a rubberized cable.
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.
Latency
The time between a device being requested to do something and the start of the device actually doing it. It’s a measurement usually used for LCDs where the shorter the latency the better. NSTC requires a latency of no more than 16ms in order to update the screen in time without leaving a ghost of the previous image.
LCD
Liquid Crystal Display. A display device for generating color images using a matrix of LCD pixel elements. Each pixel element consists of 3 sub-pixels and an RGB color filter of red (R), green (G), and blue (B). By controlling the voltage to each sub-pixel of an LCD, each cluster of RGB pixels can create a full spectrum of colored light. LCDs are used in flatscreen displays, cameras and notebook computers to name a few.
Nearly every projector made with LCD technology uses 3 separate LCDs, one each for red, green and blue. Light from the projector lamp is separated into RGB with a set of dichroic mirrors. The three light beams (RGB) are passed through separate LCDs and recombined to project a color image.
LCoS
Liquid Crystal on Silicon. Type of LCD panel that reflects light as opposed to blocking it. Usually offers a comparatively high fill rate creating a smooth image but generally has difficulty giving a high contrast ratio.
LED
Light Emitting Diode. A light generating technology that uses a semiconductor diode that emits monochromatic (single color) light when charged. They offer a very low power light source for projectors versus a gas filled lamp or a laser.
LED Lamp
A type of projector lamp that uses one or more LEDs as its light source. The benefit of LED lamps is their long life.
Lens Memory
The ability to define and recall specific zoom lens positions so the projector can automatically configure subject matter of a given aspect ratio to a particular screen. This requires a projector with a powered zoom lens. Lens memory is often used to automatically set a zoom lens to fill a 2.4:1 format screen when displaying a 2.4 format film, then reset the lens to allow 16:9 aspect ratio material to fit the vertical height of the screen. Lens memory is typically used as a substitute for an anamorphic lens.
Lens Shift
The purpose of "lens shift" is to eliminate keystone correction and provide greater flexibility in the placement of the projector relative to the screen or the alignment of stacked projectors. This is accomplished by allowing the optical lens to be physically shifted vertically and/or horizontally. These adjustments may be manual or motorized depending on the projector. See horizontal lens shift and vertical lens shift for typical adjustment ranges.
Letterbox
A method of preserving the originally aspect ratio of a production when presented on a projector with a different aspect ratio. This is accomplished by showing the full image and black where no image exists.
LFE
Low Frequency Effects. The .1 channel in 5.1, 6.1 or 7.1 sound. Used for effects and is limited to 120 Hz.
Light Valve Projector
A projector that uses an imaging system that either blocks or reflects light such as LCD, LCoS or DLP.
Line Doubler
Component device that duplicates scan lines to create a full frame from a field and then updates the screen completely every 60th of a second. Reduces flicker and the appearance of scan lines making an image look smoother.
Line-Level
A low-voltage pre-amplified signal usually between .3 and 5 volts.
Linearity
A display’s ability to show an image’s geometric characteristics accurately. Also called geometric linearity.
LNB
Low-Noise Block converter. The LNB sits at the end of a pole facing the dish of a satellite dish assembly. It converts the incoming signal to a lower set of frequencies to make them easier to send over a wire without distortion. The lower the rated degrees of an LNB, the cleaner the picture will be.
Long Throw Lens
A long throw lens allows greater distance between the projector and the screen while being able to maintain the image size and brightness of a shorter throw lens for any given projector. Depending on the room, a long throw lens may be required due to mounting constraints nearer the projected image.
Low Pass
A filter that only passes frequencies under a specified Hertz.
Lumen
A measurement unit of total illumination. Typically a 100-watt light bulb outputs 1700 lumens over a wide area. Projector light output is measured in ANSI lumens. A projector with a higher lumen number will produce a brighter image for a given image size. See ANSI Lumens
Luminance
The black and white part of a video signal. It is signified by the letter Y. Signals with a separated luminance and color signal avoid interference. This interference can result in dot crawl among other image artifacts.
Lux
A standard for measuring light equal to the amount of visible light per square meter incident on a surface. 1 lux = 1 lumen/square meter or 0.093 foot-candles.
M1-DA
A DVI connector that supports analog, digital video, a USB connection, and FireWire (IEEE1394). Used primarily with Infocus projectors.
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Maximum Distance
Sometimes used to refer to the distance from the screen that a projector can focus the image. Most of the time, it is the manufacturer's opinion of how far from a screen the projector can be to cast an image that is useable (bright enough) in a fully darkened room. Consult the Projection Calculator for guidance on proper placement of a projector for a given screen and content.
Maximum Image Size
The largest image a projector can reasonable throw in a darkened room. Consult the Projection Calculator for guidance on proper placement of a projector for a given screen and content.
Maximum Resolution
Maximum Resolution refers to the highest resolution that a given display device can support. If the Maximum Resolution exceeds the Native Resolution, , the image is usually scaled to match or approximate the Native Resolution of the projector. Some display devices allow pan and scan where rather than scaling the image, the display devices allows you to use the native resolution of the display to view portions of the higher resolution image. Scaling reduces the image resolution and produces some artifacts in the image that are more apparent when viewing text than graphics or video.
Memory Card
A feature on some projectors that allows photos, documents and/or presentation material to be projected using a memory card and thereby eliminating the need of a computer.
MHL (Mobile High-Definition Link)
Mobile High-Definition Link (MHL) is an industry standard for a mobile audio/video interface that lets you connect mobile devices such as smartphones and tablets to projectors and other HD video displays. MHL is a consortium made up of major companies in the consumer electronics industry, including SONY, Nokia, Samsung, Silicon Image, and Toshiba.
MHz
Megahertz. One million hertz or cycles per second.
Microdisplay
Sometimes referred to with the acronym 'MD' as in MD-RPTV. Refers to projection-based displays using a chip-based imager. Examples are DLP, LCD and LCoS/D-ILA.
Microlens Array
A feature of some LCD projectors where tiny lenses are aligned to individual pixels of an LCD panel in order to increase the light that passes through each pixel element. Also reduces screen-door effect.
Minimum Distance
The closest position that a projector can focus an image onto a screen.
MLA
MicroLens Array. See same.
MLP
Meridian Lossless Packing. A lossless compression format that is used on DVD-A giving a compression ratio of 1.85 to 1 without degrading quality.
Moiré Pattern
An image artifact which is an interference pattern caused by two patterns overlaying each other. Looks like cross-hatching, herringbone or other patterns.
Monitor Loopthrough
An output on the projector or large-screen monitor that allows you to connect additional monitors or projectors to display the same image. Also known as "RGB out" or "VGA out."
Mono
Single channel sound.
Mosquito Noise
An artifact of MPEG compression which looks like a mosquito buzzing around. Usually found around sharp edges and most easily seen on solid color areas. It is a time dependent video compression impairment in which the high frequency spatial detail in video images having crisp edges is aliased intermittently.
Motion Artifacts
Any artifact caused by camera panning or object movement within video. Judder and combing are motion artifacts.
MPAA
Motion Picture Association of America. Trade association of the U.S. film industry started in 1922. Advocates for film industry to public and government.
MPEG
Moving Picture Experts Group. A working group of ISO/IEC in charge of developing codecs and standards for moving pictures with synchronized audio.
MPEG-1
Older video compression format that doesn’t compress interlace video. Although the format is capable of other resolutions, the standard expected is a 352x240 pixel image running at 30 frames a second and encoded at a constant bit-rate (CBR) of 1.5Mbps. It only supports mono or stereo sound.
MPEG-2
The standard file format for DTV, DVDs and DBS, among others. Uses same techniques as MPEG-1 but adds support for interlace video and multichannel sound as well as offering higher bit rates.
MPEG-4
An audio/visual file format that is designed for multimedia applications. It allows for other types of media such as 3D objects as well as video and offers interactive capabilities. It is a more efficient compressor than MPEG-2 and can be up to 50% smaller in file size at a given quality.
MTS
Multi-channel Television Sound (MTS) provides the ability to receive multiple audio channels with a single video channel allowing the user to select the type of audio desired such as mono, stereo, or Secondary Audio Programs (SAP). See SAP.
Multi-Lamp
Some projectors use multiple lamps that can be controlled by the user to increase or decrease the brightness of the image. This lamp redundancy significantly minimizes the risk of total lamp failure during use.
Another type of multi-lamp system is a Dual Lamp. With a dual lamp projector one lamp can serve as a backup to the other lamp in the event of failure or the lamps can be programmed to switch at specific intervals.
Multiscan
A display device capable of operating at multiple scan rates, usually starting at 30KHz up.
Multizone
An audio system that can send any one of multiple sources to any one of different rooms.
NAB
National Association of Broadcasters. The U.S. trade association of over-air broadcasters started in 1923.
Native Aspect Ratio
Nearly every projector or display today will support multiple aspect ratios; however, each manufacturer must decide who their intended audience is and optimize the projector for that audience. This means each device has a native aspect ratio that is optimized for specific viewing material. Images shown in native aspect ratio will utilize the entire resolution of the display and achieve maximum brightness. Images shown in other than native aspect ratio will always have less resolution and less brightness than images shown in native aspect ratio.
Native Resolution
Native Resolution is the number of physical pixels in a display device. For example, an XGA display has a native resolution of 1024 physical pixels of resolution horizontally and 768 pixels vertically or 786,432 total pixels. See Maximum Resolution.
Negative Gain Screen
A screen with a gain rating of under 1 which actually reduces the amount of light reflected back from a projected image. Usually gray, they are used to increase apparent contrast by lowering the black level.
Noise
An unwanted random signal.
Non-Interlace
Also known as progressive scan. Describes how video frames are drawn which, in this case, is completely from top to bottom at every screen update. See Interlaced.
Notch Filter
An inexpensive filter used to separate the chroma signal from the luminance signal in composite video. A comb filter does the same task, only better, because it filters resonant frequencies as well.
NSH
New Super High pressure projector lamp is a short arc metal halide lamp.
NTSC
National Television Standards Committee. Established the first color TV standard in 1953 and is the North American standard for video and broadcasting. Also used in the Caribbean, South Korea, Japan and South America. A 30 fps signal with 525 lines of resolution of which 480 to 483 are viewable. Transmitted via a 6MHz channel.
OEM
Original Equipment Manufacturer. A company that gathers components from other manufacturers and sells under their own name. An OEM version of a product is supported by the seller, not the actual manufacturer.
Ohm
Measure of electrical resistance, inductance or reactance.
OHP
The common abbreviation for overhead projector. Used to project transparencies onto a screen or wall. Also used with transmissive LCD panels to project video or data.
OLED
Organic Light Emitting Diode. A self-illuminating, energy-efficient, direct-view imaging system. Uses an organic film sandwiched between 2 transparent electrodes.
Operate 24/7
Projectors that are identified as "Operate 24/7" means that the projector can operate continuously without a need to shutdown other than for maintenance.
Optical Digital Cable
Transfers digital signals as light pulses. Also called fibre-optic cable and is commonly used to send surround sound from a player to a receiver/decoder.
Optional Lenses
Typically the less expensive projectors come with a built-in lens that is designed to serve a specific type of setting or application. A projector that supports optional lenses can address a wide variety of installation needs. This gives a projector great flexibility at an incremental cost.
OSD
On Screen Display. Menu shown on display device screen allowing display adjustment without having dedicated physical controls such as knobs or buttons for each adjustable parameter.
Overhead Projector
A device consisting of a light source, a transmissive or reflective platform, and a focusable lens assembly. An OHP is designed to project images from tranparencies or LCD projection panels onto a screen.
Oversampling
Multiplies outgoing signal samples in order to more easily filter out aliased sounds but doesn’t create fidelity that isn’t there to begin with.
Overscan
Given as a percentage or pixel count, the amount that a particular display device crops the edges of an incoming video signal. This is done to ensure the image area contains only picture information.
PAL
Phase Alternating Line. Broadcast standard developed in Germany in 1963 and adopted in 1967. It’s used in many countries throughout Europe including the UK and transmits 576 viewable lines at 25 frames per second interlaced.
Pan-and-Scan
A method to fit source material of a different resolution or aspect ratio onto another. Sometimes used with computer input when the input resolution exceeds the resolution of the display device. Used extensively for broadcast and DVDs, it simply crops the sides of widescreen material and the transfer operator chooses the best part of the frame to show. Often an electronic camera pan is used to change the area being shown. This is used when characters are talking to each other but one is off screen due to cropping and they become the focus of the shot.
PC 3D Ready
A projector that is PC 3D Ready can accept a 120Hz frame-sequential 3D signal from a computer via either NVIDIA's 3D Vision system or one of several educational software suites. These projectors are not compatible with the HDMI 1.4 3D specification used on 3D Blu-ray players and set-top boxes. This type of projector is also refered to as 3D Ready.
PCM
Pulse Code Modulation. A technique for representing analog frequencies digitally, developed in 1937 by Alec Reeves for ITT France. The most common variant is ADPCM, Adaptive Differential Pulse Code Modulation, which compresses a signal dynamically. It does so by only storing the difference between the current and previous sample and varying the granularity of those differences.
Perceptual Coding
A data reduction method that uses the lack of sensitivity of human senses to certain characteristics. Visually, color undersampling (4:1:1) is an example where a person’s eyes are more sensitive to grayscale information than color, therefore less color information is needed for a given representation. Aurally, masking is a psychoacoustic phenomenon where a sound of less intensity but close in frequency cannot be discerned by a listener and that sound can be dropped from the data representation.
Persistence of Vision
The disposition of humans to amalgamate sequential still images into perceived motion. For most people, this occurs at around 16 fps.
Phase
The characteristic of when a wave is at its peak, trough, or zero point going up or down. Measured in degrees. Two sine waves of the same frequency that are 180 degrees out of phase will cancel each other out, yielding no signal.
Phosphor
A direct-view, flat-panel display that uses ionized gas to emit ultraviolet light that then excites phosphors. Plasma is a state of matter like solid, gas or liquid. Plasma screens are challenged by latency issues without a priming voltage, which causes manufacturers to leave a voltage running across a cell in order for it to change state quickly enough to update a picture. This tends to boost black levels as every pixel is partially on all the time. This is why plasma contrast ratios aren’t as high as CRT although still very good. Also, because plasma uses phosphors it is susceptible to possible burn-in. Plasma is subject to performance issues at higher altitudes of operation such as fan buzzing and increased power consumption.
Pico Projector
A marketing term to describe a small hand held projector that can fit in your pocket. A pico projector can be a stand-alone device that connects to a computer or other video device or a projection module that is integrated with a phone, portable computer, MP3 player or other small device.
Picture-in-picture
The ability of a projector (or any video display device) to display two independent video signals at once. One signal usually fills the main screen and the other is displayed in an inset window. Usually the audio from the image on the main screen is the default, and no audio is available on the inset picture.
PLUGE
Picture Line-up Generation Equipment. A test pattern used to set a display’s black level. Comes in many variations but is usually comprised of three black bars where the darkest should not be visible.
Poly-Si (silicon) LCD
One of several projector display technologies. Monochrome Poly-Si LCDs are typically placed in each of the three color (red, green, blue) light paths inside a projector to produce a color image from a common light source. Poly-Si technology is a bit faster than the Active Matrix TFT providing slightly smoother video.
Power Focus
A motor driven lens that adjusts focus using a button on the projector's control panel and/or a remote control.
Power Output
With audio amplifiers, the amount of power sent to drive the speakers. Peak output is quite often specified, which is somewhat misleading compared to the average amount of power an amplifier can continously produce (RMS rating).
Power Zoom
A zoom lens that is driven by a motor and controlled from the projector's control panel and/or remote control.
Pre-amp
A switching device used to select a line-level audio signal for amplification. Sometimes offers signal processing as well.
Progressive Scan
A display mode in which all the horizontal lines of an image are displayed at one time in a single frame, unlike an interlaced scan in which a frame consists of two separate fields with the first field consisting of odd horizontal lines and the second field even horizontal lines. Progressive scan is used by projectors, computer monitors, HDTV systems, and some digital camcorders. Progressive Scan requires a faster horizontal scan frequency than interlaced images of the same resolution
Projector
A projector is a device that integrates a light source, an optics system, electronics and display(s) for the purpose of projecting an image from a computer or video device onto a wall or screen for large image viewing. These devices attach to a computer or video device as you would connect a monitor or television.
PSIP
Program and System Information Protocol. ATSC standard A/65B for sending system and program guide information via DTV broadcasts or cable.
Psychoacoustics
Study of how humans hear. Used to find ways to discard sound information that is not heard and reduce data requirements for sound reproduction.
PVR
Personal Video Recorder. See DVR.
QAM
Quadrature Amplitude Modulation. A type of digital modulation technique used to carry signals in digital cable and cable modems which usually has a number before it denoting its bit density such as 64-QAM. Cable’s equivalent to 8VSB. A QAM tuner will allow you to see digital cable channels without a cable box but only those that are broadcast without restriction. A CableCARD® will add support for restricted channels.
QPSK
Quadrature Phase Shift Keying. A type of digital modulation technique used to carry DBS satellite signals and can be used in combination with QAM.
Quicktime
A computer multimedia file format used for video and other media types developed by Apple. Closely related to MPEG-4.
QXGA
QXGA is a display resolution of 2048 horizontal pixels by 1536 vertical pixels giving a total display resolution of 3,145,728 pixels. A QXGA display has 4 times the resolution of an XGA display.
Rainbow Effect
An image anomaly that can be seen by a small percentage of people when viewing a single chip DLPTM front or rear projection system. The anomaly appears as a color breakup at the edge of objects when the eye transitions rapidly between light and dark areas of the image. The problem is characteristic of sequential color systems with low refresh rates.
RCA Jacks
Unbalanced connection used extensively in consumer electronics to send a line-level signal. Also called phono.
Rear- Projection TV
All-in-one display consisting of a translucent screen with a rear projector system.
Red Push
Red push occurs when a color decoder accentuates the color of red as compared to blue and green. This is sometimes done intentionally to compensate for an overly blue color temperature.
Refresh Rate
The speed at which a display updates its picture given in Hz.
Resolution
A measure of the ability of a display or sound system to render detail.
Resonant Frequency
The frequency at which any physical object naturally oscillates. All objects have this property including rooms, which will favor certain frequencies over others and may 'color' sound.
Return Loss
Phenomenon of outgoing signals to reflect back on themselves on cables longer than ¼ of a wavelength. Measured in dB where lower is better.
Reverberation
All sound reflections within an enclosed space that continue to bounce around after the source has stopped. Also an audio effect, which mimics various room sizes.
Reverberation Time
Measurement of reflected sound to dissipate within a room by -60dB given in seconds. A home theater should be around .4 seconds.
RF
Radio Frequency.
RFI
Radio Frequency Interference.
RGB
Red, Green and Blue. A component signal representing each color separately. Sync signals can be sent on green or sent separately as a composite signal or dual H/V signals (Horizontal sync/Vertical sync). Very common signal for analog computer displays.
RGB out
An output on the projector that allows you to connect additional monitors or projectors to display the same image. Also known as monitor loop-through or VGA out.
RMS
Root Mean Square. Commonly used as a power measurement for higher-end audio amplifiers, it is an average output as opposed to peak. Usually placed as a suffix to a wattage rating.
RPTV
Rear-Projection TeleVision. All-in-one display consisting of a translucent screen with a rear projector.
RS-232
The RS-232 port on a projector is typically used to connect an external control device like a wall plate controller or integrated whole room control system to your projector for turning it on and off remotely or changing the source input. The port is usually a male 9-pin D-sub connector.
S-VHS
Super VHS. Improved resolution version of VHS that stores luma and chroma in separate signals.
S-Video
A video transmission standard that uses a 4 pin mini-DIN connector to send video information on two signal wires called luminance(brightness, Y) and chrominance(color, C). S-Video is also referred to as Y/C. Considered a higher quality video source than composite video.
S/PDIF
Sony/Philips Digital InterFace. A transport protocol related to AES/EBU for sending PCM digital audio signals between devices. Uses either 75-Ohm coaxial cable or fiber-optic cable.
SACD
Super Audio Compact Disc. Sony and Philips designed audio format competing with DVD-Audio with audiophile performance characteristics. Offers up to 6 channels using the Direct Stream Digital (DSD) format as opposed to CD’s PCM. Requires an SACD player.
Sampling Frequency
The speed at which data representations of an analog signal are duplicated. The higher the number, the better the quality. Another quality aspect is the granularity of the scale used for representation where 16 bits allows 65536 discrete levels and 24 bits allows about 17 million.
SAP
Secondary Audio Programs. SAP is a feature that allows a broadcast to contain additional audio information such as another language or perhaps weather information.
Saturation
Saturation is a measure of color intensity. In the absence of saturation the color hue is a shade of grey. A highly saturated hue has a vivid, intense color, while a less saturated hue appears more muted and grey.
Scan Rate
The line drawing speed of a display, usually given in kHz. A standard definition TV has a scan rate of 15.75 kHz which when you divide by 525 scan lines, gives a horizontal refresh rate of 30 fps or Hz.
Screen Gain
As it applies to projectors, gain is the measurement of a projection screen’s light reflectance with unity gain being one. A high gain screen will reflect more light along a narrower path than lower gain screen. Screen gains under one use a gray screen to absorb ambient light to help maintain contrast ratios.
Screen Trigger
A 12V connection from a projector to an electric screen which tells the screen to deploy when the projector is turned on and roll up when the projector is turned off.
Screendoor Effect
An image distortion caused by digital imagers with a low fill rate. Looks like the picture is seen through a screen door with thin vertical and horizontal black lines and is commonly noticeable on lower resolution LCD displays. An LCD display fitted with a microlens array helps reduce this problem.
SDI
Serial Digital Interface (SDI) is a standard for digital video transmission over coaxial cable. The most common data speed is 270 megabits per second (Mbps). However, speeds of up to 540 Mbps are theoretically possible. A related standard, known as high-definition serial digital interface (HD-SDI) provides a nominal data rate of 1.485 Gbit/s Standard 75-ohm cable is used.
SDTV
Standard Definition TeleVision. A class of digital television (DTV) that refers to the 480i format. 480i is an interlaced video format that produces a full frame of 480 lines of video in two successive fields. The first field includes the odd lines and the second field includes the even lines. Sometimes used to refer to regular television.
SECAM
Sequential Couleur avec Mémoire. A television standard closely related to PAL but with a different method of sending color information. Runs at 625 horizontal lines of resolution updating 25 frames a second. Used in France and Russia as well as other countries. Many eastern European countries are starting to phase out SECAM in favor of PAL.
Shielded
A feature of speakers and cables where a metal layer is added to contain and protect a signal from creating or receiving electromagnetic interference.
Short Throw Lens
A lens designed to project a large image from a short distance.
Short Throw Projector
A projector with a short throw lens that can typically project at least a 100 inch image from less than 8 feet away.
Short Throw Wall Mount Projector
A projector that mounts on a wall adjacent to the projection screen. The throw distance is generally just a few inches and allows people to move freely through the room without concern of intercepting the light path.
SHP
Super High Pressure. A type of projector lamp.
Signal-to-Noise Ratio
The ratio of noise to signal measured in dB. The higher the number, the better.
Skew
A signal distortion where one part of a signal arrives at a different time than another and causes color fringes to the sides of an object.
SMPTE
Society of Motion Picture and Television Engineers. A U.S. based Trade organization that develops standards and practices for the movie and television industries. Started in 1916.
Soundstage
A particular system’s ability to reproduce sound so that it seems to be coming from a particular location. Same as imaging.
Spade Lug Connector
Speaker wire U-shaped connection type which attaches to an amplifier or speaker via screw or 5-way binding post. Also used in older TV antennas to attach to a television using screws.
SPDIF
Sony/Philips Digital Interface. SPDIF is a unidirectional digital audio interface for connecting audio equipment.
SPL
Sound Pressure Level. Commonly used to describe a speaker’s efficiency at one watt at 1 meter distance. The actual amount of sound output using dB. There are various weightings used such as A, B or C which reflect the human ear’s sensitivity at different sound levels. A-weighting is used for levels up to 55dB SPL, B-weighting from 55dB SPL to 85dB SPL and C-weighting for 85dB SPL up. A quiet office is 40dB SPL and a rock concert is 110dB SPL.
Spring Connection
Also known as a guillotine connection. Speaker cable connection where a spring-loaded piece of metal is pressed against bare wire.
sRGB
sRGB stands for standard Red, Green, and Blue, and is a standard for rendering color evenly across a variety of platforms.
STB
Set-Top Box. A device used to receive and decode a DTV signal and deliver it to a television monitor. Other types of STBs are used to convert and decode video and audio for analog cable, digital cable and satellite services.
Streaking
A visual artifact of trailing colors behind an on-screen object or across a screen.
Subpixel
On a flat-panel display, one of the primary color picture elements of which 3 make up a full color capable pixel.
SVGA
SVGA is a display resolution measuring 800 pixels horizontally by 600 pixels verically giving a total display resolution of 480,000 individual pixels. SVGA has a 4:3 aspect ratio.
SXGA
SXGA is a display resolution measuring 1280 pixels horizontally by 1024 pixels vertically giving a total display resolution of 1,310,720 individual pixels. SXGA has a 5:4 aspect ratio.
SXRD
SXRD (Silicon X-tal Reflective Display) is Sony's version of LCD technology and is used in both front and rear-projection. It competes directly with JVC's D-ILA, Texas Instruments' DLP, as well as, traditional LCD technology. Sony's SXRD technology can be found in high definition home theater projectors and next generation 4K digital theater projection.
Tab-Tensioned
A projection screen type that has connections on all sides of the screen material, which pull it taut in order to have a flat screen surface.
TCO Certified Projectors
A TCO-labelled projector is certified to reproduce excellent images to a maximum projected image size, the TCO Image Size. In addition, the projector complies with stringent environmental requirements such as low energy consumption and minimal levels of environmentally hazardous substances. There is also an eco mode requirement so the projector can be set to lower luminosities, thus reducing noise, energy consumption and increasing the life of the bulb. The label also requires manufacturers to prove they are working proactively on environmental improvements to the production process and social responsibility issues. For more information go to TCO Development.
TFT
Thin Film Transistor. A type of LCD display where each pixel is controlled by one to four transistors. TFT screens are sometimes called active matrix LCDs.
THD
Total Harmonic Distortion. Expressed as a percentage, it is the measurement of distortion caused by an electronic component related to the harmonics it generates relative to a fundamental frequency.
Throw Distance
Throw distance is the measurement from the projector's lens to the screen. A projector with a zoom lens will have a range of throw distances for any given image size, while a projector without a zoom lens will only be able to project one image size at a given distance from the screen. In Projector Central's articles, throw distance is normally quoted for a 100" diagonal screen.
Throw Ratio
For any given projector, the width of the image (W) relative to the throw distance (D) is know as the throw ratio D/W. So for example, one of the most common projector throw ratio is 2.0. This means that for each foot of image width, the projector needs to be 2 feet away or D/W = 2/1 = 2.0.
THX
Tom Holman's eXperiment. A certification for audio equipment and installation done to a standard set by THX Ltd., a company owned by George Lucas. Usually geared towards audio playback for video and cinema.
THX Certified
THX video certification signifies that a product has been designed and tested to meet the rigorous performance standards defined by THX.
THX Select
THX certification for speakers, receivers and DVD players designed for small to medium sized home theaters and non-dedicated rooms of around 2000 cubic feet and performing to a specified standard.
THX Select 2
THX certification specifically for receivers to a specified standard.
THX Ultra
Certification program for speakers, receivers, amplifiers and interconnects that are not room size dependent and performing to a specified standard.
THX Ultra 2
THX certification for speakers, receivers, controllers, DVD players for dedicated home theaters of about 3000 cubic feet which perform to a specified standard.
Tint
Television control that varies the color bias of an incoming video signal. Control needed due to color variations in the NTSC signal caused by atmospheric conditions. Does not exist on PAL and SECAM televisions and adjustment should be unnecessary with directly linked video sources.
TMDS
Transition-Minimized Differential Signalling. A serial digital transfer protocol for sending information to a flat panel display. Also known as PanelLink. Used in DVI, HDMI, DFP and VESA Plug and Display (P&D) as the standard used to send digital pictures. TMDS is just one of the signals sent via DVI or Plug and Display.
Toslink
Toshiba designed fiber-optic cable connection that quite often uses the SPDIF transfer protocol. There are several variations. Transfers data using light instead of electricity.
Trailing
Replicated versions of an object that slowly fade as the object moves across the screen.
Transducer
A device that takes one kind of energy and changes it into another. Seating vibrators that take their signals from an LFE channel (.1) are called transducers.
TV lines
The analog measurement of image fidelity, it is the number of resolvable vertical lines divided by the aspect ratio. A VHS tape is typically rated at 240 lines where the live feed of a broadcast camera can be as high as 800 lines. It is not the same as pixel resolution.
Tweeter
A small speaker designed for high frequency reproduction.
UHB
Ultra High Brightness. A projector lamp type.
UHF
Ultra High Frequency. The 300MHz to 3GHz band of radio frequencies used for broadcast television among other things including Wi-Fi.
UHP
Ultra High Pressure. An acronym attributed to projector lamps with an internal pressure of over 3000 lbs per square inch. Usually a mercury arc lamp. Also stands for Ultra High Performance.
Unbalanced
A type of wiring using ground as a shielding method. More susceptible to interference than balanced wiring.
Uniformity
A measurement of the evenness of the brightness of white or a particular color across a display indicated as a percentage. A measurement of 80% means the brightness of an image is 20% less at its dimmest point compared to its brightest.
Unity Gain
A projection screen with a gain rating of one that reflects light with a wide viewing angle back to the viewer. See Gain.
Upconvert
To convert a lower resolution signal to a higher resolution. For example, 480i to 720p.
UXGA
UXGA is a display resolution measuring 1600 pixels horizontally and 1200 pixels vertically giving a total display resolution of 1,920,000 individual pixels. UXGA has an aspect ratio of 4:3.
V-Chip
V-chip technology blocks selected content and derives its name from the violence chip. Intended for parental control on the types of television children can watch. The chip reads transmitted ratings from television programs and blacks them out at the level set by the television owner. V-Chip is required on all televisions manufacturer for the U.S. market that are greater than 13 inches.
VBR
Variable Bit Rate. Refers to a variable data rate for encoding MPEG where picture quality is maintained but data rates change in accordance to the requirements of a video passage. Large amounts of movement and detail require higher data rates. VBR tends to create more space efficient MPEG files where picture quality is maintained but data rates change.
VCR
Video Cassette Recorder.
VCR Plus
A VCR feature where a user inputs a code, usually published beside a TV listing, into the VCR which tells it how long a program is, what channel it’s on and what time it starts in order to record it.
Vertical Banding
An image artifact that can appear on LCD projectors due to variations in manufacturing. Usually occurs in picture mid-grays.
Vertical Blanking Interval
Period of time that the electron beam of a CRT is turned of to reposition itself from the bottom right of the screen to the top left after painting a field or frame.
Vertical Lens Shift
The purpose of Lens Shift is to eliminate keystoning and provide greater flexibility in the placement of the projector relative to the screen. Lens shift may be a manual adjustment or motorized depending on the projector.
Vertical lens shift will typically allow the projector to be placed anywhere between 1.5 screen heights above or below the center of the projection screen and may also be used to geometrically align images when stacking projectors. Horizontal lens shift is also available on some projectors.
VGA
VGA is a display resolution measuring 640 horizontal pixels and 480 vertical pixels giving a total display resolution of 307,200 individual pixels. VGA has a 4:3 aspect ratio.
VGA out
A 15-pin D-sub output on the projector that allows you to connect additional monitors or projectors to display the same image. Also known as monitor loop-through or RGB out.
VHS
Vertical Helical Scan. Also known as Video Home System and is the most common consumer videotape format. It is a ½” magnetic tape format introduced in 1976 by JVC. Offers about 240 vertical lines of resolution.
Video Mirroring
An output connector on the projector that allows a monitor or another projector to share the same video source.
Volt
A measurement of electrical pressure.
Watt
A unit of power. Volts multiplied by amperage equals watts.
White Level
The signal level that corresponds to the maximum picture brightness. The white level is set by the contrast control.
Widescreen
Any aspect ratio that is wider than 4:3. Widescreen televisions are 16 units wide and 9 units tall. Common widescreen film aspect ratios are 1.66:1, 1.85:1 and 2:35:1.
WMA
Windows Media Audio. Similar to MP3 but considered a more efficient compressor allowing for smaller file sizes for a given quality.
WSXGA
WSXGA defines a class of SXGA displays with a width resolution sufficient to create an aspect ratio of 16:9. A WSXGA display has 1920 to 1600 pixels horizontally and 1080 to 900 pixels vertically.
WXGA
WXGA defines a class of XGA displays with a width resolution sufficient to create an aspect ratio of 16:9. A WXGA display has 1366 to 1280 pixels horizontally and 768 to 720 pixels vertically.
XGA
XGA is a display resolution measuring 1024 pixels horizontally and 768 pixels vertically giving a total display resolution of 786,432 individual pixels. XGA has a 4:3 aspect ratio.
XLR
Balanced connection for audio components and used professionally.
XviD
A free and open source MPEG-4 video codec that was created by a group of volunteer programmers trying to overcome the closed source and platform limitations of DivX (XviD spelled backwards).
Y/C
Denotes a separated luminance/chrominance signal. Also called S-video. Offers higher resolutions and no cross interference between color and black and white (luminance) signals which shows itself as dot crawl.
Y/Cb/Cr
Digital component video. Y stands for the luma signal itself and Cb is the blue signal subtracted from luma and finally, Cr equals the red signal subtracted from the luma signal.
Y/Pb/Pr
Analog component video. Y stands for the luma signal itself and Pb is the blue signal subtracted from luma and finally, Pr equals the red signal subtracted from the luma signal.
Zipcord Cable
A flat cable looking like two cables glued together commonly used for audio applications.
Zoom Lens
A lens with a variable focal length providing the ability to adjust the size of a projected image without moving the projector or provide a range of projector placements that can produce the same size image. See Zoom Ratio.
Zoom Ratio
Zoom ratio is the ratio between the smallest and largest image a lens can projector from a fixed distance. For example, a 1.4:1 zoom lens ratio means that a 10 foot image without zoom would be a 14 foot image with full zoom. Conversely, a 10 foot diagonal image at 15 feet with no zoom would still be a 10 image at 21 feet at maximum zoom (15 x 1.4 = 21 feet). A zoom lens is "not as bright" as a fixed lens, and the higher the ratio, the less light output.
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