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.
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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.
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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.
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Method for transferring 24 frame-per-second film to PAL/SECAM video running at 25 frames per second.
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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:
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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"Amorphous Silicon"
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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.
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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.
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Audio Engineering Society/European Broadcasting Union. Three pin XLR type connector used to send digital audio.
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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.
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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.
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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.
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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.
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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.
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A projector that supports anamorphic projection using an optional anamorphic lens.
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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.
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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.
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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.
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A device that controls amount of light admitted.
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Compensation for the loss in sharpness of detail because of the finite dimensions of the image elements or the dot-pitch of the monitor.
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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.
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Flaws and aberrations in a video image that derive from technical limitations in the capture, encoding/decoding, transmission, and display of a video signal.
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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.
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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'.
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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.
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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.
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To reduce. Turning the volume down on your television set is attenuating it.
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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.
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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.
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The direction to point a satellite dish when coupled with altitude. Due north has an azimuth of 0 degrees and due east, 90 degrees and so on.
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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.
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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.
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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.
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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.
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Sony’s competing home recording standard to VHS in the 1970s. It produced etter quality than VHS, but at a higher price.
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The frame or face of a device, such as, a projector grill, or CRT or LCD display frame.
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Type of amplifier or speaker connection.
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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.
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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.
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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.
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Video distortion where color “bleeds” from an object onto other parts of the image which are not supposed to be that color.
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Video distortion where an overly bright screen object causes phosphors near it to excite therefore enlarging the object and softening its edges.
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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.
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Bayonet Nut Connector or British Naval Connector. A high quality, locking cable plug which is used extensively in professional video.
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Video distortion where lines which should be straight are curved. See barrel distortion and pincushioning.
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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.
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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.
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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
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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.
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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.
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To adjust with reference to a standard.
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Analog display device that generates an image on a layer of phosphors that are driven by an electron gun.
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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.
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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.
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Charged Coupled Device. Electronic sensors used in video cameras that convert light energy into electrical.
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Compact Disc - Recordable. See CD.
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Compact Disc – Re-Writable. See CD.
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Consumer Electronics Association. An industry association of some 2000 electronics manufacturers. Produces the Consumer Electronics Show or CES.
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Custom Electronic Design and Installation Association. International industry association for home electronics installation and design related businesses. It also certifies members with professional designations.
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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.
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A separate signal or signal path.
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(C) The color part of a video signal.
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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.
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The color quality of light that is defined by the wavelength (hue) and saturation. Chromaticity defines all the qualities of color except its brightness.
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(C) Color portion of a video signal.
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State where color signal lags behind the brightness signal, which shows as color smearing or bleeding at the edge of objects.
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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.
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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.
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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.
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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.
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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.
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A device for measuring the color accuracy of a display device relative to the standard of D65 or 6500 degrees Kelvin.
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Calibration pattern used to adjust the brightness, saturation and hue of video displays.
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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.
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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.
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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.
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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.
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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).
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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.
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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.
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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.
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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.
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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.
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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.
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Contrast increases as the white point increases. Increasing the white point creates a greater difference between white and black.
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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.
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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.
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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.
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Interference of an electrical signal by another electrical signal in close proximity caused by its electromagnetism.
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Cathode Ray Tube.
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Direct Drive Image Light Amplifier. Proprietary JVC version of LCoS light valve technology.
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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.
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Digital to Analog Converter. Electronic component that converts a digital signal to an analog.
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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.
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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.
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Directional Correlation Deinterlacing (DCDi)was developed by Faroudja and is a video algorithm designed to eliminate jagged edges that are generated by interlaced video.
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Electric coil used to deflect the electron beams in a CRT display.
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Method to get rid of magnetic fields that build up in CRT monitors and distort the video signal causing discoloration.
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Electronic component that converts an interlace video signal to progressive scan.
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Act of converting an interlace video signal to progressive scan.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Display device where the imager is viewed directly as opposed to a projection surface.
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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.
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A usually undesirable variation from an intended output caused by the characteristics of a particular device.
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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.
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Method of displaying intermediate colors that don’t exist in a limited palette by using a pattern of small dots out of that palette.
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Video format based on the MPEG 4 standard. Commonly used for downloadable video files.
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DLP (Digital Light Processing) is a commercial name for a display technology from Texas Instruments (TI). The technology inside is often referred to as DMD (Digital Micro-Mirrors). It consists of an array of mirrors where each mirror represents a pixel element. For example, a high-definition DLP projector or rear projector with 1920 x 1080 pixel resolution would have over 2 million tiny mirrors. Each mirror is attached to an electronically driven hinge that controls the amount of colored light that is reflected from the mirror into the projection lens and onto a screen. Projection systems using DLP technology use 1 to 3 DMD devices.
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Digital Micromirror Device. Name of the actual imaging chip used in a Texas Instruments DLP projection systems.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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The distance between side-by-side phosphor color groups (RGB) on a direct view display that uses phosphors. The smaller the better.
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To convert a higher resolution signal to a lower resolution. For example, 720p to 480p.
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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.
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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.
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Digital Satellite System and now called DBS. A system for sending and receiving digital satellite broadcast signals using small receiver dishes.
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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.
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Digital Transmission Licensing Administrator. Controls the licensing of the DTCP copy-protection technology.
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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.
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Digital Theater Systems. A version of DTS that plays back a 96kHz sampling rate, 24-bit resolution recording at full fidelity.
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Digital Theater Systems Extended Surround. Backward compatible system to DTS with a center rear channel added.
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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.
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Digital Television. A system that uses digital signals instead of analog including the ATSC standards, DBS and digital cable.
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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.
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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.
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A projector with an integrated DVD player.
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Digital Versatile Disc + Recordable. A write-once recordable DVD format with 4.7GB capacity supported by the DVD+RW Alliance. More robust that DVD-R.
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Digital Versatile Disc + Read Write. A rewriteable DVD format with 4.7GB capacity supported by the DVD+RW Alliance. Can be rewritten up to 1000 times.
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Digital Versatile Disc-Audio. Allows for very high quality audio with up to 6 channels. Sample rates can be up to 192KHz at 24 bits of resolution. It allows for video as well as asynchronous slide shows of up to 99 still pictures per track. MLP (Meridian Lossless Packing) is supported as a lossless compression alternative to PCM.
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Digital Versatile Disc - Recordable. A recordable write-once DVD format with 4.7GB capacity supported by the DVD Forum. Not as robust as DVD+R.
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Digital Versatile Disc Random Access Memory. More robust as a rewritable format for computers than DVD±RW, it is housed in a cartridge and is incompatible with DVD-ROM drives and video players. Can be rewritten up to 100,000 times.
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Digital Versatile Disc - Read Write. A rewriteable DVD format with 4.7GB capacity supported by the DVD Forum. Can be rewritten up to 1000 times.
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Digital Visual Interface. DVI is a standard that defines the digital interface between digital devices such as projectors, flatscreens and personal computers. For devices that support DVI, a digital-to-digital connection can be made that eliminates the conversion to analog and thereby delivers an unblemished image.

It can also carry an analog signal and comes as DVI-I (integrated - analog and digital), DVI-D (digital only) and DVI-A (analog only). Dual link DVI connections add additional resolution capabilities. Digital cable lengths should not exceed 15 feet. Specifications on DVI are available at www.ddwg.org. Click for more details on DVI.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Electro-Magnetic Interference.
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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.
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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.
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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.
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Sends signals as light pulses instead of electrical energy. Made of glass or plastic, these cables are not susceptible to electromagnetic interference.
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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.
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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.
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High speed serial bus with a speed up to 400Mbps. See IEEE 1394.
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Any device that has a 'native' pixel resolution. CRTs are the only non-fixed-pixel displays where resolution is determined by bandwidth.
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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.
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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.
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A remote control that broadcasts its instructions with an FM transmitter, normally required in large rooms and no line of site requirement.
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The distance from the surface of a lens to its focal point.
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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.
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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.
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Frames Per Second.
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A frame is one complete video image. When all lines of the video image are delivered sequentially, it is called progressive video. When the odd lines and even lines are delivered as separate fields, it is called interlace video.
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Measures the frequencies a component is capable of reproducing and how well it does it. Usually stated as a set of frequencies with a variance measured in decibels (dB). The ideal is to have no variance or flat response, along with a wide range of frequencies.
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A system where the projector sits in front of the screen with the image getting reflected back to the audience.
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Contrast is the ratio between white and black. The larger the contrast ratio the greater the ability of a projector or flat panel to show subtle color details and tolerate extraneous room light. There are two methods used: 1) Full On/Off contrast measures the ratio of the light output of an all white image (full on) and the light output of an all black (full off) image. 2) ANSI contrast is measured with a pattern of 16 alternating black and white rectangles. The average light output from the white rectangles is divided by the average light output of the black rectangles to determine the ANSI contrast ratio. When comparing contrast ratio, make sure you are comparing the same type of contrast. Full On/Off contrast will always be a larger number than ANSI contrast for a given product.
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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.
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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.
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Wire thickness measure. The lower the gauge, the larger the wire.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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HDMI (High Definition Multimedia Interface) is an uncompressed, all-digital audio/video interface that supports audio/video sources such as a set-top box, DVD player, A/V receiver, and video monitors such as a digital projector or digital television (DTV). HDMI is backward compatiable with DVI 1.0 specification and supports HDCP.

HDMI supports standard, enhanced, or high-definition video, plus multi-channel digital audio, and interactive controls on a single cable. It transmits all ATSC (Advanced Television Systems Committe) HDTV standards and supports 8-channel digital audio. First product releases using HDMI occurred in 2003.
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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.
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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.
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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.
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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.
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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.
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Amount of pixels across an image, from left to right. A 1920 x 1080 HDTV has a horizontal resolution of 1920 pixels.
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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.
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High Temperature Poly-Silicon. An active matrix transmissive LCD technology used in 3LCD projectors.
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Hue or tint is the parameter of color that allows us to distinguish between colors.
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Hertz. Also called cycles per second and in video displays is the rate at which an image is refreshed.
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Detection of widescreen signalling (WSS) from a broadcaster. Allows broadcaster to configure television to proper aspect ratio.
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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.
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Institute of Electrical and Electronics Engineers. An international, non-profit, technical organization based in the U.S. that develops standards.
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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.
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High speed serial bus with a speed up to 400Mbps. See IEEE 1394.
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In audio, a particular system’s ability to reproduce sound so that it seems to be coming from a particular location.
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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.
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An infra-red (IR) remote control transmits in the spectrum of infra-red light, such as a television remote. Unlike RF remotes, IR remotes must point at the receiver (line of sight) or reflect the IR from the screen to the receiver. Typical range is limited to 30 feet including the distance to and from reflected surfaces.

For example, if you are controlling a projector and you point the remote at the screen which is 12 feet from you and the projector is 10 feet from the screen, then the total distance is 22 feet. Unlike RF remotes, IR remotes must have a clear path or a clear reflected path to the IR receiver to operate.

Most projectors have an IR sensor in both the front and rear of the projector, whereas, flatpanels generally have a single IR sensor in the front of the unit. When working at or near the maximum distance, pointing right at the receiver will give better results.
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Interactive projectors became popular in 2010 and come in many variations. As the name implies, the presenter is allowed to interact with either the projected image and/or the projector or, in some cases, another device using either an electronic pen or a mechanical pen or even a finger.

These Interactive Projectors essentially create an electronic whiteboard on any surface where the image is projected. As the presenter "writes" on the projected surface the motion of the electronic or mechanical pen is captured and overlaid on the video image.

This ability to capture motion of the pen or object can also be used to control a device such as a computer slide show. On some system the annotation and/or control can be captured and replayed, printed, copied or distributed. There are even homemade solutions. For example, using a Nintendo Wiimote and infrared LED light pens.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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A temperature measurement scale where 0° Kelvin (0°K) is equal to absolute zero, the temperature at which all molecular movement ceases. One degree of Kelvin is equal to 1 degree of Celsius. The color temperature of large image devices is measured in Kelvin. The higher the temperature, the bluer the light.
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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.
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Keystoning occurs when the projector is not perpendicular to the screen, thereby creating an image that is not rectangular.
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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.
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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.
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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.
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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.
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Light Emitting Diode. A light generating technology that uses a semiconductor diode that emits monochromatic (single color) light when charged. LEDs are used in remote controls that are used to control electronic devices such as large displays. They are also used in pocket projectors as a light source, large outdoor electonic displays, and as indicators on electoronic devices such as power supplies and cameras.
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A type of projector lamp that uses one or more LEDs as its light source. The benefit of LED lamps is their long life.
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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.
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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.
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Low Frequency Effects. The .1 channel in 5.1, 6.1 or 7.1 sound. Used for effects and is limited to 120 Hz.
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A projector that uses an imaging system that either blocks or reflects light such as LCD, LCoS or DLP.
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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.
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A low-voltage pre-amplified signal usually between .3 and 5 volts.
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A display’s ability to show an image’s geometric characteristics accurately. Also called geometric linearity.
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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.
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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.
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A filter that only passes frequencies under a specified Hertz.
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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
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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.
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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.
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M1-DAA DVI connector that supports analog, digital video, a USB connection, and FireWire (IEEE1394). Used primarily with Infocus projectors.M1-DA (EVC or P&D) is 3 rows or 10 pins and looks a lot like the DVI-I except for 6 more pins. The maximum video resolution supported is 1280x1024.
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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.
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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.
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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.
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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.
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Megahertz. One million hertz or cycles per second.
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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.
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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.
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The closest position that a projector can focus an image onto a screen.
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MicroLens Array. See same.
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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.
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An image artifact which is an interference pattern caused by two patterns overlaying each other. Looks like cross-hatching, herringbone or other patterns.
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Single channel sound.
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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.
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Any artifact caused by camera panning or object movement within video. Judder and combing are motion artifacts.
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Motion Picture Association of America. Trade association of the U.S. film industry started in 1922. Advocates for film industry to public and government.
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Moving Picture Experts Group. A working group of ISO/IEC in charge of developing codecs and standards for moving pictures with synchronized audio.
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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.
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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.
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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.
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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.
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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.
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A display device capable of operating at multiple scan rates, usually starting at 30KHz up.
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An audio system that can send any one of multiple sources to any one of different rooms.
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National Association of Broadcasters. The U.S. trade association of over-air broadcasters started in 1923.
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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.
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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.
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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.
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An unwanted random signal.
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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.
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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.
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New Super High pressure projector lamp is a short arc metal halide lamp.
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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.
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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.
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Measure of electrical resistance, inductance or reactance.
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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.
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Organic Light Emitting Diode. A self-illuminating, energy-efficient, direct-view imaging system. Uses an organic film sandwiched between 2 transparent electrodes.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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The disposition of humans to amalgamate sequential still images into perceived motion. For most people, this occurs at around 16 fps.
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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.
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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.
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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.
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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.
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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.
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A motor driven lens that adjusts focus using a button on the projector's control panel and/or a remote control.
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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).
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A zoom lens that is driven by a motor and controlled from the projector's control panel and/or remote control.
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A switching device used to select a line-level audio signal for amplification. Sometimes offers signal processing as well.
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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
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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.
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Program and System Information Protocol. ATSC standard A/65B for sending system and program guide information via DTV broadcasts or cable.
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Study of how humans hear. Used to find ways to discard sound information that is not heard and reduce data requirements for sound reproduction.
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Personal Video Recorder. See DVR.
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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.
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Quadrature Phase Shift Keying. A type of digital modulation technique used to carry DBS satellite signals and can be used in combination with QAM.
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A computer multimedia file format used for video and other media types developed by Apple. Closely related to MPEG-4.
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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.
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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.
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Unbalanced connection used extensively in consumer electronics to send a line-level signal. Also called phono.
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All-in-one display consisting of a translucent screen with a rear projector system.
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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.
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The speed at which a display updates its picture given in Hz.
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A measure of the ability of a display or sound system to render detail.
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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.
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Phenomenon of outgoing signals to reflect back on themselves on cables longer than ¼ of a wavelength. Measured in dB where lower is better.
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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.
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Measurement of reflected sound to dissipate within a room by -60dB given in seconds. A home theater should be around .4 seconds.
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Radio Frequency.
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Radio Frequency Interference.
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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.
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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.
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Rear-Projection TeleVision. All-in-one display consisting of a translucent screen with a rear projector.
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Super VHS. Improved resolution version of VHS that stores luma and chroma in separate signals.
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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.
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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.
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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.
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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.
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Secondary Audio Programs. SAP is a feature that allows a broadcast to contain additional audio information such as another language or perhaps weather information.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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A feature of speakers and cables where a metal layer is added to contain and protect a signal from creating or receiving electromagnetic interference.
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A lens designed to project a large image from a short distance.
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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.
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Super High Pressure. A type of projector lamp.
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The ratio of noise to signal measured in dB. The higher the number, the better.
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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.
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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.
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A particular system’s ability to reproduce sound so that it seems to be coming from a particular location. Same as imaging.
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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.
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Sony/Philips Digital Interface. SPDIF is a unidirectional digital audio interface for connecting audio equipment.
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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.
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Also known as a guillotine connection. Speaker cable connection where a spring-loaded piece of metal is pressed against bare wire.
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sRGB stands for standard Red, Green, and Blue, and is a standard for rendering color evenly across a variety of platforms.
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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.
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A visual artifact of trailing colors behind an on-screen object or across a screen.
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On a flat-panel display, one of the primary color picture elements of which 3 make up a full color capable pixel.
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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.
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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.

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.
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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.
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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.
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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.
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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.
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THX video certification signifies that a product has been designed and tested to meet the rigorous performance standards defined by THX.
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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.
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THX certification specifically for receivers to a specified standard.
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Certification program for speakers, receivers, amplifiers and interconnects that are not room size dependent and performing to a specified standard.
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THX certification for speakers, receivers, controllers, DVD players for dedicated home theaters of about 3000 cubic feet which perform to a specified standard.
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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.
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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.
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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.
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Replicated versions of an object that slowly fade as the object moves across the screen.
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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.
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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.
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A small speaker designed for high frequency reproduction.
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Ultra High Brightness. A projector lamp type.
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Ultra High Frequency. The 300MHz to 3GHz band of radio frequencies used for broadcast television among other things including Wi-Fi.
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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.
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A type of wiring using ground as a shielding method. More susceptible to interference than balanced wiring.
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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.
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A projection screen with a gain rating of one that reflects light with a wide viewing angle back to the viewer. See Gain.
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A remote control capable of running multiple components of multiple brands.
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To convert a lower resolution signal to a higher resolution. For example, 480i to 720p.
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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.
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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.
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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.
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Video Cassette Recorder.
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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.
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An image artifact that can appear on LCD projectors due to variations in manufacturing. Usually occurs in picture mid-grays
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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.
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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.
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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.
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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.
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An output connector on the projector that allows a monitor or another projector to share the same video source.
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A measurement of electrical pressure.
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A unit of power. Volts multiplied by amperage equals watts.
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The signal level that corresponds to the maximum picture brightness. The white level is set by the contrast control.
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Wi-Fi is Wireless Fidelity, and is a type of wireless network used to connect digital devices without the need for cables. It is mostly used for wireless broadband access and inexpensive consumer wireless antennas are available at electronics stores. There are four specifications currently in the family: 802.11, 802.11a, 802.11b, and 802.11g.
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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.
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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.
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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.
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Windows Media Audio. Similar to MP3 but considered a more efficient compressor allowing for smaller file sizes for a given quality.
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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.
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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.
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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.
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Balanced connection for audio components and used professionally.
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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).
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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.
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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.
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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.
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A flat cable looking like two cables glued together commonly used for audio applications.
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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.
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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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