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What is ...? The Dictionary I hope that some of the definitions below will help. A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
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AAcademy Format The earliest standard motion picture aspect ratio was 1.37:1. NTSC adopted this aspect ratio but rounded the number off to 1.33:1 or 4:3. The motion picture industry then invented the wide screen format to be able to compete with the television industry. Active Video Video that is actually visible on the display screen and does not show blanking, burst or sync information. Aliasing is shimmering in the video image and is a interlaced video artifact that shows up when the camera pans across straight objects that are not completely horizontal with respect to the camera. ANSI Lumens American
manufacturers measure the brightness of data / video projectors using
the ANSI standard. ANSI stands for American National Standard Institutes
– it is similar to the German DIN. Measuring according to ANSI is
carried out in a dark room with fixed conditions. For the adjustment of
the projector a standard test image is projected. This test image is
used to regulate brightness and contrast. When the projector has been
adjusted a completely white image is projected for the measurement. The
image is divided into 9 equal areas. The brightness is measured in the
center of each area. Artifact (film) An artifact is anything in the image you see on your monitor caused by defects in the source film material such as dirt, hairs, or missing film emulsion. ATSC Advanced Television Standards
Committee, appointed by the FCC to set guidelines for terrestrial
television broadcast. The ATSC standard defines 18 picture formats
allowable for broadcast. See below.
BBack PorchThe area of the video waveform between the rising edge of the horizontal sync and right before the active video. Black levelThe video signal level corresponding to black areas in a scene. For a composite signal, black is standardized at +7.5 units as viewed on a waveform monitor IRE scale. This elevated black level is often referred as "setup" and serves as a guard band between video and sync. For component video, black is at 0 units. See video waveform. Of a television baseband signal (e.g., NTSC composite video), the voltage level corresponding to black or to the maximum limit of black peaks. On a display or television monitor, black level is the technical term for what is usually called brightness. Black level determines the amount of light that a picture display emits for the darkest areas of an image. A PLUGE pattern is a test pattern used to calibrate the black level on a display monitor to that of a DVD player, a VCR, or some other source. Blanking The process of turning off the electron scanning beam of a camera or picture tube so it will not be seen while it repositions itself for the next scan of a field or line. There are two forms of blanking pulses in a television signal. The horizontal (H) blanking pulse cuts off the beam during the retrace period from the right to left side of the picture. The vertical (V) pulse cuts off the beam as it moves from the bottom of the screen back to the top to start the scan of the next picture field. The blanking signal is part of the video waveform. Blocking Detectable to objectionable blocking is sometimes seen on lower priority DBS channels, often visible where there is rapid movement in a close-up image. This is caused by insufficient bandwidth being allocated to the channel in question. A second order cause is that with a contemporary DBS system, the service providers are continuously faced with the need to add "just one more channel". Eventually, there are just too few system resources available to faithfully reproduce the video signal. Breezeway The portion of the video waveform between the edge of the horizontal sync and the start of the color burst Brightness of an image displayed on a display device. Refers to to the amount of light that is being emitted from the display. on a display device is the knob or slider that is used to set the black level while displaying a PLUGE test pattern. Also see Brightness & Contrast. Brightness uniformity The brightness uniformity compares the brightness in the center of the projection to that along the edges of the projection. The higher the indicated value (in %), the more even is the brightness uniformity. Good are values >75%. Byte/bi:t/ An amount of memory or data smaller than a word; usually eight bits; enough to represent one character; the smallest addressable unit of storage. On modern architectures a byte is nearly always 8 bits and characters are usually represented in ASCII in the least significant seven bits. A byte is abbreviated with a "B". (A bit is abbreviated with a small "b".) Computer storage is usually measured in byte multiples. For example, an 820 MB hard drive holds a nominal 820 million bytes - or megabytes - of data. Byte multiples are based on powers of 2 and commonly expressed as a "rounded off" decimal number. For example, one megabyte ("one million bytes") is actually 1,048,576 (decimal) bytes. Historical note: The term was coined by Werner Buchholz in 1956 during the early design phase for the IBM Stretch computer. Originally it was described as 1 to 6 bits (typical I/O equipment of the period used 6-bit chunks of information). The move to an 8-bit byte happened in late 1956, and this size was later adopted and promulgated as a standard by the System/360 computer. The word was coined by mutating the word "bite" so it would not be accidentally misspelled as bit. Chroma Bug The "Chroma Bug" can be seen as streaky or spiky horizontal lines in colored images and are most noticeable along diagonal lines. While the Chroma Bug has been around for some time, it became most visible with DVD's been displayed on good quality monitors and is caused by the MPEG decoder in many DVD players not properly up converting the chroma information from 4:2:0 back to 4:2:2 or 4:4:4 format. It is a DVD player software problem. Click on the link below
for more details. This link will lead you off site. Use your browsers
"Back" button to return to this page. CIE Chromaticity Diagram © Al griffin All the colors we see are a mix of the primary colors of red, green and blue, which from the vertices of the standard triangular "chromaticity" diagram reproduced here. The Commission International De I'Eclairage (illumination), or CIE created this representation of "color space" in 1931, and it is now used in all industries involved with color imaging, from video to photography and printing. Point D, slightly to the left of center, is the NTSC standard white, which is exactly defined by its coordinates in the diagram: x = 0.3127, y = 0.3290. The curved black line cutting through the center represents the color of light emitted by a "black body" heated to various temperatures (think of a piece of carbon heated in a furnace), as measured on the "absolute" Kelvin scale, where 0K = a total absence of heat (no movement of electrons). If white on a video display falls to the right of D in the diagram, it has a lower color temperature, which yields a reddish grayscale, while a white that falls to the left of D has a higher color temperature, which gives a bluish cast to images on that display. While point D itself doesn't actually fall on the black body curve, it is close enough to the 6,500 K point on the curve for this color temperature to be used as a loose definition of the standard, which is sometimes referred to as D6500 for that reason. ©Al Griffin
Color Burst The portion of the video waveform that is located between the breezeway and the start of the active video. The color burst tell the color decoder how to decode the color information in the active video. Color Temperature Kelvin The color of the light
affects the impression of brightness. A white light seems to be brighter
than a yellow one. A measurement for the color of the light is the color
temperature which is measured in Kelvin (K). With halogen lamps, color
temperatures of 3,400 K can be reached. If the temperature is higher the
filament would melt. Daylight has a color temperature of 5,600 K. With
metal vapor lamps color temperatures of 6,000 K can be reached. They are
very close to the color of daylight and are especially suitable for a
natural color display. Contrast Control on a display device is the knob or slider that is used to set the maximum useable light output of a display device. Also see Brightness & Contrast. Contrast ratio The contrast ratio states how much brighter is the projected white compared to projected black. The higher the indicated value, the better is the contrast. An electronically generated standard set of colors used as a reference for proper equipment setup. Color bars include the three additive primary colors (red, green, and blue) and their complements (cyan, magenta, and yellow) displayed in vertical rows, plus gray and black. The bars appear left to right in order of decreasing luminance – yellow, cyan, green, magenta, red, and blue. Videotape machines, cameras, telecine chains, and monitors all use color bars as a reference for proper setup. The waveform can be examined on a waveform monitor or vector scope to verify that the encoding process was proper and/or that it was not changed by any subsequent transmission or recording process. Color bars are readily available and easily interpreted and so have become a de-facto set standard. There are several variations of color bars. Full field bars show the color bars running the full height of the screen. EIA (Electronic Industries Association) bars assigns the bottom third of the pattern to the –I, Q, and black level set signals, which are useful for setup of camera encoders. SMPTE bars are the same as EIA, but insert another set of short color bars above the I and Q bars. These bars run in the reverse color order of the regular bars and are a convenient aid for the setup of color monitors. All versions allow the overall amplitude of the sub carrier (chrominance) to be set at 100% or 75% of the standard value. The 75% value is usually used for recording to avoid possible overload problems from highly saturated yellows and cyans. The amplitude of the gray bar can be set at 100% or 75% IRE units. Color Control on a display device is the knob or slider that is used to set the saturation of the colors in the picture being displayed and is set with only the blue channel (gun, crt...) turned on while a SEMPTE color bar is displayed. DMD DLP
DTV Digital TV (DTV): 480p (720 x 480 progressive scan) DVD Digital Versatile Disk or Digital Video Disk. The video on a DVD is stored in a digital format (MPEG-2), as 720 pixels wide and 480 pixels high interlaced 24fps. Each frame contains two fields. When the movie is played back, the conventional DVD player performs the 3:2 (2:3) pull down in real time to restore the 30fps needed for NTSC interlaced video that is normally done with the Telecine in the case of transfer of film to video for TV broadcast, laser disk or VHS tape. Also see 2:3 pull down. EDTV Enhanced Definition Television, which is a subset of the new ATSC's Digital Television (or Digital TV) specification. The EDTV format is essentially 480 lines of resolution in progressive scanning, or 480p (the "p" stands for progressive scanning). The complete Digital TV standard consists of no less than 18 different picture formats. Field For an interlaced video signal, a "field" is the assembly of alternate lines of a frame. Therefore, an interlaced frame is composed of two fields, a top field and a bottom field. A TV scanning device that scans the film frame in a continuous motion using an electronic shutter rather than the conventional claw intermittent pull-down. The most popular type uses a monochrome kinescope as the light source and the pickup devices are red, green, and blue filtered photocells. This type of telecine device is much easier on film than an intermittent movement projector because it does not jerk the film down each time a frame changes, but rather moves continuously past the scanner so there is less chance of scratching or other film damage. Frame A frame contains lines of spatial information of a video signal. For progressive video, these lines contain samples starting from one time instant and continuing through successive lines to the bottom of the frame. For interlaced video a frame consists of two fields, a top field and a bottom field. One of these fields will commence one field later than the other. The Gibbs Effect is an MPEG compression artifact that appears around sharp transition from one object to another if the compression ratio is too high. This effect is very apparent on The Weather Channel when they show maps. All the roads have the Gibbs Effect round them. You can also pick up this effect on DVD movies. Also see simulation of Gibbs Effect HDTV HDTV (HDTV): 720p or 1080i (1280 x 720 progressive or 1920 x 1080 interlaced) Horizontal scan rate
Hue Control see Tint Control Interlacing NTSC USA TV Standard, 525 lines, 30 frames/sec. 60 fields/sec. Interlaced video signal displays first only the odd lines in the first field of the frame and then refines the picture with drawing the even lines in the second field of the frame. Of the 262.5 lines in each field, only about 240 lines are used for picture information (active video). The remaining 22.5 lines are hidden in the vertical blanking interval (VBI) and are also used to transmit extended data services such as closed caption, text, and time. 240 * 2 = 480. This where the acronym "480i" or "480 interlaced" comes from. Interlacing is a form of compression that is necessary for NTSC (480i) and HDTV (1080i) because of the 6MHz bandwidth limitations of the transmission channel. Kelvin (temperature) The SI (International System of Units or Systeme Internationale) unit of temperature is the kelvin, a fundamental unit of the SI. Since 1967, the kelvin has been by definition the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. The triple point of water is the temperature at which ice, water, and water vapor can all exist in equilibrium and its value is +0.01o Celsius.The kelvin (which is correctly written without a degree sign) is used for measuring both temperature and temperature interval; thus one can say, "The temperature is 300 K" or "This pan is 20 K hotter than that one." Temperatures in kelvin can only be positive and so they require no sign. The kelvin scale of temperature is also known as the absolute scale and the thermodynamic scale. Conversion factors between temperatures in degrees Fahrenheit (oF) and in degrees Celsius (oC) and temperatures in kelvin are: temperature (oC) + 273.15 (exactly) = temperature (K) ((temperature (oF) -32) x 5/9) + 273.15 = temperature (K) The degree Celsius, the unit of the common metric temperature scale, is not part of the SI but its use is not discouraged. A temperature interval in degrees Celsius is identical to a temperature interval in kelvin, although a temperature in degrees Celsius is not identical to a temperature in kelvin. Luminance The intensity of light: specifically, the monochrome component or the brightness potion of a video image. The symbol "Y" is used to identify the luminance signal in composite and component color systems. Mosquito Noise See Gibbs Effect MPEG MPEG (pronounced M-peg), which stands for Moving Picture Experts Group, is the name of family of standards used for coding audio-visual information (e. g., movies, video, music) in a digital compressed format. The major advantage of MPEG compared to other video and audio coding formats is that MPEG files are much smaller for the same quality. This is because MPEG uses very sophisticated compression techniques that predict what most frames will look like (motion prediction). MPEG is also a lossy compression technique that will discard information that is identical between frames and only encode that information once. The MPEG compression algorithms is very good, but not perfect, and sometimes the compressor deems areas of the image to be less important than others. This typically affects the back ground of images, and particularly affects darker background areas of the image. Also see: Pre-processing Noise, Video A random signal generated by most electronic equipment, which is present throughout the video signal spectrum. Video noise is somewhat analogous to film grain. In a home receiver, it is most obvious in the transmitted signal in weak reception areas. OTA Over The Air broadcast of NTSC and HDTV Picture level Also called "contrast". The picture level determines the light output of the crt and needs to be set to a point where the high voltage power supply of the monitor is not overloaded and that color is not overly saturated. One of the ways MPEG-2 achieves bit rate reduction is to eliminate any information from the picture that already exists in previous frames of the movie. This redundant information is usually areas if the picture that remain the same from frame to frame. Noise and any other imperfections in the picture will be encoded as they are detected as changes in the picture by the MPEG encoder which in turn will increase the bit rate. Pre-processing will attempt to "clean up" the video before encoding takes place and so allowing for better video quality at a lower bit rate. The method and amount of pre-processing needs to be carefully chosen so that the original "look" of the movie is not altered. A PLUGE (picture line-up generating equipment) pattern is a test pattern used to calibrate the black level on a video display. Black level is the technical term for what we typically refer to as brightness. It determines the amount of light that a picture display emits for the darkest areas of an image. PLUGE patterns vary in format, but all consist of lighter and darker areas of black (and sometimes white and/or gray) shades. A typical PLUGE pattern is made up of three dark vertical bars, each of which is called a PLUGE pulse. When the black level is set to below actual black, the bars register as: black, black, and dark gray. This level will make the colors in a display look overly saturated. When the black level is too high, all three bars are visible in the picture. This level will make the colors in a display look de-saturated and give the picture an overall washed out look. In either case, the colors surrounding the dark areas will lack vibrancy and will be less distinct than they should be. PLUGE patterns are included in most display calibration products. RGB Why do CRTs Use Red, Green, and Blue rather than Red, Yellow, Blue?So you were taught in grade school that any color could be made up of red, yellow, and blue paint. Why are these not used in CRTs?Nearly any color that we can perceive can be made from some combination of primary colors. There are two types - additive and subtractive. RGB are primary additive colors - anything that emits light will use these. The three types of cone (color) recepters in the retina of the human eye have peaks (roughly) sensitive to these primary colors. Those red, yellow, and blue primaries you used to create your works of art should actually not have been red, yellow, blue but rather magenta, yellow, cyan - close but no cigar. Red, yellow, and blue are approximations good enough for basic painting or printing but are not capable of reproducing the widest range of colors. CMY (cyan, magenta, yellow) are subtractive colors. Printing processes and color photography use these because layers of ink or dye absorb light. Basically, each of CMY removes a single color from (RGB).
SDTV Standard Definition TV: 480i (640 x 480 interlaced). This term is used to signify a digital television system in which the quality is approximately equivalent to that of NTSC.SMPTE Society of Motion Picture and Television Engineers. Also see SMPTE Color bars. Telecine is a machine that transfers film to video in either NTSC, PAL or HDTV formats. See Flying Spot Scanner Telecine Formats The most popular type of television projector/camera configuration is called a flying spot scanner. Most film is transferred in the 35mm format in the form of filmed television programs or feature films. Wide screen film formats such as Cinemascope and Panavision may be transferred to videotape for use on television by using a sophisticated pan and scan method to select the most desirable areas of a scene. This preprogrammed information and selection of scene framing or panning is stored in a computer and may then be duplicated in real time as the film is recorded on videotape. Color balance and scene density information, as "painted" by the telecine operator, is also stored in the computer for later use. A relatively new form of telecine format is the three-perforation frame as opposed to the conventional four-perforation 35mm-picture frame. Since only three perforations are used in each film frame instead of four, an appreciable savings results by using 25% less of the film raw stock during production than would normally be used. The three-perf format affords similar savings for theatrical production and the entire frame area is used. The ideal format for TV would be three perf, 30 frame, which would result in slightly less film being used as in the present format. A 30-frame film format has greatly improved motion rendition, less grain pattern and an apparent increase in resolution. Most important for TV, which is the ultimate market for theatrical films, is the absence of 24 to 30 frame conversion artifacts, which are quite noticeable. However, the cost of theater conversion throughout the world, and the fact that the rest of the world’s TV systems demand 24/25 frame film make this an unlikely improvement. Both the camera used in production and the telecine used to transfer this special format have to be modified to accommodate this special format. The second popular format is 16mm used in many industrial applications and some television programming film. Although not as widely used as in the past decade, 16mm, because of its comparatively low cost, fine grain, and good resolution, is still used to some degree by the military, industrial and documentary producers. A third format is Super 8mm. Although not as popular as 16mm and 35mm, it has a following among industrial and documentary producers who use this format to shoot on location in difficult areas where video may be too cumbersome to use. In many circumstances, it may important to avoid the appearance of professional equipment. Another option is a device that reduces or eliminates the side to side picture weave of motion picture film. Conventional telecines exhibit some small amount of side to side picture weave because of the way the film is guided in the gate. Now, mechanical and electronic methods have been developed to almost completely eliminate this problem, which is very noticeable when electronic artwork or lettering is combined with moving motion picture images. Variable speed telecines also provide the film producer with limited special effects. For example, film shot at 16 frames per second, maintaining a real time look to the image. Other frame rates may also be programmed for special effects. TFT Technology for
controlling liquid crystals. TFT stands for “Thin Film Transistor”. Tint Control on a display device is the knob or slider that is used to set the balance of the color information in the image and is set with only the blue channel (gun, crt...) turned on while displaying the SMPTE color bars. Uncompressed Audio 176 Kbytes/sec Uncompressed NTSC, 640x480 (480i) 27 Mbytes/sec 900 Kbytes/frame Uncompressed HDTV, 1280x720 (720p) 79 Mbytes/sec 2.6 Mbytes/frame Uncompressed HDTV, 1920x1080 (1080i) 178 Mbytes/sec 6 Mbytes/frame Uncompressed 16mm film, 2048x1536, 24fps 216 Mbytes/sec 9 Mbytes/frame Uncompressed 35mm film, 3656x2664, 24fps 836 Mbytes/sec 35 Mbytes/frame Vertical Blanking Interval. Signal that "hides" or blanks the return of the electron beam in a crt from the bottom to the top of the raster. This signal is part of the video waveform.
Video Communication medium that electronically transmits images and sounds. May use magnetic tape as a recording method. The visual, or picture, component of an electronically based communication medium. This includes the black and white part of the electronic signal, color information, and synchronizing signals.
Viewing distance
Visible Light Electromagnetic radiation capable of eliciting an optical response in the human eye. Approximately from wavelengths of 400nm (violet) to 700nm (red). White level The level corresponding to the specified maximum excursion of the luminance signal in the white direction of a video signal. 0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 2:3 pulldown is the usual process of transferring 24 frames/sec (23.976 fps) film to 30 frames/sec (29.97 fps) video with a Telecine machine in which the first frame of film is represented by two fields if video, the second frame of film is represented by 3 fields of video, the third frame of film is represented by two fields of video and the fourth frame of film is represented by three fields of video and so on. Field sequence is: 1122233444, see figure below:
3:2 pulldown is the un-common process of transferring 24 frames/sec (23.976 fps) film to 30 frames/sec (29.97 fps) video by repeating the first film frame as three fields, then the next film frame has two fields and so on. Most people mean 2:3 pulldown when they talk about 3:2 pulldown. While the 3:2 (2:3) pulldown resolves the speed difference between 24 fps film and 30 fps video it also creates motion artifacts since two sequential frames of video contain fields with information from two different film frames. Along with the usual interlace artifacts, this can look very messy along diagonal, slanted or bowed objects if there is motion in the picture from the objects with a stationary camera or when the camera is panning with stationary objects. The
earliest method used of dealing with these artifacts is to de-interlace
the 480i video with a line doubler. The line doubler with 3:2 (2:3)
reverse pull down has to analyze the field sequence and combines fields
with information from the same film frame in one frame of video.
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