Progressive scan - This is the opposite of interlaced scan.
Video-on-Demand (VOD) - A programming library service offering the individual viewer the choice of the available content on demand. When the program is requested and confirmed (by telephone or Internet) it is then delivered to the viewer over an available channel in encrypted form. VOD services are generally arranged on a "Pay per View" basis, analogous to the cinema.
4DTV - This is a DTV subscription service for C-band and Ku-band (a satellite service requiring an 8 foot dish).
Multipoint convergence - Projection TVs with 3 CRTs require periodic adjustment to keep the 3 images perfectly aligned. Typically this is a simple 5 minute procedure the consumer must do every month or so.
Plasma Displays (PDP). A technique that builds an image from a large number of pixels formed in a glass panel. The pixels are individually controlled, yielding a picture free of flicker and of high brightness. Displays of excellent resolution and color are available and the display approaches the "television picture on the wall" ideal. PDP displays up to 160 cm (63in.) are available, making them suitable for the home theatre.
Luminance - Component of the video signal that represents the brightness of the image.
Fps - Frames per Second. To give the illusion of motion, television actually transmits a series of snapshot pictures referred to as frames. Increasing the frame rate improves motion smoothness and may reduce flicker in some displays. In Canada both analog and digital television transmits 30 Fps.
Multicasting - Term given to the sharing of the digital television channel among 2, 3, 4 or more individual programs and/or data services
YPrPb - Color representation requires three independent variables. CRTs - prefer red, green, and blue. Ink jet printers prefer yellow, magenta, and cyan. NTSC encodes color as luminance (brightness), hue (color), and saturation (absence of white in colors). Storage media such as DVDs prefer Y, Pr, and Pb, where Y is luminance, Pr is Y-red, and Pb is Y-blue. This is because Pr and Pb can be at lower resolution and not degrade the image noticeably, thus saving storage space.
Dolby Digital 5.1 - Also known as AC-3, it provides 6 channels of sound: left, center, right, left rear, right rear, and sub-woofer. It is also called "5.1 channels" since the 6th channel has reduced bandwidth. Dolby Digital 5.1 is the audio standard for all U.S. digital TV stations, most DVDs, some DBS programs, and many theaters.
AC-3 - (see Dolby Digital 5.1)
LCD - (Liquid Crystal Display) - A common display technology. LCD is likely to replace CRTs in the smallest HDTV's.
Downconvert - The process which reduces the number of pixels in the scanning format used to represent an image, so that it may be reproduced on a display of lower resolution, such as a conventional television. For example, an HDTV image may be downconverted to an SDTV or NTSC image, but in the conversion significant detail information may be lost.
Aspect ratio - The ratio of screen width to screen height. For TVs it is either 4:3 (1.33:1) or 16:9 (1.78:1). Theater film uses many different aspect ratios, some as high as 2.5:1.
