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HDTV Glossary

Aspect Ratio: Aspect Ratio refers to the ratio of image width to image height. Aspect Ratio can apply to configuration display, or simply, what shape content takes when it is displayed. (See Letterboxing) HDTV uses an aspect ratio of 16 units wide by 9 units high (16:9) (See 16:9). In comparison, the aspect ratio of standard television programming is 4:3 (see 4:3).

Aspect Ratio Comparison Diagram

Dolby Digital® 5.1: Dolby Digital provides five full-bandwidth channels, front left, front right, center, surround left, and surround right, for true surround sound quality. A low frequency effect (LFE) channel is included that provides the sound needed for special effects and action sequences in movies. The LFE channel is one-tenth of the bandwidth of the other channels and is sometimes erroneously called the subwoofer channel. This multi-channel scheme is known as 5.1 channel.

DTV: DTV is also known as Digital Television. DTV signals are recorded, broadcast, and processed in a digital format. Currently, 18 different DTV formats have been specified, including SD and HD formats. DTV broadcasts are usually sharper than analog broadcasts.

The three main formats of Digital television are SDTV (Standard Definition Television); EDTV (Enhanced Definition Television) and HDTV (High-Definition Television).

EDTV : EDTV is also known as Enhanced Definition Television. EDTV is defined as television that displays the picture (either from SDTV or HDTV) at a resolution of 480p lines in either 4:3 or 16:9 aspect ratio. EDTV is not HDTV.

HDTV: HDTV is also known as High Definition Television. HDTV is defined as a TV system having approximately two times the vertical and horizontal picture resolution of today's standard definition TV (SDTV) and having an aspect ratio of 16:9. Two HDTV formats are currently in use; (a) 1080i:1920 pixels per line and 1080i lines per frame and (b) 720p:1280 pixels per line and 720p lines per frame. HDTV can be easily recognized by its spectacular picture resolution and impressive 5.1 channel surround sound.

Interlaced Scanning: Some HD televisions and most conventional televisions use the "interlace" method of scanning, by which pictures are transmitted and "painted" on the television screen in two passes. In the first pass, every other line is painted and in the second, the lines in between are painted. The intersection of these two passes "interlace" each other, providing viewers with an image.

LCD : Liquid Crystal Displays are flat-panel televisions designed to offer superior images. A liquid crystal solution is sandwiched between two panels and electrified. This causes the crystals to act as ‘shutters’, some allowing light to pass through, other blocking light out. These ‘shutters’ on the electrified crystals form the image on the LCD TV. The typical LCD screen size ranges from 24 to 46 inches.

Letterboxing: "Letterboxing" typically refers to the display seen by viewers with a wide aspect ratio 16:9. On a TV with the aspect ratio 4:3 this usually results in those "black bars" you may see above and below the picture when watching a movie. This is typically referred to as "letterboxing" and is often seen during movies shown on television when viewed on standard 4:3 screens but is not apparent, or less noticeable, on HDTV displays with aspect ratios of 16:9.

Pixels: Pixels are tiny dots or elements that make up a picture. You may be familiar with the term "DPI" or "Dots Per Inch" - this is the same type of terminology -- the more pixels, or dots, the clearer your picture or document will resemble the original. The word "pixel" comes from a combination of the words "picture element." A significantly high number of pixels in a given image, which is especially evident in viewing HDTV, provide greater clarity and image detail. The number of pixels is usually referred to as the resolution.

Plasma: Plasma Televisions contain a mixture of neon and xenon gases that fill a small space between two sheets of glass. When this mixture is stimulated by electricity, a bright, clear picture is produced. The typical size of a Plasma TV is 32 to 63 inches.

DLP (Digital Light Processing): DLP televisions use a technology called digital light processing that uses an optical semiconductor. The chip contains more than 1 million microscopic mirrors that move back and forth to generate an image. The typical DLP screen size is from 14 to 46 inches.

Progressive Scanning: Typically, some HD televisions use a "progressive" scanning method. Progressive scanning refers to the entire picture being transmitted and presented on the screen in one pass (as opposed to the two passes referred to in the "interlace" scanning definition). As a result, the image is usually free of "flicker," thereby appearing more true to life.

Resolution: Resolution refers to picture clarity, usually determined by the number of vertical and horizontal pixels -- the more pixels in a given image, the greater the resolution.

SDTV: Also known as Standard Definition Television. SDTV is based on 480 lines of vertical resolution and may have either 4:3 or 16:9 aspect ratios, and may include surround sound. Several SDTV programs are sent together to form the simulcast bundle.

16:9: 16:9 is sometimes called (sixteen times nine) or (sixteen by nine) -- whatever term you prefer to use, it simply means 16 units wide by 9 units high. 16:9 typically refers to how wide screen televisions are viewed -- by comparison, standard television screens are viewed in 4:3, or 4 units by 3 units. Both viewing phases describe the shape of television sets or television programs, not an actual measurement in inches or feet. Both 16:9 and 4:3 are also called aspect ratios.

4:3: As with 16:9, 4:3 is sometimes called (four times three) or (four by three) -- whichever term you prefer to use, it simply means 4 units wide by 3 units high. Besides being known as the "standard" aspect ratio, before 1954 the 4:3 aspect ratio was also known as the "Academy Ratio" (same Academy as the famous one that gives out the Oscars ®).

480i: Stands for 480 interlaced (i). Interlaced "i" scanning alternates and refreshes pixels, first the odd lines, then the even lines. 480i is the standard interlaced form of standard-definition digital television, whereas high-definition digital television (HDTV) has 1080i, more than double the interlacing scanning of a standard television.

480p: Stands for 480 progressive (p). Progressive scanning is refreshed on screen simultaneously, as opposed to interlaced scanning (i), which scans odd lines then even lines on screen. 480p still may fall short of most high-definition television scanning, which typically uses 720p.

720p: Stands for 720 progressive (p). 720p is made up of 720 vertical pixels and 1,280 horizontal pixels. The (p) stands for progressive, as opposed to interlaced scanning, also known as 1080i. Interlaced scanning and progressive scanning are two of the formats of high-definition television as defined by the ATSC (Advanced Television Systems Committee), a government-sanctioned, industry-led standard-setting body that adopted the official digital television standard for the United States in 1997.

1080i: Stands for 1080 interlaced (i) -- 1,080 vertical pixels by 1,920 horizontal pixels. The "i" in 1080i stands for interlaced. Interlaced "i" scanning alternates and refreshes pixels, first the odd lines, then the even lines. Interlaced scanning and progressive scanning are two of the formats of high-definition television as defined by the ATSC (Advanced Television Systems Committee), a government-sanctioned, industry-led standard-setting body that adopted the official digital television standard for the United States in 1997.

Resolution HDTV Progressive scan Widescreen
1080p 1,920x1,080 Yes Yes Yes
1080i 1,920x1,080 Yes No Yes
720p 1,280x720 Yes Yes Yes
480p 852x480 No Yes Yes
Regular TV Up to 480 lines No No No