Glossary of HDTV terms and definitions
You have certainly heard about Digital TV and HDTV. You may belong to the people who decided to buy one for themselves but the available information about HDTV seems to confuse you. Much information is rather technical and there are many things hard to understand about HDTVs for common people. So, if you do not belong to the few people who are familiar with the topic, have a look at this HDTV terminology glossary. Check it out and you will find out that things like 1080i, PIP and EPG will no longer mean any problem for you and you will find the whole HDTV issue much more clear when talking for example with a shop assistant. Feel free to read full HDTV glossary for free and make your problem disappear.
1080i means that the resolution of the picture is 1920 vertical pixels by 1080 horizontal pixels and i stands for interlaced scanning. Interlaced scanning is based on the principle that the screen shows every odd line at one scan of the screen and then all the even lines in a second scan.
1080p means that the resolution of the picture is 1,920 vertical pixels by 1,080 horizontal pixels and p stands again for progressive scanning. This format works on the same principle as 720p; the only difference is that in this type there are more pixels and the resolution is better.
16:9 is aspect ratio of movie screen and widescreen DTV formats used in all HDTV (High Definition TV) and some SDTV (Standard Definition TV); it stands for 16 arbitrary units of width for every 9 arbitrary units of height.
4:3 is aspect ratio of traditional squarish National Television Systems Committee (NTSC) TV screens; it stands for four arbitrary units of width for every three arbitrary units of height.
720p means that the resolution of the picture is 1,280 vertical pixels by 720 horizontal pixels and p stands for progressive scanning. Progressive scanning offers a smoother picture as 720 horizontal lines are scanned progressively or in succession in a vertical frame that is repeated 30 times a second.
Advanced Television Systems Committee (ATSC)
Advanced Television Systems Committee is responsible for establishing and developing digital television standards, as well as all 18 formats of Digital TV.
Artifacts are defined as unwanted visible effects in the picture caused by disturbances and errors in the video transmission or digital processing. Artifacts include “edge crawl” or “dot crawl” or “hanging dots” in analog pictures, and “pixelation”, “contouring” or “blockiness” in digital pictures.
Aspect ratio is ratio of width to height of a TV screen. It may be either traditional squarish 4:3 ratio of the National Television Systems Committee (NTSC) TV screen or 16:9 ratio of widescreen DTV formats for all HDTV (High Definition) and some SDTV (Standard Definition).
Bandwidth, in general, means amount of information that can be carried in a given time period (usually a second). More exactly, it is a range of frequencies used for transmitting picture and sound information from transmitter to your TV. Federal Communications Commission (FCC) has allocated 6 MHz for TV broadcasters for each channel.
Bit rate is measured as "bits per second" (bps) and refers to the rate at which the data is transmitted. For Digital TV, the maximum possible bit rate within the bandwidth is 19.4 Mbps while SDTV has a lower bit rate. The higher the bit rate, the more data is processed which usually results to higher picture resolution or better sound quality.
Codec is a short term for “Coder-decoder.” This device is used to convert analog video and audio signals into digital format, and vice verse, it can also convert received digital signals into an analog format.
Compression allows the delivery of more programs in a single channel. It is an electronic manipulation of digital data that reduces and removes redundant and/or non-critical information in the digital picture and sound without noticeably degrading picture quality. One of the compression methods is called MPEG-2.
CRT (Cathode-Ray Tube)
CRT stands for cathode-ray tube. Invented in 1897, even nowadays it is the most common display technology for televisions. The tube uses an electron beam to scan lines on the screen coated with phosphor, which glows when struck by the beam. The other display technology being used more and more often nowadays in television sets is LCD.
Dolby Digital (Dolby AC-3)
Dolby Digital, also called Digital 5.1 or AC-3, is a five-channel surround sound system which delivers CD-quality digital audio and provides five channels of full frequency for front left, front right, center, surround left and surround right speakers, plus one channel for LFE (low frequency effect) subwoofer. It is the official audio standard for Digital TV and HDTV.
DTV (Digital Television)
DTV stands for Digital Television. It refers to all digital television formats and standards established by the Advanced Television Systems Committee (ATSC). Two basic DTV standards are HDTV (high-definition television) and SDTV (standard-definition television)
EDTV (Enhanced-Definition Television)
EDTV stands for Enhanced Definition Television. The picture quality of EDTV is superior to that of standard analog TV (480i) but not as good as HDTV (1080i or 720p). EDTV displays the picture at a resolution of 852x480 (480p) lines in either 4:3 or 16:9 aspect ratios and it includes Dolby Digital sound system.
EPG stands for electronic program guide. It is a system displaying channels and program data on-screen.
Flat-panel TV typically displays picture using gas plasma or LCD technology and is only a few inches thick.
Front-projection TVFront-projection TV comprises 2 parts – a separate front projector (usually placed on a table or ceiling-mounted) and a reflective screen (or simply a wall). The projector is placed at one end of the room, the screen is at the other end, and the speakers may be placed wherever they will provide you good sound experience. The picture can be rather large but remember – the larger the picture, the more visible the pixels or scan lines and the darker the image.
Ghosting means multiple overlaid TV images or “ghosts” which you can notice around the objects while watching TV. Ghosting is caused by the broadcast signal traveling to your TV through various obstacles, for example hills or tall buildings, and your antenna picks up the original TV signal along with signals reflected by the obstacles. If the ghosting is changing rather than static, it may be caused by the signal reflected by flexible objects, for example trees.
HDTV (High-Definition Television)
HDTV stands for High Definition Television. This highest-resolution subset of Digital Television offers filmlike picture quality with impressive surround sound. With twice the vertical and horizontal picture resolution, the picture of HDTV is approximately twice as sharp as that of NTSC. HDTV has widescreen aspect ratio of 16:9 and Dolby Digital sound system. Currently used HDTV formats - 1080i and 720p both offer reduced motion artifacts like ghosting and dot crawl.
Interlaced scanning is a method based on the principle that the screen shows every odd line at one scan of the screen and then all the even lines in a second scan. There are 30 frames shown per one second and this can make larger screen flicker, which is the usual problem with interlacing. However, LCD and plasma screens cannot display interlaced signals and must first convert them to a progressive format and then they can display the transmitted images.
LCD (Liquid Crystal Display)
LCD stands for Liquid Crystal Displays. It refers to a flat panel technology which uses liquid crystals sandwiched between two glass plates for example in laptop computers, other small portable displays and also in televisions. Wide-screen HDTVs are available with displays of adequate resolution up to about 37 inches.
Letterboxing means copying the widescreen format with aspect ratio of 16:9 to video format with aspect ratio of 4:3. The result of this process is that the full picture is presented only on the middle part of the screen, with black bars above and below it. This arrangement is referred to as “Letterbox” and you can see it on your 4:3 TV while watching movies. On a 16:9 TV letterboxing does not block out so much of your screen and makes your experience more profound.
NTSC (National Television Systems Committee)
NTSC or National Television Systems Committee is the organization that develops technical standards for black-and-white television and color television. The term is also used to refer to the video-transmission standard used in the western hemisphere, Japan, and other Asian countries. NTSC established the 525-line (480 visible) analog broadcast TV standard. It is supposed to be soon replaced by digital broadcast standards.
Over-the-air Broadcast (OTA)
Over-the-air Broadcast is also called Terrestrial Broadcast. It is standard over-the-air broadcast to an antenna, as opposed to satellite or cable transmission.
Picture-in-picture is a television feature in which you can see one program inside a small window on the screen, while watching another program on the large background screen. You can choose whatever you wish – you can watch two TV programs simultaneously or you can watch TV and video or DVD at the same time.
Pixel comes from the words “picture element” and it refers to the smallest element in a television picture. Pixels are single displayable video dots from which the overall picture is made up.
Plasma Displays (PDP)
Plasma display is created by thousands of tiny tubes filled by ionized gas in a plasma state. Ionized gas is very light and flat panel TVs made by this technique can be even hanged on the wall! Plasma displays offer excellent resolution and color and they are the most suitable for the home theatre.
Progressive scanning is used by some HDTVs. Progressive scanning offers rather smooth picture as 720 or 1080 horizontal lines are scanned progressively or in succession in a vertical frame that is repeated 30 times a second. Some displays, for example LCD and plasma use progressive scanning method, while CRTs may use progressive (e.g. in computer monitors) or interlaced scanning method.
Rear projection is a TV system where the picture is projected against a mirror inside the cabinet and you can watch it as you would an average television. Until recently, the rear projection TVs comprised three CRTs but the new types of rear projection TVs include LCD.
Resolution reflects the density of lines, and dots per line which make up a visual image. It is measured by the number of pixels displayed. The level of resolution directly affects picture quality. Usually the higher number of lines and dots means also sharper and more detailed picture. Analog TV has a little over 200,000 color pixels while HDTV, with 1080 vertical pixels and 1920 horizontal ones, has more than 2 million pixels creating the image.
SDTV (Standard-Definition Television)
SDTV stands for Standard Definition Television. The SDTV picture, having either in 4:3 or 16:9 aspect ratios, is better and of higher quality than the one of NTSC, however, it does not reach the quality and resolution of HDTV. SDTV is based on 480 lines of vertical resolution and in both interlaced and progressively scanned formats.
Set-top Box (STB)
Set-top box is responsible for receiving, converting and sending the picture and sound of the broadcast to the associated television. If your HDTV-ready TV has no built-in HDTV tuner you must connect it to a compatible HDTV STB first. Until then it will not receive and display digital television programs.
Widescreen TV is the television with 16:9 aspect ratio. 16:9 is the aspect ratio of movie screen and widescreen DTV formats used in all HDTV (High Definition TV) and some SDTV (Standard Definition TV); it stands for 16 arbitrary units of width for every 9 arbitrary units of height.
Can you see the difference now? The terminology, which seemed to be so confusing and baffling just few minutes ago is not as complicated as you thought. Now you know what the most common HDTV acronyms stand for and you are familiar with basic terms you will probably get into contact with when buying your new HDTV.
Submitted by Martin Sojka
Reprinted from Zongoo.com Daily Press & Consumer Information