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480i: The term for Analog TVs use of 480 lines, interlaced scanning at 30 frames (complete pictures) per second and a 4:3 aspect ratio screen.
720 progressive (p): 1280 pixels per line and 720p lines per frame. HDTV also can be broadcast and displayed as a "progressive image" (720p), like a computer monitor, where a full frame fills the screen from top to bottom, eliminating lines altogether.
1080 interlaced (i): 1920 pixels per line and 1080i lines per frame with many DTVs, doubling the number of scanning lines.
4:3: Aspect ratio of traditional NTSC TV screens, with 4 unit width by 3 unit height.
16:9: Aspect ratio of widescreen DTV formats for all HDTV and some SDTV (Standard Definition) content, 16 unit width by to 9 unit height.
8-VSB: Acronym for the transmission method used for over-the-air DTV broadcasting in the USA. Eight discreet amplitude level, "vestigial side-band" broadcast transmission technology. VSB is an analog modulation technique used to reduce the amount of spectrum needed to transmit information through cable TV, or terrestrial broadcasting.
AC-3: The 5.1-channel compressed digital sound system specified for DTV broadcasting. AC-3 delivers CD-quality digital audio and provides five full-bandwidth channels for front left, front right, center, surround left and surround right speakers, plus an LFE (low frequency effect) subwoofer, for a total of 5.1 channels. AC-3 is one member of a family of sound systems developed by Dolby Labs.
A/D: Electronic device that connects an analog television signal to a digital system.
Addressable Resolution: The highest resolution signal that a display device (television or monitor) can accept as input. Some display devices may not be capable of displaying such signals and may down convert them to a lower resolution prior to display.
Analog Video: The conventional NTSC television system in use today uses analog technology, in which the image sound and the picture brightness and color are represented by signals proportional to these values. The values of these signals are vulnerable to interference and noise. Digital television overcomes this vulnerability and delivers signals that are totally clean.
Anamorphic: the squeezing horizontally of a 16:9 image into a full screen 4:3 display, resulting in distortion of the image geometry.
Artifacts: Unwanted visible effects in the picture created by errors in the video processing or noise/interference in analog circuits. Common artifacts include 'edge crawl' or 'hanging dots' in analog pictures or 'blockiness', noise or 'contouring' in digital pictures.
Aspect Ratio: the ratio of image width to image height. The term may apply to the display device configuration, or the shape of the content being displayed. (See Letterboxing) HDTV uses an aspect ratio of 16 units wide by 9 units high. Conventional television programming and displays are at an aspect ratio of 4:3. Digital SDTV programs may aspect ratios from 4:3 to 16:9, dependant on content and its source (e.g. up converted NTSC is likely to be 4:3).
ATSC: "Advanced Television Systems Committee." Formed to establish technical standards for U.S. advanced television systems. ATSC is now used as the catch-all nomenclature for DTV broadcast standards.
Bandwidth: The range of frequencies used to transmit the television signal, including picture and sound. Analog television signals have been allocated at 6 Megahertz for each over-the-air channel. Digital channels are allocated the same 6 Megahertz. However, by the use of digital compression, a combination of up to 5 SDTV programs and/or one HDTV program can be carried in this 6 MHz digital channel.
Baseband Video: Unmodulated analog video signal.
Bit Rate: The rate at which the data is transmitted, expressed as ¡°bits per second¡± (bps). The higher the bit rate, the more data that is transmitted, generally resulting in better picture or sound quality. Video data rates are usually expressed as Megabits per second (Mbps, 106) and audio data rates in kilobits per second (kbps, 103).
CEMA: Consumer Electronics Manufacturers Association. A U.S. industry group representing manufacturers of consumer electronics products
Channel: A 6 MHz (bandwidth) section of spectrum for over-the-air broadcast (channels 2 - 69) or in TV cable that carries one analog NTSC program or one or more DTV programs.
Cliff Effect: describes the sudden loss of digital signal reception. Unlike analog signals, which gradually fade when signal strength decreases or electromagnetic interference or multipath increases, a digital signal provides data which is either perfect or non-existent at the receiving end. It is named for a graph (shown at right) of reception quality versus signal quality, where the digital signal "falls off a cliff" instead of having a gradual rolloff.
Closed Captioning: A data stream included in broadcast signal that provides text and/or narrative description of dialogue, sounds, and other elements of the picture for viewers with visual or auditory impairments.
Composite Video Connection: A method to interconnect video devices (such as a DTV set-top box and the analog television) by sending the signal over a single cable. This method is suitable only for analog NTSC signals
Composite Video: An analog video signal (NTSC, PAL or SECAM) that includes both luminance (brightness) and chrominance (color) signals encoded together to form a single signal.
Compression: A method of reducing the number of bits required to store or transmit programs by the removal of redundant and/or non-critical information in the digital picture and sound.
CRT: An analog vacuum tube technology that has been the mainstay of conventional TV displays for many years, writing the picture on a phosphor coated screen with an electron beam. It can produce bright pictures of excellent resolution but the size and weight of a unit suitable for the large, wide-screen displays needed for HDTV may be, for some, a disadvantage.
Datacasting: The inclusion of additional data in the broadcasting stream. Such data may be related to the current program (e.g. sports statistics) or may be completely independent (e.g. software downloading or traffic advisories).
D/A: Conversion of digital signals to analog signals. Most set-top boxes decode the digital signals broadcast and then convert them to analog signal for interconnection to the display device.
DLP (Digital Light Processing): A technique in which the displayed image is produced by an array of dynamic micro-mirrors formed on a chip, each reflecting some of the light source to form a pixel on the screen. Each micro-mirror controls the level of the light sent to the screen for its pixel. Resolution is set by the size of the mirror array and versions suitable for wide-screen HDTV are now in production for uses in both front and rear projection televisions.
Dolby? Digital Audio (Dolby AC-3): The 5.1 channel audio standard for DTV and HDTV.? It includes six discreet audio channels: Left, Center, and Right, Left Surround (or side), Right Surround (or side), and a subwoofer -- LFE, "low frequency effects". This is particularly beneficial within a home theater system.
Dot Pitch: The distance between pixels (picture elements) in a display. In a CRT for HDTV, the dot pitch is typically 0.25 - 0.3 mm. For full resolution HDTV display approximately 1400 pixels are required across the screen.
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.
DTH: Direct-to-Home satellite delivery. May also be called DBS or Direct broadcast satellite.
DTV: "Digital television." This comprises all the components of digital television, including HDTV, SDTV, datacasting, and multicasting, falling under the standards established by the ATSC.
DTS: Digital Theatre Sound System. A Dolby proprietary discrete 5.1 channel surround system similar to, but not the same as Dolby Digital AC-3, the DTV standard. DTS is used in cinema presentations and in DVD¡¯s.
DVD: Digital Versatile Disk. An optical recording media similar to the familiar CD but having seven times its capacity on a single side. In television applications, DVD¡¯s are capable of carrying full-length commercial movies, plus additional material such as outtakes, director's notes, movie trailers, etc.
EDTV: Enhanced Definition Television. A term defining a 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 and which includes Dolby Digital AC-3 multichannel sound.
Encryption: The process of coding signals so that a specific code or key is required by the viewer to recover the data so encrypted. Without this key, the data is meaningless. Encryption is used to provide conditional access for private television services.
EPG: Electronic program guide. An on-screen display of channels and program data.
Fire Wire: A digital interface originated by Apple Computer that can transport data at 100, 200, or 400 Mbps. It is widely used to interconnect digital video devices, such as cameras and displays. Also referred to as IEEE- 1394.
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.
HDTV: High Definition Television: The best digital television, widescreen (16 x 9) display with at least 720 progressive (p) scanning lines or 1080 interlaced (i) lines and Dolby digital surround sound. High-definition TV (HDTV) is the best quality DTV. HDTV¡¯s sound and picture quality is five times better than today¡¯s analog.
HDTV Monitor: Any monitor (display) with the inputs and capability to become an HDTV display set with the addition of an HDTV tuner.
Interactive Television: TV programming with interactive content and enhancements, blending traditional TV viewing with the interactivity of a personal computer.
Interlaced Scanning: Some HD televisions and most conventional televisions use the "interlace" method of scanning, in which the picture is transmitted and painted on the screen in two passes, using two fields of alternating horizontal scanning lines to form a full picture. This picture is referred to as "480 interlace," or 480i. In the first pass, every other line is painted and in the second, the lines in between. Some display types, such as LCD, plasma and DLP cannot display directly images transmitted as interlaced signals and must convert them to a progressive format prior to their display.
Letterbox: The full display of a wide aspect ratio 16:9 picture on a display of aspect ratio 4:3 will result in black bars above and below the picture. This arrangement is referred to as ¡°Letterbox¡± and is often seen during movies shown on television.
LCD. (Liquid Crystal Displays): A flat panel technology, using thin-film crystal techniques, widely used in laptop computers, other small portable displays and more recently in televisions. Image brightness can be very high and color performance can be good. For HDTV, wide-screen displays of adequate resolution are available up to about 94 cm (37 in.) for direct viewing. LCD devices are also widely used as the key element in many projection televisions, both front and rear screen, up to very large sizes.
Line Doubling: A method used in some televisions to improve the visual quality of an NTSC interlaced picture, making it comparable to a progressively scanned picture.
Luminance: Component of the video signal that represents the brightness of the image.
Metadata: Informational data about the data, included in a signal's data stream.
MPEG-2: Compression standards for moving images and for audio as set by Motion Pictures Expert Group (MPEG). MPEG-2 video coding is the basis for ATSC digital television transmission.
Multicasting: The term given to the sharing of the digital television channel among 2, 3, 4 or more individual programs and/or data services, allowing broadcasters to offer several different TV programs at the same time at lower resolution.
NTSC: National Television Systems Committee. The organization that created the standards for production and broadcasting of analog color television programming. The term is widely used to mean a composite analog television signal.
Over-the-air Broadcast (OTA): Also called Terrestrial Broadcast. The delivery of TV and radio signals, using UHF/VHF frequencies, directly to consumer devices. Broadcasts may be either analog or digital.
Pixel: A picture element; a single displayable video dot. HDTV requires from 1 to 2 million pixels in the display for full resolution images to be shown. The greater the number of pixels, the sharper or better defined the picture will be. HDTV can display up to 10 times as many pixels as analog televisions.
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.
Primary Color Components: Red, Green and Blue (R,G,B)
Progressive Scanning: Some HD televisions use the ¡°progressive¡± method of scanning, in which the whole picture is transmitted and presented on the screen in one pass. The resulting image is thus remarkably free of flicker and motion artifacts, appearing more ¡°life-like¡±. Some display types, such as LCD, plasma and DLP are inherently of the progressive scan type, while CRT¡¯s may be scanned progressively (as in computer monitors) or interlaced.
PSIP: Acronym for "Program and system information protocol", an ATSC DTV specification that enables a DTV receiver to identify the program information and to create on-screen electronic program guides and content advisories.
RGB: Primary Color Components of Red, Green and Blue
Resolution: A measure of the density of lines and dots per line which make up a visual image. Usually, the higher the numbers, the sharper and more detailed the picture will be. In terms of DTV, maximum resolution refers to the number of horizontal scanning lines multiplied by the total number of pixels per line.
Resonate: Modulate an incoming signal and send it to the ATSC decoder chip.
Reverse 3:2 Pull-Down: DTV material originating on film at 24 fps is converted to the 30 fps of DTV by repeating field or frames, resulting in some motion artifacts. Some film presentations remove these repeated images before transmission and send a signal to the television causing it to process (termed Reverse 3:2 Pull-Down) this material appropriately to make it suitable for
display. In this way, the displayed material closely matches the original film quality, avoiding the motion artifacts.
SDTV: "Standard Definition Television." SDTV are based on 480 lines of vertical resolution and may have either 4:3 or 16:9 aspect ratios, and surround sound. Several SDTV programs can be sent together to form the simulcast bundle. While SDTV pictures are of significantly better quality than NTSC, they are not up to the standard of HDTV. At a minimum, over-the-air SDTV offers a picture 640 pixels wide by 480 pixels high, totaling 307,200 pixels - about 50 percent more than today¡¯s analog TV.
Scanning Lines:
480i: ?The term for Analog TVs use of 480 lines, interlaced scanning at 30 frames (complete pictures) per second and a 4:3 aspect ratio screen.?
720 progressive (p): 1280 pixels per line and 720p lines per frame. HDTV also can be broadcast and displayed as a "progressive image" (720p), like a computer monitor, where a full frame fills the screen from top to bottom, eliminating lines altogether.
1080 interlaced (i): 1920 pixels per line and 1080i lines per frame with many DTVs, doubling the number of scanning lines.
Set-top box (STB): A box, similar to the familiar cable box, that is capable of receiving, decoding and sending to the associated television the picture and sound of the selected DTV broadcast. The use of an STB would allow the use of conventional televisions to receive DTB programs, but at reduced levels of resolution and with imperfections due to aspect ratio differences, leading to letterboxing or cropping of the sides of the picture.
Simulcast: The broadcast of the same program simultaneously over two or more different systems or channels, such as in HDTV and in NTSC. CRTC regulations require today that broadcasters simulcast much of their schedules.
SMPTE: "Society of Motion Picture and Television Engineers." A professional organization that is responsible for the standards for film and television production.
Standard-definition Television (SDTV): Digital TV can offer a second type of signal, SDTV. Its signals also deliver high-quality video and audio, occupies less space on the allocated spectrum than high-definition signals and give broadcasters the flexibility to multicast programming. This would include any display of digital transmissions, down converted to 480 line interlaced format (480i).
Stream: To send data on a network, such as the Internet, in such a way as to provide or simulate real-time delivery of video and/or audio.
S-Video Connection: A method to interconnect video devices (such as a DVD player and the analog television) by sending the two signals luminance (Y) and an encoded color difference signal (C). The S-Video connection is made using a cable terminated in a small 4-pin connector (in some cases a 7 pin connector is used on computers to allow inclusion of an NTSC composite signal). S-video can greatly improve the picture when connecting SDTV or NTSC displays to a high quality video source such as DVDs.
TCP/IP: ¡°Transmission Control Protocol/Internet Protocol." TCP/IP is the method most commonly used in the Internet to transfer data, including streaming video and audio, between computers.
Terrestrial: A broadcast signal transmitted "over the air" to an antenna.
Upconvert: The process which increases the number of pixels or frame rate used to represent an image by creating new pixels at closer spacing. For instance SDTV video having 720 x 480 pixels may be upconverted to 1280 x 720 pixels for use as HDTV. The upconversion process does not increase the resolution of image.
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.
VSB: ¡°Vestigial side band." VSB is an analog modulation technique used to reduce the amount of spectrum needed to transmit information through cable TV, or over-the-air broadcasts.
Wide Screen Format: HDTV provides for a wide screen presentation similar to what you see in movie theatres. The new screen has a width-to-height (or aspect) ratio of 16:9 compared to today¡¯s 4:3 width-to-height ratio on conventional television sets.
Y, PB, PR: A method for carrying the video between HDTV or SDTV devices that retains the maximum quality and is recommended for HD television. The video is carried on three cables, respectively carrying luminance (Y) and the two color difference signals (PB, PR). |
