Glossary of Terms for DTV and
Aspect ratio of traditional NTSC TV screens, with 4 unit width by 3 unit height.
Aspect ratio of widescreen DTV formats for all HDTV and some SDTV (Standard Definition)
content, 16 unit width by to 9 unit height.
Acronym for the transmission method used for over-the-air DTV broadcasting in Canada and
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 in Canada. 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
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
downconvert them to a lower resolution prior to display.
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
the squeezing horizontally of a 16:9 image into a full screen 4:3 display, resulting in
distortion of the image geometry.
Artefacts: Unwanted visible effects in the picture created by errors
in the video processing or noise/interference in analog circuits. Common artefacts 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. upconverted 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.
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 by Industry Canada. 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).
Cable Modem: A data modem that provides an Internet connection
over the TV cable network. Video-on-demand or interactive services may require such a
CDTV: Canadian Digital Television, a not-for-profit,
government-approved body, with members from all sectors of the TV industry. CDTV is
mandated to advise its members, Industry Canada and the CRTC on the roll out of DTV in
CEMA: Consumer Electronics Manufacturers Association. A U.S. industry
group representing manufacturers of consumer electronics products
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.
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
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
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. The DTV broadcasting standard
for Canada, uses the MPEG-2 video and the AC-3 audio compression coding. Compression
allows the delivery of more programs in a single channel.
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.
CRTC: Canadian Radio-television and Telecommunications Commission, the
federal regulatory body for television programming and broadcasting in Canada.
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.
(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 (Dolby AC-3): The 5.1 channel audio standard for DTV
and HDTV in Canada and the USA. It includes six discreet audio channels: Left, Center,
Right, Left Surround (or side), Right Surround (or side), and a subwoofer -- LFE,
"low frequency effects" -- (considered the ".1" as it is limited in
bandwidth). Many televisions process these six channels into a two channel stereo pair and
do not provide the full 5.1 channel surround sound.
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. In Canada, Bell ExpressVu and Star Choice provide DTH services
in both HDTV and SDTV.
"Digital television." This comprises all the components of digital television,
including HDTV, SDTV, datacasting, and multicasting, falling under the standards
established by the ATSC.
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 DVDs.
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, DVDs 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
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
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. In Canada
both analog and digital television transmits 30 Fps.
HDTV: High Definition Television: HDTV is a TV system having approximately
twice the vertical and horizontal picture resolution of today's NTSC TV and having a wide
aspect ratio of 16:9. Two HDTV formats are currently in use; (a) 1920 pixels per line and
1080i lines per frame and (b) 1280 pixels per line and 720p lines per frame. HDTV can be
recognised by its spectacular picture resolution, freedom from annoying artefacts and
impressive 5.1 channel surround sound.
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. 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
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
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.
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.
Multichannel, Multipoint Distribution System. A wireless cable system capable of being
encoded for pay-per-view and subscriber services.
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 in
the U.S and Canada.
Multicasting: Term given to the sharing of the digital
television channel among 2, 3, 4 or more individual programs and/or data services
National Television Systems Committee. The organisation that created the standards for
production and broadcasting of analog color television programming in Canada and the
United States. 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.
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.
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 artefacts, appearing more life-like. Some display types,
such as LCD, plasma and DLP are inherently of the progressive scan type, while CRTs
may be scanned progressively (as in computer monitors) or interlaced.
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.
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.
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
artefacts. 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 artefacts.
"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 are 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.
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.
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.
" Transmission Control Protocol/Internet Protocol." TCP/IP is the method most
commonly used in the Internet to transfer data, including streaming video and audio,
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.
" 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
Widescreen: see 16:9
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).