To help you better understand KQED's transition to digital technology, here are some terms you may be seeing in the coming months.
Advanced Digital Television (ATV):
The FCC's original name for Digital Television (DTV).
Advanced
Television Systems Committee (ATSC): The current digital United States television standards
(HD, SD and Data).
Analog:
The technology in use for more than 50 years to transmit conventional TV signals. Vinyl recordings and audio cassettes are also examples of analog technology.
Aspect Ratio:
The ratio of screen width to screen height. For HDTV, the aspect ratio is 16:9 (16 units wide by 9 units high), much like a movie screen. Today's analog television screens are 4:3, or nearly square.
Back Channel: A means of communication from users back to content
providers. At the same time that content providers are
transmitting interactive television (analog or digital)
to users, users can connect through a back channel to
a Web site - for example, to the original content provider
or an advertiser. The back channel can be used to provide
feedback, purchase goods and services, request more information,
play games and so on. A simple type of back channel is
an Internet connection using a modem.
Bandwidth: The amount of spectrum available to each communications
licensee. For digital conversion, the FCC has allocated
6 MHz (megahertz) of the broadcast spectrum for each television
broadcaster. That channel will carry 19.4 Mb/s of data.
It can be used for one HDTV signal, or four multicast
digital signals, and/or data transmission.
Channel: As in television channel; the television broadcast
frequency. The over-the-air television channel assignments
are set by the FCC and are currently found in the VHF
or UHF band. Each television broadcast station is being
assigned a matching channel for DTV.
The DTV Channel assignment is different than the channel
currently being used by the analog station. KQED's assigned
DTV channel is 30. However, KQED transmits its "virtual
ID," which designates the channel as 9.1, 9.2, etc.
During the transition period, scheduled to end
2/17/2009, U.S. television stations will be able
to broadcast on their current channel and their new DTV
frequency. At the end of the transition, the stations
will broadcast only their DTV signal.
Datacasting: The broadcast of information services through
a television channel. Because digital broadcasters can
send more data over the airwaves, viewers get a lot more
than just television. Broadcasters can use their bandwidth
to offer additional data or services.
For example, a travel
program might be transmitted along with data consisting
of lodging, sightseeing and transportation information,
which the viewer can access while watching the program.
Teachers will be able to access lesson plans and learning
materials while watching TV. This information might appear
as a menu of choices on the TV or computer screen, which
the viewer can read on the screen, store on a hard drive,
or print out for future reference.
One of the major benefits of a digital broadcast
system is the ability not only to send pictures and sound,
but also to send data. Program related data enhances the
television show you are currently watching. For instance,
Real Science could include science quizzes for teachers,
periodic table graphs, a molecule building game, audio
clips of various animal vocalizations, or anything else
you can imagine that can be transmitted digitally.
Descriptive Video Information (DVI): Some programs provide an additional narration,
which enables visually impaired persons to hear enriched
verbal descriptions of the action being seen on the program.
Most TVs and VCRs require that you select the SAP channel
in order to receive DVI. DVI used to be called DVS.
Digital Television (DTV): Refers to transmitting a broadcast signal by encoding
it as 0s and 1s - the digital binary code used in computers.
DTV can provide high quality programming (HDTV) or provide
four, five or more channels in the same bandwidth required
for one channel of the current analog television. Calculators,
computers, compact discs and the Internet are examples
of digital technology.
Digital TV Tuner: The receiver or tuning part of a TV set. May be sold separately.
Display: The picture part of a Digital TV set. May be sold separately.
Federal Communications Commission (FCC): Independent US government agency, directly responsible
to Congress and charged with regulating local, interstate
and international communications by radio, television,
wire, satellite and cable. The FCC's jurisdiction covers
the 50 states, the District of Columbia, and U.S. Possessions.
Flat Screen Display: Television screens that flatten the shape of television
sets to that of a framed picture. The screens on yesterday's
television sets use bulky cathode ray tubes (CRTs). CRTs
are made of a glass envelope and use a controlled beam
of electrons striking light-emitting material to display
the picture. Flat screen displays use plasma display systems
or LCD displays.
High Definition Television (HDTV): Offers approximately twice the vertical and horizontal
resolution (clarity) of NTSC television. Provides crystal-clear
widescreen pictures with compact disc-quality surround
sound. The aspect ratio of HDTV pictures is 16:9, similar
to a movie screen's dimensions, as opposed to the 4:3
format of today's television. HDTV approaches movie theater
display quality. The HDTV standard can also use 5.1 channels
of CD-quality sound plus additional SAP channels.
Interactive
Television: A combination of television with interactive content
and enhancements. Interactive television provides better,
richer entertainment and information, blending traditional
TV-watching with the interactivity of a personal computer.
Programming can include graphics, one-click access to
Web sites through TV crossover links, electronic mail
and chats, and online commerce through a back channel.
Some applications may be displayed on TVs, others on computers.
Interlaced: A system which skips every other line of a picture
on the first pass, then fills in those lines on the second
pass. When talking about resolution, this method is indicated
by an "i" after the number of lines, as in "480i" or "1080i".
When you watch analog television, you're looking at an
interlaced video display. Because early television tubes
couldn't draw the whole screen before the top began to
fade, TV engineers implemented interlacing. On some digital
TVs, as on computer monitors, the whole screen is "progressive"
(drawn line by line, top to bottom).
Letterbox: When a widescreen picture is viewed on a 4:3 TV
screen, a black border may appear at the top and bottom
of the screen creating a "letterbox" effect, but allowing
the viewer to see the whole width of the wide-screen image.
For example, this allows movies to be broadcast as originally
formatted for theaters, allowing the viewer to see the
image as originally produced, rather than a cropped or
"panned and scanned" version (techniques used to downsize
an image to fit a 4:3 screen).
Multicasting: Broadcasting several DTV programs at once on a
single channel. A KQED-DT viewer might be able to receive
Sesame Street and Nova at the same time, and choose the
program s/he prefers by selecting that "channel"
from our digital bouquet.
National Television Systems Committee (NTSC):
The group that set the analog television standard 50 years ago. The abbreviation is used to refer to the current US standard.
Near Video On Demand (NVOD): Usually describes a service where a provider (e.g.
cable company) starts the same movie at closely staggered
times (e.g. 9pm, 9:05pm, 9:10pm, etc.), so that a viewer
who wants to see the movie need wait only a few minutes
at most to see it.
Nonlinear
Editing: Nonlinear distinguishes editing operation from
the "linear" methods used with tape. Nonlinear refers
to not having to edit material in the sequence of the
final program and does not involve copying to make edits.
It allows any part of the program to be accessed and modified
without having to recopy the material that is already
edited. Nonlinear editing is also nondestructive, as it
uses computer hard disks to play this material in the
random access order the editor has selected rather than
playing a linear videotape.
Offline
Editing: A decision-making process using low-cost equipment
to produce a rough cut "edit decision list," which can
then be used to make the high quality final version of
the program.
Personal Video Recorder (PVR): STB which records programs onto an internal hard-drive
to be played back at viewer's convenience (e.g. TiVo system
or ReplayTV).
Pixel: A shortened version of "picture element," the
smallest element in a television picture. The total number
of pixels limits the detail that can be seen on a television.
A typical television set has the equivalent of less than
half a million pixels. The pixel count for HDTV is over
two million.
Plasma Monitor:
Flat screen display technology. Most susceptible of the flat screens to having frequent images
(e.g. picture frame edges and white logos) becoming "burned into" the display.
Program
and System Information Protocol (PSIP):
A DTV-required signal which contains various lists of information needed by the receiver.
The signal is transmitted from the program supplier (network, station, or cable system) to the viewer's
receiver or STB. The signal contains information for the TV set about where to find the program
(e.g. telling the set that channel 9.2 really comes from DTV channel 30).
The PSIP signal also announces the content of present and future programs for the viewer including:
program titles and promotional material, duration of the programs, and time of day.
PSIP also helps the TV set know about the contents of the signal (e.g. closed captioning, type of audio,
where to find the program within the channel).
Progressive Scanning: The ability of most computer monitors and high
resolution sets to display all the lines of a picture
at the same time. When talking about resolution, this
method is indicated by indicated by a "p" after the number
of lines, as in "720p".
Resolution: A measure of the finest detail that can be seen,
or resolved, in a reproduced image. While influenced by
the number of pixels in an image (for HDTV 1920 x 1080;
current broadcast NTSC TV 640 x 480), the pixel numbers
do not define ultimate resolution but merely the resolution
of that part of the system. The quality of lenses, display
tubes, film process and film scanners, etc., used to produce
the image on the screen must all be taken into account.
Secondary Audio Programming (SAP):
Options offered on some programs accommodated by recent TVs and VCRs, including sound with
video description for the vision impaired, a director's narration, foreign language narration,
or other possible services. May be called MTS (Multi-channel TV Sound) or 2nd Channel Sound on some sets.
Server (file): A storage system that provides data files to all
connected users of a local network. Typically the file
server is a computer with large disk storage which is
able to record or send files as requested by the other
connected (client) computers. The file server often appears
as another disk on client systems. The data files are
typically around a few kilobytes in size and are expected
to be delivered within moments of request.
Server (video):
A storage system that provides audio and video storage for a network of clients. While there are some
analog systems based on optical disks, most used in professional and broadcast applications are based
on digital disk storage.
Aside from those used for video on demand (VOD), video servers are applied
in three areas of television operation: transmission, post production and news.
Compared to general purpose file servers, video severs must handle far more data, files are larger and
must be continuously delivered. Store sizes are very large, typically up to 500 gigabytes or more.
Set-Top
Box (STB):
A box which decodes or otherwise translates the signals coming to it so they can be used by the
customer's TV set.
The set top box may provide functionality of translating
HD signals to analog, may allow interactivity, may allow
tuning of other channels, may allow reception of VOD,
reception of pay-per-view channels, may contain a hard-disc
to provide storage of data or time-shifting of programs
(e.g. PVRs). The STB may contain a modem for connection
via telephone line for ordering services or other upstream
communication.
Simulcast: To broadcast the same program over two different
transmission systems at the same time. Currently, some
AM and FM radio stations simulcast the same program for
part of the day. The FCC plans to have mandatory simulcast
of analog programming over the new DTV system. This requirement
should speed the transition to DTV.
Standard
Definition Television (SDTV): A digital television system that is similar to
current standards in picture resolution and aspect ratio.
The picture and sound quality will be clearer than NTSC.
It offers the ability to transmit four or more standard-quality
programs at once (equivalent to NTSC), using the digital
channel. SDTV also incorporates stereo sound plus a wide
range of data services.
Stream:
1. To transmit multimedia files that begin playing upon arrival of the first packets, without needing to wait for all the data to arrive. 2. To send data in such a way as to simulate real-time delivery of multimedia.
Video On Demand (VOD): A service which allows viewers to receive and
play programs (usually movies) at their convenience from
cable. May allow viewer to stop, pause, play, rewind,
etc.
Widescreen: Term given to picture displays that have a wider
aspect ratio than normal. Historically, TV's normal aspect
ratio is 4:3 and widescreen is 16:9. Although this is
the aspect ratio used by HDTV, widescreen is also used
with normal definition systems.
Widescreen
SD Programs:
Term used by PBS to denote programs produced in the widescreen aspect
of 16:9, but not broadcast in HDTV.
If you would like to receive twice-monthly email updates about upcoming programs, along with occasional
alerts regarding KQED's continuing conversion, visit our
Newsletters Subscriptions page, and sign up for HDTV Alerts.
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