A
AC-3 - Audio coding 3 (see Dolby Digital).
anamorphic downconversion - Processing present in all
DVD players that converts the image from an anamorphic
DVD for display on a regular 4:3 TV. In the initial setup
of a DVD player is a choice between a 16:9 or a 4:3 TV;
the 4:3 options engage this processing, which often introduces
artifacts such as jaggies and undulations during pans.
anamorphic squeeze - See vertical compression.
ANSI lumens - Light-output specification set in 1993 used
mainly to measure brightness of front-projection televisions;
more exact than undefined lumens. The average 7-inch, CRT
front-projection television is capable of between 150 and
175 ANSI lumens, while 9-inch CRT sets emit between 200
and 240. DLP and LCD projectors range from 600 to 7,000,
depending on the model.
artifact - Any abnormality in a video image; typically
results from digital processing, the interlaced-scanning
method, the conversion from one video format to another,
or signal transmission issues.
aspect ratio - The relationship between the width and
height of an image; the standard DTV wide-screen ratio
is 16:9 (1.78:1), as compared to the squarer NTSC ratio
of 4:3 (1.33:1).
B
black level - The intensity of black in the television
picture, frequently referred to as brightness; adjusted
to compensate for ambient room light. Black level is
set with a TV's brightness control using a PLUGE test
pattern.
broadcast flag - Copy-protection scheme for over-the-air
DTV broadcasts that restricts recording of "flagged" shows.
Blu-ray - Format for next-generation recordable HD DVD
that uses a shorter-wave blue laser and is supported by
most major DVD manufacturers. A single-sided, single-layer
disc can hold 25GB of data.
C
calibration - In televisions, the process of adjusting
a picture to comply with standards used in DVD and HDTV
production. More info
CEA - Consumer Electronics Association, the principal
industry association for companies that manufacture consumer
electronics.
chrominance - Technical name for the TV signal that carries
the color information (red, green, and blue) needed to
produce a color picture; often called chroma.
color temperature - Sometimes called white balance and
expressed in degrees kelvin or just Kelvins, this is the
color of gray at different levels from black to white.
comb filter - Component in all televisions that separates
the chrominance and luminance from one another in composite-video
connections.
component video - The elements that make up a video signal,
consisting of luminance and two separate chrominance signals,
expressed either as Y R-Y B-Y or Y Pb Pr. More info
composite video - Analog video signal that includes vertical
and horizontal synchronizing information. Since both luminance
and chrominance signals are encoded together, only a single
connection wire or jack is needed. More info
compression - Method of electronically reducing the number
of bits required to store or transmit data. The method
adopted for DTV is called MPEG-2. Four full-range channels
of programming and data can be compressed into the same
space required by a single analog channel.
contrast ratio - Difference between the brightest whites
and the darkest blacks a display can show. The higher the
contrast ratio, the greater the ability to show subtle
color details and tolerate ambient room light (for example).
Most contrast-ratio specs reported by manufacturers are
inflated.
CRT - cathode-ray tube, the original and still the most
common display technology for televisions. Invented in
1897 by German physicist Karl Ferdinand Braun, the tube
uses an electron beam to scan lines on the screen. It does
not have an exact resolution as a fixed-pixel display does.
D
Digital Cable Ready - Official term for an HDTV that conforms
to the plug-and-play digital cable TV standard using
POD (point of deployment) access cards, also called CableCARDs.
With cable systems that comply to the standard, users
can plug the cable directly into an HDTV set, then enjoy
HDTV and digital cable without having to use a separate
set-top box.
digital comb filter - Device that separates the luminance
and chrominance parts of a video signal in the digital
domain, which provides enhanced color purity and reduced
dot crawl over the analog variety.
direct view - Any television not based on projection technology.
Most often refers to standard CRT televisions, as opposed
to rear- or front-projection TVs.
DivX - MPEG-4-based compressed digital video format (or
codec) used for Internet distribution of movies; often
called the MP3 of video. DivX Networks is the name of the
company that sells DivX content and is not to be confused
with Circuit City's defunct Divx DVD format.
DLP - Digital light processing. A microdisplay technology
invented by Texas Instruments, DLP is based on a digital
micromirror device (DMD), a chip with millions of hinged,
microscopic mirrors attached, each of which corresponds
to a single pixel in the projected image.
Dolby Digital - Six-channel digital audio standard that
is part of the U.S. digital television standard; also called
AC-3 or Digital 5.1. The channels consist of front left,
front right, front center, surround or rear left, surround
or rear right, and a separate subwoofer (the .1).
downconvert - In DTV, the conversion from a higher-resolution
input signal number to a lower one. For example, some DTV
receivers can be set to downconvert an HDTV 1080i signal
to a standard 480i signal that any TV can display.
DRM - Digital Rights Management. General term that describes
a variety of technical and/or legislative efforts for securing
and protecting different forms of digital content for the
benefit of copyright holders.
DTCP - Digital Transmission Copy Protection. HDTV copy-protection
scheme more commonly called 5C.
DTV - Digital television. Generic term that refers to
all digital television formats, including high-definition
television (HDTV) and standard-definition television (SDTV).
DVI - Digital visual interface. Omnidirectional digital
connectivity standard that conveys an uncompressed digital
signal from a digital source, such as an ATSC tuner, to
a display. HDCP copy protection is often used in conjunction
with the DVI connection. DVI connections do not carry audio.
More info
DVR - Digital video recorder. A television recorder such
as Replay and TiVo that uses a hard drive, an EPG, and
internal processing to drastically simplify programmed
recording and playback of recorded programs. A DVR vastly
increases recording time compared to VCRs or DVD-recording
decks; often enables smart programming, in which the device
records an entire series or programming defined by keywords,
genre, or personnel; and offers pause control over "live" broadcasts.
Also called personal video recorder (PVR) or hard disk
video recorder.
E
EDTV - Enhanced Definition Television (see 480p). Also
used to describe plasma and other fixed-pixel displays
that have 852x480 resolution. They can show an HDTV image
but don't provide as much detail as higher-resolution
displays. More info
EPG - Electronic program guide. Feature found on satellite
and cable tuner boxes and DVRs, and increasingly on TVs
and DVD recorders, that provides an onscreen listing of
available channels and program data for an extended time
period (typically 36 hours or more).
F
FireWire - Bidirectional high-speed digital video/audio
and data interface technology adopted by the Institute
of Electrical and Electronics Engineers (IEEE). Sometimes
referred to as i.Link (Sony's name), DISH Wire (by Echostar),
and EIA-775.
fixed-pixel display - Digital televisions that use discrete
pixels to create a picture image, such as plasma, LCD,
DLP, LCoS, or any non-CRT display device. In the case of
DLP, for instance, each pixel is represented by one of
the hundreds of thousands of tiny mirrors mounted on a
DLP chip.
flat-panel TV - Video display typically using gas plasma
or LCD technology and that measures only a few inches thick.
fps - Frames per second. The number of individual still
pictures that pass by every second to create a moving image.
Film runs at 24fps, while video, including DVD, runs at
30fps. To compensate for the difference, 2:3 pull-down
detection is used.
front projection - Type of TV system in which the picture
is projected onto a reflective screen or even a wall. The
larger the picture, the more visible the pixels or scan
lines and the darker the image. CRT systems use three tubes
(red, blue, and green), whereas LCD and DLP uses a single
projection lens.
G
gain - Measures the light-reflecting ability of a projection
screen. The higher the number, the greater the amount
of light reflected back to the viewer.
ghosting - Multiple overlaid TV images noticeable around
the edges of objects; occurs when an antenna picks up the
original TV signal along with duplicate signals reflected
by tall buildings and other similar obstacles. DTV broadcasts
can suffer from ghosting, which is sometimes called multipath.
grayscale - Range of gray at different intensities from
completely black to completely white. Since color information
is overlaid atop black-and-white information in a composite,
S-Video, and component-video signal, the ideal is to set
the entire range of the grayscale as close to the standard
of 6,500K as possible to preserve color fidelity.
H
HDCP - High-bandwidth Digital Content Protection. Copy-protection
scheme developed by Intel to be used in conjunction with
DVI and HDMI connections.
HDMI - High-Definition Multimedia Interface. USB-like
digital video connectivity standard designed as a successor
to DVI; can transmit both uncompressed digital audio and
video signals; protected by HDCP digital copy protection.
HD-DVD - High-definition digital video disc. Several formats
have been proposed for these high-capacity DVDs, including
Blu-ray.
HDTV - High-definition television. High-resolution digital
television broadcast and playback system composed of roughly
a million or more pixels, 16:9 aspect-ratio screens, and
AC3 digital audio. A subset of digital television, HDTV
formats include 1080i and 720p resolution.
HDTV-ready - Used to describe any TV that can display
high-definition formats when connected to a separate HDTV
tuner or source. These TVs generally have built-in tuners
for receiving regular NTSC broadcasts, but not ATSC digital
broadcasts. The CEA's official term for an HDTV-ready TV
is HDTV monitor.
HDTV monitor - Official CEA term for HDTV-ready.
HDTV tuner - See DTV tuner
horizontal resolution - Number of vertical lines (or pixels)
that can be resolved from one side of an image to the other.
While the vertical resolution of all analog video sources
is the same (480 lines), the horizontal resolution varies
according to the source. Some examples for typical sources:
VHS VCRs (240 lines), analog TV broadcasts (330 lines),
non-HDTV digital satellite TV (up to 380 lines), and DVD
players (540 lines). DTV signals have horizontal resolution
that ranges from 640 lines for SDTV to 1,280 lines (for
720p HDTV) or 1,920 lines (for 1080i HDTV).
I
integrated HDTV tuner - The terrestrial ATSC high-definition
tuner built into an HDTV, it allows the set to receive
over-the-air HDTV broadcasts without having to attach
a set-top box.
Interactive Digital Cable Ready - See Digital Cable Ready.
interlaced scanning - Scan method used by the majority
of televisions and the 1080i HDTV format. As opposed to
progressive scanning in which the CRT's electron beam scans
or "paints" all lines at once, interlaced scanning
TVs paint odd-numbered lines in succession, then go back
and fill in the remaining even-numbered lines. This method
is more prone to artifacts and less stable than progressive.
J
jaggie - Type of video artifact that looks like a jagged
edge as opposed to a smooth line. It often appears on
diagonal lines in 30fps material.
K
keystone correction - Feature found in front projectors
designed to compensate for mounting situations when the
centerline of the projector's lens is not perpendicular
to the screen.
L
LCD - Liquid-crystal display. System used on many DTVs,
clocks, answering machines, handheld organizers, camcorders,
and personal computers. Liquid crystals are sandwiched
between two glass plates. Minor temperature variations
are introduced to particular points in the display using
pinpoint electric charges, illuminating or causing the
crystals to change colors in predetermined patterns.
LCD TV - A television that employs a liquid-crystal display
screen rather than a CRT; used in small, personal TVs,
portable video equipment, front projectors, and larger
flat-panel displays. An LCD projector uses a lamp to shine
light through liquid-crystal panels, then through mirrors
and lenses to the screen.
LCoS - Liquid Crystal on Silicon. Whereas LCDs uses liquid
crystals sandwiched between two glass plates, this newer
hybrid projection TV technology employs liquid crystals
coated on a silicon chip, which results in easier, lower-cost
manufacturing and higher-resolution images. More info
letterbox - A wide-screen movie on DVD, laserdisc, or
videotape presented in its original theatrical wide-screen
width on a standard square 4:3 TV. The film is shown with
black bars above and below the picture area to create the
wider, theatrical image. Often used to indicate a nonanamorphic
DVD.
line-doubler/tripler/multiplier - Technology used in televisions
to create a higher-quality picture by increasing the number
of lines of resolution displayed; it can be a separate
device or a feature built-in TVs, primarily DTVs. A poor-quality
line-doubler can actually degrade the image from lower-resolution
analog or digital signals.
lumens - The unit of measure for the light output of a
projector.
luminance - Portion of a television transmission that
controls brightness of the red, green, and blue proportions
in a television picture. The standard luminance setting
in a picture is 30 percent red, 60 percent green, and 10
percent blue. These numbers are adjusted to produce varying
colors, grays, whites, and blacks.
M
microdisplay - Type of fixed-pixel projection television
that uses a chip illuminated by a lamp to produce the
image--as opposed to projection technologies that use
CRTs. Examples include DLP, LCD, and LCoS rear-projection
HDTVs.
MPAA - Motion Picture Association of America. Industry
association for producers of motion pictures.
MPEG - Moving Pictures Experts Group. Pronounced EM-peg,
this group establishes standards in computerized digital
video compression and reproduction.
MPEG-2 - Moving Picture Experts Group-2. Video-compression
scheme used to condense digital video content for broadcast
over thin TV bandwidths or via the Internet, and to squeeze
full-length digital films onto a DVD.
MPEG-4 - Advanced compression scheme finalized October
1998, designed to enable transmission and reception of
high-quality audio and video over the Internet and next-generation
mobile telephones. Two major versions are MPEG-4 Simple
Profile for low-resolution digital video content, usually
for distribution over the Internet, and MPEG-4 AVC (Advanced
Video Coding), which offers faster and higher-quality compression
than MPEG-2 for HDTV content.
N
native resolution - The resolution at which a TV or monitor
is designed to display images. Image signals higher or
lower than a specified native resolution must be converted
to be displayed accurately. For example, a TV with a
native resolution of 1080i can display 1080i images but
may upconvert 480p images to 1080i. In contrast, a TV
with a native resolution of 480p must downconvert a 1080i
signal to 480p for display. CRT-based projection TVs
can have more than one native resolution, but fixed-pixel
displays such as LCD and DLP are limited to display one
resolution and convert all others. More info
NTSC - National Television Standards Committee. NTSC is
also the video-transmission standard used in the western
hemisphere, Japan, and other Asian countries. NTSC standards
are 525 lines of resolution transmitted within a 6MHz channel
at 30fps.
O
P
pan-and-scan - Process of transferring a movie or other
source material to videocassette, DVD, or broadcast so
that it fits the 4:3 aspect ratio of most current TVs.
This results in a significant amount of lost picture
information, particularly in the width of the image,
and sometimes involves panning unnaturally across the
frame. At the beginning of a movie, there is often a
disclaimer about the movie having been "...formatted
to fit your TV." That means it's been converted
to pan-and-scan. See also anamorphic.
pixel - Dots of color, sometimes composed of separate
red, green, and blue subpixels, that combine to create
an image; from the words picture element.
plasma - Display technology used in large-screen, flat-panel
TVs. Each plasma panel contains thousands of tiny tubes
that are like miniature fluorescent lights, filled by ionized
gas in a plasma state. When excited by electricity, the
tubes--which are backed by red, green, or blue phosphors--glow
in different colors and intensities to create an image.
More info
progressive scanning - Also called sequential scanning,
this is the antithesis of interlaced scanning used in broadcast
television, the process by which all odd and even scanning
lines are "painted" by an electron beam every
1/60 of a second. This method reduces flicker and increases
stability.
PVP - Personal video player. Portable device designed
to play back video files from a hard drive; may or may
not include a small LCD screen.
PVR - Personal video recorder. See DVR.
Q
R
rear projection - TV system where the picture is projected
onto the rear of a translucent screen via a series of
mirrors and viewed as you would an average television.
resolution - The sharpness of a video image, signal or
display, generally described either in terms of lines of
resolution, or pixels. Visible resolution depends on both
the resolution of the display and the resolution of the
video signal. Since video images are always rectangle-shaped,
they are described with both horizontal and vertical resolution.
RF jack - Radio frequency jack. Audio/video connection
commonly used to bring signals from antennas, cable systems,
and satellite dishes to components with some type of tuner,
such as cable boxes, cable modems, HDTV set-top boxes,
VCRs, satellite receivers, TVs, and so on. It can carry
video and stereo-audio information simultaneously. When
used to connect two components, such as a VCR and a TV,
RF provides the lowest video quality of any connection.
RF cable connectors usually screw or push onto the jack.
Also called F-type, 75-ohm, or coaxial connections.
S
scaler - Circuitry or device that converts a video signal
to a resolution other than its original format. Scaling
can involve upconversion or downconversion, and may also
include a conversion between progressive- and interlaced-scan
formats. A scaler can be built into a TV, an HDTV set-top
box, a DVD player, or another video source, or it may
be a standalone component.
SDTV - Standard-definition television. Digital television
format that includes 480-line resolution in both interlaced
(480i) and progressively scanned (480p) formats; offers
discernible improvement over conventional analog NTSC picture
resolution, with less noise; similar to DVD or satellite
TV quality but not considered high-definition television
(HDTV).
selectable aspect ratios - TV feature, especially on a
wide-screen and/or digital model, that allows the adjustment
of screen proportions for the material being viewed; an
image can be adjusted to fill the screen or to have blank
bands placed at the top and bottom of a wide-screen image,
or the left and right for a 4:3 image on a wide-screen
set. More info
selectable color temperature - Large-screen TV feature,
especially a high-end set, that allows the adjustment of
the color temperature. More info
service menu - Menu in televisions and some other electronics
gear that's normally accessible only by inputting a special
code. The service menu controls many parameters that, if
changed, could permanently damage the product, and damage
of this kind is usually not covered by the manufacturers'
warranty. More info.
set-top box (STB) - External receiver that converts broadcasts
(such as analog cable, digital cable, or DTV) for display
on a television. HDTV-ready TVs must be connected to a
compatible HDTV tuner set-top box in order to receive digital
television programs.
sidebars - See windowbox bars.
spatial artifact - A compression-induced DTV image imperfection
that occurs in a single field or frame when an image on
screen is not translated accurately; often results in fuzzy
or slanted edges, often on text. Similar to temporal artifacts,
both often referred to as mosquito noise.
S-Video - Common video connection that provides better
picture than composite by transmitting the luminance and
chrominance portions of a video signal separately. More
info
T
temporal artifact - In a digital video image, a picture
imperfection that occurs over several frames, often in
smooth-textured areas and around high-contrast edges
of moving video objects. Similar to spatial artifacts,
both often referred to as mosquito noise.
temporal resolution - One of two possible ways to measure
resolution in a video image; the other is spatial. Describes
the amount of picture detail in a moving image, measured
by the number of lines of resolution delivered over a given
period of time. When an image moves rapidly, a 720p HDTV
display will provide more picture information than a 1080i
HDTV display because progressive scan produces twice as
many frames in the same period of time as 1080i.
terrestrial broadcast - Standard over-the-air broadcasts,
as opposed to satellite or cable transmission.
U
upconvert - In DTV, the conversion from a lower-resolution
input signal to a TV capable of displaying higher resolutions,
such as from an SDTV 480p signal to an HDTV 1080i native
display.
V
vertical compression - Feature found on 4:3 TVs designed
to take advantage of the extra resolution in anamorphic
DVDs and other wide-screen content. Pioneered by Sony,
this feature squeezes the TV raster so that the electron
beam scans in a smaller area. It requires setting the
DVD player to 16:9 mode, eliminates anamorphic downconversion
artifacts, and ideally provides a 33 percent increase
in resolution in the letterboxed image.
vertical resolution - The number of horizontal lines (or
pixels) that can be resolved from the top of an image to
the bottom. (Think of hundreds of horizontal lines or dots
stacked on top of one another.) The vertical resolution
of the analog NTSC TV standard is 525 lines. Some lines
are used to carry other data such as closed-captioning
text, test signals, and so on, so we end up with about
480 lines in the final image. All of the typical NTSC sources,
including VHS VCRs, cable, and over-the-air broadcast TV
(analog), non-HD digital satellite TV, DVD players, camcorders,
and so forth, have a vertical resolution of 480 lines.
DTV signals have vertical resolution that ranges from 480
lines for SDTV, to 720 or 1,080 lines for HDTV.
W
wide-screen - Image with an aspect ratio greater than 1.33:1
or a picture wider and narrower than a standard television
image. Typically refers to TVs in the 16:9 aspect ratio.
windowbox bars - The blank bars on the left and right
of a 4:3 image when displayed on a wide-screen 16:9 display.
They can often be adjusted in intensity from black to gray;
gray bars help exercise CRT and plasma displays more evenly
across the screen. More info
X
Y
Y Pb Pr - Luminance, two chrominance channels of blue minus
luminance, red minus luminance. Technical shorthand for
component video.
Y Cb Cr - Luminance, two chrominance channels of blue
minus luminance, red minus luminance. Technical shorthand
for component video.
Y R-Y B-Y - Luminance, two chrominance channels of red
minus luminance, blue minus luminance. Technical shorthand
for component video.
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