A
Absorption: Reduction of acoustical energy usually by converting it
into heat via friction by using soft, fibrous materials.
Acoustic Suspension: A sealed speaker enclosure that uses the
air trapped in the cabinet as a reinforcing spring to help control the
motion of the woofer.
Active: Powered. An active cross-over is electrically powered and divides the line-level
signal prior to amplification. Active speakers includes an active crossover and built-in
amplifier.
Amplifier: A component that increases the level or gain of an audio signal.
Anamorphic: Process that horizontally condenses a 16:9 image into a 4:3 space,
preserving 25% more vertical resolution than letterboxing into the 4:3 space. For the signal
to appear correct geometrically, the display must either horizontally expand or vertically
squash the image. Used on about two or three promotional laser discs and many DVDs. Also
called Enhanced for widescreen or Enhanced for 16:9.
Aspect Ratio: The ratio of image width to image height. Common motion-picture ratios are
1.85:1 and 2.35:1. Television screens are usually 1.33:1 (also known as 4:3). HDTV is
1.78:1, or 16:9. When widescreen movies (films with aspect ratios wider than 1.33:1) are
displayed on 1.33:1 televisions, the image must be letterboxed, anamorphically squeezed, or
panned-and-scanned to fit the screen.
ATSC: Advanced Television Systems Committee. A government-directed committee that
developed our digital television transmission system.
B
Bandwidth: For audio, the range of frequencies a device operates within. For video, the
range of frequencies passed from the input to the output.
Black Level: Light level of the darker portions of a video image. A black level control sets
the light level of the darkest portion of the video signal to match that of the display's black
level capability. Black is, of course, the absence of light. CRT-based displays usually have
better black levels than DLP, plasma, and LCD, which rank, generally, in that order.
Brightness: In video, the overall light level of the entire image. A brightness control makes
an image brighter; however, when it is combined with a contrast, or white level control, the
brightness control is best used to define the black level of the image (see Black Level). In
audio, a sound referred to as bright has too much treble or high-frequency sound.
C
Cathode Ray Tube: (CRT) An analog display device that generates an image on a layer of
phosphors that are driven by an electron gun.
Center Channel: The center speaker in a home theater setup. Ideally placed within one or
two feet above or below the horizontal plane of the left and right speakers and above or
below the display device, unless placed behind a perforated projection screen. Placement is
important, as voices and many effects in a multichannel mix come from this speaker.
Channel: In components and systems, a channel is a separate signal path. A four-channel
amplifier has at least four separate inputs and four separate outputs.
Chrominance: (C) The color portion of a video signal.
Coaxial: 1) A speaker with typically one driver in the middle of, and on the same axis as,
another driver. 2) An audio or video cable with a single center pin that acts as the hot lead
and an outer shield that acts as the ground.
Codec: Mathematical algorithms used to compress large data signals into small spaces with
minimal perceived loss of information or data.
Component Video: A signal that is transmitted or recorded in its separate components.
Typically refers to Y/Pb/Pr, which consists of three 75-ohm channels: one for luminance
information, and two for color. Compared with an S-video signal, a Y/Pb/Pr signal carries
more color detail. HDTV, DVD, and DBS are component video sources, though most DBS
material is transcoded to component from composite signals.
Composite Video: A signal that contains both luminance and chrominance on the same
75-ohm cable. Used in nearly all consumer video devices. Chrominance is carried in a
3.58-mHz sideband and filtered out by the TV's notch or comb filter. Poor filtering can result
in dot crawl, hanging dots, or other image artifacts.
Contrast: The relative difference between the darkest and brightest parts of an image. A
contrast control adjusts the peak white level of a display device.
CRT: See Cathode Ray Tube.
D
Damping: Pertaining to the control of vibration by electrical or mechanical means.
Damping Material: Any material that absorbs sound waves and eliminates acoustic energy
by converting it into a different form. Fibrous material, for example, turns acoustic energy
into heat by way of friction.
DBS: Direct Broadcast Satellite. Replaces the term DSS to describe small-dish, digital
satellite systems such as DirecTV and Dish Network.
De-interlacing: The process of converting an interlaced-scan video signal (where each
frame is split into two sequential fields) to a progressive-scan signal (where each frame
remains whole). De-interlacers are found in digital TVs and progressive-scan DVD players.
More advanced de-interlacers include a feature called 3-2 pulldown processing. For TVs,
de-interlacing is often referred to as "line-doubling" or "upconversion."
Delay: The time difference between a sonic event and its perception at the listening position
(sound perception is delayed according to the distance it travels). People perceive
spaciousness by the delay between the arrival of direct and reflected sound (larger spaces
cause longer delays).
Diffusion: For audio, the scattering of sound waves, reducing the sense of localization. For
video, the scattering of light waves, reducing hot spotting, as in a diffusion screen.
Diffusor: Acoustical treatment device that preserves sound energy by reflecting it evenly in
multiple directions.
Digital Theater Systems: See DTS.
Direct-View Television: Display whose image is created on the viewing surface.
Distortion: Any undesired change in an audio signal between the input and the output.
DLP: Digital Light Processing. A process (developed by Texas Instruments) of projecting
video images using a light source reflecting off of an array of tens of thousands of
microscopic mirrors. Each mirror represents a pixel and reflects light toward the lens for
white and away from it for black, modulating in between for various shades of gray.
Three-chip versions use separate arrays for the red, green, and blue colors. Single-chip
arrays use a color-filter wheel that alternates each filter color in front of the mirror array at
appropriate intervals.
DMD: Digital Micromirror Device. Texas Instruments engine that powers DLP projectors. It
uses an array with tens of thousands of microscopic mirrors that reflect a light source toward
or away from the lens, creating an image. Each mirror represents a pixel. See DLP.
DTS: Digital Theater Systems. A digital sound recording format, originally developed for
theatrical film soundtracks. Records 5.1 discrete channels of audio onto a handful of laser
discs, CDs, and DVDs. Requires a player with DTS output connected to a DTS processor.
DTS ES: An enhanced version of the 5.1 DTS system. Like Dolby's Surround EX, a sixth
channel is added. In some cases (DTS ES Discrete), the sixth channel is discrete. Software
is backwards-compatible with 5.1 systems, but requires an ES or 6.1 processor to obtain
additional benefit. Neo:6 is a subset of DTS ES that creates 6.1 from material with fewer
original channels.
DTV: Digital Television. Umbrella term used for the ATSC system that will eventually replace
our NTSC system in 2006. HDTV is a subset of the DTV system. While the FCC does not
recognize specific scan rates in the adopted DTV system, typically accepted rates include
480i, 480p, 720p, and 1080i.
DVD: Officially known as the Digital Video Disc. DVD uses a 5-inch disc with anywhere from
4.5 Gb (single layer, single-sided) to 17 Gb storage capacity (double-layer, double sided). It
uses MPEG2 compression to encode 720:480p resolution, full-motion video and Dolby
Digital to encode 5.1 channels of discrete audio. The disc can also contain PCM, DTS, and
MPEG audio soundtracks and numerous other features. An audio-only version, DVD-A uses
MLP to encode six channels of 24-bit/96-kHz audio.
DVI: Digital Visual Interface. Connection standard developed by Intel for connecting
computers to digital monitors such as flat panels and DLP projectors. A consumer
electronics version, not necessarily compatible with the PC version, is used as a connection
standard for HDTV tuners and displays. Transmits an uncompressed digital signal to the
display. The latter version uses HDCP copy protection to prevent unauthorized copying. See
also HDMI.
E
EDTV: Extended Definition Television. Defined as those products that can display DTV
images as 480p or higher.
Efficiency Rating: Level of sound output measured at a prescribed distance with a
standard input power. Efficiency rating standard is 1 watt (2.83V at 8 ohms) at 1 meter over
a specified frequency range and is measured in decibels.
Enhanced for 16:9: See Anamorphic.
Enhanced for Widescreen: See Anamorphic.
F
Fiber Optic Cable: Glass, plastic, or hybrid fiber cable that transmits digital signals as
pulses of light.
FireWire: See IEEE 1394.
G
Gray Scale: The ability for a video display to reproduce a neutral image color with a given
input at various levels of intensity.
H
Hanging Dots: An artifact of composite video signals that appears as a stationary,
zipper-like, horizontal border between colors.
HDCP: High-Bandwidth Digital Content Protection. Created by Intel, HDCP is used with HDTV
signals over DVI and HDMI connections and on D-Theater D-VHS recordings to prevent
unauthorized duplication of copywrite material.
HDR: Hard-Drive Recorder. Device that uses a computer hard drive to store compressed
digital audio and video signals.
HDMI: HDTV connection format that uses a DVI interface that transfers uncompressed
digital video with HDCP copy protection and multichannel audio.
HDTV: High-Definition Television. The high-resolution subset of our DTV system. The ATSC
defines HDTV as a 16:9 image with twice the horizontal and vertical resolution of our existing
system, accompanied by 5.1 channels of Dolby Digital audio. The CEA defines HDTV as an
image with 720 progressive or 1080 interlaced active (top to bottom) scan lines. 1280:720p
and 1920:1080i are typically accepted as high-definition scan rates.
H-Sync: Horizontal Sync. Number of times per second that the projector can trace a line of
pixels from side to side. Measured in hertz (Hz).
High Gain Screen: Material that reflects more light than a reference material. Increases a
projector's light output at the expense of uniformity.
I
IEEE 1394: Networking standard for PCs. It is used as a two-way connection to transfer the
MPEG-compressed digital bitstreams between consumer electronics items, including HDTV
tuners and displays, D-VHS recorders, DVD players, and DBS receivers. Also called
FireWire, iLink, É
iLink: See IEEE 1394.
Interconnects: Any cable or wire running between two pieces of A/V equipment. (i.e. RCA
cables connecting a receiver and speakers).
Interlace: The process of alternating scan lines to create a perceived complete image. In
CRT displays, every second field/frame is scanned between the first field/frame. The first
field represents the odd lines; the second field represents the even lines. The fields are
aligned and timed so that, with a still image, the human eye blurs the two fields together and
sees them as one. Interlace scanning allows only half the lines to be transmitted and
presented at any given moment. A 1080i HD signal transmits and displays only 540 lines per
60th of a second. 480i NTSC transmits and displays only 240 lines per 60th of a second.
Motion in the image can make the fields noticeable. Interlaced images have motion artifacts
when two fields don't match to create the complete frame, often most noticeable in
film-based material.
K
Keystone: A form of video image distortion in which the top of the picture is wider than the
bottom, or the left is taller than the right, or vice versa. The image is shaped like a trapezoid
rather than a rectangle.
L
LCD: Liquid Crystal Display. A display that consists of two polarizing transparent panels and
a liquid crystal surface in between. Voltage is applied to certain areas, causing the crystal to
turn dark. A light source behind the panel transmits through transparent crystals and is
mostly blocked by dark crystals.
LCOS: Liquid Crystal on Silicon
Letterbox: Format used widely on laser disc and many DVDs to fit wide-aspect-ratio movies
(1.85:1 and 2.35:1, for example) into a smaller frame, such as the 1.78:1 area of an
anamorphic DVD or the 1.33:1 area of a laser disc or video tape. The image is shrunk to fit
the screen, leaving blank space on the top and bottom. This process sacrifices some vertical
detail that must be used to record the black bars.
Luminance: The black and white (Y) portion of a composite, Y/C, or Y/Pb/Pr video signal.
The luminance channel carries the details of a video signal. The color channel is laid on top
of the luminance signal when creating a picture. Having a separate luminance channel
ensures compatibility with black-and-white televisions.
M
Mono: Monophonic sound. One channel.
Multiple-Rate Encoding: Instead of locking encoding at a certain constant data rate, it
allows the codec to choose whatever rate is best for that portion of the recording. It usually
reduces file size with proportionally less loss in quality.
Multisource: System with multiple sources. Can also be used to describe a receiver that
can provide multiple different sources into different rooms.
Multiroom: System that provides audio or video to multiple areas. Usually with only one
source.
Multizone: System that provides different sources into multiple areas simultaneously.
N
Negative Gain Screen: Material that reflects less light than a reference material. Often
used for DLP and LCD projection.
Noise: An unwanted portion of a signal such as static, hum, hiss or buzzing.
NTSC: National Television Standards Committee. A government-directed committee that
established the U.S. color TV standard in 1953.
O
Optical Digital Cable: Fiber optic cable that transfers digital audio signals as pulses of light.
P
Passive: Not active. A passive crossover uses no external power and results in insertion
loss. A passive speaker is without internal amplification.
Pixel: The smallest element of data in a video image.
Pixel Pitch: A measurement of distance between pixels on the screen, measured in
millimeters (mm). A smaller pixel pitch means sharper images.
Plasma: Flat-panel display technology that ignites small gas pockets to light phosphors.
Port: An aperture in a loudspeaker enclosure that helps to extend the usable low-frequency
output. A ported enclosure is also called vented or bass reflex.
Power Output: A measure, usually in watts, of how much energy is modulated by a
component.
Progressive Scanning: Each frame of a video image is scanned complete, from top to
bottom, not interlaced. For example, 480p means that each image frame is made of 480
horizontal lines drawn vertically. It requires more bandwidth (twice as much vertical
information) and a faster horizontal scan frequency than interlaced images of the same
resolution. Computer images are all progressively scanned.
Projection System: Display that projects an image onto a screen.
R
RCA Jacks: Also called phono-type connectors. Receptacles for coaxial cables carrying
line-level audio signals.
Rear-Projection Television: Display that projects an image on the backside of a screen
material, usually being reflected off of a mirror.
Receiver: Any component that receives, or tunes, broadcast signals, be it NTSC, HDTV,
DBS, or AM/FM radio. Typically refers to the single component that includes a preamp,
surround processor, multichannel amplifier, and AM/FM tuner.
RF: Radio Frequency. Television signals are modulated onto RF signals and are then
demodulated by your television's tuner. VCRs and DBS receivers often include channel 3 or
4 modulators, which allows the output signal to be tuned by the television on those channels.
RGB: Red, Green, Blue. Refers to an unprocessed video signal or the color points of a
display device. Together these three colors make up every color seen on a display device.
RPTV: Rear-Projection Television
S
Scan Lines: The lines drawn by an electron gun in a CRT system to create the picture.
Drawn horizontally, from left to right, starting at the top left and working to the bottom right.
SDTV: Standard Definition Television. Lower resolution subset of the ATSC's DTV system.
480i is typically accepted as an SD signal. Digital broadcasters can offer multiple
sub-programs at SDTV quality, as opposed to one or two HD programs.
Source: A component from which the system's signals originate, such as DVD players,
AM/FM tuners, and VCRs.
S-Video: See Y/C.
T
3:2 Pulldown Recognition or 3:2 Inverse Telecine: Film is usually recorded at 24 frames
per second. NTSC video (North America) is 30 frames (60 fields) per second. To get smooth
motion, the film frames are broken into video fields in a 3-2-3 sequence. 3 fields for the first
film frame, 2 fields for the second film frame, and so on. If a line doubler doesn't compensate
for the extra field during playback on a progressive-scan display, the image will have
noticeable motion artifacts. A line doubler with 3:2 pulldown recognition or 3:2 inverse
telecine can see this sequence in the signal and correct for it by making sure the last field in
the first frame isn't mixed with the first field of the second frame.
Throw Distance: Measure of the size of the image a projector can produce from a given
distance. Use of a manufacturer's "projector calculator" will aid in determining proper
distance for the desired image.
U
Uniformity: Even distribution across a given space. In video, uniformity can refer to the
distribution of light (hot spotting) or color.
Unity Gain: Output equals the input. Unity gain screen material reflects as much light as the
reference material. Has an even dispersion of light.
Universal Remote: Remote that has the commands of various brands stored into memory
and can control several different devices simultaneously.
V
Volt: The unit of electrical potential, or difference in electrical pressure, expressing the
difference between two electrical charges.
V-Sync: Vertical Sync. Number of times per second that the projector can trace a line of
pixels from top to bottom. Measured in hertz (Hz).
W
Watt: A unit of power or energy.
X
X-curve: An intentional roll-off in a theatrical system's playback response above ~2kHz at
3dB per octave. A modern convention specified in ISO Bulletin 2969, it is measured at the
rerecording position in a dubbing stage or two-thirds of the way back in a movie theater. Pink
noise should measure flat to 2kHz and then should roll-off above that. Home THX processors
add this roll-off, when engaged, so that a home video soundtrack will have the same
response as it would in a theatrical setting.
Y
Y/C: Abbreviation for luminance/ chrominance, a.k.a. S-video signal. Color and detail signals
are kept separate, thus preventing composite video artifacts. The cable uses a four-pin
connector, and is used with S-VHS VCRs, DVD players, Hi-8, and DBS receivers.
Y/Pb/Pr: See component video.
Z
Zone: One or more rooms powered by one or more amplifiers, which are all fed by one
source. A home can be divided into multiple zones, which can play multiple sources, even
though several rooms all play the same source.
