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Audio Visual Terms:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Absorption
Reduction of acoustical energy usually by converting it into heat via friction
using soft, fibrous materials.
Acoustical balance
A sound system which is fine-tuned
for optimum reproduction, taking into account the acoustical characteristics of the
presentation site.
Active Matrix
A common type of LCD used in laptops, cameras, and
LCD projection panels that were produced in the late 1980's to early 1990's. Another
name for it is thin-film transistor (TFT). A typical active matrix TFT display is
a single panel of LCD glass that controls all three primary colours. TFT displays
are noted for their quick response time and their ability to display full motion
video and animations without image ghosting.
Aliasing
(1) Aliasing occurs when smooth
curves and lines become rough or jagged because of a lower Resolution device, or
by an event.
(2) In analogue video, aliasing is typically caused by interference between
the luma and chroma frequencies or between the chroma and field scanning frequencies.
It appears as a moiré or herringbone pattern, straight lines that become wavy, or
rainbow colours.
(3) In digital video, insufficient sampling or poor filtering of
the signal causes aliasing. Defects typically appear as jagged edges on diagonal
lines and twinkling or brightening in picture detail.
Ambient Light
Light within the
room or space coming from non-projector related Sources (windows, overhead lights…etc.).
The higher the Ambient Light present, the higher ANSI Lumen rated projector needed
Analogue
A
method of transmitting information by a continuous but varying signal, rather than
discrete (or digital) impulses.
Anamorphic Lens A lens that has the ability to convert
native Aspect Ratio of a projector to 16:9 Aspect Ratio.
Anechoic
The state of being
entirely free of echoes, and incapable of producing echoes. A term applied to headsets
and headphones, as well as chambers used to check the sensitivity of microphones.
ANSI
An
acronym for American National Standards Institute, which denotes the measurement
standard for lamp brightness. The higher the application's Ambient Light, and/or
the larger the screen, the higher the ANSI Lumens required.
Artifacts
Artifacts are
visible corruption of the image or undesirable elements or defects in a video picture.
These may occur naturally in the video process but must be eliminated to produce
a high quality picture. The most common reasons for video artifacts are cross colour
and cross luma.
Aspect Ratio
The ratio of image width to image height. Standard TV
is normally 4:3. Widescreen displays are 1.78:1 or 16:9.
Auto Source
The ability of
the projector to automatically recognize and synchronize to the horizontal and vertical
scan frequencies of an input signal for proper display.
Balanced Input
A connection with three conductors: two identical signal conductors
that are 180 degrees out of phase with each other, and one ground. This type of connection
is very resistant to line noise.
Bandwidth
The speed at which data can be sent across
a network. LANs usually run at 10 or 100 million packets per second, which means
that the data can be transferred at up to 100 million packets per second. A WAN usually
transfers data at up to 1.5 to 45 million packets per second, but can go much faster.
Bass
Low
frequencies; those below approximately 200 Hz.
Bi-Directional
A microphone which accepts
sound waves from two directions while deflecting sound from any other direction
Black
level
More commonly referred to as "brightness", the black level is the level of light
produced on a video screen. The level of a picture signal corresponding to the maximum
limit of black peaks. The bottom portion of the video wave form, which contains the
sync, blanking and control signals. The black level is set by the "brightness" control.
BNC
Bayonet
Neill-Concelman. A cable connector used extensively in television and named for its
inventor. A cylindrical bayonet connector that operates with a twist-locking motion.
To make the connection, align the two curved grooves in the collar of the male connector
with the two projections on the outside of the female collar, push and twist. This
allows the connector to lock into place without the need for tools.
Brightness
For
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). For audio, something referred to as bright has too much treble or high-frequency
sound.
Buffer
Generally referred to as a unity gain amplifier used to isolate the source
from the load. This is for both digital and analogue signals.
Burn-In
Static, non-moving
images left on-screen for extended periods of time can leave a "shadow" on plasma
& projection displays known as "burn-in"
TV channels that have a static logo permanently
on screen have a real negative effect on plasma TV’s. Pixels begin to memorise these
images, upon switching channels you will still see the logo in the form of a shadow.
There
are different types and levels of burn in. The most severe of which occurs in the
first 200 hrs of the panel's life when pixels are at there most excitable. In this
time frame pixels can permanently memorise static images that have been left on screen
for prolonged periods.
Cache
A small amount of relatively high-speed storage, which is used as an intermediary
between the data user and a larger, slower storage device (the backing store).
Capacitor
or Condenser Microphone
A microphone with a conductive diaphragm that varies a high-voltage
electromagnetic field to generate a signal. Requires a miniaturized amplifier and
power supply.
Cardioid microphone
A microphone whose heart-shaped pickup pattern is
sensitive to sounds coming from the front and sides of the microphone, while deflecting
sounds from the rear of the microphone
Cathode Ray Tube (CRT)
Analogue display device
that generates an image on a layer of phosphors that are driven by an electron gun.
CATV
1.
Community antenna television.
2. Cable television.
CCTV
Closed circuit television. A
distribution system which Emits reception of an image to those receivers which are
directly connected to the origination point by coaxial cable or microwave link.
Ceramic
Microphone
A microphone which uses a piezoelectric element to generate voltage when
the element is deflected by sound.
Centre Channel
The enter speaker in a home theatre
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 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.
Coaxial
1) A speaker typically with one driver in the middle
of, and on the same axis as, another driver. 2) An audio or video cable with a single
enter pin that acts as the hot lead and an outer shield that acts as a ground
Colour
Temperature
The colouration (reddish, white, bluish, greenish, etc) of white in an
image, measured using the Kelvin temperature scale. Higher temperatures output more
light.
Component Video
Component Video is a type of analogue video information that
is transmitted or stored as two or more separate signals (red, green, blue). Component
Video can be contrasted with Composite video in which all the video information is
combined into a single signal such as a TV broadcast. Currently, Component Video
connections are gradually being superseded by the higher quality digital DVI and
HDMI interface.
Composite video
An all-in-one video signal - technically, the lowest
video quality but much can go wrong with component types making them worse in reality.
Contrast
Ratio
The measurement of the difference in light intensity between the brightest white
and the darkest black. The higher the Contrast Ratio, the better the information
will appear against a darker background.
Convergance
The alignment of the Red, Green
and Blue video on a projector display.
Decibel (dB)
A logarithmic measurement unit that describes a sound's relative loudness,
though it can also be used to describe the relative difference between two power
levels. A decibel is one tenth of a Bel. In sound, decibels generally measure a scale
from 0 (the threshold of hearing) to 120-140 dB (the threshold of pain). A 3dB difference
equates to a doubling of power. A 10dB difference is required to double the subjective
volume. A 1dB difference over a broad frequency range is noticeable to most people,
while a 0.2dB difference can affect the subjective impression of a sound.
Decoder
A
device used to separate the RGBS (red, green, blue and sync) signals from a Composite
video signal.
Display Resolution
fixed-pixel-array displays such as flat-panel plasmas
(PDPs), LCDs, front and rear projectors using LCD, DLP or similar technologies and
is simply the physical number of columns and rows of pixels creating the display
(eg, 852x480; 1368x768 etc). A consequence of having a fixed grid display is that
for multiformat video inputs all displays need a "scaling-engine" (a digital video
processor that includes a memory array) to match the incoming picture format to the
display.
DLP
Digital Light Processing. A Texas Instruments process 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 grey. Three-chip
versions use separate arrays for the red, green, and blue colours. Single-chip arrays
use a colour-filter wheel that alternates each filter colour in front of the mirror
array at appropriate intervals.
DMD
Digital Micromirror Device. Texas Instruments engine
that powers DLP projectors. 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.
DVD
Digital Versatile Disc. Same physical size as a compact
disc but has a capacity to hold a minimum of 4.7GB of data, 9.4GB if dual layer and/or
dual sided. DVD-Video discs can hold about 4 hours of video on a dual layer disc
depending upon the amount of compression applied. It uses MPEG-2 compression at a
maximum rate of 9.2 Mbps with most video compressed at about 4Mbps at 720x480 pixels.
All players support AC-3 (Dolby Digital), PCM, and MPEG-2 audio with up to 8 separate
tracks. DTS is usually supported but isn't mandatory to the format. DVD-Audio supports
up to 6 channels of 24 bit, 192KHz sampled PCM audio.
Distribution Amplifier
An active
device used to split one input into multiple outputs, keeping each output isolated
from the others, and the signal level constant to each.
Dolby B
A noise-reduction system
that increases the level of high frequencies during recording and decreases them
during playback.
Dolby C
An improvement on Dolby B that provides about twice as much
noise reduction.
Dolby Digital
An encoding system that digitally compresses up to 5.1
discrete channels of audio (left front, enter, right front, left surround, right
surround, and LFE) into a single bitstream, which can be recorded onto a DVD, HDTV
broadcast, or other form of digital media. When RF-modulated, it was included on
some laser discs, which requires an RF-demodulator before the signal can be decoded.
Five channels are full-range; the .1 channel is a band-limited LFE track. A Dolby
Digital processor (found in most new receivers, pre amps, and some DVD players) can
decode this signal back into the 5.1 separate channels. Most films since 1992's Batman
Returns have been recorded in a 5.1 digital format, though a number of films before
that had 6-channel analogue tracks that have been remastered into 5.1.
Dolby EX
An
enhancement to Dolby Digital that adds a surround back channel to 5.1 soundtracks.
The sixth channel is matrixed from the left and right surround channels. Often referred
to as 6.1. Sometimes referred to as 7.1 if the system uses two surround back speakers,
even though both speakers reproduce the same signal. Software is backwards-compatible
with 5.1 systems, but requires an EX or 6.1 processor to obtain additional benefit.
Dolby
Pro Logic
An enhancement of the Dolby Surround decoding process. Pro Logic decoders
derive left, enter, right, and a mono surround channel from two-channel Dolby Surround–encoded
material via matrix techniques.
Dolby Pro Logic II
An enhanced version of Pro Logic.
Adds improved decoding for two-channel, non-encoded soundtracks and music.
Double
Band Projector
A special motion picture projector designed to present picture and
optical/magnetic sound for two separate prints. The double band projector is generally
used for preliminary screenings before the sound track is married to the final print.
DSP
Digital
Signal Processing. Manipulating an audio signal digitally to create various possible
effects at the output. Often refers to artificially generated surround effects derived
from and applied to two-channel sources.
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 unauthorised copying.
Dynamic Microphone
A pressure-sensitive
microphone of moving-coil design. A dynamic microphone can be unidirectional or omnidirectional.
It can stand up to rough handling.
Encoder
A device that superimposes electronic signal information on other electronic
signals. Encodes RGBS to form PAL format
Electret condenser microphone
A capacitor
microphone. It is highly sensitive and requires a DC power supply, usually furnished
by a built-in battery.
Electrostatic Microphone
A microphone with a conductive diaphragm
that varies a high-voltage electromagnetic field to generate a signal. Requires a
miniaturized amplifier and power supply.
Equalization
Loosely, any type of relative
frequency adjustment. Specifically, the process of changing the frequency balance
of an electrical signal to alter the acoustical output.
Equalizer
A component designed
to alter the frequency balance of an audio signal. Equalizers may be graphic, parametric,
or a combination of both.
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Feedback
The transmission of current or voltage from the output of a device back to
the input, where it interacts with the input signal to modify operation of the device.
Feedback is positive when it's in phase with the input and negative when it's out
of phase.
Fibre Optic Cable
Glass, plastic, or hybrid fibber cable that transmits digital
signals as light pulses.
FireWire
See IEEE 1394.
Frequency
The number of cycles (vibrations)
per second. In audio, audible frequencies commonly range from 20 to 20,000 cycles
per second (Hz). In video, frequency is used to define the image resolution. Low-frequency
video images depict large objects or images. Higher frequencies depict smaller objects
(finer details).
Frequency Response
A measure of what frequencies can be reproduced
and how accurately they are reproduced. A measurement of 20 to 20,000 Hz ± 3dB means
those frequencies between 20 and 20,000 Hz can be reproduced no more than 3 dB above
or below a reference frequency level.
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Gain
Increase in level or amplitude.
Graphic Equalizer
A type of equalizer with sliding
controls that create a pattern representing a graph of the frequency-response changes.
Raising sliders boosts the affected frequencies; lowering sliders cuts (attenuates)
the affected frequencies.
Grey Scale
The ability for a video display to reproduce a
neutral image colour with a given input at various levels of intensity.
Headphone
A device consisting of one or two electro-acoustic receivers attached to
a headband for private listening.
Heterodyne
The artificial creation of a signal by
the combining of two signals.
HD-DVD
High-Definition Digital Versatile Disc. Two formats
have been proposed for these high-capacity DVDs, including Blu-ray and the generically
named HD-DVD. Blu-ray is backed by Sony and Panasonic among others through the Blu-ray
Disc Association and HD-DVD is backed by NEC and Toshiba through the DVD Forum. Blu-ray
uses a higher Resolution blue laser allowing for more disk capacity than HD-DVD,
25GB compared 15GB per layer. At present Blu-ray is more expensive and cannot be
replicated on existing manufacturing lines.
HDCP
High-Bandwidth Digital Content Protection.
Created by Intel, HDCP is used with HDTV signals over DVI and HDMI connections to
prevent unauthorised duplication of copywritten material.
HDMI
High Definition Multimedia
Interface. HDTV connection format using a DVI interface that transfers uncompressed
digital video with HDCP copy protection and multichannel audio.
HDTV
High-Definition
Television. A 16:9 Aspect Ratio 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.
High Fidelity
Hi-fi, or hi fidelity. Accurate and faithful reproduction of the
original. Absence of distortion
High Gain Projection Screen
Material that reflects
more light than matte material. Increases a projector's light output at the expense
of Uniformity.
Hue
Colour value or saturation, as opposed to brightness or intensity.
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IEEE 1394
Networking standard for PCs. Combined with 5C copy protection, 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
Impedance
Resistance to the flow of electricity.
Measured in ohms and abbreviated ? or Z. Low impedance circuits (low - Z) are 600
ohms or less. High impedance circuits (high - Z) may be 50K ohms or more.
Inductive
Loop
A wire loop connected to the output of a tape recorder, phonograph or PA system
that produces an electromagnetic field in and around the loop. A small battery-powered
amplifier connected to a cordless headphone amplifies this signal to audible levels.
Infra
Red Filter
A stage in a condenser lens system which filters out infrared light, reducing
heat on film. Also called heat filter.
Infra Red Remote
An infra-red (IR) remote control
transmits in the spectrum of infra-red light, such as a television remote. Unlike
RF remotes, IR remotes must point at the receiver (line of sight). Typical range
is limited to 30 feet including the distance to and from reflected surfaces. For
example, if you are controlling a projector and you point the remote at the screen
which is 12 feet from you and the projector is 10 feet, the total distance is 22
feet. Most projectors have a IR sensor in both the front and rear of the projector,
whereas, flat screens generally have a single IR sensor in the front of the unit.
When working at or near the maximum distance, pointing right at the receiver is necessary.
IR remotes must have clear path or reflected path to the receiver to operate.
Inter-Connects
Any
cable or wire running between two pieces of A/V equipment. For example, RCA terminated
cables connecting pre/pros and amps.
Interface Module
A device or module that operates
as a link between dissimilar modules, usually because those modules cannot communicate
directly with each other. An interface may act as a translator or interpreter, and
could be in the form of hardware and/or software. A video interface allows computer-video
signals to be used by large screen video displays
Interference
Any extraneous energy
that tends to disrupt the reception of desired signals in a signal transmission path.
Interlaced
Process
of alternating scan lines to create a 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 artefacts when two fields don't match to create the complete frame,
often most noticeable in film-based material.
Interlacing
A video frame is made up
of two fields. Interlacing is the process of scanning the picture onto a video screen
whereby the lines of one scanned field fall evenly between the lines of the preceding
field
Interlock Projector
A projector which can be connected to a second projector
or audio recorder for synchronous play. Used for screening separate picture and sound
tapes, and in multi-projection systems.
Jack
Receptacle for the plug connector to the input and output circuits on audio and
video equipment. Example of common sizes and formats are: Standard phone - 0.25"
or 6.35mm diameter, Small phone - 0.206" or 5.23 diameter, Mini - 0.140" or 3.6mm
diameter, Micro - 0.097" or 2.5mm diameter, Phono, or RCA, BNC, UHF, XLR, F
Jack Box
A
device with one input jacks, and several jacks for output to permit the connection
of several reception devices to a single source
Jaggies
A video problem in which stair
step-like lines appear where there should be straight-angled lines or smooth curves.
JPEG
(Joint
Photographic Experts Group) - A working committee under the auspices of the International
Standards Organisation (ISO) that is attempting to define a proposed universal standard
for the digital compression and decompression of still images for use in computer
systems. The JPEG algorithm reduces image size by as much as 65:1, while maintaining
image integrity by eliminating imperceptible colour information.
Junction Box
A portable
set terminal for power cables.
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Kelvin
A unit of measurement in degrees, used to measure the colour temperature of
a light source.
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.
Keystone Correction
Keystone
correction makes a projected image rectangular. This can be accomplished by positioning
the projector to be perpendicular to the screen. Since this is not always possible,
most projectors are equipped with Keystone correction that allows the image to be
Keystone corrected (made rectangular) by adjusting optics, making mechanical adjustments,
or applying digital scaling to the image. Keystone correction can be one or two dimensional
and manual or automatic depending on the projector and the manufacturer. Be aware
that digital scaling will introduce some artifacts that are more evident when viewing
small text and less evident in presentation type material or video.
kHz
Kilohertz or
one thousand Hz.
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Lag
The ghost image of an object which remains visible after the video image of the
object has been removed from the screen.
Lavaliere (Lapel) microphone
A small microphone
designed to be worn either around the neck or clipped to apparel.
LCD
Liquid Crystal
Display. A display that consists of two polarising transparent panels and a liquid
crystal surface sandwiched 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.
LCD Projector
Self-contained projection
device that incorporates a light source,liquid crystal display (LCD) panels and a
lensing system to reproduce computer and video images in larger screen sizes.
LED
Light
emitting diode. A bright semi-conductor component often used in VCR and other equipment
display panels.
Lens
A series of optical elements contained within a barrel or tube,
which collect and focus light,projecting an image.
Lens Hood
A cylindrical cover attached
to the end of a lens to keep ambient light from reaching the lens.
Lens Shift
Displacement
of the lens with the prism (horizontal or vertical) or vice versa, resulting in the
enter of the image being offset from the enter of the lens. Lens Shift is used to
help eliminate key-stoned images and geometrically align images when multiple projectors
are used simultaneously.
Lens Speed
The ability of a given lens to collect light. Lens
speed is expressed as the focal length of the lens divided by the lens's diameter.
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.
Line Out
Audio output.
In consumer systems this may be 10,000 - 50,000 ohms, at - 10B or - 20 dB.
Luminance
The
black and white (Y) portion of a composite, Y/C, or Y/Pb/Pr video signal. The luminance
channel carries the detail of a video signal. The colour 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.
Lumens
The unit of measure
for the amount of visible light emitted by a light Source. The most common standard
for measuring light output is known as ANSI Lumens.
Lux
The amount of visible light
per square meter incident on a surface. 1 lux = 1 lumen/square meter = 0.093 foot-candles.
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MHz
Megahertz, or 1 million Hz
Microphone
A device that converts sound into electrical
signals for use by other pieces of audio equipment. Microphones vary in quality,
generating systems, pickup patterns and impedance. See also: Omni-directional, Cardiod,
Unidirectional, Bidirectional, Dynamic, Condenser, Electrostatic, Capacitor, Electret,
Ribbon, Ceramic.
Mixer
A device for blending multiple audio/video source
MP3
MPEG-1 Audio
Layer-3. Compression scheme used to transfer audio files via the Internet and store
in portable players and digital audio servers.
Monitor Loop-through
A feature that
allows the video signal to be passed through a device relatively unprocessed and
sent to a local monitor or other device. The loop-through is separate from the circuits
that process a signal for output to the main presentation or recording device.
Moving
Coil Microphone
A dynamic microphone, capable of picking up sound in any direction.
This microphone works with a diaphragm connected to a fine wire coil moving in a
magnetic field.
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.
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Negative Gain Screen
Material that reflects less light than a reference material.
Often used for DLP and LCD projection systems.
Noise
Any unwanted signal, such as in
audio and video that adversely affects the quality of the picture or sound
Noise
Cancelling
A microphone designed to cancel ambient noise so that it will not be broadcast
or recorded. The housing of the microphone allows noise to reach both sides of the
diaphragm simultaneously, one side cancelling the other out. A close speaking voice
strikes the diaphragm on only one side, generating a stronger signal with less background
noise.
Non-Composite Video
A video signal that contains picture and blanking information
only, with no sync information.
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Objective Lens
A convex lens or lens system that creates an enlarged image on the
screen. Also called projection lens.
Ohm
A measure of how much something resists (impedes)
the flow of electricity. Larger numbers mean more resistance.
Omni-directional
Referring
to a microphones directional pattern: Picks up sound from all directions.
Opaque Projector
A
device which uses the principle of light reflection to create an image of a non-transparent
object such as a page of text. Screen images require a darkened room.
Optical Digital
Cable
Fibre optic cable that transfers digital audio signals as light pulses.
Optical
Sound
Sound that is recorded by photographic means on 16mm film. The soundtrack is
printed along the edge opposite the sprocket holes. The sound is reproduced by projecting
a narrow beam of light from an exciter lamp through the soundtrack, into a photoelectric
cell. The cell converts the information carried on the light beam into electrical
impulses for amplification.
Overhead Projector
A device which produces an image on
a screen by transmitting light through a transparent acetate placed on the stage
of the projector. Can project transparencies up to 10" x 10". Can also be supplied
with a continuous roll of acetate which can be moved over the stage by means of a
crank.
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PAL
(Phase Alternate Line) - The phase of the colour carrier is alternated from line
to line. It takes four full fields, two full pictures for the colour to horizontal
phase relationship to return to the reference point. This alternation helps cancel
out phase errors, the reason the hue control is not needed on PAL TV sets. PAL in
its forms is used extensively in Western Europe.
Parabolic Microphone
A microphone
mounted with a large, dish-shaped reflector, used for picking up sounds at a distance.
Phosphor
The
substance which glows when struck by an electron beam, providing the image in a CRT.
The higher the quality of the phosphor, the brighter and more vivid the image.
Pixel
(picture element)
The smallest discernible element of the composition of an image
on a display device or a image generating device
Pixelization
Sometimes referred to
as 'the screen door effect', Pixelization refers to images with noticeable lines,
or darkened areas, between each pixel element on the screen.
Plasma
Flat-panel display
technology that ignites small pockets of gas to light phosphors.
Preamplifier
A control
and switching component that may include equalization functions. The preamp comes
in the signal chain before the amplifiers.
Processing Amplifier
Abbreviated proc amp.
An electronic device which stabilizes or rebuilds signals
Progressive Scan
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.
Computer images are all progressively scanned. Requires more bandwidth (twice as
much vertical information) and a faster horizontal scan frequency than Interlaced
images of the same Resolution.
Projection
The process of presenting visual media by
light transmitted through an optics system
Projection Lens
A convex lens or lens system
that creates an enlarged image on the screen. Also called objective lens.
Pulse Distribution
Amplifier
An amplifier that strengthens sync as well as other signals.
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Quadruplex
A video recording system that uses four video heads and scans the tape
at a ninety degree angle.
QXGA
QXGA is used to define a specific display resolution.
Resolution is defined by the number of individual dots that a display uses to create
an image. These dots are called pixels. A QXGA display has 2048 horizontal pixels
and 1536 vertical pixels giving a total display resolution of 3,145,728 individual
pixels that are used to compose the image delivered by a projector. A QXGA display
has 4 times the resolution of an XGA display.
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RCA Jacks
Receptacles for coaxial cables carrying line-level audio signals. Also called
phono-type connectors
Rear-Projection Television
Display that projects an image on
the backside of a screen material, usually after having been 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.
Resolution
Fixed-pixel-array displays
such as flat-panel plasmas (PDPs), LCDs, front and rear projectors using LCD, DLP
or similar technologies and is simply the physical number of columns and rows of
pixels creating the display (eg, 852x480; 1368x768 etc). A consequence of having
a fixed grid display is that for multiformat video inputs all displays need a "scaling-engine"
(a digital video processor that includes a memory array) to match the incoming picture
format to the display.
RF
Radio frequency. A frequency at which coherent electromagnetic
radiation of energy is useful for communications purposes.
RF Adaptor
A device that
allows video and audio signals from a VTR or computer to be shown on a standard TV
receiver. This device produces comparatively poor resolution and picture quality.
Also call RF converter.
RF Amplifier
An amplifier used to strengthen RF signals.
RF
Control
A medium of remote control where signals are sent to the controlled equipment
via data pulses modulated on an RF carrier signal.
RF Converter
A device that allows
video and audio signals from a VTR or computer to be shown on a standard TV receiver.
This device produces comparatively poor resolution and picture quality.
RGB
Red, Green,
Blue. Can refer to an unprocessed video signal or the colour points of a display
device. Together these three colours make up every colour seen on a display device.
RS232
An
Electronic Industries Association (EIA) serial digit interface standard specifying
the electrical and mechanical characteristics of the communication path between two
devices. This standard is used for relatively short range communications and does
not specify balanced control lines.
RS422
An EIA serial digital interface standard
which specifies the electrical characteristics of balanced voltage digital interface
circuits. This standard is usable over longer distances than RS232C. Although originally
designed for use with 9-pin and 37-pin D-type connectors. It is often used with others,
including 25-pin D-types. It is also used as a serial port standard for Macintosh
computers. this signal governs the asynchronous transmission of computer data at
speeds of up to 920,000 per second.
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S-Video
Colour and detail signals are kept separate, thus preventing Composite video artefacts.
Cable uses four-pin connector. Used with S-VHS VCRs, DVD players
Saturation
The intensity
of the colour is called saturation. For example, a lightly saturated red looks pink.
Fully saturated red is like the red of a crayon. On a display device, it can be adjusted
with the colour control. Not to be confused with the brightness, saturation is the
amount of pigment in a colour, and not the intensity. Low saturation is like adding
white to the colour.
SCART
Analogue AV connection used commonly across Europe, especially
with televisions and DVD players but less commonly with projectors. An advantage
of SCART is that it carries both video and audio in one cable. SCART will be overtaken
in popularity by its digital equivalent, HDMI.
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. Digital satellite and digital cable often refer
to the majority of their programs as SDTV, somewhat erroneously, as neither system
has anything to do with DTV, though both, technically, consist of a digital 480i
signal.
Source
A component from which the projector's signals originate. DVD player,
Sky or freeview boxes are examples of Source components
Subwoofer
A speaker designed
to reproduce very low bass frequencies, usually those below about 80 Hz.
Switcher
Term
often used to describe a special effects generator; a unit which allows the operator
to switch between video / audio signals. Switchers are often used in industrial applications
to switch between video cameras monitoring certain areas for display on a monitor,
or system of display devices. These kinds of switchers do not have sync generators.
SXGA
The
projected image is made up of 1280 x 1024 pixels
SXRD
Silicon X-tal Reflective Display
: panels with rapid 5msec response time and over 6 Million pixels with narrow spacing
and high density - no screen door effect.
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Throw
1. The distance from projector lens to screen.
2. The distance from light source
to subject.
THX
Certification program for home theatre equipment. Uses some proprietary
features, but mostly assures a base quality level for a given room size. (See THX
Select or Ultra.) Is compatible with any and all soundtrack formats. Stands for either
Tom Holman's experiment, after the engineer who drafted the original standard, or
is named after the company's founder George Lucas' first movie, THX 1138. Nobody
agrees on which.
THX Select
Certification program for speakers and receivers that assures
a base level of quality and performance when played in a room that's between 2,000
and 3,000 cubic feet.
THX Ultra
Certification program for speakers, receivers, and
amplifiers that assures a base level of quality and performance when played in a
room that's greater than 3,000 cubic feet.
THX Ultra 2
The newest certification from
THX, THX Ultra 2 requires amplification for seven channels, boundary compensation
for subwoofers, and stricter requirements for amplifiers and speakers than THX Ultra.
Dipole speakers are used for the side surround channels. Monopole speakers are used
for the surround back channel and are placed next to each other. The Ultra 2 processor
accommodates both 5.1 EX/ES soundtracks, as well as multichannel audio recordings
by directing ambient sounds to the dipole speakers and discrete effects/sounds to
the back channels.
Touchpanel
A smooth-surfaced control unit replacing the conventional
push buttons and manual switches. Working by capacitance, resistance or physical
contact, a control is activated when sensors under the flat surface detect pressure
or warmth.
Tweeter
A speaker driver designed to reproduce high frequencies; usually
those over approximately 5,000 to 10,000 Hz.
UHF
1. Ultra high frequency. Television broadcast frequency range between 300 and
3000 MHz, on. channels 14 through 83.
2. A type of connector used for video cables
Unidirectional
Referring
to a microphones directional pattern: Picks up sound primarily in the direction the
the microphone is pointed in. Deflects sound from the rear.
Uniformity
Even distribution
across a given space. In video, Uniformity can refer to the distribution of light
(hot spotting) or colour.
Unity Gain
Output that 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 numerous brands stored into
memory and can control several different devices simultaneously.
UXGA
The projected
image is made up of 1600 x 1200 pixels.
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Video Amplifier
A low-pass amplifier with a bandwidth of 2 - 10 MHz, used to strengthen
the video signal for TV transmission and reception.
Video Distribution Amplifier
A
device that splits one input into multiple outputs while maintaining signal strength
and isolation between outputs.
Video Gain
The amplitude of a video signal.
VGA
The projected
image is made up of 800 x 600 pixels.
Video Player
A device to reproduce sound and
picture from a pre-recorded videotape or disc. The video player cannot record images
or sound.
Video Projector
A device which projects a video image onto a presentation
surface.
Video Tape Recorder
VTR. A device which signals from a video camera and microphone,
recording the signals on video tape. The VTR can play back the recorder program on
a television monitor or receiver. Some units contain a modulator to allow transmission
directly to a standard television receiver.
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WUXGA
The projected image is made up of 1920 x 1200 pixels
WVGA
The projected image
is made up of 854 x 480 pixels
WXGA
The projected image is made up of 1280 x 720 pixels.
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Xenon arc Lamp
A point source arc lamp filled with high pressure xenon gas. Xenon
arc lamps have no filament. The arc is formed by electrical current flowing through
the xenon gas between two tungsten electrodes. Used mainly in motion picture projectors
slide projectors and spotlights for medium-to high intensity uses.
XGA
The projected
image is made up of 1024 x 768 pixels
XLR Connector
A type of audio connector featuring
three leads, two for the signal and one for overall system grounding. A secure connector
often found on high quality audio and video equipment. Also called cannon connector.
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YcbCr
A high-end digital component video signal.
YPbPr
A high-end analogue component
video signal. Sometimes called YUV, Component, or Y, R-Y, B-Y, the YPbPr signal by-passes
the video decoder in this projector.
Zoom Lens
A lens with a variable focal length providing the ability to adjust the
size of the image on a screen by adjusting the zoom lens, instead of having to move
the projector closer or further.
Zoom Lens Ratio
Is the ratio between the smallest
and largest image a lens can project from a fixed distance. For example, a 1.4:1
zoom lens ratio means that a 10 foot image without zoom would be a 14 foot image
with full zoom. Conversely, a 10 foot diagonal image at 15 feet with no zoom would
still be a 10 foot image at 21 feet at maximum zoom (15 x 1.4 = 21 feet). A zoom
lens is "not as bright" as a fixed lens, and the higher the ratio, the less light
output.
Glossary of commonly used audio visual terms
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