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REVOLT PRO MEDIA
Glossary - Video Terminalogy
A
A/A
(A/X/A) roll editing
Editing from a single source using effects
to transition from the source to itself
(source "A" to "A")
using a picture freeze at the end of
one scene to transition the start of
the next scene.
A/B ROLL
EDITING
Editing from two source VCRs ("A"
and "B") to a third (recording)
VCR. Typically a switcher or mixer,
such as the Digital Video Mixer, is
used to provide transition effects between
sources. Control over the machines and
process can be done manually or automatically
using an edit controller.
AGC (Automatic
Gain Control)
Circuitry used to ensure that output
signals are maintained at constant levels
in the face of widely varying input
signal levels. AGC is typically used
to maintain a constant video luminance
level by boosting weak (low light) picture
signals electronically. Some equipment
include gain controls which are switchable
between automatic and manual control.
ALC (Automatic
Level Control)
Circuitry used to automatically adjust
the audio recording level to compensate
for variations in input volume. Some
equipment includes level controls which
are switchable between automatic and
manual control.
ALIASING
Undesirable video display effects caused
by too much high frequency video information.
Examples are:
* Temporal aliasing - e.g., rotating
wagon wheel spokes apparently reversing
direction
* Raster scan aliasing - e.g., twinkling
or strobing effects on sharp horizontal
lines
* Stair-stepping - Stepped or jagged
edges of angled lines, e.g., at the
slanted edges of letters.
* (See ANTI-ALIASING)
AM
(Amplitude Modulation)
Amplitude modulation is a process used
for some radio (AM broadcast) and television
video transmission. A low frequency
(program) signal modulates (changes)
the amplitude of a high frequency RF*
carrier signal (causing it to deviate
from its nominal base amplitude). The
original program signal is recovered
(demodulated) at the receiver. This
system is extensively used in broadcast
radio transmission because it is less
prone to signal interference and retains
most of the original signal quality.
In video, FM is used in order to record
high quality signals on videotape.
ANALOG
A method of representing data using
continuously varying electrical voltages.
Analog video whether transmitted over
cables, read from videotapes or broadcast,
is subject to degradation due to noise,
distortion and other electronic phenomena.
Normal signal levels should be within
0.7-1 volt. (See DIGITAL)
ANALOG
MONITOR
A video monitor which accepts analog*
signals. Several types of inputs are
accepted by analog monitors: composite
video*, RGB* & sync, Y/C*, YUV*
and any combination of these formats.
The signals transmitted to an analog
monitor are usually between 0 and 1
V and use 75 ohm coaxial cables.
ANTI-ALIASING
The process of electronically reducing
aliasing*, especially letters and genlocked
graphic elements.
APERTURE
An adjustable opening in a lens which,
like the iris in the human eye, controls
the amount of light entering a camera.
The size of the aperture is controlled
by the iris adjustment and is measured
in f-stops. A smaller f-stop number
corresponds to a larger opening which
passes more light. (See also: Depth
of Field). (This definition includes
contribution from Jim Freeman, JFree40923@aol.com.)
ASPECT
RATIO
The ratio between the height and width
of the TV picture on the screen. The
aspect ratio for a standard TV or monitor
is 4 to 3 (4:3). The HDTV* video format
has an aspect ratio of 16 to 9 (16:9).
AUDIO
The "other half" of any video
production consisting of frequencies
corresponding to a normally audible
sound wave (20 Hz to 20,000 Hz), the
"soundtrack" of a videotape.
Both the Video Equalizer and Sound Effects
Mixer offer audio mixing/editing capabilities.
AUDIO
BANDWIDTH
The range of audio* frequencies which
directly influence the fidelity of a
sound. The higher the audio bandwidth,
the better the sound fidelity. The highest
practical frequency which the human
ear can normally hear is 20 kHz. An
audio amplifier which processes all
frequencies equally (flat response to
20 kHz) and a reasonably high signal
to noise ratio*, will faithfully reproduce
the audio soundtracks of a video recording.
AUDIO
DUB
VCR feature allowing replacement of
the audio signals on a previously recorded
tape without disturbing the video signal.
When dubbing is not available via the
video recorder, audio dubbing can be
performed while recording using an audio
mixer.
AUDIO
EDITING
Similar to video editing*. Various portions
of audio material are combined and recorded
onto the videotape in one continuous
form. For example, when a sound track
is added to a videotape, various sounds
such as background music, sound effects
and voice narration, may be introduced
in order to highlight particular movie
scenes. The Video Equalizer and Sound
Effects Mixer offer audio mixing/editing
capabilities.
AUDIO-FOLLOW-VIDEO
During video recording, the video signal
is usually accompanied by an audio signal.
Sometimes, during video editing*, it
is often necessary to separate the audio
from the video signal. Audio-follow-video
mixers allow accompanying audio to "follow"
the video when switching video sources
or not. The Digital Video Mixer provides
either function.
AUDIO
LEVELS
Proper audio* levels are crucial. If
the audio level is too high when recording,
overload of the input electronics will
cause audio distortion*. If audio levels
are too low, the signal-to-noise ratio*
deteriorates. Audio levels are typically
indicated either by mechanical VU-meters
or electronic LED bar graph meters.
AUDIO
MIXING
The blending of two or more audio signals
to generate a combined signal which
is often used for audio dub*. During
video processing, audio mixing may be
used to insert narration or background
music.
B
B-ROLL
Stock footage acquired for miscellaneous
needs.
BACK LIGHT
1. A light source that illuminates a
subject from behind, used to separate
the subject from the background and
give them depth and dimension. Back
lights are often improperly applied
or overlooked completely.
2. Also, a switch on some camcorders
used to compensate exposure for situations
where the brightest light is coming
from behind the subject.
BANDWIDTH
(See AUDIO BANDWIDTH and VIDEO BANDWIDTH)
BETAMAX
Consumer videocassette record/playback*
tape format using half-inch wide magnetic
tape. Developed by Sony, Betamax was
the first home VCR format.
BETACAM
Portable, professional camera/recorder
format developed by Sony. Betacam uses
a component video* system.
BETACAM
SP
A superior performance version of Betacam.
SP uses metal particle tape and a wider
bandwidth recording system.
BLACK
A TAPE
The process of recording a black burst*
signal across the entire length of a
tape. Often done before recording edited
footage on the tape to give the tape
clean, continuous video and sync and
to insure there is no video already
on the tape.
BLACK
BURST
A composite color video signal comprised
of sync*, color burst* and black video.
It is used to synchronize (genlock*)
other video sources to the same sync
and color information. Black burst generators
are used in video studios to "lock"
the entire facility to a common signal
("house sync" or "house
black").
BLACK
LEVEL
The voltage in a video signal which
corresponds to black.
BLANKING
LEVEL
Also known as the pedestal, it is the
voltage level produced at the end of
each horizontal picture line which separates
the portion of the video signal containing
the picture information from the portion
containing the synchronizing information.
This voltage makes the electron beam
"invisible" as it moves to
draw the next visible line.
BLANKING
INTERVAL (Horizontal
& Vertical)
The horizontal blanking interval is
the time between the end of one scanning
line and the beginning of the next.
The vertical blanking interval is the
time between the end of one video field*
and the beginning of the next. Blanking
occurs when a monitor's electron beam
is positioned to start a new line or
a new field. The blanking interval is
used to instantaneously reduce the beam's
amplitude so that the return trace is
invisible. (See VERTICAL INTERVAL SWITCHING)
BNC CONNECTOR
A type of connector used on some VCRs,
video and RF* equipment providing twist-lock
capability.
BORDER
The boundary between two merged video
pictures, as created with chroma key*
or wipe* effects.
C
CCORDER
Combination of camera and video tape
recorder in one device. Camcorders permit
easy and rapid photography and recording
simultaneously. Camcorders are available
in most home video formats: 8mm*, Hi-8*,
VHS*, VHS-C*, S-VHS*, etc.
CAMERA
SUPPLY
Most video cameras* use an external
DC voltage supply which is derived either
from a battery belt worn by the camera
operator, from a battery within the
video recorder itself, or from the mains
power supply (after voltage conversion).
CANDLEPOWER
The unit measure of incident light.
CATV
Acronym for cable TV, derived from the
older term, community antenna television.
CCD (Charge
Coupled Device)
A semiconductor device (IC) that converts
optical images to electronic signals.
CCDs are the most commonly found type
of image sensor in consumer camcorders*
and video cameras*.
CCIR (Comite Consulatif
International Des Radiocommunications)
A European committee situated in Paris
responsible for creating and approving
professional standards related to audio
and video.
CCTV (Closed Circuit
TV)
A video system used in many commercial
installations for specific purposes
such as security, medical and educational.
CHARACTER
GENERATOR
Device that electronically generates
text which can be superimposed* over
a video signal. Text is usually entered
via a keyboard, allowing selection of
various fonts, sizes, colors, styles
and background colors, then stored as
multiple pages for retrieval. The Video
TitleMaker 2000 is a full-featured character
generator.
CHROMA
The color information contained in a
video signal, consisting of hue (phase
angle) and saturation (amplitude) of
the color subcarrier signal.
CHROMA
CORRECTOR
A device used to correct problems related
to the chroma* of the video signal,
as well as color balance and color noise*.
CHROMA
NOISE
Noise which manifests itself in a video
picture as colored snow*.
CHROMA
KEY
The process of overlaying one video
signal over another by replacing a range
of colors with the second signal. Typically,
the first (foreground) picture is photographed
with a person or object against a special,
single-color background (the key-color).
The second picture is inserted in place
of the key-color. The most common example
is in broadcast weather segments where
pictures of weather maps are inserted
"behind" the talent*. The
Digital Video Mixer incorporates this
feature.
CHROMINANCE & CHROMINANCE LEVEL
The color portion of a video signal
separate from the luminance* component,
representing the saturation and tint
at a particular point of the image.
Black, gray and white have no chrominance,
but any colored signal has both chrominance
and luminance. The higher the chrominance
level, the stronger the color (e.g.,
a strong signal produces red, and a
weak signal, pink). Color saturation
level can be changed using a color processor*
such as the Video Equalizer.
CLIPPING
The electronic process of shearing off
the peaks of either the white or black
excursions of a video signal for limiting
purposes. Sometimes, clipping is performed
prior to modulation*, and sometimes
to limit the signal, so it will not
exceed a predetermined level.
COAXIAL
CABLE
The standard cable consisting of a central
inner conductor and a cylindrical outer
conductor. Used for many video connections,
especially by CATV* companies.
COLOR
BARS
An electronically generated video pattern
consisting of eight equal width colors,
used to establish a proper color reference
before recording and playback* and for
adjustment purposes.
COLOR
BURST
The portion of a color video signal
which contains a short sample of the
color subcarrier* used to add color
to a signal. It is used as a color synchronization
signal to establish a reference for
the color information following it and
is used by a color monitor to decode
the color portion of a video signal.
The color burst acts as both amplitude
and phase reference for color hue* and
intensity. The color oscillator of a
color television receiver is phase locked
to the color burst.
COLOR
CORRECTION
A process in which the coloring in a
television image is altered or corrected
by electronic means. (See CHROMA CORRECTOR)
COLOR
DECODER
A device which divides a video signal
into its basic color components. In
TV and video, color decoding is used
to derive signals required by a video
monitor from the composite or Y/C* signals.
COLOR
PHASE
The phase of the chroma* signal as compared
to the color burst*, is one of the factors
that determines a video signal's color
balance.
COLOR
PROCESSING
A way to alter a video signal to affect
the colors. The Video Equalizer is suited
to this task. (See CHROMA CORRECTOR)
COLOR
TEMPERATURE
A method for specifying the overall
color of a light source, measured in
degrees Kelvin (deg.K). Higher numbers
indicate bluer light, lower numbers
indicate a warmer light.
* Daylight = 5000-5500 deg.K
* Fluorescent = approx. 4100 deg.K
* Indoor incandescent = 2800 deg.K
COLOR
SUBCARRIER
The 3.58 MHz/NTSC* (4.43 MHz/PAL*) signal
added to a black and white television
signal to add color information. The
subcarrier frequency is too high to
be detected by black and white televisions
ensuring compatibility. Color sets employ
special circuitry which detects and
decodes the color component for display.
COLORIZATION
Special effect* (also called paint)
which colors a monochrome or color image
with artificial colors. This feature
is found on both the Digital Video Mixer
and Video Equalizer.
COMMUNICATION
PROTOCOL
A specific software based protocol or
language for linking several devices
together. Communication protocols are
used between computers and VCRs or edit
controllers to allow bi-directional
"conversation" between the
units. (See RS-232/RS-422*)
COMPONENT
VIDEO
Most home video signals consist of combined
(composite) video signals, composed
of luminance* (brightness) information,
chrominance* (color) information and
sync* information. To get maximum video
quality, professional equipment (Betacam*
and MII*) and some consumer equipment
(S-VHS* and Hi-8*) keep the video components
separate.
Component video comes in several varieties:
RGB* (red, green, blue), YUV* (luminance,
sync, and red/blue) and Y/C* (luminance
and chrominance), used by S-Video (S-VHS*
and Hi-8*) systems. All Videonics video
products support the S-Video (Y/C) component
format in addition to standard composite
video*.
COMPOSITE
SYNC
A signal consisting of horizontal sync
pulses, vertical sync pulses and equalizing
pulses only.
COMPOSITE
VIDEO
A video signal in which the luminance
(brightness), chrominance (color), blanking
pulses, sync pulses and color burst
information have been combined using
one of the coding standards. (NTSC*,
PAL*, SECAM*)
COMPRESSION
1. The process of electronically processing
a video picture to make it use less
storage or to allow more video to be
sent down a transmission channel.
2. The process of removing picture data
to decrease the size of a video image.
CONTRAST
1. The degree to which the various luminance
values in a picture are mapped to very
dark and very light values. A high-contrast
picture is dominated by black and white
and few values between. A low contrast
picture has a lot of middle tones without
many very dark or very light areas.
2. A control on a television or monitor
which adjusts the white level of the
picture.
CONTROL-L
Sony's wired edit control protocol,
also called LANC (Local Application
Control), which allows two-way communication
between a camcorder or VCR and an edit
controller such as the Thumbs Up. Control-L
allows the controller to control the
deck (fast forward, play, etc.) and
also allows the controller to read the
tape position (tape counter) information
from the deck.
CONTROL-M
Panasonic's wired edit control protocol.
Similar to Control-L * in function but
not compatible. Also called Panasonic
5-pin edit control *. (See CONTROL-L)
CONTROL-S
Sony wired transport control protocol
which duplicates a VCR's infra-red remote
transport control (play, stop, pause,
fast forward and rewind). Unlike Control-L*,
Control-S does not allow the controller
to read tape counter information.
CONTROL-T
Similar to Control-L* but allows multiple
units to be controlled. Not used in
current equipment.
CONTROL
TRACK
The magnetized portion along the length
of a videotape on which sync* control
information is placed. The control track
contains a pulse for each video field
and is used to synchronize the tape
and the video signal.
CROSSFADE
The audio equivalent of the video dissolve*
where one sound track is gradually faded
out while a second sound track simultaneously
replaces the original one.
CROSSTALK
The interference between two audio or
two video signals caused by unwanted
stray signals.
In video, crosstalk between input channels
can be classified into two basic categories:
luminance*/sync* crosstalk; and color
(chroma*) crosstalk
When video crosstalk is too high, ghost*
images from one source appear over the
other.
In audio, signal leakage, typically
between left and right channels or between
different inputs, can be caused by poor
grounding connections or improperly
shielded cables.
D
D1/D2/D3
Digital video recording and playback
formats. The D1 system uses component
video* while the D2 and D3 systems use
composite video*. By using fully digitized
video in recording and playback, many
problems such as generation loss* and
distortion* are minimized or eliminated.
The digital formats use mainly a 19mm
wide magnetic tape (3/4").
DAT (Digital Audio
Tape)
A consumer digital audio recording and
playback system developed by Sony, with
a signal quality capability surpassing
that of the CD.
DB (Decibel)
A unit for expressing the ratio of two
amounts of electric or acoustic signal
power, used for measuring audio and
video signals. Technically, this is
equal to 20 times the common logarithm
of the voltage or current ratio.
DECODE
To separate a composite* video signal
into its component parts.
DEFINITION
The aggregate of fine details available
on-screen. The higher the image definition,
the greater the number of details that
can be discerned.
During video recording and subsequent
playback, several factors can conspire
to cause a loss of definition. Among
these are the limited frequency response*
of magnetic tapes and signal losses
associated with electronic circuitry
employed in the recording process. These
losses occur because fine details appear
in the highest frequency region of a
video signal and this portion is usually
the first casualty of signal degradation.
Each additional generation* of a videotape
results in fewer and fewer fine details
as losses are accumulated.
DELAY
CORRECTION
When an electronic signal travels through
electronic circuitry or even through
long coaxial cable runs, delay problems
may occur. This is manifested as a displaced
image and special electronic circuitry
is needed to correct it.
DEMODULATOR
An electronic circuit which separates
the audio and video signals from the
RF* carrier frequency.
DEPTH
OF FIELD
The range of objects in front of a camera
lens which are in focus. Smaller f-stops
provide greater depth of field, i.e.,
more of the scene, near to far, will
be in focus.
DIGITAL
A method of representing data using
binary numbers. An analog* signal is
converted to digital by the use of an
analog-to-digital (A/D) converter chip
by taking samples of the signal at a
fixed time interval (sampling frequency).
Assigning a binary number to these samples,
this digital stream is then recorded
onto magnetic tape. Upon playback, a
digital-to-analog (D/A) converter chip
reads the binary data and reconstructs
the original analog signal.
This process virtually eliminates generation
loss* as every digital-to-digital copy
is theoretically an exact duplicate
of the original allowing multi-generational
dubs* to be made without degradation.
In actuality of course, digital systems
are not perfect and specialized hardware/software
is used to correct all but the most
severe data loss.
Digital signals are virtually immune
to noise, distortion, crosstalk, and
other quality problems. In addition,
digitally based equipment often offers
advantages in cost, features, performance
and reliability when compared to analog
equipment.
DIN (Deutsche Industrie Norme)
An international connector standard.
DIN connectors carry both audio and
video signals and are common on equipment
in Europe.
DISSOLVE
A process whereby one video signal is
gradually faded out while a second image
simultaneously replaces the original
one.
DISTORTION
In video, distortion usually refers
to changes in the luminance* or chrominance*
portions of a signal. It may contort
the picture and produce improper contrast*,
faulty luminance levels, twisted images,
erroneous colors and snow*.
In audio, distortion refers to any undesired
changes in the waveform of a signal
caused by the introduction of spurious
elements. The most common audio distortions
are harmonic distortion, intermodulation
distortion, crossover distortion, transient
distortion and phase distortion.
DISTRIBUTION
AMPLIFIER
A device which splits (distributes)
one audio and/or video source to several
audio/video device inputs. Typically,
distribution amplifiers are used in
duplication studios where many tape
copies must be generated from one source
or in multiple display setups where
many monitors must carry the same picture,
etc.
DOLBY(TM)
A compression/expansion (companding)
noise reduction system developed by
Ray Dolby, widely used in consumer,
professional and broadcast audio applications.
Signal-to-noise ratio* improvement is
accomplished by processing a signal
before recording and reverse-processing
the signal upon playback*.
DROPOUT
A momentary partial or complete loss
of picture and/or sound caused by such
things as dust, dirt on the videotape
or heads, crumpled videotape or flaws
in the oxide layer of magnetic tape.
Uncompensated dropout produces white
or black streaks in the picture.
DSK (Downstream Keying)
An effect available in some special
effects generators* and video mixers
in which one video signal is keyed on
top of another video signal. The lightest
portions of the DSK signal replace the
source video leaving the dark areas
showing the original video image. Optionally,
the DSK signal can be inverted so the
dark portions are keyed rather than
the lightest portions allowing a solid
color to be added to the keyed portions.
The DSK input is most commonly a video
camera* or character generator*. The
DSK signal must be genlocked* to the
other signals.
DUB
A duplicate copy made from one recording
medium to another.
DVE (TM)
(Digital Video Effects)
These effects are found in special effects
generators* which employ digital signal
processing to create two or three dimensional
wipe effects. DVE generators are getting
less expensive and the kind of effects
they create getting more popular. The
Digital Video Mixer includes such effects.
DVI (Digital
Video Interface)
Multimedia* standard for computer generated
text and graphics merged in video production.
E
8
mm
A compact videocassette record/playback*
tape format which uses eight millimeter
wide magnetic tape. A worldwide standard
established in 1983 allowing high quality
video and audio recording. Flexibility,
lightweight cameras and reduced tape
storage requirements are among the format's
advantages.
EDGE ENHANCING
(See ENHANCING)
EDIT CONTROL
A connection on a VCR or camcorder which
allows direct communication with external
edit control devices. (e.g., LANC (Control-L*)
and NEW (Panasonic) 5-pin). Thumbs Up
works with both of these control formats
and with machines lacking direct control.
EDIT POINt
The location in a video where a production
event occurs. (e.g., dissolve or wipe
from one scene to another)
EDL (Edit Decision
List)
A list of a video production's edit
points*. An EDL is a record of all original
videotape scene location time references,
corresponding to a production's transition
events. EDLs are usually generated by
computerized editing equipment and saved
for later use and modification.
EIA RS-170A
The timing specification standard for
NTSC broadcast video equipment. The
Digital Video Mixer meets RS-170A.
ENCODE
The process of combining analog* or
digital* video signals, e.g., red, green
and blue, into one composite* signal.
ENHANCING
Improving a video image by boosting
the high frequency content lost during
recording. There are several types of
enhancement. The most common accentuates
edges between light and dark images.
F
FADE
The act of dissolving a video picture
to either a color, pattern or titles.
Fading a video image is often used as
an artistic tool in video productions,
most commonly seen as a fade to black.
The Thumbs Up, Video TitleMaker 2000
and Digital Video Mixer offer fade effects.
In audio, there is a decrease in the
sound level until it is no longer audible.
Audio fading is often used in conjunction
with video fading causing the sound
and image to fade simultaneously. (See
AUDIO-FOLLOW-VIDEO)
FIELD
One-half of a complete television picture
consisting of one complete vertical
scan of the video image containing 262.5
line for NTSC* and 312.5 lines for PAL*.
Two fields make up a complete television
picture frame*. (See INTERLACING)
FILL LIGHT
Fill lights*, commonly referred to as
"scoops," provide a soft-edged
field of light used to provide additional
subject illumination to reduce harsh
shadows or areas not highlighted by
the key light*.
FILM CHAIN
Projectors, multiplexors and cameras,
connected for the purpose of transferring
film to video.
FLICKER
A strobing picture artifact, similar
to an old-time movie effect, mainly
related to vertical syncs and video
field display rates. Some flicker normally
exists due to interlacing*, but is more
apparent in 50 Hz systems (PAL*) and
when converting film (24 fps) to video
(30 fps). Flicker may also be a problem
when static computer images are transferred
to video.
FLIP
Special effect* in which the picture
is either horizontally or vertically
reversed.
FLYING
ERASE HEAD
Facilitates smooth, seamless edits whenever
the camcorder recording begins. Without
a flying erase head, a video "glitch"
may occur at scene transitions. The
erase head is mounted on the spinning
(flying) video head drum.
FM (Frequency
Modulation)
Frequency modulation is a process used
for radio (FM broadcast) and television
audio transmission and videotape recording.
A low frequency (program) signal modulates
(changes) the frequency of a high frequency
RF* carrier signal (causing it to deviate
from its nominal base frequency). The
original program signal is recovered
(demodulated) at the receiver. This
system is extensively used in broadcast
radio transmission because it is less
prone to signal interference and retains
most of the original signal quality.
In video, FM is used in order to record
high quality signals on videotape.
FORMAT (Videotape)
A variety of formats are used to record
video. They vary by tape width: (8mm*,
1/2 inch, 3/4 inch, 1 inch), signal
form: (composite*, Y/C*, component*),
data storage type (analog* or digital*)
and signal standard (PAL*, NTSC*, SECAM*).
FRAME
A complete video image consisting of
2 fields*. Also used to describe the
total visible area of a video image.
FRAME
SYNCHRONIZER
A digital electronic device which synchronizes*
two or more video signals. The frame
synchronizer uses one of its inputs
as a reference and genlocks* the other
video signals to the reference's sync
and color burst signals. By delaying
the other signals so that each line
and field* starts at the same time,
two or more video images can be blended,
wiped and otherwise processed together.
(A TBC* takes this a step further by
synchronizing both signals to a stable
reference, eliminating time base errors
from both sources.) The Digital Video
Mixer includes a frame synchronizer
and dual TBCs.
FREEZE (Frame)
Special effect* in which the picture
is held as a still image.
It is possible to freeze either one
field* or a whole frame*. Freezing one
field provides a more stable image if
the subject is moving, however, the
resolution of the video image is half
that of a full frame freeze.
Digital freeze frame is one special
effect* that could be created with a
special effects generator* or a TBC*.
The Digital Video Mixer includes this
feature.
FREQUENCY
RESPONSE
A measure of the quality of reproduction
of various frequencies (audio and video)
by a circuit or device. If the frequency
response of a video processor is adequate,
there is no deterioration in image quality
at the bandwidth* extremes.
For video, the NTSC* broadcast bandwidth
is 4.2 MHz and the PAL* broadcast bandwidth
is 5.5 MHz.
For audio, full bandwidth implies a
frequency response extending from 20
Hz to 20,000 Hz or higher.
G
GENERATION
The number of duplication steps between
an original recording and a given copy.
A second generation duplicate is a copy
of the original master and a third generation
duplicate is a copy of a copy of the
original master, etc.
GENERATION
LOSS
When an analog master videotape is duplicated,
the second-generation copy is usually
inferior in some way to the master.
This degradation appears as loss of
detail, improper colors, sync loss,
etc. Limited frequency response* of
audio/video magnetic tape and imperfections
in electronic circuitry are the main
causes of generation loss. Higher performance
formats (such as 1-inch) exhibit much
less generation loss than more basic
formats. Digital* formats make generation
loss negligible because each copy is
essentially an exact duplicate of the
original.
Video enhancing* equipment can minimize
generation loss. Some video processors
pre-enhance the video signal to overcome
generation loss.
GENLOCK
A method of synchronization involving
the generation of a video signal sync-locked
with another signal. Because they are
synchronized, a genlocked signal can
be mixed with the original signal, allowing
dissolves*, wipes*, and other transition
effects.
Genlock and frame synchronization* differ
in that genlock is the generation of
a new signal synchronized to a video
signal that is already present while
frame synchronization takes two already-generated
signals and synchronizes them.
Genlocking two VCRs requires the use
of a time base corrector (TBC*). The
Video TitleMaker 2000 uses this technique
when superimposing titles over video.
GHOSTING
A weak, secondary, ghost-like duplicate
video image in a video signal caused
by the undesired mixing of the primary
signal and a delayed version of the
same signal.
GROUP
DELAY
A phenomenon involving timing differences
between video signal components. For
example, a long cable run may introduce
a substantial delay between the transmission
of the color and brightness video information
resulting in shadows.
H
HARMONIC
DISTORTION
When any signal is passed through an
electronic circuit, the signal may be
changed in many ways.
In video, the image may become blurred,
noisy or contain shadows.
In audio, odd harmonics (third, fifth,
etc.) produce harsh and unpleasant sounding
audio.
HDTV (High Definition
Television)
A television format for producing high
resolution video. Typically, these systems
provide about 1125 lines of horizontal
resolution (compared to 525 for NTSC*
and 625 for PAL*) and an aspect ratio
of 16:9, for image quality approaching
35mm film photography.
HELICAL
SCAN
A method of recording video information
diagonally on a tape, used in home and
professional VCRs. High speed rotating
video heads scan these diagonal video
tracks, giving an effective tape speed
much higher than the actual tape speed
allowing more information to be recorded
on a given length of magnetic tape.
HI-8
An improved version of the 8mm* tape
format capable of recording better picture
resolution (definition*). A higher-density
tape is required which provides a wider
luminance bandwidth*, resulting in sharper
picture quality (over 400 horizontal
lines vs. 240 for standard 8mm) and
improved signal-to-noise ratio. Camcorders
using this format are very small, light
and provide a picture quality similar
to S-VHS*.
HI-FI (High
Fidelity)
Most commonly used to refer to the high
quality audio tracks recorded by many
VCRs. These tracks provide audio quality
approaching that of a CD. However, because
they are combined with the video signal
before recording, audio dubs using them
are impossible without re-recording
the video.
HISS
The most common audible noise* component
in audio recording, stemming from a
combination of circuit and tape noise.
Several noise reduction* systems are
available, such as Dolby*, DBX, DNR
(Dynamic Noise Reduction), DNL (Dynamic
Noise Limiter), to help alleviate such
problems.
HORIZONTAL
RESOLUTION
Rating of the fine detail (definition*)
of a TV picture, measured in scan lines.
The more lines, the higher the resolution
and the better the picture. A standard
VHS* format VCR produces 240 lines of
horizontal resolution, while over 400
lines are possible with S-VHS*, S-VHS-C*,
and Hi-8* camcorders.
HORIZONTAL
SYNC
The sync* pulse signal produced at the
beginning of each video scan line which
keeps a video monitor's horizontal scan
rate in step with the transmission of
each new line. (See BLANKING LEVEL)
HUE
Often used synonymously with the term
tint. It is the dominant wavelength
which distinguishes a color such as
red, yellow, etc. Most commonly, video
hue is influenced by:
* 1. A camera's white balance*
* 2. Scene lighting
Video color processors
such as the Video Equalizer are the
main tools used to adjust and correct
hue problems.
I
IMAGE
STABILIZATION
A camcorder* feature which takes out
minor picture shakiness, either optically
or electronically.
IMPEDANCE
MATCHING
A video signal occupies a wide spectrum
of frequencies, from nearly DC (0 Hz)
to 6 MHz. If the output impedance of
either the video source, cable or input
impedance of the receiving equipment
are not properly matched, a series of
problems may arise. Loss of high frequency
detail and color information as well
as image instability, oscillations,
snow*, ghost* images and component heat-up
may result. Proper connections and cable
types provide correct impedances. (See
LOAD RESISTANCE)
INSERT
EDITING
Camcorder*/VCR feature which allows
a user to insert new audio/video segments
into the middle of a previously recorded
tape. Some camcorders insert both audio
and video simultaneously; others can
insert audio and/or video separately.
INTERLACING
A system developed for television which
divides each video frame* into two fields*.
This is done by first drawing one field
consisting of an image's odd scan lines
(1, 3, 5...525) and then drawing the
remaining even scan lines (2, 4, 6...),
interweaving both fields. Interlacing
reduces the perception of screen flicker.
Interlacing can cause annoying effects
with images such as computer generated
text and graphics when transferred to
video.
J
JITTER
Small, rapid variations in a waveform
or image due most often to mechanical
disturbances. (See TBC*)
JPEG (Joint
Photographic Experts Group)
JPEG is a digital compression standard
for still video images that allows the
image to occupy less memory or disk
space. Like the MPEG* standard, it includes
options for trading off between storage
space and image quality.
K
KEY
LIGHT
The term used to describe a subject's
main source of illumination. When shooting
outdoors, the key light is the sun.
L
LANC
(See CONTROL-L)
LAVALIERE
MICROPHONE
Small microphone worn around the neck
or clipped to clothing.
LCD (Liquid
Crystal Display)
A screen for displaying text/graphics
based on a technology called liquid
crystal, where minute currents change
the reflectiveness or transparency of
the screen.
The advantages of LCD screens are: very
small power consumption (can be easily
battery driven) and low price of mass
produced units. Its disadvantages presently
include narrow viewing angle, somewhat
slower response time, invisibility in
the dark unless the display is back-lit,
difficulties displaying true colors
and resolution limitations.
LINEAR
EDITING
Editing using media like tape, in which
material must be accessed in order (e.g.,
to access scene 5 from the beginning
of the tape, one must proceed from scene
1 through scene 4). (See NONLINEAR EDITING)
LINE COMPENSATION
Use of a video line amplifier to pre-compensate
for high frequency video signal transmission
losses resulting from long distance
cable runs (several hundred meters)
by boosting those signal frequencies
most effected. Without such compensation,
deterioration is manifested as loss
of fine details and color distortion*.
LOAD RESISTANCE
The impedance or resistance (load) that
a cable places on a signal being transmitted
through it. In the case of a high frequency
signal, signal-to-cable matching is
essential to prevent signal deterioration.
The cable should be terminated by a
specific load resistance, usually 50
or 75 ohms. Improper cable loading results
in signal distortion*, ghost images,
color loss and other adverse phenomena.
Most video inputs have the proper termination
built in.
LOOPING
A term used to describe the chaining
of a video signal through several video
devices (distribution amplifiers*, VCRs,
monitors, etc.).
A VCR may be hooked up to a distribution
amplifier which is supplied with a video
input connector and a loop output connector.
When a signal is fed to the distribution
amplifier, it is also fed unprocessed
to the loop output connector (parallel
connection) on the distribution amplifier.
In turn, the same signal is fed to another
device which is attached to the first
one and so on. Thus a very large number
of VCRs or other video devices can be
looped together for multiple processing.
LTC (Longitudinal Time Code)
SMPTE (Society of Motion Picture and
Television Engineers) time code standard
usually recorded onto the linear audio
track of a VCR or audio tape machine.
LUMINANCE
The degree of brightness (black and
white portion of the video signal) at
any given point in the video image.
A video signal is comprised of luminance,
chrominance* (color information) and
sync*. If luminance is high, the picture
is bright and if low the picture is
dark. Changing the chrominance does
not affect the brightness of the picture.
LUMINANCE
NOISE
Noise which manifests itself in a video
picture as white snow*, typically caused
by one of the following situations:
* 1. Low signal level due to poor lighting
conditions
* 2. Poor video signal processing
* 3. Low quality videotapes
* 4. Excessively long video cables used
without pre-compensation
* 5. Dirt on the video recorder heads
which interferes with reading and writing
* 6. Over-enhancement of the video signal
LUX
A measurement of light intensity, which
is used in photography for the comparison
of camera sensitivities. (1 Footcandle
= 10.76 Lux)
M
MII
Portable, professional video component
camera/recorder format, utilizing 1/2"
metal particle videotape.
MATRIX
SWITCHER
A device which uses an array of electronic
switches to route a number of audio/video
signals to one or more outputs in almost
any combination. Production quality
matrix switchers perform vertical interval
switching* for interference free switching.
Matrix switchers may be operated with
RS-232 or RS-422* controls, enhancing
flexibility.
MICROPHONE
PREAMPLIFIER
A microphone is a device which converts
sound waves to electrical impulses (transducer).
Microphones typically generate very
low signal levels requiring low noise*,
high fidelity, pre-amplification to
boost the output signal to a level compatible
with audio amplifier circuitry. Good
microphone preamplifiers provide precise
matching of microphone impedance* and
low noise electronic components.
MICROPHONE
IMPEDANCE
In order to obtain the highest quality
output signal from a microphone, a preamplifier
input should provide a load (impedance)
which exactly matches a microphone's
output impedance. Microphone output
impedances vary from 150 ohms to several
megohms.
MOIRÉ
A distracting wavy effect produced when
converging lines in a video image are
nearly parallel to a monitor's scanning
lines.
MONITOR
A display that gets its signal directly
from a camera or VCR, as opposed to
a television, which relies on RF signals,
such as those from cable television
or broadcast. A monitor uses composite
(RCA-style), S-Video (Y/C*) and/or BNC
video jacks. (See ANALOG MONITOR)
MOSAIC
Special effect* in which the picture
is divided up into tiles.
MPEG (Motion/JPEG)
MPEG is a digital compression standard
for moving video images that allows
the images to occupy less memory or
disk space. Like the JPEG* standard,
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