This Glossary was originally compiled by dhomas trenn. What a
A/B Roll : An analog technique of
recording from two source VCRs (A and B) to a third
VCR, using a mixer to create transitions .
Alpha Channel : A grayscale image used
as a filter when compositing two other
images. The alpha channel is used between the two images and dictates
what parts, and to what degree, the picture in behind shows through
onto the front picture. The gray shade of each pixel
determines the amount of transparency, ranging from black (0%) to white
Analog Video : A video signal where an
infinite number of smooth steps is used to describe levels (colors).
Antialiasing : A process used to
reduce rough/jagged edges in computer images by blending colors of
nearby pixels . Commonly used to generate text
with smooth looking curves.
Aspect Ratio : The comparison of an
image or screen's height to its width.
Blue Screening : See
BNC Connector : A twist-lock cable
connector used commonly on video equipment such as video cameras.
Buffer : Generally, a RAM based device
that temporarily holds computer data. Because of the very fast speed
of RAM, these buffers can increase efficiency for time insistant
processes such as digital video .
Character Generator : Hardware or
software that creates text for use in video. Generally, hardware
devices are referred to as character generators, while software
applications are often called video titlers.
Chroma Keying : A
real time technique used to overlay one video signal on another,
by allowing the front image to be transparent in certain areas (the
key). One common use is by television weather news programs to place a
reporter in front of a computer generated weather display. Also
referred to as color keying and
Chrominance : The part of a color
video signal that represents the saturation
and hue of a specific point in an image. The
lower the chrominance level is the weaker the color. Black and white
video does not contain chrominance information.
Clipping (Audio) : When recording
audio, if an input signal is louder than can be properly reproduced by
the hardware, the sound level will be cut off at its maximum. This
process often causes distortion in the sound, so it is recommended that
the input signal level be reduced in order to avoid this.
Clipping (Video) : With video signals,
clipping refers to the process of recording a reduced image size by
ignoring parts of the source image. Also referred to as
Codec : Refers to hardware or software
used to encode and/or decode a signal or data file.
Color Keying : See
Chroma Keying .
Component Video : Refers to video
signals where the components (luminance ,
synchronization ) are kept separate in order to achieve maximum
video quality. There are several forms, including RGB
, S-Video , Y/C and
Composite Sync : A
synchronization signal where horizontal and vertical signals are
Composite Video : See
Compositing : The process of merging
two or more images into one.
Compression : The technique of
processing data to reduce storage space and, as a result, improve
Control-L / Control-M
/ Control-S: Special
edit control systems designed for
communication between two video systems, allowing control of fast
forward, rewind, pause, play, and other related functions. The
different protocols are used by different manufacturers to perform
similar functions, but are not compatible.
Cropping : See
Clipping (Video) .
CVBS : Composite
Video Burst Signal. A type of video signal where
luminance and chrominance
signals are combined. Designed to be compatible with the black
and white video signal. Generally uses an RCA type connector. Also
referred to as composite video.
Datarate : The amount of data that can
be transferred in one second. The higher the datarate the better the
video output can be. On the Amiga, a video card's datarate is
restricted because of limitations imposed by the
Digital Video : A video signal where a
limited number of steps is used to describe levels (colors).
Digitization : The process of
converting analog video or audio signals to digital data.
DSP : Digital
Signal Processor. Hardware specifically designed to compute
floating point math at very high speeds. Among other things, DSP
hardware can be used to do real time
compression and decompression of video/audio
Dynamic Range : An image processing
function used to force an image's color palette to fit within a defined
range. Also, see Hot Signal .
Edit Control : Communication
connections on video hardware which allow device control of editing
functions. Also, see Control-L .
EDL : Edit Decision
List. A manual or computer generated list of locations in video
detailing scene changes, transitions and
other points of interest; used in the editing process.
Field : One frame
of video consists of two interlaced fields.
For NTSC video, each field is drawn in 1/60th of a
second. Since the human eye has a persistence of about 1/50th of a
second, the two fields seem to be displayed simultaneously. Also, see
Firewire : A high speed communication
protocol designed for transfer between digital
video hardware such as cameras, editing systems and computers.
Flicker : If a video display does not
have a fast enough update rate, it will be perceived by the human eye
as blinking or flickering. This is commonly experienced by Amiga users
when viewing an interlaced screenmode (such
as 640x400) on a non-interlaced monitor
such as the Amiga 1080/1084 monitors.
FPS : Frames Per
Second. The number of images displayed during a period of one
Frame : Motion video is made up of a
series of still images, called frames, that change rapidly. For
PAL video, frames are displayed every 1/25th of a
second. NTSC video is updated every 1/30th of a
Frame Buffer : Generally, a RAM based
device that temporarily holds one or more frames
of image data. Also, see Buffer .
Frame Grabber : A hardware device that
can digitize one or more
frames of video in real time . Also, see
Video Digitizer .
Frame Synchronizer : A hardware device
that synchronizes two or more video timing signals. One input signal
is used as the sync reference and other video signals are synchronized
to it by slightly delaying them. Also, see Genlock
, TBC .
Genlock : GENerator
LOCKing. A hardware device that provides synchronization
signals, to be used as timing for other connected devices, by
generating a signal in sync with an input signal. Genlocking is
commonly used to combine graphics from a computer with the video signal
from another video source such as a video camera. Also, see
Frame Synchronizer ,
Hertz : A unit of frequency equivalent
to one cycle per second.
Hi-8 : An enhanced version of the 8mm
video tape format. A higher density tape allows for improved
luminance which results in sharper image
quality and a horizontal resolution
of 400 lines (compared to 240).
Horizontal Resolution : A measurement
of detail, rated in scan lines. The greater
the number of lines, the higher the resolution and the better the
Horizontal Sync : The part of the
composite video signal that synchronizes the
display so that images will start at the same horizontal position
during scanning .
Hot Signal : When a video signal
exceeds the limitations of a display, color bleeding and oversaturation
can occur. This is referred to as a hot signal. Computer graphics are
able to display a wider range of color than video. It is important to
keep this in mind when performing image processing functions destined
for video. It is often necessary to perform a
dynamic range function, or similar, to limit the color range.
Hue : The shade of a color.
Interlaced : A
scanning method that displays alternating lines, first odd and then
even. 1,3,5... 2,4,6... Also, see Field .
JPEG : Joint
Photographic Experts Group. JPEG is a lossy
image compression method for single images.
It works on the principal that some color information is beyond the
limits of human vision and can therefore be removed. The compression
ratio is adjustable from 1 (maximum compression, minimum image quality)
to 100 (minimum compression, maximum image quality). It is important to
note that not all software follows the JFIF Q-table standards for
ratios, therefore a level of 60 in one program may not be equivalent in
KHz : Kilohertz.
One thousand hertz (cycles per second).
LANC : See Control-L
Linear Editing : A process of editing
using a medium, such as tape, that must be accessed in a sequential
order. Example: Recording from one VCR to another,
using fast forward and record/pause to perform searching and record
Lossless : A
compression method that does not discard data is often called
lossless. These methods are often preferred because they accurately
represent the original data. GIF is an example of a lossless image
Lossy : A
compression method that discards data is often called lossy. These
methods are not always preferred because they cause degradation in the
quality of the data. JPEG and MPEG
are examples of lossy compressions.
LTC : Longitudinal
Time Code. A system of time code
where information is recorded as an audio signal, generally, on an
audio track of a video deck. Because the system is based in audio,
tracking is only possible while a tape deck is in play mode.
Generally, LTC is accurate to a single frame ,
in the form HH:MM:SS:FF (hours:minutes:seconds:frames).
Luminance : The brightness information
contained within a video signal.
MHz : Megahertz.
One million hertz (cycles per second).
Motion-JPEG : Not specifically a
compression method, but rather a method of
storing images compressed using JPEG . Unlike,
MPEG , each digital frame is stored as a separate
file. This has the advantage that editing functions, such as
re-ordering and deleting, are very quick. But, it has the disadvantage
of requiring more storage space.
MPEG : A lossy
image compression method for a series of
images (movies) based on the JPEG standard. The
advantage of this method, in comparison to
Motion-JPEG , is that it requires less harddisk space. However,
editing functions are much slower because the entire MPEG file has to
be re-written every time changes are made. MPEG-1 specifies a
resolution of 352 x 240 played at 30
frames per second. MPEG-2 specifies 720 x 480 at
60 fields per second.
Non-Interlaced : A
scanning method that displays lines in sequential order.
Nonlinear Editing : The process of
editing using a medium, such as harddisk, that can be accessed in a
random order. Generally, a very fast system with nearly instantaneous
recall or indexing. Often abbreviated as NLE.
NTSC : National
Television Standards Committee. Video is displayed with 525
lines per frame at a rate of 30
FPS . It is the standard used in North America, Japan, etc.
PAL : Phase
Alternation Line. The video standard used in most European
Countries. Video is displayed with 625 lines per frame
at a rate of 25 FPS .
Pixel : PIcture
ELement. The dots of light that make up a computer display. The
smallest unit of display information.
Post-Roll : Extra video at the end of
a video clip that is used for making scene
Pre-Roll : Extra video at the
beginning of a video clip that is used for scene
transitions and synchronization purposes.
Real Time : Operation at the speed in
which something occurs naturally.
Resolution : The number of
pixels or dots that can be displayed
horizontally and vertically on a monitor. Generally, the higher the
resolution the better the quality.
RPN : Reverse
Polish Notation. In digital video
editing, it provides a method for processing multiple simultaneous
transitions and effects. Based on a concept
of data and function stacks . Commonly used
with calculators, where the RPN equivalent of "1 + 2" is "1 2 +".
RGB : Red Green Blue
. A type of video signal, used mostly for computer displays,
where color is defined as percentages of red, green and blue.
RS-232 / RS-422
: Serial communication interfaces used in video to control
VCRs and other editing equipment.
Sample : Often used to refer to a file
that contains digitized audio data. However,
this is a very common misuse of the word. A sample is a single digital
value which represents a waveform amplitude from a single point in
time. A group of samples, taken over a period of time, is called a
sound or waveform (file).
Saturation : The amount in which a
color is absent of white light, where a 100% saturated color contains
no white light. It is the property of color that makes, for example,
pink and red different.
Scanning : The process of displaying
an image on a monitor by moving an electron beam from point to point,
row to row; starting at the top and moving down to the bottom.
Scene : A grouping of one or more
video frames .
SECAM : SEquential
Coluleur A'Memorie. The television broadcast standard for
various Eastern European countries. Like PAL , it
displays at 25 FPS ; but with a higher
horizontal resolution of 819 lines.
SMPTE : Society of
Motion Picture and Television Engineers. An organization of
technical experts who help to develop standards related to the video
Stack : Used with RPN
processing. A stack is a pile where elements are always added and
taken from the bottom.
Steady Shot : A system designed to
improve hand-held camera video recording by compensating for
S-VHS : Super
VHS. An enhanced version of the VHS
tape format. A higher density tape allows for improved
luminance which results in sharper image quality and a
horizontal resolution of 400
S-Video : A type of video signal,
where luminance (Y)
and chrominance (C)
signals are kept separate, providing a higher quality signal than
CVBS . Usually uses a multi-pin DIN type connector.
Also referred to as Y/C.
SYNC : Synchronous.
Signals used to synchronize the horizontal and vertical
scanning of video.
SYNC Generator : A hardware device
that generates horizontal and vertical synchronization signals.
TBC : Time Base
Corrector. A hardware device that corrects errors in a video
signal's timing information by generating a new time base and
re-synchronizing the bad signal to it. VCRs
inherently have unstable timing and tape jittering problems which can
cause problems when used with other video hardware. A TBC can be used
to correct these errors. Also, see Frame
Synchronizer , Genlock .
Thermal Recalibration : When a
harddisk heats up, its platters expand in size. As a result of this, a
harddisk has to compensate for changes in data position by performing a
thermal recalibration function. This can cause interruptions in data
flow which would delay video output. This problem is commonly solved
by using a data buffering system.
Time Code : A system used to
accurately track positioning on video tape, where every frame can be
individually identified. There are three main time code systems used
in video: VITC , LTC and RC.
Transition : An effect applied to
video to progress from one scene into the
next. Common transition effects include: wipes, dissolves, fades, page
turns, shifts and rolls. Additionally, digital
video editing provides much more complex transition effects such
as: bounce, melt, swirl and liquid.
VCR : Video
Cassette Recorder. Consumer level video recording device.
Vertical Sync : The part of the
composite video signal that indicates to the
scanning process when to move from the bottom
of a frame to the top again.
VHS : Video Home
System. A consumer level video format using half-inch magnetic
tape, with a horizontal resolution
of 240 lines.
Video Digitizer : Similar to a
frame grabber but requires longer than
1/30th of a second to digitize a complete
frame and therefore can not be used for motion
video. Among the more popular Amiga video digitizers is NewTek's
Video Titler : See
Character Generator .
VITC : Vertical
Interval Time Code. A system of time
code that is embedded into a video signal. Its main advantage
over LTC is that tracking information is available
as long as a video signal is present, even when the video deck is in
pause mode. Accurate to a single field ,
in the form HH:MM:SS:FF:F (hours:minutes:seconds:frames:fields).
VTR : Video Tape
Recorder. Professional level video recording device.
Y/C : See S-Video
YUV Component : A professional video
format that uses three separated signals, one for
luminance and two for chrominance . This
results in a picture quality that is higher than CVBS
and S-Video .
YUV 4:2:2 : The current standard for
storage of video on non-linear digital
editing systems. It represents the bits used for each of the three
components, four for luminance and two for
each chrominance signal. Also, see
YUV Component .
Zorro II/III : Amiga expansion slots.
Zorro III, because of its 32-bit design improvements, provides a much
faster datarate and therefore is preferred over
Zorro II for use with video editing systems.
Updated on Fri Mar 8 20:37:57 EST 2002