Glossary
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National Instruments Corporation
G-5
F
field
For an interlaced video signal, a field is half the number of horizontal lines
needed to represent a frame of video. The first field of a frame contains all
the odd-numbered lines, the second field contains all of the even-numbered
lines.
FIFO
First-in first-out memory buffer. The first data stored is the first data sent
to the acceptor. FIFOs are used on IMAQ devices to temporarily store
incoming data until that data can be retrieved.
flash ADC
An ADC whose output code is determined in a single step by a bank of
comparators and encoding logic.
frame
A complete image. In interlaced formats, a frame is composed of two fields.
front porch
The area of a video signal between the start of the horizontal blank and the
start of the horizontal synchronization signal (HSYNC).
ft
Feet.
function
A set of software instructions executed by a single line of code that may
have input and/or output parameters and returns a value when executed.
G
gamma
The nonlinear change in the difference between the video signal’s
brightness level and the voltage level needed to produce that brightness.
genlock
The process of synchronizing a video source to the signal from a separate
video source. The circuitry aligns the video timing signals by locking
together the horizontal, vertical, and color subcarrier frequencies and
phases and generates a pixel clock that clocks pixel data into memory for
display or into another circuit for processing.
GUI
Graphical user interface. An intuitive, easy-to-use means of
communicating information to and from a computer program by means
of graphical screen displays. GUIs can resemble the front panels of
instruments or other objects associated with a computer program.
