Glossary
G-2
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DMA
Direct memory access. A method by which data can be transferred to and
from computer memory from and to a device or memory on the bus while
the processor does something else; DMA is the fastest method of
transferring data to/from computer memory.
driver
Software that controls a specific hardware device, such as an image
acquisition device.
E
external trigger
A voltage pulse from an external source that triggers an event such as
A/D conversion.
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.
frame
A complete image. In interlaced formats, a frame is composed of two fields.
G
gamma
The nonlinear change in the difference between the video signal’s
brightness level and the voltage level needed to produce that brightness.
I
interlaced
A video frame composed of two interleaved fields. The number of lines in
a field are half the number of lines in an interlaced frame.
