Epiphan VGA2USB Pro - Manual (Page 48)

11. About Epiphan frame grabbing technology Glossary of Terms
Page 48 Epiphan Frame Grabber
Record
The process of saving (or recording) captured frames as video
files or as sets of image files. Recording requires that frames are
first captured before being recorded.
VGA
Video Graphics Array (VGA) is an analog standard for
transmitting visual data from a graphics source (such as a PC
video card) to a display device (such as a computer monitor).
VGA originated in 1988. Most PCs and many other devices that
output analog visual images use the VGA standard or extensions
to the VGA standard for transmitting visual data. All Epiphan
VGA2USB Frame Grabbers capture analog VGA frames and
convert them to digital signals that are transmitted to the Epiphan
video capture application using a USB connection. This USB data
is then interpreted and displayed using the Epiphan video
capture application.
VGA modes
A VGA mode describes the timing of the VGA signals sent by a
VGA source to a VGA display device (or Frame Grabber). The
VGA source and receiver (for example a monitor) must agree on
the VGA mode so that the VGA display device can decode the
timing of the VGA signal and display images.
A VGA signal consists of a series of frames. Each frame is a single
image displayed by a VGA display device or captured by a Frame
Grabber. A VGA frame is made up of horizontal lines. Each line is
made up of pixels. The pixels in each line are transmitted from
left to right. The lines in each frame are transmitted from top to
bottom. If the VGA signal is interlaced each frame consists of
every other line of the frame. An interlaced signal contains less
data and so displays faster but also results in a lower quality
image.
The timings in a VGA mode start with the refresh rate; which
defines how often a new frame is sent. A VGA mode also
indicates if the signal is interlaced.