User manual
Small Vision System User Manual 11
3. Use a single framegrabber, and a stereo head that interlaces two video signals onto a single
video stream. The STH-V3 from Videre Design (www.videredesign.com) is one such stereo
head.
4. Use a digital stereo head, the MEGA-D (STH-MD1) from Videre Design. This stereo head
outputs a digital signal on the 1394 bus, and any OHCI (Open Host Controller Interface) card
can be used to input the video.
The SVS libraries can work with any size video frame up to 1288 by 1032 pixels. Standard NTSC
cameras capture frames up to 640 by 480, as a set of two fields, each 640 by 240. The camera first
captures a field in 1/60 of a second (the even field), then captures a second field 1/60 of a second later (the
odd field). The framegrabber can put these together to form a single image of 640 by 480 size. However,
the same problem with motion between non-genlocked cameras can occur on a single camera that
combines fields. There is a slight time delay between fields, leading to motion blur in the composed
frame. For this reason, the SVS libraries use fields rather than frames, so the maximum video size for
NTSC signals is 640 by 240.
PAL cameras are also support by the SVS libraries, as long as the framegrabber can input PAL video.
They involve similar considerations, but their maximum field size is 768 by 288.
Larger frame sizes with synchronized cameras are possible by using nonstandard progressive scan
analog cameras, or digital cameras.
2.1.2 Analog Framegrabbers
The SVS libraries include support for a number of popular analog signal framegrabbers, as well as
IEEE 1394 digital cards. The table below lists them according to their operating system.
Under MS Windows 95/NT, a particular framegrabber is accessed from the SVS libraries by copying
the corresponding DLL to svsgrab.dll, and the library file (.lib) to svsgrab.lib. For
example, if you have installed the Matrox Meteor board, then copy the file bin/svsmet.dll to
bin/svsgrab.dll, and bin/svsmet.lib to bin/svsgrab.lib. Whenever the SVS libraries
are invoked, the default framegrabber will be the PXC200 driver. The default must be set up before
starting smallv; it cannot be changed while the program is running.
Under Linux, the interface to either the Matrox Meteor cards or a Bt848 card (PXC200, Intel Smart
Video Recorder, etc.) is with the shared library metcap.so. Copy this library to bin/libcap.so to
use it. You must load the proper low-level driver for the card; see
ftp://ftp.rwii.com/pub/linux/system/Meteor/meteor-1.5.4.tar.gz for Meteor cards, and
http://robots.activmedia.com/bt8xx for Bt848 cards. SVS expects the devices to be called /dev/fg0 and
Operating System Framegrabber Library
Linux Matrox Meteor, Meteor RGB, Meteor PPB
libmet.so
Any Bt848-based card, e.g.
Intel Smart Video Recorder III
Imagenation PXC2000
libmet.so
1394 OHCI card
libpix.so
MS Windows 95/98/2000 Matrox Meteor, Meteor RGB, Meteor PPB
svsmet.dll
Matrox Meteor II
svsmet2.dll
Imagenation PXC200
svspxc.dll
MRT VideoPort Pro PC card (single card only,
slow)
svsvpp.dll
Any Video for Windows card (single card only)
svsvfw.dll
1394 OHCI card (Windows 98/2000 only)
svspix.dll
MS Windows NT 4.0 Matrox Meteor, Meteor RGB, Meteor PPB
svsmet.dll
Meteor II
svsmet2.dll
Imagenation PXC200
svspxc.dll
Table 2-1 Framegrabbers supported by SVS.