New this year, we have the computational sensor machines
(Shark-name Linux boxes) most of which contain twin "Osprey" digitizer cards
that use the BT848 digitizer chip.
These digitizers each have one S-video, and 3 color composite input channels.
Presumeably you can feed in a monchrome signal as well, and have it
digitize to (nearly) identical r, g and b components.
You can switch between these channels in software in a frame time or so,
which means you can hook up multiple composite cameras to a single chip
(if two cameras per machine is not enough).
The program, bt_get_image in /u/nelson/programs/bin/[PCLinux], source in
/u/nelson/programs/src/digitizer/bt848/bin, will grab
an image from this digitizer and store it in a tiff, pgm or iff file
depending on the suffix of the output file.
By default this grabs a monochrome image from the green channel,
digitized from the S-video input of board zero, but these
defaults can be changed by providing appropriate options
(e.g. -color). Use -h to get a list.
Looking at the source for this program will illustrate how to
use library calls to incorporate image input into a program.
The program bt_showlive (also in my bin) will show a live feed from
the camera on the screen.
This is useful for adjusting the image.
However, it must be terminated before grabbing an image, because
the bt848 digitizers can currently be accessed by only a single process
There are KTV300 digitizers on several of the lab machines,
(1 on Brain, 2 on Aorta at the moment, and two in the 7th floor software lab
on Milli and Kilo).
These are rgb devices, and need an rgb input for color.
The easiest way to get a gray-scale image is to use the green channel
of an rgb signal.
If you have a monchrome camera, you can feed the mono signal to the green input
and synch on green.
Feeding a composite color signal into the green channel, though it
works on many digitizers, causes problems in the KTV devices in the form
of high-frequency noise in the digitized image.
Feeding the Y component of a YC signal to the green channel seems to work ok.
The main drawback of these digitizers is that they are S-bus devices, and
thus can be installed only on our older (and slower) Suns.
The program, ktv_get_image in
/u/nelson/programs/bin/[SunOS, Solaris], source in
/u/nelson/programs/src/digitizer/ktv300/bin, will grab a monochrome off
the green channel, and store it in a tiff, pgm or iff file depending
on the suffix of the output file.
ktv_get_color_image will get a color tiff, iff or sun raster image (.ras)
again depending on by the suffix of the output file.
ktv_getras, will also get a color sun raster file.
The program xv
can be used to convert tiff and Sun raster (.ras) images into other formats
The program ktv_showlive will display a live feed from the camera
on the screen. The ktv digitizers will allow simultaneous access by
multiple processes. This means that you can grab a picture without
shutting down ktv_showlive, but it also means that someone can
asynchronously foul up your carefully arranged digitizer setting without
your say-so. Oh well...
The program ktv_getiff_sequence will grab a (monochrome) sequence
and store it as an iff sequence file, which can be read back
in for analysis by programs in the ipp libraries.
Currently no analog for BT848, but it would be easy to convert.
Sorry, no MPEG grabbers for either digitizer...
One of the older computational sensors has
Matrox meteor digitizers installed.
It is currenently in the Med center, but could be useable if anyone
needs special capabilities of these digitizers.
They are not integrated into the department infrastructure,
and utility programs for using the digitizers have not been publicly
installed. Brandon Sanders can probably give you enough pointers to get
off the ground if you are interested in trying to use them.
The SGI machines can be used to obtain images from a video stream,
but they need a specific digital video format.
We have converters in the lab for producing this format from
analog inputs. I'm not sure of the details.
Kyros Kutulakos was the local expert on this, but is not here now.
Paul Illardi might know how to digitize from them if anyone has
a hankering to know, as he works with the graphics end of these machines.
There is (or used to be) MPEG video grabber for the SGI called "capture".
Not sure of current status, but it will probably still work.
Some of the Macintosh computers will also digitize images.
Seems to me that George Ferguson once did something with a video camera
and one of our Macs, so you may want to talk to him if you like apples.
vision course main page