through the opaque looking glass

elliot smith (smithe@minot.com)
Sat, 8 Jun 1996 14:38:37 -0500


Yeah, it's kind of hard breaking through the sludge of low-bandwidth...
Here is what I have figured out about using a www slide show for conferencing.
It's an exciting prospect. A W3 slide show would have a maximum
rate of 1 or 2 fps and more probably 5 or 10 fps, so it is not full
motion video like cu-see-me, but it does have some advantages over
cu-see-me and it is in it's self useful so it could be used to
supplement a cu-see-me conference or it could be used at times where
cu-see-me might not work such as with low-bandwidth participants or
if you had lots of participants.
The way it works: One or more of the participant's computers is
designated a 'reflector.' This simply means it is a www server.
(WWW servers, web-cam programs, ftp programs, unix-talk programs,
and bbses are availaible inexpensively or for free, and are mostly
easy to set up. Distribution of settings files (preferences files)
would make it even easier)
A set of FTP scripts can be set up to allow anyone to send the
picture from their web-cam program to the reflector.
Use of a BBS would allow everyone to type into the same ascii-text
window. Maybe using some kind of Internet telephone program would be
cool too. But I don't know anything about that. Also, use of
unix-style talk clients can allow up to 6 people to chat in private
via the keyboard.
The refelctor, or server, need not be all that powerful.
Compression can reduce the picture down to about 6k or so. This is a
picture from a quick cam, thus 4 bit greyscale, 3 or 4 inches square.
I figure that my crummy old Performa 475 (68040, 8/160, 33 MHZ or
so) could support 20 people downloading the picture at 1 Frame per 10
seconds. This is on localtalk. If you get a powermac, PPC, or
pentium (yech) on ethernet you could easily have 100 people access
the image at this frame rate. FTP scripts can link together the
reflectors. So if the conferencing group can scrape together enough
computers there is less limit to the size of the conference than
there is with cu-see-me.
The server would have an html page with an in-line reference to
where the ftp scripts are dumping the .gif or .jpg. It would have
auto-refresh so that it would automatically load. You would have
several identical pages with different auto refresh rates, all of
them interlinked so that people can choose their own rate. NEtscape
1.0 or later would be required for the auto-refresh feature, but
people could manually update the page by using any other browser.
I think the best frame rate you can get is 1 FPS, but if you have
the hardware and bandwidth to do that you should be using cu-see-me
:-)
That's as far as I'm going to take this idea for now, but if anyone
would like any help implementing the macintosh end of the software
let me know. Or if you just have any questions e-mail me. I had a
demo up at http://165.234.217.240/vm.html and last I checked it was
still working, but won't be for long in anycase. NOte: if you get a
black picture, it's because the room is dark. By looking at the fuzz
in the picture induced by the compression you can tell if the web-cam
program is still updating it every 5 seconds. If all you get is
static, well the I guess someone stole the camera :-)

http://minot.com/~smithe/ http://admin.gat240.misu.nodak.edu/
PPP setup info. for Macintosh. Add your page to the VWeb index
PGP, Francais/English CS student, MSU, Minot ND, USA