Re: What good is Aux Data, anyway?

Larry Chace (
Sun, 5 Feb 1995 21:28:08 -0500

David Winet recently (and resonably) asked: "What can one do usefully with
the Aux Data, please?"

At present, one can just implicitly use it, either with the "Talk" plug-in
routine or with the "Slide Projector" built-in routine. In the (near?)
future we will be releasing a "Software Development Kit" for those folks
who are brave enough to try writing their own plug-ins; these routines will
be able to use the Auxiliary Data Transport facility to send their own data
items, as may be appropriate.

This development kit will be a MetroWorks CodeWarrior project written in C.
We will provide a "shell", a basic prototype program designed and written
by Aaron Giles, formerly of the Cornell University Medical School;
developers may expand upon that basic shell as they see fit. As a part of
his work at CUMC, Aaron has written other plug-in routines for particular
tele-pathology applications, and we expect that there might ultimately be
quite a variety of plug-in routines because they provide a (somewhat)
simpler method of expanding and enhancing CU-SeeMe.

The Auxiliary Data Transport facility is a part of CU-SeeMe that provides
for the one-to-many delivery of arbitrary data items and includes "pretty
good" error recovery. These data items are sent in parallel with the
normal CU-SeeMe video and audio data and are further identified by an
internal 4-byte type field. The facility is of a "low-level" nature and
does not actually appear as any part of the user interface. However, if
you run the Aux Data Trace plug-in, you will be able to observe some of its
activity (even if that activity might not be all that intuitively obvious,
at least to the casual observer).

While this facility is currently available only in the Mac versions of
CU-SeeMe, we have started to begin to enter into the initial phases of a
Windows version as well. (That is to say, I now have a Windows development

Larry Chace (