Inconsistent references to H.281

Toby Nixon tnixon at MICROSOFT.COM
Fri Nov 21 18:01:28 EST 1997

We were poking around a bit for information on far-end camera control, and
ended up searching for references to H.281 in most of the documents being
decided in January. As a result, we uncovered some inconsistencies that may
require editorial correction of the decided texts of H.245, H.246, and

(1) H.245 section 2 refers to 1996 versions of H.281 and H.224. We can find
only versions published in 1994. However, I note that although H.224 and
H.281 are listed as references, they are not actually referenced in the text
of H.245 anywhere, either by name or by the reference number.  Either these
references should be deleted from section 2, or the dates changed to

(2) H.246 refers to H.281 and H.224 in section A.9, but they are not
included in the references in section 2. The solution here could be to
simply remove section A.9, since it is "for further study"; if this is not
done, H.281 and H.224 should be added to section 2.

(3) H.323 version 2 refers to H.281 and H.224 in section 6.2.7, but neither
of these are included in the references in section 2. H.281 and H.224 should
be added to section 2. Note that H.323 version 1 had the same problem.

The reference in H.323 and the presence of
DataApplicationCapability.application.h224 in H.245 seem to imply that
H.281/H.224 can be used in H.323 terminals. It would seem fairly
straight-forward to open a camera control data logical channel associated
with a video channel and send H.281 commands. Does anybody actually do that
today? Has it even been prototyped? Have details been worked out, such as
whether it would be a TCP or UDP connection? Or was this intentionally
postponed while T.130 work proceeded? If that's the case, should it be
resurrected considering the state of T.130? Is H.281 simply considered not
suitable for use on IP/Internet (due to latencies)? If so, is there desire
to work out H.245 extensions to do the same things?  I'm sure you've all
discussed this before I was around; sorry.

        -- Toby
Toby Nixon, Program Manager - NetMeeting
Microsoft Corporation, Applications and Internet Client Group, Redmond  WA
+1 (425) 936-2792     Fax: +1 (425) 936-7329    mailto:tnixon at

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