Subject: [dispatch] Telepresence charter comments

From: Ted Hardie <[email-masked]>
Date: Tue, 21 Sep 2010 10:20:14 -0700

Howdy,

I was asked off-list to take a look at the Telepresence charter
currently under discussion,
and to try to relate it to work previously done in CONNEG or other
APPS groups (I chaired
the CONNEG group donkey's years ago, and some sins seem to follow you
no matter what).
For those not familiar with CONNEG, the charter is here:
http://www.ietf.org/wg/concluded/conneg
Some additional backstory is that the two working groups with strong
needs in the area
were HTTP and Internet Fax.  The fax folks had a long history of
negotiation using T30
frames, and needed a way to accomplish the same thing on the internet;
the HTTP group
wanted to get away from user-agent based content negotiation and
toward something
that allowed description of media features "and enable  the
development of a cross-protocol
vocabulary for exchanging  information on recipient capabilities,
characteristics, and
preferences."  This same system was later adapted in SIP contexts in
ways no doubt
familiar to you.

Reading through the telepresence charter, I do see some potential
parallels.  You have
a need to be able to describe the systems in use (number of cameras
and their angles,
number of mics, etc.), for example, in ways that are "system features"
similar to media features.  You also
seem to be heading down a path that will lead either to active
negotiation or recipient selection
from a set/collection of system aspects that the sender believes works together.
The main difference is in the charter's description of "semantic
information about what
each media stream represents."

Trying to draw helpful lessons learned from conneg for this work, I
have three pieces of charter
advice.

First, set an early milestone that describes the framework by which
physical system
features will be described.  This is a relatively concrete piece of
work and it is useful in
a variety of contexts.  Deciding early whether the group wants
registration or some other
interoperability mechanism for describing those will also inform later
discussion in useful ways.
At least to a first-time reader the two current milestones seem to
require the entire system
to be described and then the entire solution to be specified.  In
general, smaller chunks may be easier,
and they will certainly help the group focus, given the broad set of
issues you are tackling.

Second, make one of the use cases one in which there is no human
present at one or more
ends of the telepresence system.  A use case recording a telepresence
session could be
enormously useful in keeping the semantic discussion on target.  It is very
difficult to avoid saying "user selects among...." in these case or to
presume that the
users under semantic statements because they can parse natural
languages.  If the system
works when there is no user present on one side, it will work far
better when users are
present on both.  This will require a lot of discipline on the part of
the working group, and
some stuckee (probably a chair) to say "how will this work in the
recording case" a lot,
but I firmly believe it will help make the system more usable overall.

Third, the current charter notes that the group will define a
transport mechanism, but
also says that it expects the work may be applicable beyond audio and
video streams.
There is a tension between these two.  If this will be applicable
beyond those, there
is a fairly hard requirement that the syntax/semantics be transport
agnostic.  The group
should decide early on whether or not it will define a
transport-agnostic syntax or not.
Given the likely growth in collaboration environments that combine
audio/video with
other types of media, I personally suspect that this aspect could end
up being the
most important part of the overall system.

I hope you'll forgive my parachuting in with such a long set of
comments.  I'm also not
currently following dispatch closely, and I would appreciate being
cc'ed on any questions
or comments to which you'd like me to respond.

regards,

Ted Hardie

NB:  My current employer has products in this space (along with
bicycles, photovoltaic
panels, avionics-focused entertainment systems, and pretty much
anything else you
can think of).  I am not involved in that work at this time, and my
opinion in no way
reflects their thinking on this matter.

---

From: Marshall Eubanks <[email-masked]>
Date: Tue, 21 Sep 2010 14:42:16 -0400

> but I firmly believe it will help make the system more usable overall.

Dear Ted;

I have no trouble with any of this.

The second point is (IMO) not as artificial in immersive Telepresence as it might seem. There is a strong desire
to "just have things work" in these multi-screen units or, to put it another way, interop is now frequently done
behind the scenes by humans at some service provider, and getting telepresence interop truly automated is a major driver in this work.

Regards
Marshall

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