Subject: [clue] Notes from today's interim meeting.

From: Marshall Eubanks <[email-masked]>
Date: Tue, 23 Aug 2011 15:50:10 -0400

It ended just in time, as I lost cell service when the Earthquake happened.

Regards
Marshall

-----------------------
Notes :

Clue Interim August 23 2011 Noon EDT.

Attendance via WEBEX

Mary Barnes
Marshall Eubanks
Andy Hutton
Andy Pepperell
Basavaraj
Brian Baldino
3 Call in Users
Charles Eckel
Claude Lamblin
Dan Romascanu
Espen Berger
John Elwell
Jonathan Lennox
Mark Duckworth
Michael Lundberg
Paul C
Paul Kyzivat
PM
Robert Sparks
Roni Even
Sfry
Sohel
Spencer Dawkins
Stephan Wenger
Tom Kristensen
Allyn Romanow

Started with the usual administrivia

Allyn -

<I missed the beginning of this short presentation>

We would like to encourage people with other use cases to step forward.

Mark Duckworth - Attributes

Audio attributes
Video attributes
Mixed attributes

The sender can tell the receiver a little something about the streams they
might want to receive.

The Audio Channel Format (Mono, Stereo, Linear array) could be extended

In Video, spatial scale is how wide it is in real world units.

If there are three people, Image width might be 1.5 meters.

Capture scene : Various options for how captures might be done.

Say there are 6 people - might be 3 screens, 2 people each, might be 2
screens, 3 people each, might be 1 screen, switched based on voice with PIP
for the rest.

A capture set is used to form capture set rows, each being the screens from
one of the previous examples.

Andy Pepperell - Choosing streams

The 3 element handshake

                                  Media Stream Consumer     Media Stream
Provider

Consumer capability advertisement |----------------------------->

Media Capture Advertisement       <-----------------------------|

Consumer config of provider       |----------------------------->
streams

Roni : How does this relate to the previous part ?

Andy : This is more to do with the mechanics to make things happen.

Roni : This is a whole different set of parameters.

Andy : That's correct.

Roni : It's currently not in the document.

Andy : The document is not up to date.

Capabilities sent by consumer (at start of the session)

It sends hints about itself, such as the number of screens, software
limitations, etc.

Then the MSP uses that in a media capture advertisement, using facts such as
the number of cameras available.

Also dynamic factors could cause a new Media Capture Advertisement, such as
starting to share a document.

The MSC then combines media capture advertisements with its characteristics
to send a stream configure message

Media Capture Advertisement == Provider Capture Advertisement

Capture attributes, simultaneous transmission sets, capture sets, and
encoding groups.

Encoding groups - multiple potential encodes - to enable provider to convey
restrictions to the consumer

Brian Baldino

Examples

If I have only one screen, I want a single capture of the entire video and
audio scene

This could come directly from a physical device, or from a composition of
some devices.

There is a spatial relationship between elements and a ROW of capture set

VC0, VC1, VC2 implies a spatial ordering (left to right)

There is nothing to prohibit a consumer from picking different capture set
rows for audio and video

MCU Scenarios

What might a MCU want ? It might want to accommodate everything connecting
to it. It may chose to receive ALL captures available to it, or only the raw
captures, or only one choice, etc.

Presentation streams are part of a separate capture scene, with no spatial
relation between them.

Questions ?

Roni : I am not sure about the concept of the capture set. What can be sent
at the same time.

Brian : There is a separate simultaneous transmission set, what can be sent
at the same time.

Andy : Multiple capture sets represent the same scene.

Roni : Does a capture set mean what can be sent simultaneously.

Brian : They don't convey any information as to what can be set at the same
time.

Suppose you have a camera that can be zoomed in to capture 2 people, or
zoomed out to capture the entire scene. It can't do both at the same time.

Roni ; So, Vc3 could be a zoom out, or a composite picture. How do you
distinguish between these two cases.

Brian : That cannot be conveyed in the capture set.

Roni : So there is one part to describe capture sets, and another to convey

Paul K. : If you have mutual exclusion, then when you pick one (say zoomed
out) that exclude the other

Stephan : You are excluding a model where the MCU is hiding all attributes
of other endpoints.

Brian : If an end point can only do one or the other, somehow a decision
must be made.

? : The MCU can be a producer or a consumer, and they have very different
models.

Roni : If there are physical limitations you have to pick one.

Mary : Roni, if you think this is something people are doing or are likely
to do, please write it up.

We are not designing for all possible cases.

Andy : We wanted to focus on the simplest MCU cases. There are so many
possibilities.

Brian : From my point of view I don't think you should send all possible
capture sets. A middlebox might have to make some sort of reasonable
decision on what to exclude.

Andy : There might be other constraints, such as middlebox CPU.

Paul K : I am having trouble with understand what "mix" means.

Brian : In video we used the term "composed."

Paul : Would this be conveyed even if you didn't say the term "mixed" ? It
could be composed, or produced by zooming out, for example.

Andy : A stream might be happy to receive a composed stream while a MCY
might not.

Paul : I would like to see a more precise definition of what it means.

Andy : We are keen not to specify algorithms.

Roni : What is repeated ? Can a consumer change its Consumer capability
advertisement  mid-meeting. In the MCU case it may change mid-call.

Andy : I so reason why not.

Brian : The word "hint" is a little of a misnomer.

Paul Cloverdale : What we want is what does each end point got ?

Andy : The number of physical screens - some people thought this would be
useful.

Paul Cloverdale  : The users may want to have some control over what they
see.

The protocol should provide all the information you need to reconstruct a
telepresence session at the far end, no more and no less.

In the end you don't want you design the whole system…

My point is that the key aspect is that all of the key attributes are known
to the other end, we are putting all of the hooks in place.

Allyn : That is exactly what we have tried to do. We are trying to find the
minimum set of information necessary, not the maximum.

Paul Cloverdale : I clued in on the terms, hints.

Allyn : We can certainly take the term out.

Roni : Are we trying to support just some low level system, or are we
supporting telepresence.

It says something here about "good enough" or strange terms like that.
 "Satisfactory reproduction."

Paul C. : I think that your letter has opened a big can of worms.

Roni : The manufacturers will always have some secret sauce.

Paul C. : This is way beyond CLUE. CLUE should just be about providing
hooks.

Jonathan L : Roni, you should come

Mark : You didn't think the issues are related to use cases

Roni : Today, when systems talk, they know the architecture of the other
site, where the cameras, etc. The current model doesn't address this?

? : Can you provide a use case ?

Roni : I will give an example about why this is important.

Paul : Is there a difference between stereo and linear array with 2 elements
?

Charles  E. : You might have a stereo mike in the middle, rather than two
mikes.

Paul : Is there a difference between that and 2 mono mikes ?

Charles : I would assume so. I am not an expert.

Mark : A very specific case of stereo could be considered a linear array,
but saying that they are always the same isn't quite accurate.

Meeting ended 1346 EDT.

5.9 Earthquake at 1351 EDT.