Subject: [clue] describing composed streams

From: Paul Kyzivat <[email-masked]>
Date: Tue, 24 Jan 2012 11:08:54 -0500

Based on what I have heard, I see the following possibilities:

1) there is no explicit indication of whether streams are composed or 
not. But still a composed stream will ideally indication the portion of 
the scene it covers, which would presumably be a union of those for the 
streams being composed. This could be nasty if that portion isn't a 
rectangle. (E.g. composition of left and right streams, but not the 
center screen.) It also is a problem if the streams being composed 
aren't part of the same scene. In that case it can't really describe the 
geometry of the composed scene at all. In the case of switching, such as 
active speaker, presumably the portion of the scene reported would be 
the union of all the potential speakers.

2) same as (1), but with a boolean indication for composed streams. IMO 
this doesn't add anything useful.

3) same as (1) but with addition of a free text description of what the 
stream contains. This isn't of any use for automated selection of 
streams to receive/display, but at least it can enable a user interface 
that can allow an end user in the receiving room to manually configure 
what streams should be displayed. Not ideal, but perhaps still useful 
for dealing with interop problems.

4) enumeration of the streams that are inputs to the composition of a 
composed stream. This is independent of the composition algorithm. 
stream that tiles the input streams would be described the same as one 
that switches among them. This would require that the streams that go 
into the composition also be (separately) described. This would be no 
issue if they are also available for independent selection. But if there 
are to be cases where the composition is available but the independent 
streams are not, then this would require more work.

5) description of how the composition is accomplished. It might be time 
or space multiplexing of the pixels. If time multiplexing, then the 
algorithm for doing so (active speaker, ...). If space multiplexing, 
then it could include which region of the composed stream contains each 
composed stream. There could also be a combination of time and space 
multiplexing. And this could also be hierarchical, if one or more of the 
input streams for composition are themselves composed.

	Thanks,
	Paul