Subject: [XCON] Concerns about mahy-xcon-media-policy-control

From: Cullen Jennings <[email-masked]>
Date: Mon, 03 Nov 2003 21:25:37 -0800

I'm concerned that it will be incredibly difficult to build clients that
read the current media flow graph and can decided what needs to be changed
to perform some operation. I'm also concerted it will be very difficult to
build media processors that receive some graph and understand what they need
to actual do on the DSPs in a way that is efficient on the DSP resources.

Let me give an example. Alice has phoned a call center and is in a
conference that includes a call center agent Bob. Bob has conference in a
third party, called Carla, that validates that Alice said something was ok
to Bob. Bob supervisor, Doug, is listening to the call and can whisper to
Bob but currently has himself muted. A recording system is recording
everything Bob hears (including the whisper) and another recording system
monitor system records the stuff Carla hears and says. Carla's supervisor,
Zoe, joins the call and tries to form a sidebar with Carla and Bob but Doug
would still need to hear this sidebar since he hears everything Bob hears.

There are an infinite number of ways of forming a media graph that does this
conference. 

I have a hard time figuring out how Zoe's client is going to get the current
media graph and figure out what change it needs to make to this media graph
to form the sidebar and not violate the other constraints about the what the
recording systems need to record. I don't even know how Zoe's client is
going to present a user interface for what it can change about this
conference. 

Let's say that it did figure this all out and sent back a new media graph.
This new media graph needs to be run on a DSP platform that has several
DSPs. There are constraints to what can be cascaded. There are constraints
on how much can be run on a single DSP. There are other conferences running
on the same DSPs at the same time. There is highly optimized code for some
common situations. 

I don't know how the media graph is going to be compiled into a highly
optimized version of the conference that takes optimal use of the DSP and
does not violate any of the constraints. I worked on a compiler for a data
flow language that ran on a VLIW processor in a past life. The state of the
art in data flow optimizations is not all that great.

It's not that any of this is impossible, it's just that it seems very hard
to implement. Perhaps I am just being dense and not seeing how all of this
would be done. I think I need some convincing that either 1) it actually
fairly easy to do or 2) it's only hard in really weird cases and we don't
care about those. I would like to hear from other people that might actually
implement such a system on how hard it would be and what tweaks could be
made that make it simpler.

I was initially fairly keen on media graphs as a way of describing
conferences but the more I think about implementing them, the less convinced
I am that they are practical.

Cullen

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---

From: Marcus Brunner <[email-masked]>
Date: Tue, 04 Nov 2003 10:45:49 +0100

Cullen,

I agree, your example scarce me as well. I don't think media graphs are 
helpful in most of the cases. Naturally, there are some very specific case 
where it might make sense.

Marcus

--On Montag, 3. November 2003 21:25 -0800 Cullen Jennings 
<[email-masked]> wrote:

> build media processors that receive some graph and understand what they
> need to actual do on the DSPs in a way that is efficient on the DSP
> resources.
>
> Zoe, joins the call and tries to form a sidebar with Carla and Bob but
> Doug would still need to hear this sidebar since he hears everything Bob
> hears.
>
> There are an infinite number of ways of forming a media graph that does
> this conference.
>
> I have a hard time figuring out how Zoe's client is going to get the
> current media graph and figure out what change it needs to make to this
> media graph to form the sidebar and not violate the other constraints
> about the what the recording systems need to record. I don't even know
> how Zoe's client is going to present a user interface for what it can
> change about this conference.
>
> on how much can be run on a single DSP. There are other conferences
> running on the same DSPs at the same time. There is highly optimized code
> for some common situations.
>
> flow language that ran on a VLIW processor in a past life. The state of
> the art in data flow optimizations is not all that great.
>
> care about those. I would like to hear from other people that might
> actually implement such a system on how hard it would be and what tweaks
> could be made that make it simpler.
>
> conferences but the more I think about implementing them, the less
> convinced I am that they are practical.
>
> Cullen
>
>
>
>
>
>
>
>
>

--------------------------------------
Dr. Marcus Brunner
Network Laboratories
NEC Europe Ltd.

E-Mail: [email-masked]
WWW:    http://www.ccrle.nec.de/
Phone: +49 (0) 6221 905 11 29
Mobile: +49 (0) 163 275 17 43
personal home page: http://www.brubers.org/marcus