[AG-TECH] Echo question - need 3 sites?

[Robert Olson]

you don't even need a loop.

Consider two nodes and their audio pathways:

Mic 1	 ------> [agnode 1] ----> [network] -----> [agnode2] ----> Spkr2

Spkr 1	 <------ [agnode 1] <---- [network] <----- [agnode2] <---- Mic2

If Mic2 is picking up audio from Spkr2 and sending it to the network, site
2 will be generating echo from site 1 on the Mic1->network->Spkr2->[via
air]->Mic2->network->Spkr1 path.

This precisely defines the job of the EC hardware:  since Mic2 most likely 
*will* pick up audio from Spkr2, the EC gear must stop that audio from 
being transmitted to teh network.

If there were more than two nodes, you can rewrite the above picture with 
site3, site4, etc in place of site 1, and see how one faulty site can 
generate echo that everyone hears. (since everyone will hear both the 
input from mic1 and the echoed and time-delayed sound of mic1 as picked up 
by mic2).

--bob

On Mon, 20 Oct 2003, Sam Liston wrote:

> Point 1: correct.
> 
> Point 2: Two sites can experience echo problems.  If both sites are not
> canceling in their mics the signal coming out of their speakers (from
> the other site) a loop is created and the result is echo.
> 
> Sam 
> 
> 
> -----Original Message-----
> From: owner-ag-tech at mcs.anl.gov [mailto:owner-ag-tech at mcs.anl.gov] On
> Behalf Of Michael Daw
> Sent: Monday, October 20, 2003 10:56 AM
> To: AG Technical Developers
> Subject: [AG-TECH] Echo question - need 3 sites?
> 
> I just wanted to confirm something that I (think I) heard quite early on
> in
> my Access Grid life:
> 
> 1. If a site has an echo problem, they don't hear it, right?
> 
> 2. If you're having a meeting where only 2 nodes are involved, neither
> node
> will hear echo, even if one of those nodes would have an echo problem if
> 3
> nodes were involved.
> 
> Can anyone confirm/correct me on this, please?
> 
> Thanks,
> Mike
> 
> _______________________________________________________
> 
> Michael Daw, e-Science Consultant
> SVE Group (Supercomputing, Visualization and e-Science)
> 
> Manchester Computing, Kilburn Building,
> University of Manchester, Manchester M13 9PL, UK
> 
> Tel: +44 (0)161 275 7026
> Fax: +44 (0)161 275 6800
> E-mail: michael.daw at man.ac.uk
> 
> http://www.sve.man.ac.uk/General/Staff/daw
> _______________________________________________________
> 
> 
>