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

Michael Daw mike.daw at man.ac.uk
Tue Oct 21 02:33:33 CDT 2003


Thanks to everyone for their full answers. Misconceptions are corrected!

> -----Original Message-----
> From: owner-ag-tech at mcs.anl.gov [mailto:owner-ag-tech at mcs.anl.gov]On
> Behalf Of Robert Olson
> Sent: 20 October 2003 19:43
> To: Sam Liston
> Cc: 'Michael Daw'; 'AG Technical Developers'
> Subject: RE: [AG-TECH] Echo question - need 3 sites?
>
>
> 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
> > _______________________________________________________
> >
> >
> >
>
>




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