[AG-TECH] Re: AGN PIG echo cancel?

Jay Beavers jbeavers at microsoft.com
Thu Sep 19 19:17:22 CDT 2002

On the low end, Windows XP ships with software audio processors to
handle acoustic echo cancellation, noise reduction, and automatic gain
control.  These were implemented to support the IP telephony features of
Windows Messenger.

The limitations of these filters are twofold:

 * Optimized for a 10'x10' room
 * Only works with one microphone

Since these are showstoppers for even small group collaboration and
since my scenarios are in the small group or large group scenarios, I
haven't investigated this technology in an AG context.  However, given
the length of this thread looking for an inexpensive 1-mike solution,
perhaps there's some significant interest here.

When I've looked in the past, these filters are visible to DirectShow
but undocumented.  If someone expresses significant interest in this low
end functionality, I can try to do the digging / persuading to get this
functionality documented.  Success is not guaranteed, sometime code like
this is too coupled to be easily separated from the hosting application,
but I'm willing to try if someone is willing to commit to attempting to
use them inside a DirectShow / DMO environment.

The ConferenceXP code is based on DirectShow and DMOs can be inserted
with a few lines of code.  Since source code for this is available, it
would make a good testbed to try this out.

 - jcb 

-----Original Message-----
From: Matthew Wolf [mailto:mwolf at cc.gatech.edu] 
Sent: Thursday, September 19, 2002 8:07 AM
To: Don Morton
Cc: pwilson at lookout.itrc.umt.edu; gerdes at selway.umt.edu; Sergeant A. G.
Subject: Re: [AG-TECH] Re: AGN PIG echo cancel?

I did quite a bit of searching on this not too long ago.  It seems that
there's a big gap in price/quality on echo cancellation.  You go from
$400 to $2000 without much in between.

At the low end, for less than $500 you can get a speaker phone with
built-in echo cancellation and an interconnect to your PC.  ClearOne's
phone does the pc interconnect by default -- from polycom you need to
buy it separately.  Total cost is about a dead heat -- Polycom was a bit
cheaper in my case, so that's what I went with.

You then jump up to the dedicated echo cancellation gear plus
microphones, which is in that $2-5k range.  Polycom & ClearOne are the
two players, near as I can tell.  Polycom bought ASPI recently, and it's
the ASPI products that Polycom's pushing (the Vortex line). 
Unfortunately, you need to go through a local vendor in order to get
prices & info, since the polycom/ASPI web page meshing is still under

Here are some useful price links for the low end stuff I was talking

Soundstation phone

Video interconnet for polycom soundstation (to hook to PC)

ClearOne phone

I hope this helps!


Don Morton wrote:
> Paul,  I'm forwarding your question to the AG-Tech list,
> since I really don't have a clue.  Maybe someone out there
> can help?
> pwilson at lookout.itrc.umt.edu wrote:
> >
> > Hello,
> >
> > I have been reading about echo cancellation and background noise
> > filtration in reference to the Polycom and Clearone (used to be
> > Do you have any opinions about either of these companies?  I have
not yet
> > been successful in tracking down polycom prices.  The decent Gentner
> > products seem to be in the $2000 to $5000 range.  Do you know if
there are
> > other quality echo and background noise cancellation devices in a
> > price range?
> >
> > Thank you advance, for your help.
> >
> > Paul
> --
>    Don Morton                   http://MRoCCS.cs.umt.edu/~morton/
>    Department of Computer Science       The University of Montana
>    Missoula, MT 59812 | Voice (406) 243-4975 | Fax (406) 243-5139

        -- Matthew Wolf 
        -- Research Scientist, IHPC Laboratory
        -- College of Computing, Georgia Tech
        -- mwolf at cc.gatech.edu

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