Re: [vmeet] Audio echo

[Douglas Otis <[e-mail]>]

On Fri, 2009-04-24 at 17:58 -0400, Henning Schulzrinne wrote:
>
> However, you only need these fancy boxes if you run full-duplex. If
> you mute the floor microphones when the remote caller speaks (and vice
> versa), i.e., in half-duplex mode, there can be no acoustic echo. This
> is, I think, what Doug is proposing. This is more human effort, but a 
> whole lot simpler to install.

Agreed. Even assuming the PA and the RMC were somehow closely
integrated, depending upon the location of the remote speaker, the
data-center offering the RMC services, and the location of the meeting,
transmission line effects still introduce complex and unstable delays.  

In addition, acoustic echo canceling is never perfect even when all
audio sources are fed through a common system.  These system are
expensive and difficult to configure when the goal is to allow both near
and far sides an ability to talk freely. Dealing with acoustic residuals
when both sides are talking represents a rather daunting problem. 

A manual half duplex mode ensures that those in the meeting room will be
able to ensure good audio quality and its use at a very low cost.  Also
note that the suggested low cost BTC wireless keyboard has both volume
and mute buttons to make the effort of controlling the Net-Box audio
fairly minimal.  Use of RDP protocols would eliminate passing around a
keyboard, but this would be dependent upon the network.

A wireless keyboard might be handy during network disruptions as it
would enable a meeting to continue when the hotel router gets depressed.
Slides for the meeting should also be stored in the Net-Box prior to the
start of the meeting.  While these devices also accept nearly any type
of memory stick and contain system recovery images, it may be unwise
from a security standpoint to rely on memory sticks being freely passed
around.

-Doug