[Sems] Silence Suppression

Dave Bath dave at fuuz.com
Tue Apr 19 09:18:17 UTC 2005

Hi Raphael..

Thanks for a swift reply, although with quite frustrating news!! 

I am in desperate need of a conference server which fully supports
discontinuous transmission.... such that if there is no data in the
conference it doesn't send any data to the clients. 

I am not really a coder.. but I have had a quick look at the source code
for SEMS and it appears that the outgoing RTP stream is assembled in
AmRtpStream.cpp.  How easy would it be to add a conditional statement
there just before the RTP was actually sent out which looked at the
contents of what I assume comes from the mixer module and says "if the
packet contains silence, then don't bother sending it out". 

I know this would break functionality for clients which don't support
discontinuous transmission... but might provide me with a quick and
dirty hack to achieve the goal.

I know that SEMS has a 2min timeout (if nothing is received from a
client in 2 mins then it kills the client connection).  However, the
client can be modified to send a couple of silence packets every 90
seconds or something.. this would keep the timeout from triggering.. but
as the "hack" would be placed *after* the mixer, it seems like full
discontinuous transmission might be achieved.

Does anyone have any ideas? Or a little bit of code which would work?

All help would be amazing!



-----Original Message-----
From: Raphael Coeffic [mailto:rco at iptel.org] 
Sent: 19 April 2005 09:06
To: Dave Bath; Stefan Sayer
Cc: sems at lists.iptel.org
Subject: Re: [Sems] Silence Suppression

Hi Dave,

as we said that SEMS supports silence suppression, we meant that it
have any problem if a client uses silence suppression.


----- Original Message ----- 
From: "Dave Bath" <dave at fuuz.com>
To: "Stefan Sayer" <sayer at cs.tu-berlin.de>
Cc: <sems at lists.iptel.org>
Sent: Monday, April 18, 2005 10:39 PM
Subject: [Sems] Silence Suppression

Hey there...

Sorry to prevail upon your help again.. but I was wondering about the
state of silence suppression in SEMS - in the conference module.  An old
forum post I read said that it was supported... but it appears from my
trials that it's not.. if two clients join a conference, even if they're
not sending any data themselves, SEMS seems to keep sending out data.

Perhaps this is a config option?

Any help would be very very much appreciated!


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