[Asterisk-Users] Tweaking AGGRESSIVE_SUPPRESSOR

[Steve Kann]

Andrew Kohlsmith wrote:

>On March 7, 2005 01:23 pm, Dennis Webb wrote:
>  
>
>>Using TDM400's here and I have tried everything to cure the echo.  I
>>have used the Milliwatt test from the telco and from asterisk to tune
>>RX/TX gain via a patched ztmonitor.  What happens is I experience
>>midcall echo.  I turned on aggressive_suppressor and it seems to do
>>great.  The problem happens with misc. noise around the office will
>>cause it to mute the other end of a phone call while they are talking.
>>I haven't been able to find anywhere in the MEC2 source to limit when it
>>mutes the remote party.  It seems to do it with just the slightest bit
>>of sound coming from the room.  What are my options besides getting mad
>>and ordering a PRI and a TE100?
>>    
>>
>
>PRI and TE110 won't save you; we've had echo issues with our TE405P and a Bell 
>Canada PRI.  All the PRI does is ensure *you* are not causing echo.
>
>Now I'm curious -- What physical phones are on either side of this call?  Do 
>you have a speakerphone on?  I've never heard of an echo canceller acting how 
>you describe, but lots of speakerphones do exactly that.
>  
>

What he describes is echo suppression.  Because an echo canceller can, 
generally, only remove some part of an echo, not the entire echo, 
systems are generally designed to suppress the residual echo in some 
circumstances.  Old speakerphones had poor on no echo cancellation, so 
the suppression kicked in like that, because it was the only choice.  In 
modern systems, the echo cancellation is much better, so suppression is 
not needed as much, and when it is used, it's probably done much more 
imperceptibly (with comfort-noise and stuff like this).

The AGGRESSIVE_SUPPRESSOR option enables, as it is named, more 
aggressive echo suppression.

-SteveK