[Asterisk-Users] Fun with Echo

[Andrei (MPI)]

Brian,

You may actually get better results lowering size of the buffer. Here 
are my settings that have been working nice so far on TDM400 (1+ year):

echocancel=64
echotraining=800
echocancelwhenbridged=yes
rxgain=2.0
txgain=-4.0

Notice difference between receive and transmit levels. That's essential, 
too.

Andrei (MPI)

Brian Swan wrote:
> I've spent the last week or so troubleshooting echo problems at my 
> Wife's business, and I've been able to clear up about 99% of the echo, 
> but there is still a little residual echo that I can't seem to "tweak 
> out".  The users describe it as "buzzing or crackling", but what it 
> sounds like to me is a slight echo, but just of one syllable of the word.
>
> I've followed the numerous suggestions in the mailing list archives 
> which is what has enabled me to get this far.  After trying all the 
> echo cancelers, and all the settings on each I settled on:
>
> - KB1 (with AGGRESSIVE_SUPRESSOR)
> - echocancel=128
> - echotraining=600
> - rxgain=0
> - txgain=0
>
> If I turned up the echocancel to 256 I'm able to eliminate the 
> "buzzing" echo, however, on inbound calls I get a HUGE very loud echo 
> that takes a good 20 seconds to go away (which I don't get on 
> echocancel=128).  Does anyone have any suggestions on how 
> troubleshoot/tune this to eliminate the "buzz"?
>
> Here's my setup:
>
> Asterisk 1.2.9.1
> Zaptel 1.2.6
> TDM400P (3xFXO, 1xFXS)
> 6 Cisco 7960's running chan_sccp2
>
> Along the same lines, in my hunt for echo, I was rather disappointed 
> that I couldn't really find any tools to help troubleshoot the issue.  
> It seemed like the general consensus was "Play with all the settings 
> until it sounds good".  I did manage to compile the Zaptel driver with 
> the Zaptel "preload" patch, which helped me visualize my echo problems 
> a bit, but preloading didn't get rid of the buzz.  Also, I've 
> eliminated inside wiring by moving the Asterisk box to my demarc to 
> test, I also tried the TDM400P on different hardware to ensure it's 
> not a motherboard issue.  But, at the end of the day, those are all 
> just stabs in the dark...
>
> If anyone has any suggestions, I'd sure appreciate it!
>
> Thanks!
> Brian
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