[Asterisk-Users] Fun with Echo

[Tim C. Lewis]

yeah this post is old and there have been dozens of replies, but here's 
some feedback for the list, now that i have some.

we're using a sangoma a102 card (no hw ec) with 2 pris from sbc. 
asterisk 1.2.7.1, zaptel 1.2.6 (much testing previously with 1.2.5).  we 
first used:

KB1 (not aggressive), echocancel yes (128), echotraining yes (400), 
rxgain/txgain 0.

most calls with this setup were fine, but maybe 5% of pri calls were 
reported as having anywhere from slight to completely unbearable echo.

playing with echocancel yielded worse results.  256 got results similar to 
Brian's report below.  64 yielded echo on calls from numbers that never 
had echo before.

we're now pretty settled on similar settings to Brian's: KB1 (WITH 
aggressive), cancel yes (128), training yes (400), gains 0.

AGGRESSIVE_SUPRESSOR made a huge difference for us.  reports of bad echo 
on calls dropped from one or two reports per day to 0 since we started 
using this setup about 2.5 weeks ago.  i still receive the occassional 
report of slight echo on a call or two (or slight echo at the beginning of 
a call that goes away), from people who i actively ask about it, but for 
the most part everyone is very content.

i also played around with MG2 (non-aggressive), per suggestions on this 
thread, but aggressive KB1 showed better results in a few tests.  i have 
not as of yet tried aggressive MG2.

looking over our cacti logs, load average on the system didn't noticeably 
change between any of our echo handling changes.

anyway, i know there's no silver bullet for software ec, and anyone 
reading this looking for ideas should be sure to keep that in mind, but 
this thread gave us a number of ideas to try, so i wanted to report some 
of the results.

good luck, all!

-tcl.


On Thu, 8 Jun 2006, 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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