[Asterisk-Users] Will Echo problems EVER be solved, I'm scared

[Andrew Kohlsmith]

On Wednesday 24 August 2005 16:37, canuck15 wrote:
> As others have recommended, I created a test system with the proposed
> production parts.  I bought a couple different SIP phones to try and a
> Digium TDM01B card.  I am using an older PIII 1Ghz system with 815chipset
> (PCI Rev2.2) with 256MB for my test system.  The only thing that will be
> different on a production system is that I will be using a newer chipset PC
> with faster processor and 512MB.  Probably Intel 7505, 7210, or 7211
> chipsets which seem to be the most compatible with Asterisk.

So in other words, everything will be changing on your production system.  Not 
a good way to start.

> My problem is that I cannot eliminate echo no matter what I try.  I
> seriously doubt that a newer chipset faster PC with more memory will
> eliminate or even reduce my echo problems based on what I have read.   I am
> not about to drop more cash to try and find out.  Essentially, my findings
> are that Asterisk is NOT production capable for my configuration which is
> via FXO and PSTN.  That is probably THE most common configuration so if it
> is not production capable like that it isn't production capable period as
> far as I'm concerned.  What a disappointment :(.

Most of us don't have any trouble.

> *Buy latest TDM400P with latest FXO module
> *Ensure copper connection to analog telco lines and telco are not causing
> problems including running a separate shielded line to the demarc AND
> having the telco guy come out and test the levels, impedance etc.

I'd be damn curious to know what you got out of this -- most telco guys will 
do a basic metallic check, throw on a butt-set and say "yup, I got dialtone." 
-- hardly a real check but that's neither here nor there.  I'm also in Canada 
(1.5hrs from Toronto, ON) so I'm *really* curious who you got on the line to 
do a real line test with you.  I have resorted to buying my own telco test 
equipment off ebay and using that, even though our techs here are excellent.

> *Adjust RX/TX levels as per Asterisk Wiki using the quick Ztmonitor method
> and by using the detailed Ztmonitor method via a Telco 102milliwatt test
> phone #.  The end result was RX=8.0, TX=-1.0.  Since I still have echo
> problems I have tried all sort of other settings without success.

Ok good.  Can you detail exactly what you did to reach these numbers?  I'm 
curious.

> *After ALL of the above, try every possible combination of all of the
> following on Asterisk v1.0.9: echocancel (off, on, 128, 256, 16, 32, 64),
> echowhenbridged (on, off), echotraining (off, on, 800), Mark 2 (default,
> aggressive, CVS head developments, bugs.digium.com patches, adjust
> threshold level as per wiki etc. etc.)

I'd posted something earlier that basically says this:  Without measured, 
controlled tests, you're just pissing up a rope.  Wildly changing settings 
and hoping for the best does nothing but cost you time and energy.

> *Run fxotune which did not find a need to adjust the FXO levels
> (1=0,0,0,0,0,0,0,0)

fxotune doesn't adjust FXO levels, it adjusts a very simple FIR filter which 
is part of the DAA in the FXO module.  IMO it helps with audio quality but 
not much with echo.

> Still have echo.  Aggressive mode helps a bit but then the other persons
> voice get's cut off a lot especially when I talk and the cutting in and out
> of the canceller is more noticeable and objectionable in general than if
> Aggressive is turned off.

Agressive mode turns the phone line into a half-duplex environment.  When your 
voice energy is detected it mutes the receive audio.

> I have two SIP phones.  An Aastra 9133i and a Grandstream GXP2000.  Echo
> problem is the same on both phones.

Do you have echo between the two phones?  What about when calling out to a 
VOIP provider, dialing a DID you own that comes back in and hits the other 
phone?

> Any comments and/or suggestions would be greatly appreciated as I am pretty
> much out of ideas and ready to give up on Asterisk as a suitable
> traditional small business phone system replacement.

I haven't seen your zconfig.h nor your zaptel Makefile, and you didn't tell us 
anything about your network (network card, switch, etc.).

My general advice for zaptel is to do the following:
zaptel Makefile: underneath the comments about zconfig.h add
KFLAGS+=-march=pentium4 (or pentium3 or pentiumpro, use the exact proc)
CFLAGS+=-march=pentium4 (or pentium3 or pentiumpro, use the exact proc)

and in zconfig.h
- enable XLAW (optimize for small # of zap channels)
- enable MMX
- MARK2, no agressive mode.

Whenever I've done that my echo has largely disappeared.  

Have you also tried flipping tip and ring going into the TDM card?

-A.