[Asterisk-Users] UPDATE - Echo cancellation, when softwaredoesn't cut it. Whats next?

[Anton]

No it points to Cell phone companies having better hardware echo
cancellation on their lines, also cell phones themselves have a hardware
echo can built in.
----- Original Message ----- 
From: "Mike Benoit" <ipso at snappymail.ca>
To: <asterisk-users at lists.digium.com>
Sent: Monday, July 12, 2004 1:52 AM
Subject: Re: [Asterisk-Users] UPDATE - Echo cancellation, when
softwaredoesn't cut it. Whats next?


> Here's an update on my progress for all who are interested.
>
> After carrying out many more hours of testing, the only thing that made
> a significant difference was changing the mainboard/CPU of my asterisk
> server.
>
> My original Asterisk server was a Celeron 533 with 128mb ram. Now, keep
> in mind, even with 5 channels in use at a time, the CPU usage was always
> minimal, the load never went above 0.2 that I saw.
>
> First I upgraded to a brand new Celeron 2.4Ghz with 128mb ram, and
> immediately noticed an improvement in the echo.
>
> Incoming calls now have virtually no echo. I have to really try to hear
> it. Outgoing calls still have echo, but after about 30 seconds it mostly
> goes away during normal conversation. Still not 100% acceptable though.
> However it is a huge improvement.
>
> The weird part though is this. Outgoing calls to cell phone numbers
> (tried 3 different ones) have virtually no echo. Outgoing calls to land
> line numbers do seem to have echo.
>
> I then downgraded my asterisk server to a P3-800 with 128mb ram, and I
> didn't notice any difference from the Celeron 2.4. So in my case just
> upgrading a Celeron 533 to P3-800 made a noticeable difference, but
> anything more than that did not. What I did notice is
> in /proc/interrupts, the P3-800 displays:
>
> IO-APIC-level  wcfxo
>
> Whereas I believe the older Celeron 533 displayed:
>
> XT-PIC wcfxo
>
> So my guess is its not the CPU speed at all, just the way interrupts are
> handled.
>
> So the two questions remain.
>
> 1. Why do incoming calls have nearly no echo (sound great), and outgoing
> calls are bad during the first 30 seconds, and okay (but not good) after
> that.
>
> 2. Why do outgoing calls to cell phone numbers sound great?
>
> Seeing as an outgoing call to a land line has echo, but the same land
> line calling in has virtually no echo, does this point the finger at
> Asterisk code having issues?
>
>
> On Wed, 2004-06-30 at 16:36 -0700, Mike Benoit wrote:
> > Over the last couple weeks I've tried everything I could get my hands on
> > in an attempt to get rid of my echo problems. Using a CVS checkout of
> > just yesterday, I've tried every echo cancellation routine in zconfig.h
> > (including Mark2 w/Aggressive) , as well as the echotraining=800
> > mentioned on this list just last week.
> >
> > While some things worked better then others, I would consider none
> > acceptable solutions in my situation. Playing with rx/tx gain values
> > just seemed to quiet the voice down and along with that the echo
> > happened to be less noticeable. I could almost get the echo to disappear
> > with a low enough rx/tx gain, but then the voice could barely be heard,
> > or DTMF tones stopped working.
> >
> > So whats the next step?
> >
> > I only get echo when dialing over the PSTN. Using Nufone to dial a PSTN
> > number results in absolutely zero echo. Do I put in a request for a
> > Telco technician to come out and take a look at the lines?
> >
> > One page on the Wiki says:
> >
> > "Most of the telco's have technicians with the equipment necessary to
> > help find the problem if the problem really is their outside plant.
> > However, getting to that person can be a real challenge."
> >
> > Any suggestions on ways to overcome the challenge of getting the right
> > technician on the phone?
> >
> > Thanks.
> >
> -- 
> Mike Benoit <ipso at snappymail.ca>
>
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