Thursday, January 11, 2007

Echo-Free Combinations, Asterisk & Digium Hardware

How do I get echo-free with Digium boards (a running list) ...

Something that has plagued almost everyone in the Asterisk, Asterisk @ Home & TrixBox communities has been getting a nice clean echo-free experience with Digium Boards on various hardware platforms!

To that end, we felt it maybe wise to at least share our immediate experience & working combinations and continue to augment this list as people choose to throw in their tips in the comments over time!

So what's *really* the scoop on echo & Digium boards anyway?

There are various schools of thought on this, some say it's the server platform hardware incompatibility at issue, some an issue of dedicated IRQ's and correct BIOS isolation, and still others a matter of correct manipulation of the Zaptel echo settings & selected echo algorithms.

As for ourselves, we have found empirically that although all of these can be at issue and all of these can help reduce or even remove the echo, there is a far simpler and more subtle issue at the root that doesn't require any of these manipulations & trouble --- a correct combination of Linux kernel version & Zaptel driver version.

What we've found so far ...

In every case without exception, we have found that picking the right Linux kernel build & corresponding Zaptel driver release removes the echo completely and perfectly (or near enough the stock echo canceller configuration removes the minor remaining difference in a matter of minutes automatically)! We have tried every one of the other prescribed methods with varying degrees of success & alot of headache in every case.

However, correctly selecting the correct kernel/Zaptel combination seems to work everytime with the stock Asterisk @ Home / Trixbox installations with an absolute minimum of fuss. Now granted, this doesn't always provide the latest software releases of either but we've found in most cases the typical installation rarely if ever falls prey to the issues that get fixed or added from release to release of either the kernel or Zaptel.

Proven / Known Working Combinations (by Hardware Platform)

Dell Poweredge Servers & Digium TDM400P cards
-- Tower: SC420 / SC430 / 800 / 830
-- Rackmount: 750 / 1650

-- CentOS Kernel Build 34.0.2
-- Zaptel Driver Version 1.2.6

(alternatively, we found CentOS Build 43.0.2 from TrixBox v1.2.2 and Zaptel v1.2.9.1 seemed to work as well, but have been unable to further duplicate this combo for testing due to kernel source complications in the various TrixBox releases -- which have reverted to 34.0.2 ultimately).

We welcome any community feedback & more interestingly echo-free combinations for various hardware platforms that folks have been able to consistently & successfully reproduce!

Have fun!
posted by Kennon Software at 12:29 PM | 4 comments







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