[Asterisk-Users] Echo problem update - POSSIBLE SOLUTION

[Joshua M. Thompson]

On Fri, 2004-07-16 at 12:07 -0600, Rich Adamson wrote:

> No echo on eMachine T2240 2.2ghz Celery, 360m RAM, with either tdm04b
> or x100p running any Head cvs after June 23rd (totally stock install).
> 
> Wouldn't necessarily recommend this box for any commercial production
> use, but...
> 
> What's common and not so common between these _very_ diverse boxes?

My guess would be interrupt and/or PCI latency. Echo is produced by
delays in the audio path so if some motherboards are adding delays it's
going to make the echo worse. Fiddling with PCI bus settings both in the
BIOS and from Linux (using the pci tools) may help in some cases.

The unfortunate part about this is that there are SO many variables that
can influence latency that you can't really tell if a motherboard is
going to work or not until you try it. Even two MBs with the same CPUs
and the same north/south bridges could produce different results.
Probably the best we can hope for right now is to start building a
whitelist of known good motherboards for people to reference when
building Asterisk systems.

-- 
Joshua M. Thompson <funaho at jurai.org>