asterisk users - Feb 2005 - TDM-400P Sound Quality issues

I'm running a TDM-400P with 2 x FXS and 2 x FXO.    I'm finding that
there seems to be an odd relationship to sound quality on the card to my local
when connecting via a SIP client.

When I'm on my local network, if I connect to Asterisk via a SIP client
(such as x-pro), and dial an outside line through the card, sound quality seems
quite good.

However, when I'm at a remote location and connect via the same SIP client
and dial an outside line, the audio quality is fuzzy, sometimes quiet, and
generally more difficult to understand.

I spent a bunch of time troubleshooting the SIP end of things, thinking
that's where the problem was, until I realized that every other SIP
connection I make (from remote) yields a high quality call.  ie.  I can dial
another SIP client and maintain high quality audio.  Additionally, I can dial an
extension that not only SIP connects to my server, but from there goes out an
IAX2 connection to another remote Asterisk server, from there to another SIP
client, and the audio quality is excellent.

Therefore, I don't think the audio issue I'm experiencing is on the SIP
end.

Are there some wierd SIP -> ZAP timing / conversion / other issues that could
be causing this?

thoughts?

regards,

Paul
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> I spent a bunch of time troubleshooting the SIP end of things, thinking
that's where the
problem was, until I realized that every other SIP
> connection I make (from remote) yields a high quality call.  ie.  I can
dial another SIP
client and maintain high quality audio.  Additionally, I
can
> dial an extension that not only SIP connects to my server, but from there
goes out an IAX2
connection to another remote Asterisk server, from
> there to another SIP client, and the audio quality is excellent.
>  
> Therefore, I don't think the audio issue I'm experiencing is on the
SIP end.
>  
> Are there some wierd SIP -> ZAP timing / conversion / other issues that
could be causing this?
>  
> thoughts?
Pure guess... you're probably bumping into some of the same issues
that many of us TDM users are hitting. Seems like either an interrupt
handling (latency) or pci bus issue. You'll find hundreds of postings
relative to this over the last six months or so. Not everyone has
problems with the TDM, but some have found that swapping motherboards
does clear up the issue. 

Processor speed and ram have nothing to do with it, nor does single vs
dual processors, etc. 

Several people have opened trouble tickets with digium, but seems all
have gone into a black hole (thus far).