[Asterisk-Users] Re: Polycom sound quality problems

[Max W Blackmer Jr]

> There's no transcoding going on.  It's ulaw on IAX with Sixtel and ulaw
> on SIP to the phone.  I considered that as a possibility originally, and
> even tried using GSM with Sixtel to force it to do transcoding, but had
> the exact same problem.
>
> The Asterisk box is a 2.4ghz P4 with 512MB RAM, doing nothing but
> Asterisk.  I have only 9 extensions.

That should not be a problem with those specs.

>
> I would think there's a possibility of packet loss on the IAX channel,
> except the other SIP phones (SJPhone softphone) work flawlessly.  Also,
> OUTBOUND calls are just fine on the Polycoms.  Only incoming calls are
> messed up.

There is one other possibility. Are you using Switches or hubs?  if you
are using hubs you could have collisions that cause data loss. 
Switches with store and forward are the best especially if they have
QoS, ToS and CoS management features in the switch.  Switches typically
do not loose packets but they do expire on rare occasions due to high
traffic volume.

Max