[Asterisk-Users] Re: Polycom sound quality problems

[Noah Miller]

> 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.
>
> 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.

Just to cover all the bases, have you tried any other IAX providers or 
connections?