[Asterisk-Dev] codec negotiation issue

[Goldenear]

Hi,

I've the following problem :
I have an Asterisk box (* 1.07 / Debian 3.0) that I only use with IAX2
clients (mostly softphones). I setup iax.conf so that only GSM (first)
and ulaw (second) codecs are allowed. I have to avoid codec translation
(to save some CPU power) and I also prefer native bridging (to save
bandwidth on the Asterisk server).
Most of my users use the GSM codec by default, so they are directly
briged by my Asterisk box and that's exactly what I want.
Each iax2 client supports several codecs and can do codec negotiation
(eg. they can use GSM to connect to my * box or ulaw when connecting to
a ulaw only device).
I setup a _**393. extension for dialing Free World Dialup. FWD only
allow ulaw and that's not a problem as my Asterisk box also allow ulaw.
The issue is that when a user place a call to a FWD user (using the
**393 extension on my Asterisk box) the call go this way :

my user -- GSM -- my * box -- ulaw -- FWD

So my Asterisk box says it can't make native bridging between my user
and FWD as they don't use the same codec... and it stays in the path :(
This is very strange because my user softphone perfectly support ulaw
and even use it in the other direction (receiving a call from FWD):

FWD -- ulaw -- my * box -- ulaw -- my user
my * box then make transfer/native bridging so I have :
FWD -- ulaw -- my user
And this is exactly what I want.

So my question is, why Asterisk doesn't ask my user softphone to use
ulaw when connecting to FWD (so it can do native bridging) ?

Isn't this a bug ?