[asterisk-users] My G729 problem re-visited

[Scott Moseman]

Ok, I built a test system to duplicate my problem and provide myself
a platform that I can mess around with to try and break any features.
My problem is G729 pass-through from a gateway to a phone. I think
I even have transcoding working, which makes me more confused on
what's wrong with my pass-through. It must be a configuration issue.

The basics...

*CLI> core show version
Asterisk 1.4.11 built by root @ fwd-tst02 on a i686 running Linux

*CLI> show modules like 723
Module Description Use Count
codec_g723.so G.723.1 Coder/Decoder 0
format_g723.so G.723.1 Simple Timestamp File Format 0

*CLI> show modules like 729
Module Description Use Count
codec_g729.so G.729 Coder/Decoder 0
format_g729.so Raw G729 data 0

*CLI> show translation
[truncated]
g723 gsm ulaw alaw g726aal2 adpcm slin lpc10 g729 speex ilbc g726 g722
ulaw 5 2 - 1 2 2 1 3 7 - 11 2 -
alaw 5 2 1 - 2 2 1 3 7 - 11 2 -
g729 5 2 2 2 2 2 1 3 - - 11 2 -

The configuration...

[gateway]
type=friend
host=gateway
context=default-inbound
disallow=all
allow=g729

[phone]
type=friend
context=sip
host=dynamic
username=phone
secret=scott
dtmfmode=RFC2833
disallow=all
allow=g729
callerid=Scott
qualify=yes
canreinvite=no

exten => 1266,1,Dial(SIP/[number],30,t)
exten => 1266,2,Congestion

exten => 1266,1,Dial(SIP/[number],30)
exten => 1266,2,Congestion

(The same results using both of the above dialplans...)

The environment...

PSTN -> Gateway -> Asterisk -> Phone

What I'm seeing works...

With the gateway setup to send both G711 and G729, it sends
an INVITE which includes both G711 and G729 codecs. Asterisk
sends an INVITE to my phone with only G729. The call is made
and there's a conversation in G711 with the gateway and G729
with the phone. I assume this means Asterisk is transcoding.

What I"m seeing fails...

With the gateway setup to send only G729, it sends an INVITE
to Asterisk which includes only G729. Asterisk send an INVITE
to the phone using G729, too. The 200 OK from the phone to
the Asterisk includes G729. The 200 OK going from Asterisk to
the gateway doesn't include ANY codec. The call is dropped the
moment I pickup the phone to answer the call.

My question...

Why does Asterisk not want to respond to my gateway in G729?
Even if the gateway requests it, Asterisk seems to just ignore it.