asterisk users - Oct 2008 - command - set sip_codec- does not work with asterisk-1.4.21

hello:
i want to test the g729 with asterisk. my scenario  is sipp(ulaw)->asterisk1
with g729->asterisk2 with g729.
I want to test g729 module with asterisk-1.4.21, when i make calls from asterisk
1 to asterisk 2, the asterisk 1 always send ulaw to asterisk 2. my sip in
asterisk 1 is with codec g729 and enforce that use g729, the sip in asterisk 2
also work with G729 only, but asterisk 2 reports the condec compatibility 
problem. both of asterisks can show g729 are there.
==================================exten => 2005,1,Answer
exten => 2005,2,Set(${SIP_CODEC}=g729) // does not work
exten => 2005,3,DIAL(SIP/1000 at 192.168.2.127,30,r)
exten => 2005,4,Hangup
===use sipp t call asterisk 1 then forward to asterisk 2 with sip 1000.
------------------sip.conf ----------------------------------------------------
[1000]
username=1000
allowtransfer=yes
type=friend
secret=1000
qualify=yes
canreinvite=yes
host=dynamic
insecure=very
fromuser=1000
;dtmfmode=rfc2833
disallow=all
allow=g729
;allow=ulaw
;allow=alaw
context=internal
--------------------------------------------
when the calls coming from asterisk 1, i can not see any g729 inforamtion, the
Noop(${SIP_CODEC}) show nothing.
some people reported the bug for sip_codec, i followed that, but i still can
not. sovle. anyone knows how  to set sip_codec in dialplan or have any right
format for set sip_codec in dialplan?
thanks!
zhu


       
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