Cannot get additional SDP info from outbound SIP Server

Hi all,

I setup my Asterisk to be a SIP client and connect to another SIP server. My video phone makes a phone call to outbound SIP server through my Asterisk. The outbound SIP server may contain additional video SDP information back to my Asterisk. However, my Asterisk responses my video phone with the SDP according to the configuration in sip.conf. Therefore, the additional SDP information do not send to my video phone and cause some problems.

Is there any way to set Asterisk to be a transparent SIP server? I mean, the Asterisk should not modify any content from peers and just transmit the same SDP info to other side. Thus, my video phone ought to get the complete SDP information from my outbound SIP Server instead of just the configuration defined in sip.conf.

Thank you.