Change connection information to DNS instead of IP in SDP

We have a client that wants to see a DNS entry in our SDP information, instead of the IP.  I figured out how to change the c line, but I'm struggling with the o line.  Can someone help me with this one?

name                                    AddDNS

        description                             replace ipv4 address with DNS in contact and SDP for mobile

        split-headers                          

        join-headers                           

        header-rule

                name                                    FixSDP

                header-name                             Content-Type

                action                                  manipulate

                comparison-type                         case-sensitive

                msg-type                                any

                methods                                

                match-value                            

                new-value                              

                element-rule

                        name                                    ReplaceCLine

                        parameter-name                          application/sdp

                        type                                    mime

                        action                                  find-replace-all

                        match-val-type                          any

                        comparison-type                         pattern-rule

                        match-value                             c=IN IP4 1.2.3.4

                        new-value                               "c=IN sip123.rc.com"