Remove Last Codec and Change Port

sip-manipulation
        name                           removeLastCodec
        description                    remove the last codec
        mime-sdp-rule
                name                           removeLastCodec
                msg-type                       request
                methods                        INVITE
                action                         manipulate
                comparison-type                case-sensitive
                match-value
                new-value
                sdp-media-rule
                        name                      removeLast
                        media-type                audio
                        action                    manipulate
                        comparison-type           case-sensitive
                        match-value
                        new-value
                        sdp-line-rule
                                name                   isLastCodec
                                type                   m
                                action                 store
                                comparison-type        pattern-rule
                                match-value            ^(audio )([0-9]{4,
                                                       5})( RTP/AVP 
                                                       [0-9]{1-3})$
new-value
                        sdp-line-rule
                                name                   changePort
                                type                   m
                                action                 replace
                                comparison-type        boolean
                                match-value            $removeLastCodec.
$removeLast.$isLastCodec
                                new-value              $removeLastCodec.
$removeLast.$isLastCodec.$1+0+$removeLastCodec.$removeLast.
$isLastCodec.$3