wrtc.adv.sdpModify() can be used to modify SDP-s sent to remote clients, for instance if you want to add your own entries to it.
wrtc objects does not have any adv.sdpModify() functions by default. Class wrtcObject declares it as null. You need to write your own wrtc.adv.sdpModify() function if you want to use it.
wrtc.adv.sdpModify() is for advanced users only! Incorrect use may cause webRTC stop functioning correctly.
wrtc.adv.sdpModify(sdp):
String containing modified SDP.
wrtc.adv.sdpModify = function(sdp) { return sdp.replace(/v=0\r\n/, "v=0\r\na=foo: bar\r\n") }; makes all SDP-s object wrtc_kit sends to remote clients contain "a=foo: bar" as second line (v=0 is first).