Gstreamer with webrtc

[Garry]

I have created an offer using gstreamer webrtc plugin ,The negotiation offer is :
v=0\r\n
o=- 5644333906370464742 0 IN IP4 0.0.0.0\r\n
s=-\r\n
t=0 0\r\n
a=ice-options:trickle\r\n
m=video 9 UDP/TLS/RTP/SAVPF 96\r\n
c=IN IP4 0.0.0.0\r\n
a=setup:actpass\r\n
a=ice-ufrag:9YghU5O5wmpxPB5V8jNUJESPbICwBoTe\r\n
a=ice-pwd:mwcH5ewEz2A3LuVklNuQoBfUOXEbJfKH\r\n
a=rtcp-mux\r\n
a=rtcp-rsize\r\n
a=sendonly\r\n
a=rtpmap:96 H264/90000\r\n
a=rtcp-fb:96 nack pli\r\n
a=framerate:15\r\n
a=fmtp:96 packetization-mode=1;profile-level-id=42c016;sprop-parameter-sets=Z0LAFtoCgL/lwFqDAILSgAAAAwCAAAAPR4sXUA==,aM48gA==\r\n
a=ssrc:1457400171 msid:user2354033823@host-9b082eff webrtctransceiver0\r\n
a=ssrc:1457400171 cname:user2354033823@host-9b082eff\r\na=mid:video0\r\n
a=fingerprint:sha-256 A1:77:FD:33:7F:11:20:CB:AF:9C:01:78:24:0C:2E:2E:8A:0F:27:CB:4E:87:E7:4F:2B:18:18:A8:A5:B9:F1:FF\r\n


the offer which is working is we get it from google library:
v=0\r\n o=- 4161166280619699714 2 IN IP4 127.0.0.1\r\n s=-\r\n t=0 0\r\n a=group:BUNDLE 0 1\r\n a=extmap-allow-mixed\r\n a=msid-semantic: WMS stream_id\r\n m=audio 9 UDP/TLS/RTP/SAVPF 110r\n c=IN IP4 0.0.0.0\r\n a=rtcp:9 IN IP4 0.0.0.0\r\n a=ice-ufrag:S17Y\r\n a=ice-pwd:HLJlGy3Wg3mBsChmyQZwaqoN\r\n a=ice-options:trickle\r\n a=fingerprint:sha-256 BB:22:24:32:34:96:5B:1F:B2:65:D2:C0:A2:35:8D:EA:D8:49:DE:54:5F:29:B8:74:90:45:E0:75:F9:FB:5E:CD\r\n a=setup:actpass\r\n a=mid:0\r\n a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level\r\n a=extmap:2 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\n a=extmap:3 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\n a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid\r\n a=sendonly\r\n a=msid:stream_id audio_label\r\n a=rtcp-mux\r\n a=rtpmap:110 telephone-event/48000\r\n a=ssrc:2173135338 cname:OlRnMjRP4I1jcYvM\r\n a=ssrc:2173135338 msid:stream_id audio_label\r\n m=video 9 UDP/TLS/RTP/SAVPF 96 97\r\n c=IN IP4 0.0.0.0\r\n a=rtcp:9 IN IP4 0.0.0.0\r\n a=ice-ufrag:S17Y\r\n a=ice-pwd:HLJlGy3Wg3mBsChmyQZwaqoN\r\n a=ice-options:trickle\r\n a=fingerprint:sha-256 BB:22:24:32:34:96:5B:1F:B2:65:D2:C0:A2:35:8D:EA:D8:49:DE:54:5F:29:B8:74:90:45:E0:75:F9:FB:5E:CD\r\n a=setup:actpass\r\n a=mid:1\r\n a=extmap:14 urn:ietf:params:rtp-hdrext:toffset\r\n a=extmap:2 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\n a=extmap:13 urn:3gpp:video-orientation\r\n a=extmap:3 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\n a=extmap:5 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay\r\n a=extmap:6 http://www.webrtc.org/experiments/rtp-hdrext/video-content-type\r\n a=extmap:7 http://www.webrtc.org/experiments/rtp-hdrext/video-timing\r\n a=extmap:8 http://www.webrtc.org/experiments/rtp-hdrext/color-space\r\n a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid\r\n a=extmap:10 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id\r\n a=extmap:11 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id\r\n a=sendonly\r\n a=msid:stream_id video_label\r\n a=rtcp-mux\r\n a=rtcp-rsize\r\n a=rtpmap:96 H264/90000\r\n a=rtcp-fb:96 goog-remb\r\n a=rtcp-fb:96 transport-cc\r\n a=rtcp-fb:96 ccm fir\r\n a=rtcp-fb:96 nack\r\n a=rtcp-fb:96 nack pli\r\n a=rtpmap:97 rtx/90000\r\n a=fmtp:97 apt=96\r\n a=ssrc-group:FID 1470103868 435318263\r\n a=ssrc:1470103868 cname:OlRnMjRP4I1jcYvM\r\n a=ssrc:1470103868 msid:stream_id video_label\r\n a=ssrc:435318263 cname:OlRnMjRP4I1jcYvM\r\n a=ssrc:435318263 msid:stream_id video_label\r\n

I dont know how the details are to be filled such as extmap in the sdp offer,
can anyone help me on this parameters.the response we are getting is :
404 Not found