Is there something wrong with my answer sdp?(WebRTC, Ubuntu project)

Question

The offer sdp is

v=0
o=- 7218303015490137756 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE 0 1
a=extmap-allow-mixed
a=msid-semantic: WMS
m=audio 9 UDP/TLS/RTP/SAVPF 111 63 9 0 8 13 110 126
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:nKYe
a=ice-pwd:6Zxgc+gxTwxd3ap5I/sOdcPu
a=ice-options:trickle
a=fingerprint:sha-256 DD:C2:BC:0F:E8:05:65:2F:20:72:82:20:04:50:5A:7F:9B:DF:60:50:73:C4:E8:5D:37:55:C4:1F:4D:3B:DC:13
a=setup:actpass
a=mid:0
a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level
a=extmap:2 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
a=extmap:3 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01
a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid
a=recvonly
a=rtcp-mux
a=rtpmap:111 opus/48000/2
a=rtcp-fb:111 transport-cc
a=fmtp:111 minptime=10;useinbandfec=1
a=rtpmap:63 red/48000/2
a=fmtp:63 111/111
a=rtpmap:9 G722/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:13 CN/8000
a=rtpmap:110 telephone-event/48000
a=rtpmap:126 telephone-event/8000
m=video 9 UDP/TLS/RTP/SAVPF 96 97 98 99 100 101 35 36 37 38 102 103 104 105 106 107 108 109 127 125 39 40 41 42 43 44 45 46 47 48 112 113 114 115 116 117 118 49
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:nKYe
a=ice-pwd:6Zxgc+gxTwxd3ap5I/sOdcPu
a=ice-options:trickle
a=fingerprint:sha-256 DD:C2:BC:0F:E8:05:65:2F:20:72:82:20:04:50:5A:7F:9B:DF:60:50:73:C4:E8:5D:37:55:C4:1F:4D:3B:DC:13
a=setup:actpass
a=mid:1
a=extmap:14 urn:ietf:params:rtp-hdrext:toffset
a=extmap:2 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
......

My answer sdp is

v=0
o=- 7218303015490137756 2 IN IP4 192.168.50.119
s=-
t=0 0
a=group:BUNDLE 0 1
a=msid-semantic: WMS
a=ice-lite
m=audio 9 UDP/TLS/RTP/SAVPF 0
c=IN IP4 192.168.50.119
a=ice-ufrag:sh2j
a=ice-pwd:au6tvqpf0igutargfbzq07y4
a=ice-options:trickle
a=fingerprint:sha-256 2B:4C:BA:79:27:69:77:08:16:13:BA:5E:95:98:A6:E0:09:D0:9A:C0:19:FF:8E:27:59:F5:89:E3:80:45:77:A1
a=setup:passive
a=mid:0
a=ice-lite
a=sendonly
a=rtcp-mux
a=rtpmap:0 PCMU/8000/1
a=msid:video-mslabel video-label
a=ssrc:2 cname:video-rtp
a=ssrc:2 msid:video-mslabel video-label
a=ssrc:2 mslabel:video-mslabel
a=ssrc:2 label:video-label
a=candidate:udpcandidate 1 udp 100 192.168.50.119 6000 typ host
m=video 9 UDP/TLS/RTP/SAVPF 102
c=IN IP4 192.168.50.119
a=ice-ufrag:sh2j
a=ice-pwd:au6tvqpf0igutargfbzq07y4
a=ice-options:trickle
a=fingerprint:sha-256 2B:4C:BA:79:27:69:77:08:16:13:BA:5E:95:98:A6:E0:09:D0:9A:C0:19:FF:8E:27:59:F5:89:E3:80:45:77:A1
a=setup:passive
a=mid:1
a=ice-lite
a=sendonly
a=rtcp-mux
a=rtpmap:102 H264/90000
a=fmtp:102 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f
a=msid:video-mslabel video-label
a=ssrc:1 cname:video-rtp
a=ssrc:1 msid:video-mslabel video-label
a=ssrc:1 mslabel:video-mslabel
a=ssrc:1 label:video-label
a=candidate:udpcandidate 1 udp 100 192.168.50.119 6000 typ host

I use the C++ webrtc application for video stream but without native webrtc api. And I have not implemented the rtcp transmission and rtx retransmission. I used wireshark to capture packets and found that stun and dtls handshakes were normal, and video data was also sent normally.Now the web side can parse my answer sdp but cannot play the live video stream. Is rtcp necessary? Any ideas why it doesn't work? Thanks!