webview rtc sdp获取错误

webview 打开h5
h5里面

var offer = await self.pc.createOffer()

app第一次用webview打开h5，获取offer.sdp，和第二次之后再次打开h5，获取的sdp不一样，没有H264，请问为什么？
第一次

v=0  
o=- 8273488116410174553 2 IN IP4 127.0.0.1  
s=-  
t=0 0  
a=group:BUNDLE 0 1  
a=msid-semantic: WMS  
m=audio 9 UDP/TLS/RTP/SAVPF 111 103 9 0 8 105 13 110 113 126  
c=IN IP4 0.0.0.0  
a=rtcp:9 IN IP4 0.0.0.0  
a=ice-ufrag:zEFF  
a=ice-pwd:0DV6+5yU8z1DKfzAERPljZkE  
a=ice-options:trickle  
a=fingerprint:sha-256 2F:AD:81:56:3F:7E:AD:CA:3F:C5:B0:5A:F9:B1:6A:A7:85:53:F0:85:9B:47:4C:C9:1D:F1:6D:34:C8:A8:32:FA  
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=extmap:5 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id  
a=extmap:6 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id  
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:103 ISAC/16000  
a=rtpmap:9 G722/8000  
a=rtpmap:0 PCMU/8000  
a=rtpmap:8 PCMA/8000  
a=rtpmap:105 CN/16000  
a=rtpmap:13 CN/8000  
a=rtpmap:110 telephone-event/48000  
a=rtpmap:113 telephone-event/16000  
a=rtpmap:126 telephone-event/8000  
m=video 9 UDP/TLS/RTP/SAVPF 96 97 98 99 127 100 101 102  
c=IN IP4 0.0.0.0  
a=rtcp:9 IN IP4 0.0.0.0  
a=ice-ufrag:zEFF  
a=ice-pwd:0DV6+5yU8z1DKfzAERPljZkE  
a=ice-options:trickle  
a=fingerprint:sha-256 2F:AD:81:56:3F:7E:AD:CA:3F:C5:B0:5A:F9:B1:6A:A7:85:53:F0:85:9B:47:4C:C9:1D:F1:6D:34:C8:A8:32:FA  
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  
a=extmap:13 urn:3gpp:video-orientation  
a=extmap:3 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01  
a=extmap:12 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay  
a=extmap:11 http://www.webrtc.org/experiments/rtp-hdrext/video-content-type  
a=extmap:7 http://www.webrtc.org/experiments/rtp-hdrext/video-timing  
a=extmap:8 http://www.webrtc.org/experiments/rtp-hdrext/color-space  
a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid  
a=extmap:5 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id  
a=extmap:6 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id  
a=recvonly  
a=rtcp-mux  
a=rtcp-rsize  
a=rtpmap:96 VP8/90000  
a=rtcp-fb:96 goog-remb  
a=rtcp-fb:96 transport-cc  
a=rtcp-fb:96 ccm fir  
a=rtcp-fb:96 nack  
a=rtcp-fb:96 nack pli  
a=rtpmap:97 rtx/90000  
a=fmtp:97 apt=96  
a=rtpmap:98 VP9/90000  
a=rtcp-fb:98 goog-remb  
a=rtcp-fb:98 transport-cc  
a=rtcp-fb:98 ccm fir  
a=rtcp-fb:98 nack  
a=rtcp-fb:98 nack pli  
a=fmtp:98 profile-id=0  
a=rtpmap:99 rtx/90000  
a=fmtp:99 apt=98  
a=rtpmap:127 VP9/90000  
a=rtcp-fb:127 goog-remb  
a=rtcp-fb:127 transport-cc  
a=rtcp-fb:127 ccm fir  
a=rtcp-fb:127 nack  
a=rtcp-fb:127 nack pli  
a=fmtp:127 profile-id=1  
a=rtpmap:100 red/90000  
a=rtpmap:101 rtx/90000  
a=fmtp:101 apt=100  
a=rtpmap:102 ulpfec/90000

非第一次

v=0  
o=- 7311116862801397442 2 IN IP4 127.0.0.1  
s=-  
t=0 0  
a=group:BUNDLE 0 1  
a=msid-semantic: WMS  
m=audio 9 UDP/TLS/RTP/SAVPF 111 103 9 0 8 105 13 110 113 126  
c=IN IP4 0.0.0.0  
a=rtcp:9 IN IP4 0.0.0.0  
a=ice-ufrag:0mWf  
a=ice-pwd:CiI0q/m9TP8nWoymtcspi3u8  
a=ice-options:trickle  
a=fingerprint:sha-256 77:FF:EC:BF:E9:AC:74:A6:4C:B4:BD:9C:0E:6E:A7:80:CC:9F:5C:43:68:D1:31:5B:5F:7A:08:A2:2B:53:27:DD  
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=extmap:5 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id  
a=extmap:6 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id  
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:103 ISAC/16000  
a=rtpmap:9 G722/8000  
a=rtpmap:0 PCMU/8000  
a=rtpmap:8 PCMA/8000  
a=rtpmap:105 CN/16000  
a=rtpmap:13 CN/8000  
a=rtpmap:110 telephone-event/48000  
a=rtpmap:113 telephone-event/16000  
a=rtpmap:126 telephone-event/8000  
m=video 9 UDP/TLS/RTP/SAVPF 96 97 98 99 127 125 104 122 106 107 108 109 124 121 100 101 102  
c=IN IP4 0.0.0.0  
a=rtcp:9 IN IP4 0.0.0.0  
a=ice-ufrag:0mWf  
a=ice-pwd:CiI0q/m9TP8nWoymtcspi3u8  
a=ice-options:trickle  
a=fingerprint:sha-256 77:FF:EC:BF:E9:AC:74:A6:4C:B4:BD:9C:0E:6E:A7:80:CC:9F:5C:43:68:D1:31:5B:5F:7A:08:A2:2B:53:27:DD  
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  
a=extmap:13 urn:3gpp:video-orientation  
a=extmap:3 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01  
a=extmap:12 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay  
a=extmap:11 http://www.webrtc.org/experiments/rtp-hdrext/video-content-type  
a=extmap:7 http://www.webrtc.org/experiments/rtp-hdrext/video-timing  
a=extmap:8 http://www.webrtc.org/experiments/rtp-hdrext/color-space  
a=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid  
a=extmap:5 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id  
a=extmap:6 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id  
a=recvonly  
a=rtcp-mux  
a=rtcp-rsize  
a=rtpmap:96 VP8/90000  
a=rtcp-fb:96 goog-remb  
a=rtcp-fb:96 transport-cc  
a=rtcp-fb:96 ccm fir  
a=rtcp-fb:96 nack  
a=rtcp-fb:96 nack pli  
a=rtpmap:97 rtx/90000  
a=fmtp:97 apt=96  
a=rtpmap:98 VP9/90000  
a=rtcp-fb:98 goog-remb  
a=rtcp-fb:98 transport-cc  
a=rtcp-fb:98 ccm fir  
a=rtcp-fb:98 nack  
a=rtcp-fb:98 nack pli  
a=fmtp:98 profile-id=0  
a=rtpmap:99 rtx/90000  
a=fmtp:99 apt=98  
a=rtpmap:127 VP9/90000  
a=rtcp-fb:127 goog-remb  
a=rtcp-fb:127 transport-cc  
a=rtcp-fb:127 ccm fir  
a=rtcp-fb:127 nack  
a=rtcp-fb:127 nack pli  
a=fmtp:127 profile-id=1  
a=rtpmap:125 VP9/90000  
a=rtcp-fb:125 goog-remb  
a=rtcp-fb:125 transport-cc  
a=rtcp-fb:125 ccm fir  
a=rtcp-fb:125 nack  
a=rtcp-fb:125 nack pli  
a=fmtp:125 profile-id=2  
a=rtpmap:104 H264/90000  
a=rtcp-fb:104 goog-remb  
a=rtcp-fb:104 transport-cc  
a=rtcp-fb:104 ccm fir  
a=rtcp-fb:104 nack  
a=rtcp-fb:104 nack pli  
a=fmtp:104 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=420015  
a=rtpmap:122 rtx/90000  
a=fmtp:122 apt=104  
a=rtpmap:106 H264/90000  
a=rtcp-fb:106 goog-remb  
a=rtcp-fb:106 transport-cc  
a=rtcp-fb:106 ccm fir  
a=rtcp-fb:106 nack  
a=rtcp-fb:106 nack pli  
a=fmtp:106 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=4d0015  
a=rtpmap:107 rtx/90000  
a=fmtp:107 apt=106  
a=rtpmap:108 H264/90000  
a=rtcp-fb:108 goog-remb  
a=rtcp-fb:108 transport-cc  
a=rtcp-fb:108 ccm fir  
a=rtcp-fb:108 nack  
a=rtcp-fb:108 nack pli  
a=fmtp:108 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=640015  
a=rtpmap:109 rtx/90000  
a=fmtp:109 apt=108  
a=rtpmap:124 H264/90000  
a=rtcp-fb:124 goog-remb  
a=rtcp-fb:124 transport-cc  
a=rtcp-fb:124 ccm fir  
a=rtcp-fb:124 nack  
a=rtcp-fb:124 nack pli  
a=fmtp:124 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e015  
a=rtpmap:121 rtx/90000  
a=fmtp:121 apt=124  
a=rtpmap:100 red/90000  
a=rtpmap:101 rtx/90000  
a=fmtp:101 apt=100  
a=rtpmap:102 ulpfec/90000