SessionDescription 为空。在将 Chrome 更新到最新的 v 89 后在 web rtc 中。处理以前的 Chrome 版本
SessionDescription is Null. in web rtc after updating Chrome to latest v 89. Working on previous Chrome Versions
"Answer" 的 SDP offer 未从 Android/iOS 应用程序更新后发送到 Web App（Windows/Mac/Linux 上的运行） Chrome 到最新的 v89（2021 年 3 月 9 日发布）。
它在 Chrome v88 及以下版本上运行良好。
提供 SDP:
o=- 3986944572502207628 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE 0 1
a=extmap-allow-mixed
a=msid-semantic: WMS ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew
m=audio 9 UDP/TLS/RTP/SAVPF 111 103 104 9 0 8 106 105 13 110 112 113 126
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:l4+m
a=ice-pwd:Pi7zEzH/c5fFzvNAn0giR5CJ
a=ice-options:trickle
a=fingerprint:sha-256 5F:A3:0C:CE:24:0C:7B:F3:1D:CE:B4:B3:CE:AF:71:24:44:53:14:5B:ED:29:FF:C1:03:C2:5B:4C:E0:87:B8:DF
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=sendrecv
a=msid:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew 140a2361-2018-4f1c-8bbf-10e0094357b9
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:104 ISAC/32000
a=rtpmap:9 G722/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:106 CN/32000
a=rtpmap:105 CN/16000
a=rtpmap:13 CN/8000
a=rtpmap:110 telephone-event/48000
a=rtpmap:112 telephone-event/32000
a=rtpmap:113 telephone-event/16000
a=rtpmap:126 telephone-event/8000
a=ssrc:3610133405 cname:TdZx9He99oI1ZADZ
a=ssrc:3610133405 msid:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew 140a2361-2018-4f1c-8bbf-10e0094357b9
a=ssrc:3610133405 mslabel:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew
a=ssrc:3610133405 label:140a2361-2018-4f1c-8bbf-10e0094357b9
m=video 9 UDP/TLS/RTP/SAVPF 96 97 98 99 100 101 102 121 127 120 125 107 108 109 124 119 123 118 114 115 116
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:l4+m
a=ice-pwd:Pi7zEzH/c5fFzvNAn0giR5CJ
a=ice-options:trickle
a=fingerprint:sha-256 5F:A3:0C:CE:24:0C:7B:F3:1D:CE:B4:B3:CE:AF:71:24:44:53:14:5B:ED:29:FF:C1:03:C2:5B:4C:E0:87:B8:DF
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=sendrecv
a=msid:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew ea8a9278-d344-4025-8053-1a86b2764c04
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:100 VP9/90000
a=rtcp-fb:100 goog-remb
a=rtcp-fb:100 transport-cc
a=rtcp-fb:100 ccm fir
a=rtcp-fb:100 nack
a=rtcp-fb:100 nack pli
a=fmtp:100 profile-id=2
a=rtpmap:101 rtx/90000
a=fmtp:101 apt=100
a=rtpmap:102 H264/90000
a=rtcp-fb:102 goog-remb
a=rtcp-fb:102 transport-cc
a=rtcp-fb:102 ccm fir
a=rtcp-fb:102 nack
a=rtcp-fb:102 nack pli
a=fmtp:102 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f
a=rtpmap:121 rtx/90000
a=fmtp:121 apt=102
a=rtpmap:127 H264/90000
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 level-asymmetry-allowed=1;packetization-mode=0;profile-level-id=42001f
a=rtpmap:120 rtx/90000
a=fmtp:120 apt=127
a=rtpmap:125 H264/90000
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 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f
a=rtpmap:107 rtx/90000
a=fmtp:107 apt=125
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=0;profile-level-id=42e01f
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=4d001f
a=rtpmap:119 rtx/90000
a=fmtp:119 apt=124
a=rtpmap:123 H264/90000
a=rtcp-fb:123 goog-remb
a=rtcp-fb:123 transport-cc
a=rtcp-fb:123 ccm fir
a=rtcp-fb:123 nack
a=rtcp-fb:123 nack pli
a=fmtp:123 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=64001f
a=rtpmap:118 rtx/90000
a=fmtp:118 apt=123
a=rtpmap:114 red/90000
a=rtpmap:115 rtx/90000
a=fmtp:115 apt=114
a=rtpmap:116 ulpfec/90000
a=ssrc-group:FID 3728952236 2085696953
a=ssrc:3728952236 cname:TdZx9He99oI1ZADZ
a=ssrc:3728952236 msid:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew ea8a9278-d344-4025-8053-1a86b2764c04
a=ssrc:3728952236 mslabel:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew
a=ssrc:3728952236 label:ea8a9278-d344-4025-8053-1a86b2764c04
a=ssrc:2085696953 cname:TdZx9He99oI1ZADZ
a=ssrc:2085696953 msid:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew ea8a9278-d344-4025-8053-1a86b2764c04
a=ssrc:2085696953 mslabel:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew
a=ssrc:2085696953 label:ea8a9278-d344-4025-8053-1a86b2764c04
docs/native-code/rtp-hdrext/abs-send-time - src - Git at Google
http://www.webrtc.org
错误登录 Android:
Call cannot answered: SDP Set failure: SessionDescription is NULL.
错误登录 iOS:
Error Domain=org.webrtc.RTCPeerConnection Code=-1 "SessionDescription is NULL." UserInfo={NSLocalizedDescription=SessionDescription is NULL.}. <0x6000015d6e60> unable to set remote description
此问题是由 Chrome 默认启用 extmap-allow-mixed 引起的（参见 https://www.chromestatus.com/features#offerExtmapAllowMixed）。可以通过接收方修改报价 SDP 以删除包含 a=extmap-allow-mixed
的行来解决
"Answer" 的 SDP offer 未从 Android/iOS 应用程序更新后发送到 Web App（Windows/Mac/Linux 上的运行） Chrome 到最新的 v89（2021 年 3 月 9 日发布）。
它在 Chrome v88 及以下版本上运行良好。
提供 SDP:
o=- 3986944572502207628 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE 0 1
a=extmap-allow-mixed
a=msid-semantic: WMS ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew
m=audio 9 UDP/TLS/RTP/SAVPF 111 103 104 9 0 8 106 105 13 110 112 113 126
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:l4+m
a=ice-pwd:Pi7zEzH/c5fFzvNAn0giR5CJ
a=ice-options:trickle
a=fingerprint:sha-256 5F:A3:0C:CE:24:0C:7B:F3:1D:CE:B4:B3:CE:AF:71:24:44:53:14:5B:ED:29:FF:C1:03:C2:5B:4C:E0:87:B8:DF
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=sendrecv
a=msid:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew 140a2361-2018-4f1c-8bbf-10e0094357b9
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:104 ISAC/32000
a=rtpmap:9 G722/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:106 CN/32000
a=rtpmap:105 CN/16000
a=rtpmap:13 CN/8000
a=rtpmap:110 telephone-event/48000
a=rtpmap:112 telephone-event/32000
a=rtpmap:113 telephone-event/16000
a=rtpmap:126 telephone-event/8000
a=ssrc:3610133405 cname:TdZx9He99oI1ZADZ
a=ssrc:3610133405 msid:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew 140a2361-2018-4f1c-8bbf-10e0094357b9
a=ssrc:3610133405 mslabel:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew
a=ssrc:3610133405 label:140a2361-2018-4f1c-8bbf-10e0094357b9
m=video 9 UDP/TLS/RTP/SAVPF 96 97 98 99 100 101 102 121 127 120 125 107 108 109 124 119 123 118 114 115 116
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:l4+m
a=ice-pwd:Pi7zEzH/c5fFzvNAn0giR5CJ
a=ice-options:trickle
a=fingerprint:sha-256 5F:A3:0C:CE:24:0C:7B:F3:1D:CE:B4:B3:CE:AF:71:24:44:53:14:5B:ED:29:FF:C1:03:C2:5B:4C:E0:87:B8:DF
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=sendrecv
a=msid:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew ea8a9278-d344-4025-8053-1a86b2764c04
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:100 VP9/90000
a=rtcp-fb:100 goog-remb
a=rtcp-fb:100 transport-cc
a=rtcp-fb:100 ccm fir
a=rtcp-fb:100 nack
a=rtcp-fb:100 nack pli
a=fmtp:100 profile-id=2
a=rtpmap:101 rtx/90000
a=fmtp:101 apt=100
a=rtpmap:102 H264/90000
a=rtcp-fb:102 goog-remb
a=rtcp-fb:102 transport-cc
a=rtcp-fb:102 ccm fir
a=rtcp-fb:102 nack
a=rtcp-fb:102 nack pli
a=fmtp:102 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f
a=rtpmap:121 rtx/90000
a=fmtp:121 apt=102
a=rtpmap:127 H264/90000
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 level-asymmetry-allowed=1;packetization-mode=0;profile-level-id=42001f
a=rtpmap:120 rtx/90000
a=fmtp:120 apt=127
a=rtpmap:125 H264/90000
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 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f
a=rtpmap:107 rtx/90000
a=fmtp:107 apt=125
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=0;profile-level-id=42e01f
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=4d001f
a=rtpmap:119 rtx/90000
a=fmtp:119 apt=124
a=rtpmap:123 H264/90000
a=rtcp-fb:123 goog-remb
a=rtcp-fb:123 transport-cc
a=rtcp-fb:123 ccm fir
a=rtcp-fb:123 nack
a=rtcp-fb:123 nack pli
a=fmtp:123 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=64001f
a=rtpmap:118 rtx/90000
a=fmtp:118 apt=123
a=rtpmap:114 red/90000
a=rtpmap:115 rtx/90000
a=fmtp:115 apt=114
a=rtpmap:116 ulpfec/90000
a=ssrc-group:FID 3728952236 2085696953
a=ssrc:3728952236 cname:TdZx9He99oI1ZADZ
a=ssrc:3728952236 msid:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew ea8a9278-d344-4025-8053-1a86b2764c04
a=ssrc:3728952236 mslabel:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew
a=ssrc:3728952236 label:ea8a9278-d344-4025-8053-1a86b2764c04
a=ssrc:2085696953 cname:TdZx9He99oI1ZADZ
a=ssrc:2085696953 msid:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew ea8a9278-d344-4025-8053-1a86b2764c04
a=ssrc:2085696953 mslabel:ER6BzrTgSfzSmlbwz6YLSUR0vFQmlQp6f0ew
a=ssrc:2085696953 label:ea8a9278-d344-4025-8053-1a86b2764c04
docs/native-code/rtp-hdrext/abs-send-time - src - Git at Google
http://www.webrtc.org
错误登录 Android:
Call cannot answered: SDP Set failure: SessionDescription is NULL.
错误登录 iOS:
Error Domain=org.webrtc.RTCPeerConnection Code=-1 "SessionDescription is NULL." UserInfo={NSLocalizedDescription=SessionDescription is NULL.}. <0x6000015d6e60> unable to set remote description
此问题是由 Chrome 默认启用 extmap-allow-mixed 引起的（参见 https://www.chromestatus.com/features#offerExtmapAllowMixed）。可以通过接收方修改报价 SDP 以删除包含 a=extmap-allow-mixed