所以，下面是我从yyyy (SIP)呼叫时从xxxx (webRTC)得到的响应。通话建立，但是只有视频而不是音频，具有 100% 的一致性。我的问题是有人知道正文中最后两个 sdp 标头是什么意思吗？为什么xxxx最初会使用正确的端口和可用的编解码器进行响应，但随后又提出相反的建议：“m=video 0 RTP/AVP
m=application 0 RTP/AVP”
任何帮助将不胜感激:)
报价：
2015-04-20 18:54:32,291 : Inbound Message
Transport: TCP: ip=x.x.x.x, port=60118, secure=false
INVITE sip:1234@x.x.x.x SIP/2.0
Via: SIP/2.0/TCP x.x.x.x:5060;branch=z9hG4bKa877nh3hd5624lJ1o2E-pc16vl-1194
Via: SIP/2.0/TCP y.y.y.y:5060;branch=z9hG4bKa877nh3hd5624lJ1o2E-pc16vl;rport=49528
From: "Alacrity City" <sip:2312@y.y.y.y>;tag=14295560721021025240-F--5c-4f-6a-11
To: <sip:1234@x.x.x.x>
Contact: <sip:2312@y.y.y.y;transport=tcp>
Call-ID: -119405323313131523-c16c-B2BUA@y.y.y.y
CSeq: 1 INVITE
Supported: timer,sip-stun,outbound,replaces
Allow: INVITE,ACK,CANCEL,BYE,OPTIONS,REFER,NOTIFY,UPDATE,MESSAGE
Max-Forwards: 69
User-Agent: M
X-FS-Support: update_display
Session-Expires: 1800;refresher=uac
Content-Type: application/sdp
MSS_Initial_Remote_Addr: y.y.y.y
MSS_Initial_Remote_Port: 49528
MSS_Initial_Remote_Transport: tcp
Content-Length: 1304
v=0
o=Magor 1429539042 1429539044 IN IP4 y.y.y.y
s=Magor
c=IN IP4 y.y.y.y
b=TIAS:2048000
b=AS:2048
b=CT:2048
t=0 0
m=audio 20052 RTP/AVP 115 9 120 6 70 0 8 99 97 112 101
a=rtpmap:115 G7221/32000
a=fmtp:115 bitrate=48000
a=rtpmap:9 G722/8000
a=rtpmap:120 SILK/24000
a=fmtp:120 useinbandfec=1; usedtx=0
a=rtpmap:6 DVI4/16000
a=rtpmap:70 L16/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:99 isac/32000
a=rtpmap:97 iLBC/8000
a=fmtp:97 mode=30
a=rtpmap:112 opus/48000/2
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=silenceSupp:off - - - -
m=video 20056 RTP/AVP 96 97
b=TIAS:2048000
a=rtpmap:96 H264/90000
a=fmtp:96 profile-level-id=42e016; max-fs=8192; max-mbps=244800
a=rtpmap:97 H264/90000
a=fmtp:97 profile-level-id=64e016; max-fs=8192; max-mbps=244800
a=content:main
a=rtcp-fb:* ccm fir
a=rtcp-fb:* ccm tmmbr
a=rtcp-fb:* nack pli
m=video 20060 RTP/AVP 96 97
b=TIAS:2048000
a=rtpmap:96 H264/90000
a=fmtp:96 profile-level-id=42e016; max-fs=8192; max-mbps=244800
a=rtpmap:97 H264/90000
a=fmtp:97 profile-level-id=64e016; max-fs=8192; max-mbps=244800
a=content:slides
a=rtcp-fb:* ccm fir
a=rtcp-fb:* ccm tmmbr
a=rtcp-fb:* nack pli
m=application 20064 UDP/BFCP *
a=floorctrl:c-only
a=setup:passive
a=connection:new
a=bfcpver:1
响应：
2015-04-20 18:54:35,523 : Outbound Message
Transport: TCP: ip=x.x.x.x, port=60118, secure=false
SIP/2.0 200 OK
To: <sip:1234@x.x.x.x>;tag=7-mobi-15398169_ada14cd5_e63f04c4-9dbc-4e91-b908-fa42b01af3e4_3
Via: SIP/2.0/TCP x.x.x.x:5060;branch=z9hG4bKa877nh3hd5624lJ1o2E-pc16vl-1194;rport=60118
Via: SIP/2.0/TCP y.y.y.y:5060;branch=z9hG4bKa877nh3hd5624lJ1o2E-pc16vl;rport=49528
CSeq: 1 INVITE
Call-ID: -119405323313131523-c16c-B2BUA@y.y.y.y
From: "Alacrity City" <sip:2312@y.y.y.y>;tag=14295560721021025240-F--5c-4f-6a-11
Contact: <sip:x.x.x.x:5060;transport=tcp>
Content-Type: application/sdp
Min-SE: 400
Session-Expires: 1800;refresher=uac
Allow: UPDATE,ACK,INVITE,PRACK,CANCEL
Require: timer
Supported: timer,100rel
Content-Length: 542
v=0
o=- 2017325266 1 IN IP4 z.z.z.z (internal IP of server x.x.x.x)
s=-
c=IN IP4 x.x.x.x
t=0 0
m=audio 17050 RTP/AVP 112 101
a=rtpmap:112 opus/48000/2
a=fmtp:112 minptime=10
a=rtpmap:101 telephone-event/8000
a=sendrecv
m=video 17002 RTP/AVP 97
a=rtpmap:97 H264/90000
a=fmtp:97 profile-level-id=42801E;packetization-mode=0;level-asymmetry-allowed=1
a=rtcp-fb:97 nack
a=rtcp-fb:97 ccm fir
a=rtcp-fb:97 nack pli
a=rtcp-fb:97 ccm tmmbr
a=sendrecv
a=imageattr:97 send [x=480,y=640] recv [x=480,y=640]
m=video 0 RTP/AVP
m=application 0 RTP/AVP
----------------------------