RTSP基础之RTSP/RTP OVER UDP
这里分析一下RTSP/RTP OVER UDP信令流程，主要分析工具 live555 RTSP服务器，wireshark抓包工具，vlc RTSP拉流客户端。通过UDP方式拉RTSP流，一般应用于局域网内，因特网因为防火墙原因会端口不可达。笔者参与开发的“电网视频监控系统及接口”国网标准中录像回放就是采用RTSP作为信令协议，采用RTP OVER UDP方式传输音视频流的。总体思路就是首先进行信令协商，协商完成向指定的UDP端口发送音视频流就可以了。有音视频的话，发送音频要两个端口(RTP/RTCP)，发送视频需要两个端口(RTP/RTCP)，这种方式的优缺点网上总结如下，再次摘抄如下：
- UDP协议上的RTSP/RTP需要打开许多UDP端口（每一路流媒体都需要2个UDP端口，一个用于RTP，一个用于RTCP）；
- 当因特网上的路由器没有打开这些端口的时候，第一点将会存在问题；
- 中间网络路由器很容易就过滤或者忽略掉UDP数据包；
- UDP是不可靠传输协议，媒体包在因特网上传输时会面临着丢包。
抓包分析流程
OPTIONS rtsp://192.168.1.113/Titanic.mkv RTSP/1.0
CSeq: 2
User-Agent: LibVLC/2.2.4 (LIVE555 Streaming Media v2016.02.22)
RTSP/1.0 200 OK
CSeq: 2
Date: Tue, Nov 13 2018 01:35:47 GMT
Public: OPTIONS, DESCRIBE, SETUP, TEARDOWN, PLAY, PAUSE, GET_PARAMETER, SET_PARAMETER
DESCRIBE rtsp://192.168.1.113/Titanic.mkv RTSP/1.0
CSeq: 3
User-Agent: LibVLC/2.2.4 (LIVE555 Streaming Media v2016.02.22)
Accept: application/sdp
RTSP/1.0 200 OK
CSeq: 3
Date: Tue, Nov 13 2018 01:35:47 GMT
Content-Base: rtsp://192.168.1.113/Titanic.mkv/
Content-Type: application/sdp
Content-Length: 5900
v=0
o=- 1542072947659606 1 IN IP4 192.168.1.113
s=Matroska video+audio+(optional)subtitles, streamed by the LIVE555 Media Server
i=Titanic.mkv
t=0 0
a=tool:LIVE555 Streaming Media v2016.05.18
a=type:broadcast
a=control:*
a=range:npt=0-48.090
a=x-qt-text-nam:Matroska video+audio+(optional)subtitles, streamed by the LIVE555 Media Server
a=x-qt-text-inf:Titanic.mkv
m=video 0 RTP/AVP 96
c=IN IP4 0.0.0.0
b=AS:500
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1;profile-level-id=640015;sprop-parameter-sets=Z2QAFazZQKAjoQAAAwPpAAC7gA8WLZY=,aOvjyyLA
a=control:track1
m=audio 0 RTP/AVP 97
c=IN IP4 0.0.0.0
b=AS:64
a=rtpmap:97 VORBIS/48000/2
a=fmtp:97 configuration=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a=control:track2
SETUP rtsp://192.168.1.113/Titanic.mkv/track1 RTSP/1.0
CSeq: 4
User-Agent: LibVLC/2.2.4 (LIVE555 Streaming Media v2016.02.22)
Transport: RTP/AVP;unicast;client_port=52694-52695
RTSP/1.0 200 OK
CSeq: 4
Date: Tue, Nov 13 2018 01:35:47 GMT
Transport: RTP/AVP;unicast;destination=192.168.1.108;source=192.168.1.113;client_port=52694-52695;server_port=6970-6971
Session: 97C644F3;timeout=65
SETUP rtsp://192.168.1.113/Titanic.mkv/track2 RTSP/1.0
CSeq: 5
User-Agent: LibVLC/2.2.4 (LIVE555 Streaming Media v2016.02.22)
Transport: RTP/AVP;unicast;client_port=52696-52697
Session: 97C644F3
RTSP/1.0 200 OK
CSeq: 5
Date: Tue, Nov 13 2018 01:35:47 GMT
Transport: RTP/AVP;unicast;destination=192.168.1.108;source=192.168.1.113;client_port=52696-52697;server_port=6972-6973
Session: 97C644F3;timeout=65
PLAY rtsp://192.168.1.113/Titanic.mkv/ RTSP/1.0
CSeq: 6
User-Agent: LibVLC/2.2.4 (LIVE555 Streaming Media v2016.02.22)
Session: 97C644F3
Range: npt=0.000-
RTSP/1.0 200 OK
CSeq: 6
Date: Tue, Nov 13 2018 01:35:47 GMT
Range: npt=0.000-
Session: 97C644F3
RTP-Info: url=rtsp://192.168.1.113/Titanic.mkv/track1;seq=23867;rtptime=1087186306,url=rtsp://192.168.1.113/Titanic.mkv/track2;seq=39742;rtptime=3781835924
GET_PARAMETER rtsp://192.168.1.113/Titanic.mkv/ RTSP/1.0
CSeq: 7
User-Agent: LibVLC/2.2.4 (LIVE555 Streaming Media v2016.02.22)
Session: 97C644F3
RTSP/1.0 200 OK
CSeq: 7
Date: Tue, Nov 13 2018 01:35:47 GMT
Session: 97C644F3
Content-Length: 10
2016.05.18TEARDOWN rtsp://192.168.1.113/Titanic.mkv/ RTSP/1.0
CSeq: 8
User-Agent: LibVLC/2.2.4 (LIVE555 Streaming Media v2016.02.22)
Session: 97C644F3
RTSP/1.0 200 OK
CSeq: 8
Date: Tue, Nov 13 2018 01:35:51 GMT