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分类: LINUX

2013-03-12 02:36:36

RTSP 协议分析
1.概述:
 RTSP(Real Time Streaming Protocol),实时流传输协议,是TCP/IP协议体系中的一个应用层协议,由哥伦比亚大学、网景和RealNetworks公司提交的IETF RFC标准。该协议定义了一对多应用程序如何有效地通过IP网络传送多媒体数据。类似HTTP协议的流控制协议。它们都使用纯文本来发送信息,而且rtsp协议的语法也和HTTP类似,和HTTP协议相比RTSP协议所不同的地方是,RTSP协议是有状态的协议,而HTTP是无状态的协议。RTSP通过维护一个session来维护其状态的转换。RTSP协议的默认端口是554,默认的承载协议为TCP。

2.RTSP的特性:
(1).流控分离:从控制逻辑上来说RTSP和FTP相似,控制流和数据流是分开的。
(2).可扩展性:因为RTSP协议是基于文本的协议所以其具有较强的可扩展性。
(3).安全:RTSP 使用网页安全机制。

3.RTSP 协议格式:
请求命令的格式为:
METHOD URL CR LF
Field1:value CR LF
Field2:value CR LF
......
Fieldn:value CR LF
CR LF

应答的格式为:
RTSP/major_version.minor_version status CR LF
Field1:value CR LF
Field2:value CR LF
......
Fieldn:value CR LF
CR LF

4.RTSP的主要命令:

5.RTSP命令的状态转换表

6.RTSP状态码

Status-Code = "100" ; Continue
| "200" ; OK
| "201" ; Created
| "250" ; Low on Storage Space
| "300" ; Multiple Choices
| "301" ; Moved Permanently
| "302" ; Moved Temporarily
| "303" ; See Other
| "304" ; Not Modified
| "305" ; Use Proxy
| "400" ; Bad Request
| "401" ; Unauthorized
| "402" ; Payment Required
| "403" ; Forbidden
| "404" ; Not Found
| "405" ; Method Not Allowed
| "406" ; Not Acceptable
| "407" ; Proxy Authentication Required
| "408" ; Request Time-out
| "410" ; Gone
| "411" ; Length Required
| "412" ; Precondition Failed
| "413" ; Request Entity Too Large
| "414" ; Request-URI Too Large
| "415" ; Unsupported Media Type
| "451" ; Parameter Not Understood
| "452" ; Conference Not Found
| "453" ; Not Enough Bandwidth
| "454" ; Session Not Found
| "455" ; Method Not Valid in This State
| "456" ; Header Field Not Valid for Resource
| "457" ; Invalid Range
| "458" ; Parameter Is Read-Only
| "459" ; Aggregate operation not allowed
| "460" ; Only aggregate operation allowed
| "461" ; Unsupported transport
| "462" ; Destination unreachable
| "500" ; Internal Server Error
| "501" ; Not Implemented
| "502" ; Bad Gateway
| "503" ; Service Unavailable
| "504" ; Gateway Time-out
| "505" ; RTSP Version not supported
| "551" ; Option not supported
| extension-code
extension-code = 3DIGIT
Reason-Phrase = *

以下是某省IPTV的RTSP协商过程:

DESCRIBE rtsp://118.122.89.27:554/live/ch10083121594790060557.sdp?playtype=1&boid=001&backupagent=118.122.89.27:554&clienttype=1&time=20100929182111+08&life=172800&ifpricereqsnd=1&vcdnid=001&userid=123&mediaid=ch10083121594790060557&ctype=2&TSTVTimeLife=1800&contname=&authid=0&UserLiveType=1&nodelevel=3 RTSP/1.0 
/媒体URL 
Accept: application/sdp 
//协商用于描述媒体信息协议 
CSeq: 1

User-Agent:ZTE Ltd.co RTSP protocal verion 1.0 guid-2.1.1.100/B519D290-C0EC-EE35-7368-893BE4C0B347 
//User Agnet信息,显示是中兴的服务器,1.0的版本。如果是Helix服务器的话会有Helix 服务器的标识。 
x-NAT:2.1.1.100:20081 
//主要用于NAT穿透 
x-zmssRtxSdp: yes

RTSP/1.0 200 OK 
//应答编号 
Server: ZXUSS100 1.0

Cache-Control: no-cache

Content-Base: rtsp://118.122.89.27:554/live/ch10083121594790060557.sdp/

Content-Length: 320 
//内容长度信息 
Content-Type: application/sdp 
//描述内容信息所用的协议 
CSeq: 1

Date: Wed, 29 Sep 2010 10:20:38 GMT

Expires: Wed, 29 Sep 2010 10:20:38 GMT 
// SDP 描述信息

v=0

o=- 296874273 1 IN IP4 118.122.89.27

s=envivio

c=IN IP4 0.0.0.0

b=AS:1500

t=0 0

a=range:clock=20100929T095038.00Z-20100929T102038.00Z

m=video 5140 RTP/AVPF 33 96

a=control:trackID=2

a=rtpmap:33 MP2T/90000

a=3GPP-Adaptation-Support:5

a=rtcp-fb:33 nack

a=rtpmap:96 rtx/90000

a=fmtp:96 apt=33;rtx-time=0

SETUP rtsp://118.122.89.27:554/live/ch10083121594790060557.sdp/trackID=2 RTSP/1.0 
//用于建立RTSP连接,协商传输用的协议。 
CSeq: 2

3GPP-Adaptation: url=rtsp://118.122.89.27:554/live/ch10083121594790060557.sdp/trackID=2;size=1061400;target-time=2200

Transport: MP2T/RTP/UDP;unicast;destination=2.1.1.100;client_port=8360-8361,MP2T/RTP/TCP;unicast;destination=2.1.1.100;interleaved=0-1,MP2T/UDP;unicast;destination=2.1.1.100;client_port=8360-8361,MP2T/TCP;unicast;destination=2.1.1.100;interleaved=0-1 
// MP2T/RTP/UDP表示是TS流用于RTP打包,基于UDP传输。MP2T/RTP/TCP表示是TS流用于RTP打包,基于TCP。 
User-Agent:ZTE Ltd.co RTSP protocal verion 1.0 guid-2.1.1.100/B519D290-C0EC-EE35-7368-893BE4C0B347

RTSP/1.0 200 OK

Server: ZXUSS100 1.0

CSeq: 2

Date: Wed, 29 Sep 2010 10:20:38 GMT

Expires: Wed, 29 Sep 2010 10:20:38 GMT

Session: 65565885

Transport: MP2T/RTP/UDP;unicast;destination=2.1.1.100;client_port=8360-8361;server_port=13306-13307;source=118.122.89.29 
// 通过协商MP2T/RTP/UDP表示是TS流用于RTP打包,基于UDP传输。server端端口:13306-13307。client端端口:8360-8361 
3GPP-Adaptation:url=rtsp://118.122.89.27:554/live/ch10083121594790060557.sdp/trackID=2;size=1061400;target-time=2200

PLAY rtsp://118.122.89.27:554/live/ch10083121594790060557.sdp?playtype=1&boid=001&backupagent=118.122.89.27:554&clienttype=1&time=20100929182111+08&life=172800&ifpricereqsnd=1&vcdnid=001&userid=123&mediaid=ch10083121594790060557&ctype=2&TSTVTimeLife=1800&contname=&authid=0&UserLiveType=1&nodelevel=3 RTSP/1.0 
//播放视频。对于有些视频可能会分别要对音频视频进行play。 
CSeq: 3

Session: 65565885

User-Agent:ZTE Ltd.co RTSP protocal verion 1.0 guid-2.1.1.100/B519D290-C0EC-EE35-7368-893BE4C0B347

Scale: 1.0

Range: npt=end-

//npt=end-在IPTV2.0里面有其自身的定义(可参看上海电信IPTV2.0标准)

RTSP/1.0 200 OK

Server: ZXUSS100 1.0

CSeq: 3

Range: npt=end-

Scale: 1.0

Session: 65565885

RTP-Info: url=rtsp://118.122.89.29:13306/live/ch10083121594790060557.sdp/trackID=2

......

PLAY rtsp://118.122.89.27:554/live/ch10083121594790060557.sdp?playtype=1&boid=001&backupagent=118.122.89.27:554&clienttype=1&time=20100929182111+08&life=172800&ifpricereqsnd=1&vcdnid=001&userid=123&mediaid=ch10083121594790060557&ctype=2&TSTVTimeLife=1800&contname=&authid=0&UserLiveType=1&nodelevel=3 RTSP/1.0 
//play的另外一种用法。用于快进和快退。 
CSeq: 43

Session: 65565885

User-Agent:ZTE Ltd.co RTSP protocal verion 1.0 guid-2.1.1.100/B519D290-C0EC-EE35-7368-893BE4C0B347

Scale: -32.0 
//Scale: -32.0,表示以32倍速快退。Scale: 32.0,表示以32倍速快进。 
Range: npt=now-

RTSP/1.0 200 OK

Server: ZXUSS100 1.0

CSeq: 43

Range: clock=20100929T102609.02Z-20100929T095637.75Z

Scale: -32.0

Session: 65565885

RTP-Info: url=rtsp://118.122.89.36:10084/live/ch10083121594790060557.sdp/trackID=2;seq=22277;rtptime=1792329138

GET_PARAMETER rtsp://118.122.89.27:554/live/ch10083121594790060557.sdp?playtype=1&boid=001&backupagent=118.122.89.27:554&clienttype=1&time=20100929182111+08&life=172800&ifpricereqsnd=1&vcdnid=001&userid=123&mediaid=ch10083121594790060557&ctype=2&TSTVTimeLife=1800&contname=&authid=0&UserLiveType=1&nodelevel=3 RTSP/1.0 
//获取当前的一些播放参数。 
CSeq: 44

Session: 65565885

User-Agent:ZTE Ltd.co RTSP protocal verion 1.0 guid-2.1.1.100/B519D290-C0EC-EE35-7368-893BE4C0B347

x-Timeshift_Range 
//请求时移的范围 
x-Timeshift_Current 
//获取当前的时间点

RTSP/1.0 200 OK 
//返回当前的媒体信息。 
Server: ZXUSS100 1.0

CSeq: 44

Session: 65565885

x-Timeshift_Range: clock=20100929T095638.83Z-20100929T102638.83Z

x-Timeshift_Current: clock=20100929T102530.20Z;rtptime=1788844914

中间省去了45,46,47三个包。通过CSeq: 48字段可以看出来

PLAY rtsp://118.122.89.27:554/live/ch10083121594790060557.sdp?playtype=1&boid=001&backupagent=118.122.89.27:554&clienttype=1&time=20100929182111+08&life=172800&ifpricereqsnd=1&vcdnid=001&userid=123&mediaid=ch10083121594790060557&ctype=2&TSTVTimeLife=1800&contname=&authid=0&UserLiveType=1&nodelevel=3 RTSP/1.0 
用于恢复正常的播放速度。 
CSeq: 48

Session: 65565885

User-Agent:ZTE Ltd.co RTSP protocal verion 1.0 guid-2.1.1.100/B519D290-C0EC-EE35-7368-893BE4C0B347

Scale: 1.0

Range: npt=beginning-

RTSP/1.0 200 OK

Server: ZXUSS100 1.0

CSeq: 48

Range: clock=20100929T095730.00Z-20100929T102730.61Z 
//可以时移的范围。 
Scale: 1.0

Session: 65565885

RTP-Info: url=rtsp://118.122.89.36:10084/live/ch10083121594790060557.sdp/trackID=2;seq=39900;rtptime=1637595010

<中间在Descript应答中所用的SDP协议将会在以后中描述>

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satan_emperor2013-03-13 15:41:13

好文章!