Real Time Streaming Protocol


The Real Time Streaming Protocol is a network control protocol designed for use in entertainment and communications systems to control streaming media servers. The protocol is used for establishing and controlling media sessions between end points. Clients of media servers issue VHS-style commands, such as play, record and pause, to facilitate real-time control of the media streaming from the server to a client or from a client to the server.
The transmission of streaming data itself is not a task of RTSP. Most RTSP servers use the Real-time Transport Protocol in conjunction with Real-time Control Protocol for media stream delivery. However, some vendors implement proprietary transport protocols. The RTSP server software from RealNetworks, for example, also used RealNetworks' proprietary Real Data Transport.
RTSP was developed by RealNetworks, Netscape and Columbia University, with the first draft submitted to IETF in 1996. It was standardized by the Multiparty Multimedia Session Control Working Group of the Internet Engineering Task Force and published as RFC 2326 in 1998. RTSP 2.0 published as RFC 7826 in 2016 as a replacement of RTSP 1.0. RTSP 2.0 is based on RTSP 1.0 but is not backwards compatible other than in the basic version negotiation mechanism.

Protocol directives

While similar in some ways to HTTP, RTSP defines control sequences useful in controlling multimedia playback. While HTTP is stateless, RTSP has state; an identifier is used when needed to track concurrent sessions. Like HTTP, RTSP uses TCP to maintain an end-to-end connection and, while most RTSP control messages are sent by the client to the server, some commands travel in the other direction.
Presented here are the basic RTSP requests. Some typical HTTP requests, like the OPTIONS request, are also available. The default transport layer port number is 554 for both TCP and UDP, the latter being rarely used for the control requests.
; OPTIONS

C->S: OPTIONS rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 1
 Require: implicit-play
 Proxy-Require: gzipped-messages
S->C: RTSP/1.0 200 OK
 CSeq: 1
 Public: DESCRIBE, SETUP, TEARDOWN, PLAY, PAUSE

; DESCRIBE

C->S: DESCRIBE rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 2
S->C: RTSP/1.0 200 OK
 CSeq: 2
 Content-Base: rtsp://example.com/media.mp4
 Content-Type: application/sdp
 Content-Length: 460
 m=video 0 RTP/AVP 96
 a=control:streamid=0
 a=range:npt=0-7.741000
 a=length:npt=7.741000
 a=rtpmap:96 MP4V-ES/5544
 a=mimetype:string;"video/MP4V-ES"
 a=AvgBitRate:integer;304018
 a=StreamName:string;"hinted video track"
 m=audio 0 RTP/AVP 97
 a=control:streamid=1
 a=range:npt=0-7.712000
 a=length:npt=7.712000
 a=rtpmap:97 mpeg4-generic/32000/2
 a=mimetype:string;"audio/mpeg4-generic"
 a=AvgBitRate:integer;65790
 a=StreamName:string;"hinted audio track"

; SETUP

C->S: SETUP rtsp://example.com/media.mp4/streamid=0 RTSP/1.0
 CSeq: 3
 Transport: RTP/AVP;unicast;client_port=8000-8001
S->C: RTSP/1.0 200 OK
 CSeq: 3
 Transport: RTP/AVP;unicast;client_port=8000-8001;server_port=9000-9001;ssrc=1234ABCD
 Session: 12345678
C->S: SETUP rtsp://example.com/media.mp4/streamid=1 RTSP/1.0
 CSeq: 3
 Transport: RTP/AVP;unicast;client_port=8002-8003
 Session: 12345678
S->C: RTSP/1.0 200 OK
 CSeq: 3
 Transport: RTP/AVP;unicast;client_port=8002-8003;server_port=9002-9003;ssrc=1234ABCD
 Session: 12345678

; PLAY

C->S: PLAY rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 4
 Range: npt=5-20
 Session: 12345678
S->C: RTSP/1.0 200 OK
 CSeq: 4
 Session: 12345678
 RTP-Info: url=rtsp://example.com/media.mp4/streamid=0;seq=9810092;rtptime=3450012

; PAUSE

C->S: PAUSE rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 5
 Session: 12345678
S->C: RTSP/1.0 200 OK
 CSeq: 5
 Session: 12345678

; RECORD

C->S: RECORD rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 6
 Session: 12345678
S->C: RTSP/1.0 200 OK
 CSeq: 6
 Session: 12345678

; ANNOUNCE

C->S: ANNOUNCE rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 7
 Date: 23 Jan 1997 15:35:06 GMT
 Session: 12345678
 Content-Type: application/sdp
 Content-Length: 332
 v=0
 o=mhandley 2890844526 2890845468 IN IP4 126.16.64.4
 s=SDP Seminar
 i=A Seminar on the session description protocol
 u=http://www.cs.ucl.ac.uk/staff/M.Handley/sdp.03.ps
 e=mjh@isi.edu 
 c=IN IP4 224.2.17.12/127
 t=2873397496 2873404696
 a=recvonly
 m=audio 3456 RTP/AVP 0
 m=video 2232 RTP/AVP 31
S->C: RTSP/1.0 200 OK
 CSeq: 7

; TEARDOWN

C->S: TEARDOWN rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 8
 Session: 12345678
S->C: RTSP/1.0 200 OK
 CSeq: 8

; GET_PARAMETER

S->C: GET_PARAMETER rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 9
 Content-Type: text/parameters
 Session: 12345678
 Content-Length: 15
 packets_received
 jitter
C->S: RTSP/1.0 200 OK
 CSeq: 9
 Content-Length: 46
 Content-Type: text/parameters
 packets_received: 10
 jitter: 0.3838

; SET_PARAMETER

C->S: SET_PARAMETER rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 10
 Content-length: 20
 Content-type: text/parameters
 barparam: barstuff
S->C: RTSP/1.0 451 Invalid Parameter
 CSeq: 10
 Content-length: 10
 Content-type: text/parameters
 barparam

; REDIRECT

S->C: REDIRECT rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 11
 Location: rtsp://bigserver.com:8001
 Range: clock=19960213T143205Z-

; Embedded Binary Data

C->S: SETUP rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 3
 Transport: RTP/AVP/TCP;interleaved=0-1
S->C: RTSP/1.0 200 OK
 CSeq: 3
 Date: 05 Jun 1997 18:57:18 GMT
 Transport: RTP/AVP/TCP;interleaved=0-1
 Session: 12345678
C->S: PLAY rtsp://example.com/media.mp4 RTSP/1.0
 CSeq: 4
 Session: 12345678
S->C: RTSP/1.0 200 OK
 CSeq: 4
 Session: 12345678
 Date: 05 Jun 1997 18:59:15 GMT
 RTP-Info: url=rtsp://example.com/media.mp4;seq=232433;rtptime=972948234
S->C: $\000
S->C: $\000
S->C: $\001

Rate adaptation

RTSP using RTP and RTCP allows for the implementation of rate adaptation.

Implementations

Server

Many CCTV / Security cameras, often called IP Cameras, support RTSP streaming too, especially these with ONVIF profiles G, S, T.

Client