POSTECH DP&NM Lab 1 Real-time Streaming Protocol (RTSP) Byungchul Park DPNM Lab., CSE, POSTECH

POSTECH DP&NM Lab 2 Table of Contents Introduction RTSP Message RTSP Methods Usage Scenario: Video on Demand RTSP Applications Summary

POSTECH DP&NM Lab 3 Introduction - Streaming What is Streaming? –Streaming is the process of playing a file while it is still downloading –Streaming technology lets a user view and hear digitized content – video, sound and animation – as it is being downloaded Streaming breaks the data into packets with size suitable for the transmission between server and clients RTSP establish and controls streams

POSTECH DP&NM Lab 4 Introduction - RTSP RTSP is an application level protocol for the control of real-time streaming data with syntax and operations similar to HTTP IEFT standard  RFC 2326 (April, 1998) RTSP uses RTP as the underlying data delivery protocol and offers a VCR-like control to the user: –PLAY, STOP, PAUSE, FF, REW RTSP = Network remote controller

POSTECH DP&NM Lab 5 RTSP vs. RTP RTSP allows two-way communication –Viewers can communicate with the streaming server and do things like rewind the movie, go to a chapter, and so on –It does not typically deliver the continuous streams itself RTP is one-way protocol –Send live or stored streams from the server to the client

POSTECH DP&NM Lab 6 RTSP vs. HTTP RTSP has similar syntax and operations with HTTP Both an RTSP server and client can issue requests An RTSP server needs to maintain state by default in almost all cases, as opposed to the stateless nature of HTTP Data is carried out-of-band by a different protocol (RTP) RTSP has various methods while HTTP has only two methods (GET, POST)

POSTECH DP&NM Lab 7 Message Types RTSP is a text-based protocol and uses UTF-8 (Unicode octet) encoding Messages can be either requests or responses Request contain methods, the object the method is operating upon and parameters to further describe the method After receiving and interpreting request, the recipient replies with a response message RTSP messages are based on HTTP messages, with slight changes to allow for new status codes and different primitives

POSTECH DP&NM Lab 8 RTSP Message RFC HTTP/1.1

POSTECH DP&NM Lab 9 RTSP Methods MethodDirectionRequirementDescription DESCRIBEC->SrecommendedGet description of media object ANNOUNCEC->S, S->CoptionalChange description of media object GET_PARAMETERC->S, S->Coptional OPTIONC->S, S->CrequiredGet available methods PAUSEC->SrecommendedHalt delivery, but keep state PLAYC->SrequiredStart playback RECOREDC->SoptionalStart recording REDIRECTS->CoptionalRedirect client to new server SETUPC->SrequiredEstablish transport SET_PARAMETERC->S, S->CoptionalDevice or encoding control TEARDOWNC->SrequiredRemove state

POSTECH DP&NM Lab 10 Methods - OPTIONS The OPTIONS method represents a request for information about the communication options available on the request/response chain

POSTECH DP&NM Lab 11 Methods - DESCRIBE The DESCRIBE method retrieves the description of a presentation or media object identified by the request URL from a server. The DESCRIBE reply- response pair constitutes the media initialization phase of RTSP. This description can be implemented using the SDP protocol

POSTECH DP&NM Lab 12 Methods - ANNOUNCE When sent from client to server, ANNOUNCE posts the description of a presentation or media object identified by the request URL to a server. When sent from server to client, ANNOUNCE updates the session description in real-time.

POSTECH DP&NM Lab 13 Methods - SETUP The SETUP request for a URI specifies the transport mechanism to be used for the streamed media The Transport header specifies the transport parameters acceptable to the client for data transmission; the response will contain the transport parameters selected by the server

POSTECH DP&NM Lab 14 Methods - PLAY The PLAY method tells the server to start sending data via the mechanism specified in SETUP. A client must not issue a PLAY request until any outstanding SETUP requests have been acknowledged as successful The PLAY request positions the normal play time to the beginning of the range specified and delivers stream data until the end of the range is reached Plays the whole presentation starting at SMPTE time code 0:10:20 until the end of the clip. The playback is tart at 15:36 on 23 Jan 1997.

POSTECH DP&NM Lab 15 Methods - PAUSE The PAUSE request causes the stream delivery to be interrupted temporarily. If the request URL names a stream, only playback and recording of that stream is halted. If the request URL names a group of streams, delivery of all currently active streams within the group is halted After resuming playback or recording, synchronization of the tracks must be maintained

POSTECH DP&NM Lab 16 Methods - TEARDOWN The TEARDOWN request stops the stream delivery for the given URI, freeing the resources associated with it. If the URI is the presentation URI for this presentation, any RTSP session identifier associated with the session is no longer valid. Unless all transport parameters are defined by the session description, a SETUP request has to be issued before the session can be played again.

POSTECH DP&NM Lab 17 Methods – GET_PARAMETER The GET_PARAMATER request retrieves the value of a parameter of a presentation or stream specified in the URI. The content of the reply and response is left to the implementation GET_PARAMETER with no entity body may be used to test client or server liveness (“ping”)

POSTECH DP&NM Lab 18 Methods – SET_PARAMETER This method requests to set the value of a parameter for a presentation or stream specified by the URI.

POSTECH DP&NM Lab 19 Methods - REDIRECT A redirect request informs the client that it must connect to another server location. It contains the mandatory header Location, which indicates that the client should issue requests for that URL. It may contain the parameter Range, which indicates when the redirection takes effect. If the client wants to continue to send or receive media for this URI, the client MUST issue a TEARDOWN request for the current session and a SETUP for the new session at the designated host. Useful for implementing server load balancing

POSTECH DP&NM Lab 20 Methods - RECORD This method initiates recording a range of media data according to the presentation description. The timestamp reflects start and end time (UTC). If no time range is given, use the start or end time provided in the presentation description. If the session has already started, commence recording immediately.

POSTECH DP&NM Lab 21 Protocol State Machines The RTSP client and server state machines describe the behavior of the protocol from RTSP session initialization through RTSP session termination

POSTECH DP&NM Lab 22 Usage Scenario: Video on Demand

POSTECH DP&NM Lab 23 Usage Scenario: Video on Demand

POSTECH DP&NM Lab 24 Usage Scenario: Video on Demand

POSTECH DP&NM Lab 25 RTSP Applications Streaming of multimedia via Internet Video conferencing and lectures Broadcasting of entertainment Remote digital editing Voice mail Real-world Application –Real Player ( –Cisco Application Control Engine (ACE) ( bulletin0900aecd e.html) bulletin0900aecd e.html –Nokia5300 –Unlimited TV On PC ( –Application Streaming ( –Free Premium TV for PC ( –PlayBox Technology ( –Etc.

POSTECH DP&NM Lab 26 Problems of Current Protocol The RTSP protocol says nothing about the problems of recovering state over machine or software failure Quality: packet loss, predictability No billing infrastructure: pay-per-play?

POSTECH DP&NM Lab 27 Summary RTSP provides an extensible framework to enable controlled, on-demand delivery of real-time data This protocol is intended to control multiple data delivery sessions, provide a means for choosing delivery channels, and provide a means for choosing delivery mechanisms based upon RTP

POSTECH DP&NM Lab 28 Question? ?