1. RTSP Real Time Streaming Protocol
Presented by
Group NEO
-Jitin Keith
-Prashant Morgaonkar

2. Real Time Streaming Protocol IETF RFC 2326
RTSP
Real Time Streaming Protocol
IETF RFC 2326

3. RTSP
RTSP is a signaling protocol which acts as a “Remote Control” for controlling a IP media server.
Very similar to HTTP /1.1
RTSP can request
Server to send media
Server invited to join a conference
Server announces that additional media available
Lets oversimplify this protocol a little bit  .This your protocol equivalent of a DVD or VCR player remote control . The same way a remote control issues commands such as ______________, this protocol issues commands to a media server

4. Overall Function
A presentation description file defines the type of media streams and its properties such as encoding language etc.
A presentation may contain several media streams
RTSP can use TCP, UDP or MUDP
Popular RTSP clients:
Windows Media Player
Real Player

5. RTSP Typical Method Types
Setup: Causes the server to allocate resources for a stream and start an RTSP session
Play-Record: Starts data transmission on a stream allocated via SETUP
Pause: Temporarily halts a stream without freeing server resources.
Teardown: Frees resources associated with the stream. The RTSP session ceases to exist on the server.

6. RTSP Status Codes
Success 2XX
Redirect 3XX
Client Error 4XX

7. RTSP Method types OPTIONS DESCRIBE ANNOUNCE SETUP, PLAY,
If the client is about to try a nonstandard request
DESCRIBE
The DESCRIBE method retrieves the description of a presentation
ANNOUNCE
A client can issue a SETUP request for a stream that is already playing to change transport parameters
SETUP,
PLAY,
The PLAY method tells the server to start sending data via the mechanism specified in SETUP

8. RTSP Method types PAUSE TEARDOWN GET_PARAMETER, SET_PARAMETER REDIRECT
The PAUSE request causes the stream delivery to be interrupted (halted) temporarily
TEARDOWN
The TEARDOWN request stops the stream
GET_PARAMETER, SET_PARAMETER
The GET_PARAMETER request retrieves the value of a parameter of a presentation or stream
REDIRECT
A redirect request informs the client that it must connect to another server location
RECORD
Start recording the media

9. RTSP Client FSM state message sent next state after response
Init SETUP Ready
TEARDOWN Init
Ready PLAY Playing
RECORD Recording
SETUP Ready
Playing PAUSE Ready
TEARDOWN Init
PLAY Playing
SETUP Playing (changed transport)
Recording PAUSE Ready
TEARDOWN Init
RECORD Recording
SETUP Recording (changed transport)

10. RTSP Server FSM state message received next state Init SETUP Ready
TEARDOWN Init
Ready PLAY Playing
SETUP Ready
RECORD Recording
Playing PLAY Playing
PAUSE Ready
TEARDOWN Init
SETUP Playing
Recording RECORD Recording
SETUP Recording
The "next state" column indicates the state assumed after sending a success response (2xx). If a request results in a status code of 3xx, the state becomes Init. A status code of 4xx results in no change

11. Security issues
Denial of service: Flood any arbitrary machine on the Internet with unrequested RTSP streams
Session hijacking
Authentication

12. Streaming Stored Multimedia (1/2)

13. Streaming Stored Multimedia (2/2)

14. Stored media streaming
Internet multimedia: simplest approach
Internet multimedia: simplest approach
files transferred as HTTP object
received in entirety at client
then passed to player
files transferred as HTTP
audio, video not streamed:
no, “pipelining,” long delays until playout!

15. Streaming vs. Download of Stored Multimedia
Download: Receive entire
content before playback begins
High “start-up” delay as media
file can be large
~ 4GB for a 2 hour MPEG II
movie
Streaming: Play the media file while it is being received
Reasonable “start-up” delays
Reception Rate >= playback rate.

16. Progressive Download browser GETs metafile
browser launches player, passing metafile
player contacts server
server downloads audio/video to player

17. RTSP Example Scenario: metafile communicated to web browser
browser launches player
player sets up an RTSP control connection, data
connection to streaming server

18. RTSP Operation

19. Client Buffering Client-side buffering, playout delay compensate
for network-added delay, delay jitter

20. Client Buffering Client-side buffering, playout delay compensate
for network-added delay, delay jitter

21. Streaming Multimedia: UDP or TCP?
server sends at rate appropriate for client (oblivious to
network congestion !)
often send rate = encoding rate = constant rate
then, fill rate = constant rate - packet loss
short playout delay (2-5 seconds) to compensate for network
delay jitter
error recover: time permitting
TCP
send at maximum possible rate under TCP
fill rate fluctuates due to TCP congestion control
larger playout delay: smooth TCP delivery rate
HTTP/TCP passes more easily through firewalls

22. Packet Loss network loss: IP datagram lost due to network
congestion (router buffer overflow)
delay loss: IP datagram arrives too late for
playout at receiver

23. Forward Error Correction (FEC)
For every group of n packets generate k redundant
packets
Send out n+k packets, increasing the bandwidth by factor
k/n.
Can reconstruct the original n packets provided at most k
Packets are lost from the group
Works well at high loss rate (for a proper choice of k)
Handles “bursty” packet losses
Cost: increase in transmission cost (bandwidth)

24. Another FEC Example “Piggyback lower quality stream”
Example: send lower resolution audio stream as
the redundant
information
Whenever there is non-consecutive loss, thereceiver can conceal the loss.
Can also append (n-1)st and (n-2)nd low-bit ratechun

25. Interleaving Interleaving Re-sequence packets before transmission
Better handling of “burst” losses
Results in increased playout delay

26. Multimedia Networking
Exciting, industry relevant research topic
Multimedia is everywhere
Tons of open problems

27. References [1]www.wikipedia.com [2]http://www.ietf.org/rfc/rfc2326.txt
[3]
[4]