Multimedia Over IP: RTP, RTCP, RTSP
description
Transcript of Multimedia Over IP: RTP, RTCP, RTSP
Multimedia Over IP: RTP, RTCP, RTSP
“Computer Science”
Department of Informatics Athens University of Economics and Business
Λουκάς Ελευθέριος
Problem & Solution
Problem:
Multimedia Networking is not a trivial Task High bandwidth requirements Real-time, bursty traffic
Solution: Expensive solution – ATM networks Rational solution – Internet
Rational Solution – Internet
Issues must be solved Enough bandwidth Protocol support multicast reduce traffic Resource reservation (real-time applications) Guarantees for timing issues (packet switch network)
Integrated Service Model RSVP RTP RTCP RTSP
Working foundation for real time services
Content
Real-time Transport Protocol (RTP)
Real-time Control Protocol (RTCP)
Real-time Streaming Protocol (RTSP)
Real-time Transport Protocol (RTP)IP-based protocolReal-time data transportRun on top of UDP
Support multicastDelay is better
than reliability Multicast/UnicastNo QoS guarantees
RTP Packet Format
Payload Type (7 Bits) Multimedia data type
Sequence Number (16 Bits) Frame re-construction Error detection
Timestamp (32 Bits) Play out data in correct rate Synchronize different streams (audio, video data)
Source Identification (32 Bits) Who is talking… (conference)
RTP Session
RTP Session: IP address + RTP port + RTCP port RTP session sending/receiving RTP data group of
participantsEach session is a pair of transport addresses
AudioAudioVideoVideo
Content
Real-time Transport Protocol (RTP)
Real-time Control Protocol (RTCP)
Real-time Streaming Protocol (RTSP)
Real-time Control Protocol (RTCP)Control Protocol-conjunct with RTPFeedback for data quality, information for memberships Report PDUs between sources/destinations
receiver reception report sender report source description report
Reports contain statistics the number of RTP-PDUs sentnumber of RTP-PDUs lost inter-arrival jitter
Used by application to modify sender transmission rates and for diagnostics purposes
RTCP Message Types
Recevier Reports (RR)not active senders Feedback of data deliveryPacket lost, jitter, timestamps (RTT)
Sender Report (SR) active sendersIntermedia synchronization, number of bytes sent
SDES, BYE, APP
RTCP Services
QoS monitoring and congestion control Feedback for quality of data
Source identification Canonical Namesunique identifiers
Inter-media synchronization Sender/ Receiver
Control information scaling Limit the control traffic
RTP Features
End-to-end delivery service for real-time data No mechanism to ensure timely delivery Depends on RSVP to reserve resources
No reliability, No flow/congestion control Timestamps, sequence number Implemented with applications
RTP/RTCP reports provide flow/congestion control Is not complete, is open to add new formats
Content
Real-time Transport Protocol (RTP)
Real-time Control Protocol (RTCP)
Real-time Streaming Protocol (RTSP)
Real-time Streaming Protocol (RTSP) Client-Server multimedia presentation protocol Support streaming over IP network Work with lower–level protocols (RTP, RSVP) Network Remote Control (PLAY, PAUSE, STOP) Transport methods: Unicast /Multicast RTSP Operations
Receive media from server Invite media server to conference Add media to an existing presentation
RTSP Overview
web browser
media player
Web Server
Web Server/Media serverRTSP
pres. desc,streaming commands
RTP/RTCPaudio/video content
Presentation
descriptor
HTTPpresentation descriptor
RTSP Methods
OPTIONSC S
determine capabilities of server/clientC S
DESCRIBE C S get description of media stream
ANNOUNCE C S announce new session description
SETUP C S create media session
RECORD C S start media recording
PLAY C S start media delivery
PAUSE C S pause media delivery
REDIRECT C S redirection to another server
TEARDOWN C S immediate teardown
SET_PARAMETER C S change server/client parameter
GET_PARAMETER C S read server/client parameter
RTSP Session
media server
RTSPserver
datasource
media player
AVsubsyste
m
RTSPclient
RTSP OK
RTSP PLAY
RTSP OK
RTP AUDIO
RTP VIDEO
RTSP TEARDOWNRTSP OK
get UDP portchooseUDP port
RTSP SETUP
Default port 554
RTCP
TCP
UDP
RTSP FeaturesApplication level protocolSyntax and operations similar to HTTPUse methods (SETUP, TEARDOWN)Servers & clients can issue requestsSupport multiple system platforms
Questions…?