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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:

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Multimedia Over IP: RTP, RTCP, RTSP

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  1. Multimedia Over IP: RTP, RTCP, RTSP “Computer Science” Department of Informatics Athens University of Economics and Business Λουκάς Ελευθέριος

  2. 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

  3. 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

  4. Content • Real-time Transport Protocol (RTP) • Real-time Control Protocol (RTCP) • Real-time Streaming Protocol (RTSP)

  5. Real-time Transport Protocol (RTP) • IP-based protocol • Real-time data transport • Run on top of UDP • Support multicast • Delay is better than reliability • Multicast/Unicast • No QoS guarantees

  6. 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)

  7. RTP Session • RTP Session: IP address + RTP port + RTCP port • RTP session sending/receiving RTP data group of participants • Each session is a pair of transport addresses Audio Audio Video Video

  8. Content • Real-time Transport Protocol (RTP) • Real-time Control Protocol (RTCP) • Real-time Streaming Protocol (RTSP)

  9. Real-time Control Protocol (RTCP) • Control Protocol-conjunct with RTP • Feedback 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 sent • number of RTP-PDUs lost • inter-arrival jitter • Used by application to modify sender transmission rates and for diagnostics purposes

  10. RTCP Message Types • Recevier Reports (RR)not active senders • Feedback of data delivery • Packet lost, jitter, timestamps (RTT) • Sender Report (SR)  active senders • Intermedia synchronization, number of bytes sent • SDES, BYE, APP

  11. RTCP Services • QoS monitoring and congestion control • Feedback for quality of data • Source identification • Canonical Namesunique identifiers • Inter-media synchronization • Sender/ Receiver • Control information scaling • Limit the control traffic

  12. 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

  13. Content • Real-time Transport Protocol (RTP) • Real-time Control Protocol (RTCP) • Real-time Streaming Protocol (RTSP)

  14. 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

  15. Web Server web browser HTTP presentation descriptor Presentation descriptor Web Server/Media server RTSP media player pres. desc,streaming commands RTP/RTCP audio/video content RTSP Overview

  16. RTSP Methods

  17. RTSP server TCP get UDP port data source UDP RTCP media server media player RTSP Session Default port 554 RTSP SETUP RTSP OK RTSP PLAY RTSP client RTSP OK RTSP TEARDOWN RTSP OK choose UDP port RTP VIDEO AV subsystem RTP AUDIO

  18. RTSP Features • Application level protocol • Syntax and operations similar to HTTP • Use methods (SETUP, TEARDOWN) • Servers & clients can issue requests • Support multiple system platforms

  19. Questions…?

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