CS Spring 2012 CS 414 – Multimedia Systems Design Lecture 20 – Multimedia Session Protocols Klara Nahrstedt Spring 2012

Administrative Midterm exam graded  Solution of Midterm posted HW1 graded  Solution of HW1 posted Regrading of  Midterm and HW1 until March 16!! MP2 will be posted on March 12 CS Spring 2012

Outline Multimedia Protocols – Standards  RTP/UDP/IP – Transmission Protocol  RTCP Control/Negotiation Protocol to RTP  RTSP – Control VOD Negotiation Protocol CS Spring 2012

Covered Aspects of Multimedia Image/Video Capture Media Server Storage Transmission Compression Processing Audio/Video Presentation Playback Audio/Video Perception/ Playback Audio Information Representation Transmission Audio Capture A/V Playback Image/Video Information Representation CS Spring 2012

Internet Multimedia Protocol Stack CS Spring 2012 AAL3/4 IP Version 4, IP Version 6 UDP Media encaps (H.264, MPEG-4) RTP ATM/Fiber Optics Ethernet/WiFi TCP SIP RTSPRSVPRTCP AAL5 KERNEL APPLICATION Layer 4 (Transport) Layer 3 (Network) Layer 2 (Link/MAC) Layer 5 (Session) MPLS DCCP DASH HTTP

Service Requirements for Real- time Flows (Voice/Video) Sequencing Intra-media synchronization Inter-media synchronization Payload identification Frame indication CS Spring 2012

Real-time Transmission Protocol (RTP) RTP provides end-to-end transport functions suitable for real-time audio/video applications over multicast and unicast network services RTP companion protocol – Real-time Transport Control Protocol (RTCP) CS Spring 2012 RTPRTCP User Datagram Protocol Internet Protocol Ethernet or Wi-Fi PHY (Wired or Wireless) Layer 4

Relation between RTP and RTCP CS Spring 2012 DecodingCoding RTPRTCP UDP/IP Application CodingDecoding RTCPRTP UDP/IP Application

RTCP: Control and Management Out-of-band control information for RTP flow.  Monitors QoS for RTP in the delivery and packaging of multimedia data  Used periodically to transmit control packets to participants in a streaming multimedia session.  Provides feedback on the quality of service being provided by RTP.quality of service  Gathers statistics on media connection Bytes sent, packets sent, lost packets, jitter, feedback and round trip delay.jitter round trip delay Application may use this information to increase the quality of service, perhaps by limiting flow or using a different codec. CS Spring 2012

RTCP Functions There are several type of RTCP packets:  Sender report packet,  Receiver report packet,  Source Description RTCP Packet,  Goodbye RTCP Packet and  Application Specific RTCP packets. RTCP itself does not provide any flow encryption or authentication means. SRTCP protocol can be used for that purpose.SRTCP CS Spring 2012

RTP Services Payload Type Identification  Determination of media coding  Source identification  RTP works with Profiles Profile defines a set of payload type codes and their mappings to payload formats Sequence numbering  Error detection Time-stamping  Time monitoring, synchronization, jitter calculation Delivery monitoring CS Spring 2012

Conclusion RTP usage – in several application audio and video tools (vat, vic) RTP follows the principle of application level framing and integrated layer processing RTP/UDP/IP is being used by the current streaming session protocols such as RTSP Session protocols are actually negotiation/session establishment protocols that assist multimedia applications Multimedia applications such as QuickTime, Real Player and others use them CS Spring 2012