CS 414 Multimedia Systems Design Lecture 21 Multimedia

CS 414 – Multimedia Systems Design Lecture 21 – Multimedia Session Protocols Klara Nahrstedt Spring 2012 CS 414 - Spring 2012

Administrative n Midterm exam graded ¨ Solution n HW 1 graded ¨ Solution n of HW 1 posted Regrading of ¨ Midterm n of Midterm posted and HW 1 until March 16!! MP 2 will be posted on March 12 CS 414 - Spring 2012

Outline n Multimedia Protocols – Standards ¨ RTP/UDP/IP – Transmission Protocol ¨ RTCP Control/Negotiation Protocol to RTP ¨ RTSP – Control VOD Negotiation Protocol ¨ SIP – Session Initiation Protocol CS 414 - Spring 2012

Internet Multimedia Protocol Stack APPLICATION Media encaps (H. 264, MPEG-4) DASH SIP RTSP RSVP RTP HTTP KERNEL TCP DCCP UDP IP Version 4, IP Version 6 AAL 3/4 Layer 5 (Session) RTCP AAL 5 MPLS CS 414 - Spring 2012 Layer 3 (Network) Layer 2 (Link/MAC) Ethernet/Wi. Fi ATM/Fiber Optics Layer 4 (Transport)

Multimedia Data Transmission Protocol RTP and its Control Protocol RTCP Application Decoding Coding RTP RTCP Application Coding RTCP UDP/IP CS 414 - Spring 2012 Decoding RTP

RTP Common Header 0 0 0 0 0 1 1 11 0 1 2 3 4 5 6 7 8 9 0 1 2 3 45 1 1 2 2 2 2 2 3 3 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Ver P X CC Sequence Number M PT Timestamp SSRC CSRC [0. . 15] : : : Ver – Version 2 P – Padding X – Extension, if set, the fixed head is followed by exactly one header extension CC – CSRC count M – Marker – intended to allow significant events such as frame boundaries to be marked (defined by profile) PT – Payload type SSRS – synchronization source, CSRC – contribution source CS 414 - Spring 2012

RTP Services – Support of Heterogeneity n Mixer service ¨ Allows for resynchronization of incoming audio packets ¨ Reconstructs constant 20 ms spacing generated by sender ¨ Mixes reconstructed audio streams into single stream ¨ Translates audio encoding to lower bandwidth ¨ Forwards lower bandwidth packet streams n Translator service ¨ Allows for translation between IP and other high speed protocols ¨ May change encoding data CS 414 - Spring 2012

Difference between Mixers and Translators S 3 S 1 M 1 T S 2 S 4 CS 414 - Spring 2012 M 2 R 1

Payload Formats n Static Payload formats ¨ Established in RTP Profile ¨ Payload type 0 : = µ-law audio codec n Dynamic Payload formats ¨ Applications agree per session on payload format ¨ H. 263, JPEG, MPEG CS 414 - Spring 2012

SESSION CONTROL IN LAYER 5 CS 414 - Spring 2012

Session Management (Layer 5) n n Control of multiple multimedia connections Separates control aspects from transport aspects SESSION MANAGER Participant Management Conference control Session Control Configuration control Session Control Protocol (e. g. , RTSP) Media control Presentation data communication whiteboard Continuous data communication video Continuous data communication audio CS 414 - Spring 2012

Session Manager n Tasks: ¨ Membership control ¨ Monitoring of shared workspace ¨ Coordination of Media control management ¨ Exchange of Qo. S parameters ¨ Conference control management – establishment, modification, termination CS 414 - Spring 2012

Session Control n Session Described by ¨ Session n n state Name of session, start, valid policies Session management – two steps for state processing ¨ Establishment of session ¨ Modification of session CS 414 - Spring 2012

Session Control n Conference Control ¨ Centralized n or distributed approach Media Control ¨ Synchronization n Configuration Control ¨ Negotiation of Qo. S parameters, admission control and reservation/allocation of resources n Membership Control ¨ Invitation of users; registration of users, change of membership CS 414 - Spring 2012

EXAMPLES OF SESSION CONTROL PROTOCOLS: RTSP, SIP, SAP, … CS 414 - Spring 2012

Real-Time Streaming Protocol (RTSP) n n Application Protocol for Control of multimedia streams This is not an application data transmission protocol, just remote control protocol between client and server Audio Video Decoder Session Control RTSP RTP Audio video Coder RTP CLIENT SERVER CS 414 - Spring 2012

RTSP n n Approved as Internet Draft, February 2, 1998, authors H. Schulzrinne, A. Rao, R. Lanphier Enables controlled, on-demand delivery of realtime data such as audio and video Intends to control multiple data delivery sessions Provides means for choosing delivery channels ¨ UDP ¨ Multicast UDP, ¨ TCP CS 414 - Spring 2012

RTSP Methods Request Direction Description OPTIONS S <-> C Determine capabilities of server (S) or client (C) DESCRIBE C -> S Get description of media stream ANNOUNCE S <-> C 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 S -> C Use other server TEARDOWN C -> S Destroy media session SET_PARAMETER S <-> C Set server or client parameter GET_PARAMETER S <-> C Read server or client parameter CS 414 - Spring 2012

RTSP – Aggregate and Stream Control DESCRIBE (aggregate stream) RTSP Decoder SETUP RTSP SID PLAY RTP Coder RTP ESTABLISH CLIENT PLAY CS 414 - Spring 2012 SERVER

Streaming media: meta files client CS 414 - Spring 2012 RTSP Presentation by H. Schulzrinne, 2001

Streaming Media: RTSP CS 414 - Spring 2012 RTSP Presentation by H. Schulzrinne, 2001

Conclusion n Internet protocol suite has now basic ingredients to support streaming audio and video ¨ Both for distribution and communication applications n Challenges: No session control protocol that can be used to perform floor control in distributed multimedia conferences ¨ Network reliability and deployment multicast of services with predictable quality-of-service are major hurdles beyond need for continuous upgrades in network capacity ¨ CS 414 - Spring 2012