CS 414

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CS 414 Multimedia Systems Design Lecture 21
Multimedia Session Protocols

• Klara Nahrstedt
• Spring 2012

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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

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Outline

• Multimedia Protocols Standards
• RTP/UDP/IP Transmission Protocol
• RTCP Control/Negotiation Protocol to RTP
• RTSP Control VOD Negotiation Protocol
• SIP Session Initiation Protocol

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Internet Multimedia Protocol Stack
Media encaps (H.264, MPEG-4)
DASH
APPLICATION
RTSP
RSVP
RTCP
Layer 5 (Session)
SIP
RTP
HTTP
Layer 4 (Transport)
TCP
UDP
DCCP
KERNEL
Layer 3 (Network)
IP Version
4, IP Version 6
AAL3/4
AAL5
MPLS
Layer 2 (Link/MAC)
Ethernet/WiFi
ATM/Fiber Optics
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Multimedia Data Transmission Protocol RTP and its
Control Protocol RTCP
Application
Coding
Decoding
RTCP
RTP
UDP/IP
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RTP Common Header
00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Ver Ver P X CC CC CC CC M PT PT PT PT PT PT PT Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number Sequence Number
Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp Timestamp
SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC SSRC
CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 CSRC 0..15 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
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RTP Services Support of Heterogeneity

• 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
• Translator service
• Allows for translation between IP and other high
  speed protocols
• May change encoding data

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Difference between Mixers and Translators
S3
S1
R1
M1
M2
T
S2
S4
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Payload Formats

• Static Payload formats
• Established in RTP Profile
• Payload type 0 µ-law audio codec
• Dynamic Payload formats
• Applications agree per session on payload format
• H.263, JPEG, MPEG

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Session control in layer 5
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Session Management (Layer 5)

• Control of multiple multimedia connections
• Separates control aspects from transport aspects

SESSION MANAGER
Participant Management
Conference control
Session Control Protocol (e.g., RTSP)
Session Control
Media control
Configuration control
Presentation data communication
whiteboard
Continuous data communication
video
Continuous data communication
audio
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Session Manager

• Tasks
• Membership control
• Monitoring of shared workspace
• Coordination of Media control management
• Exchange of QoS parameters
• Conference control management establishment,
  modification, termination

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Session Control

• Session Described by
• Session state
• Name of session, start, valid policies
• Session management two steps for state
  processing
• Establishment of session
• Modification of session

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Session Control

• Conference Control
• Centralized or distributed approach
• Media Control
• Synchronization
• Configuration Control
• Negotiation of QoS parameters, admission control
  and reservation/allocation of resources
• Membership Control
• Invitation of users registration of users,
  change of membership

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Examples of Session Control protocols RTSP, SIP,
SAP,
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Real-Time Streaming Protocol (RTSP)

• Application Protocol for Control of multimedia
  streams
• This is not an application data transmission
  protocol, just remote control protocol between
  client and server

AudiovideoCoder
Audio Video Decoder
Session Control
RTSP
RTSP
RTP
RTP
CLIENT
SERVER
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RTSP

• Approved as Internet Draft, February 2, 1998,
  authors H. Schulzrinne, A. Rao, R. Lanphier
• Enables controlled, on-demand delivery of
  real-time data such as audio and video
• Intends to control multiple data delivery
  sessions
• Provides means for choosing delivery channels
• UDP
• Multicast UDP,
• TCP

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RTSP Methods
Request Direction Description
OPTIONS S lt-gt C Determine capabilities of server (S) or client (C)
DESCRIBE C -gt S Get description of media stream
ANNOUNCE S lt-gt C Announce new session description
SETUP C -gt S Create media session
RECORD C -gt S Start media recording
PLAY C -gt S Start media delivery
PAUSE C -gt S Pause media delivery
REDIRECT S -gt C Use other server
TEARDOWN C -gt S Destroy media session
SET_PARAMETER S lt-gt C Set server or client parameter
GET_PARAMETER S lt-gt C Read server or client parameter
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RTSP Aggregate and Stream Control
DESCRIBE (aggregate stream)
SETUP
RTSP
RTSP
SID
Coder
Decoder
PLAY
RTP
RTP
ESTABLISH
PLAY
CLIENT
SERVER
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Streaming media meta files
client
RTSP Presentation by H. Schulzrinne, 2001
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Streaming Media RTSP
RTSP Presentation by H. Schulzrinne, 2001
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Conclusion

• Internet protocol suite has now basic ingredients
  to support streaming audio and video
• Both for distribution and communication
  applications
• 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