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

2. Administrative MP2 will be posted on March 12 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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3. 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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4. Internet Multimedia Protocol Stack
Media encaps
(H.264, MPEG-4)
DASH
APPLICATION
SIP
RTSP
RSVP
RTCP
Layer 5
(Session)
HTTP
RTP
Layer 4
(Transport)
TCP
DCCP
UDP
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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5. Multimedia Data Transmission Protocol RTP and its Control Protocol RTCP
Decoding
Coding
RTP
RTCP
UDP/IP
Application
Application
Coding
Decoding
RTCP
RTP
UDP/IP
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6. RTP Common Header Ver – Version 2 P – Padding00 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 P X CC M PT
Sequence Number
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
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7. 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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8. Difference between Mixers and Translators
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9. Payload Formats Static Payload formats Dynamic 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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10. Session control in layer 5
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11. Session Management (Layer 5)
Control of multiple multimedia connections
Separates control aspects from transport aspects
SESSION MANAGER
Conference
control
Participant
Management
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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12. 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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13. 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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14. Session Control Conference Control Media Control Configuration 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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15. Examples of Session Control protocols: RTSP, SIP, SAP, …
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16. 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
Audio
Video
Decoder
AudiovideoCoder
Session Control
RTSP
RTSP
RTP
RTP
CLIENT
SERVER
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17. 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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18. 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
Announce new session description
SETUP
C -> S
Create media session
RECORD
Start media recording
PLAY
Start media delivery
PAUSE
Pause media delivery
REDIRECT
S -> C
Use other server
TEARDOWN
Destroy media session
SET_PARAMETER
Set server or client parameter
GET_PARAMETER
Read server or client parameter
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19. RTSP – Aggregate and Stream Control
DESCRIBE
(aggregate stream)
SETUP
RTSP
RTSP
SID
Decoder
Coder
PLAY
RTP
RTP
ESTABLISH
PLAY
CLIENT
SERVER
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20. Streaming media: meta files
client
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RTSP Presentation by H. Schulzrinne, 2001

21. Streaming Media: RTSP RTSP Presentation by H. Schulzrinne, 2001
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RTSP Presentation by H. Schulzrinne, 2001

22. 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
CS Spring 2012