Download Introduction to Multimedia Systems

Multimedia Over IP Networks -- I
Hao Jiang
Computer Science Department
Boston College
Nov. 6, 2007
CS335 Principles of Multimedia Systems
Introduction
 Traffic on Internet was mainly from textual content.
 In recent years, multimedia data transmission is
occupying most of the network bandwidth.
 IP network, especially Internet, is becoming a very
attractive channel for multimedia communications.
– Dedicated networks and ATM are not widely available.
– There are many applications for Internet multimedia:
• Internet telephone, Internet TV, video conferencing, network
games, remote corroboration, ….
CS335 Principles of Multimedia Systems
Review Of TCP/IP
Application Layer (telnet, ftp, etc.)
Host-to-Host Transport Layer
(TCP, UDP)
Internet Layer (IP and routing)
Network Access Layer (Ethernet,
ATM, or whatever)
Basic TCP/IP network model
Data Encapsulation:
CS335 Principles of Multimedia Systems
Review Of TCP/IP
A TCP/IP node on 2 Ethernets
CS335 Principles of Multimedia Systems
Review Of TCP/IP
 Address Resolution Protocol (ARP)
Each machine on a network has an ARP Table in its memory
If “223.1.2.1” wants to send a packet to “223.1.2.2”, an ARP
request will be broadcasted to the Ethernet.
CS335 Principles of Multimedia Systems
Review Of TCP/IP
“223.1.2.2” found the target IP matches its IP, it fills the Ethernet
address and returns an ARP response to “223.1.2.1”
“223.1.2.1” updates its ARP table and starts sending packets to “.2”
CS335 Principles of Multimedia Systems
Review Of TCP/IP
 Routing
1
2
3
A sends E an IP packet.
On “development”,
the IP/Ethernet addresses are:
While on “account”:
CS335 Principles of Multimedia Systems
Review Of TCP/IP
 Routing Table
1
Routing table for A
--------------------------------------------------------------------network
direct/indirect
router
interface number
--------------------------------------------------------------------development direct
<blank>
1
accounting indirect
D
1
factory
indirect
D
1
---------------------------------------------------------------------
2
3
Routing table for D
--------------------------------------------------------------------network
direct/indirect
router
interface number
--------------------------------------------------------------------development direct
<blank>
1
accounting direct
<blank>
2
factory
direct
<blank>
3
---------------------------------------------------------------------
CS335 Principles of Multimedia Systems
Review Of TCP/IP
 Transport Protocols
– UDP (User Datagram Protocol): A simple protocol for short
delay and unreliable communication.
– TCP (Transmission Control Protocol): A much more complex
protocol that guarantees correct data transmission.
• By acknowledgement from the receiver.
• Retransmission if time is out or data is corrupted.
– TCP is a stream protocol. The packet size is determined by
the systems.
– TCP also needs to build up a virtual circuit before the real
communication happens.
CS335 Principles of Multimedia Systems
Multimedia over Network
 Properties of multimedia traffic
–
–
–
–
High bit rate.
Many coding schemes have variable bit rate streams.
Partial data missing or corrupted is Ok.
Tight timing constraint.
 IP networks have no guarantee for
– bandwidth allocation.
– Limited delay.
 Multimedia applications usually build on top of UDP
– which may loses packets, receives packets in wrong order,…
CS335 Principles of Multimedia Systems
Some Ad Hoc Schemes
 For some simple applications, we can in fact use TCP
to transmit videos.
User 1
Multiple-view Video
Streaming Server
User 2
User n
A Multiple-view Server Demo
CS335 Principles of Multimedia Systems
Some Ad Hoc Schemes
Some commercial products in fact use
TCP for video streaming.
Axis 206 network
camera
For example, to get a motion jpeg video stream:
http://192.168.1.10/axis-cgi/mjpg/video.cgi
CS335 Principles of Multimedia Systems
More about Ad Hoc Schemes
UDP
Header
Some
Additional
Information
Multimedia Data
What should we put here?
CS335 Principles of Multimedia Systems
Standard Solutions
 The Integrated Services working group in the IETF
(Internet Engineering Task Force) developed an enhanced
Internet service model called Integrated Services that
includes best-effort service and real-time service, see RFC
1633.
 The real-time service will enable IP networks to provide
quality of service to multimedia applications.
 Resource ReServation Protocol (RSVP), together with
Real-time Transport Protocol (RTP), Real-Time Control
Protocol (RTCP), Real-Time Streaming Protocol (RTSP),
provides a working foundation for real-time services.
CS335 Principles of Multimedia Systems