03/11/2015 Michael Chai; Behrouz Forouzan Staffordshire University School of Computing Streaming 1.

21/04/23Michael Chai; Behrouz Forouzan Staffordshire UniversitySchool of Computing

Streaming

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IADCN - Week 10Agenda

Types of Streaming Unicast and Multicast mechanisms Stream Control Transmission Protocol

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IADCN - Week 10Types of Streaming

Streaming stored audio/video refers to on-

demand requests for compressed

audio/video files.

Streaming live audio/video refers to the broadcasting of

radio and TV programs through the Internet.

Interactive audio/video refers to the use of the Internet for interactive

audio/video applications.

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IADCN - Week 10User Datagram Protocol (UDP)

Simple protocol and limited overhead as compared to IP packet.

No additional services added into the IP packet, apart from start and stop the connection.

Connectionless and unreliable transport protocol. Independent datagram - not numbered Suitable for simple request-response communication

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IADCN - Week 10Transmission Control Protocol (TCP)

Connection-oriented protocol and reliable transport protocol.

Create a virtual connection between two application programs to send data.

Virtual connection – connected as in the transport layer

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IADCN - Week 10Streaming Multimedia: UDP or TCP?UDP server sends at rate appropriate for client (oblivious to network

congestion !)

– often send rate = encoding rate = constant rate

– then, fill rate = constant rate - packet loss short playout delay (2-5 seconds) to remove network jitter error recover: time permitting

TCP send at maximum possible rate under TCP fill rate fluctuates due to TCP congestion control larger playout delay: smooth TCP delivery rate HTTP/TCP passes more easily through firewalls


IADCN - Week 10Unicasting

In unicasting, the router forwards the received packet through only one of its interfaces.

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IADCN - Week 10Multicasting

In multicasting, the router may forward the received packet through several of its interfaces

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IADCN - Week 10Multicasting versus Multiple casting

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IADCN - Week 10Streaming Stored Multimedia

1. videorecorded

2. videosent

3. video received,played out at client

Cum

ulat

ive

data

streaming: at this time, client playing out early part of video, while server still sending laterpart of video

networkdelay

time


IADCN - Week 10Web Server Streaming

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audio or video stored in file files transferred as HTTP object

– received in entirety at client

– then passed to player


IADCN - Week 10Web Server with Metafile Streaming

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browser GETs metafile

browser launches player, passing metafile

player contacts server

server streams audio/video to player


IADCN - Week 10Media Server Streaming

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allows for non-HTTP protocol between server, media player

UDP or TCP for steps (4,5)


IADCN - Week 10Media Server and RTSP Streaming

RTSP - Real Time Streaming Protocol

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IADCN - Week 10Streaming Live Multimedia

Examples: Internet radio talk show live sporting event

Streaming (as with streaming stored multimedia) playback buffer playback can lag tens of seconds after transmission still have timing constraint

Interactivity fast forward impossible rewind, pause possible!


IADCN - Week 10

Real-Time Interactive Multimedia

end-end delay requirements:– audio: < 150 msec good, < 400 msec OK

• includes application-level (packetization) and network delays• higher delays noticeable, impair interactivity

session initialization– how does callee advertise its IP address, port number, encoding algorithms?

applications: IP telephony, video conference, distributed interactive worlds


Real-Time Protocol (RTP)

RTP specifies packet structure for packets carrying audio, video data

RTP packet provides

– payload type identification

– packet sequence numbering

– time stamping

RTP runs in end systems

RTP treated like application program and encapsulated in UDP segments

interoperability: if two Internet phone applications run RTP, then they may be able to work together


Real-Time Control Protocol (RTCP) works in conjunction

with RTP. each participant in RTP

session periodically transmits RTCP control packets to all other participants.

each RTCP packet contains sender and/or receiver reports– report statistics useful to

application: # packets sent, # packets lost, interarrival jitter, etc.

feedback can be used to control performance– sender may modify its

transmissions based on feedback


Synchronization of Streams

RTCP can synchronize different media streams within a RTP session

consider videoconferencing for which each sender generates one RTP stream for video, one for audio.

timestamps in RTP packets tied to the video, audio sampling clocks

each RTCP sender-report packet contains (for most recently generated packet in associated RTP stream):– timestamp of RTP

packet – wall-clock time for

when packet was created.

receivers uses association to synchronize playout of audio, video


IADCN - Week 10

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IADCN - Week 10Stream Control Transmission Protocols

SCTP is a message-oriented, reliable protocol that combines the good features of UDP and TCP.

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IADCN - Week 10Multiple-stream Concept

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IADCN - Week 10Multihoming Concept

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IADCN - Week 10Summary

SCTP is a message oriented, reliable protocol that combines the good features of UDP and TCP

SCTP provides additional services that are not provided by UDP or TCP.

More reading from Wikipedia– http://en.wikipedia.org/wiki/

Stream_Control_Transmission_Protocol

– http://en.wikipedia.org/wiki/Unicast

– http://en.wikipedia.org/wiki/Multicast

– http://en.wikipedia.org/wiki/Streaming_media

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IADCN - Week 10Reading about Streaming Methods

Streaming from a Web Server (http://www.microsoft.com/windows/windowsmedia/howto/articles/webserver.aspx)

Streaming Methods: Web Server vs. Streaming Media Server (http://www.microsoft.com/windows/windowsmedia/compare/webservvstreamserv.aspx)

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03/11/2015 Michael Chai; Behrouz Forouzan Staffordshire University School of Computing Streaming 1.

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