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Streaming Audio and Video. 60-520 Seminar Topic Instructor: Dr. A. K. Aggarwal Presented By Mostafa Monwar. What is Streaming Technology. A technique for transferring data such that it can be processed

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Presentation Transcript
streaming audio and video
Streaming Audio and Video

60-520 Seminar Topic

Instructor: Dr. A. K. Aggarwal

Presented By

Mostafa Monwar

what is streaming technology
What is Streaming Technology

A technique for transferring data such that it can be processed

as a steady and continuous stream, client does not have to download the entire file to view it.

Data

Source

Network

The portion in the buffer

The portion client is viewing

advantages
Advantages
  • It reduces download time
  • It provides steady service
  • Slower systems can take advantage of streaming technology
  • Provide service on demand

Applications are utilizing this technology are:

Streaming Video, IP telephony, Internet Radio, Distance learning, Videoconferencing, Interactive games and so on

disadvantages
Disadvantages
  • It is difficult to keep the service steady if the bandwidth is low
  • The maintenance of streaming server is relatively expensive
  • Packet loss may occur during the transmission
3 types of delivery methods of streaming media
3 types of delivery methods of streaming media
  • Streaming Stored Audio and Video
  • Streaming Live Audio and Video
  • Real-Time Interactive Audio and Video
media player or helper application
Media Player or Helper Application

Three main streaming media companies or products are:

RealPlayer (RealNetworks),

Media Player (Microsoft) and

QuickTime (Apple).

  • Three basic tasks of media players:
  • Decompression
  • Jitter Removal
  • Error Correction
accessing audio video thru a web server
Accessing Audio & Video thru a Web server

Web

Browser

HTTP

Web Server

With Audio

Files

Client

Files

Media

Player

accessing audio video thru a meta file
Accessing Audio & Video thru a Meta File

Web

Browser

HTTP request /response

Client

for meta file

Web

Server

meta file

HTTP

Media

Player

Audio/Video file requested and sent using HTTP

A meta file contains information of URL, type of encoding, etc

about the audio/video file that is to be streamed.

rtsp diagram
RTSP Diagram

Web

Browser

HTTP request/response

Client

Web

Server

meta file

RTSP Streaming Command

Media

Player

Streaming

Server

RTP Audio / Video Content

HTTP is insufficient for user interaction. With streaming server

audio/video file can be sent over UDP,

protocols
Protocols
  • RTSP: Real Time Streaming Protocol
  • RTP : Real-time transfer Protocol
slide11
RTSP
  • RTSP is a industry standard Internet application level protocol
  • RTSP is a framework for delivering and transmission of multicast data stream
  • RTSP is a protocol that allows a media player to control the transmission of a media stream for exchanging control information
rtsp message format
RTSP Message Format

Start Line

Message Header

……

Message Header

CRLF

[message body]

Request-Line

Method SP Request-URI SP RTSP-Version CRLF

Status-Line

RTSP-Version SP Status Code SP Reason Phrase CRLF

Header

Field-name : field-value CRLF

rtsp features
RTSP Features
  • RTSP works in the conjunction with RTP to deliver streaming audio & video content
  • RTSP maintains a server state during transmission unlike HTTP
  • Client-Server architecture
  • Overcome the limitations of HTTP. RTSP enhance HTTP functions
  • RTSP provides the synchronization of events
slide14
RTP
  • RTP is used to transmit real-time data
  • RTP encapsulate segments

Payload Sequence Timestamp Synchronization Misc

type number source identifier

rtsp operation
RTSP Operation

HTTP GET

Web

Server

Web

Browser

HTTP

Presentation Description File

Setup

Play

Media

Player

Media

Player

Media Stream

RTSP

Pause

Teardown

presentation description file
Presentation Description File

<title> Music </title>

<session> <group language=en lipsync>

<switch>

<track type=audio

e=”PCMU/8000/1”

src=”rtsp://audio.com/music/audio.en/lofi”>

<track type=audio

e=”DV14/16000/2” pt=”90 DV14/8000/1”

src=”rtsp://audio.com/music/audio.en/hifi”>

</switch>

<track type=”video/jpeg”

src=”rtsp://video.com/music/video”>

</group> </session>

fixed playout delay
Fixed Playout Delay

Playout

Schedule

p-r

Missed

playout

Packets

generated

Packet

received

Playout

Schedule

p`-r

r

p

p`

forward error correction
Forward Error Correction

1

2

3

4

Original

stream

1

1

2

2

3

3

4

Redundancy

Internet

1

3

4

1

LOSS

Received

stream

2

4

1

2

3

Reconstructed stream

interleaving
Interleaving

Original Stream

1 2 3 4

5 6 7 8

9 10 11 12

13 14 15 16

1 5 9 13

2 6 10 14

3 7 11 15

4 8 12 16

Interleaved Stream

Received Stream

1 5 9 13

2 6 10 14

LOSS

4 8 12 16

1 2 4

5 6 8

9 10 12

13 14 16

Reconstructed Stream

references
References

http://www.rtsp.org/

http://www.cs.helsinki.fi/u/jmanner/Courses/seminar_papers/rtsp.pdf

http://www.javvin.com/protocol/rfc2326.pdf

http://www.cs.columbia.edu/~hgs/rtp/

James F. Kurose, Keith W. Ross. Computer Networking, 2nd Edition, Addison Wesley Longman, Inc, 2003.

http://www.webopedia.com/TERM/R/RTSP.html