COIT 475 Multimedia Network...

COIT 475

Multimedia Network Technology

Hossam M.J. Mustafa

FCITR, KAU, Rabigh

COIT 475 Multimedia Network Technology 2

Part I

Introduction to Multimedia Networking


Overview

What is Multimedia?

Characteristics of multimedia

Various media types

What is Multimedia networking?

User requirements of multimedia applications on the

network

Technologies associated with multimedia networking

Overall structure of multimedia networking


What is multimedia?

Definition of multimedia

Hard to find a clear-cut definition

In general, multimedia is an integration of text, graphics, still and

moving images, animation, sounds, and any other medium where

every type of information can be represented, stored, transmitted

and processed digitally

Characteristics of multimedia

Digital – key concept

Integration of multiple media type, usually including video or/and

audio

May be interactive or non-interactive


Various Media Types

Text, Graphics, image, video, animation, sound, etc.

Classifications of various media types

Captured vs. synthesized media

Captured media (natural) : information captured from the real world

Example: still image, video, audio

Synthesized media (artificial) : information synthesize by the

computer

Example: text, graphics, animation

Discrete vs. continuous media

Discrete media: spaced-based, media involve the space dimension

only

Continuous media: time-based, media involves both the space and the

time dimension

(Text, Image, Graphics)

(Video, Sound, Animation)


Classification of Media Type

Sound Video

Image

Animation

Text Graphics

Captured

From real world

Synthesized

By computer

Discrete Discrete

Continuous Continuous


Text

Plain text

Unformatted

Characters coded in binary form

ASCII code

All characters have the same style and font

Rich text

Formatted

Contains format information besides codes for characters

No predominant standards

Characters of various size, shape and style, e.g. bold, colorful


Plain Text vs. Rich Text

An example of Plain text Example of Rich text


Graphics

Revisable document that retains structural information

Consists of objects such as lines, curves, circles, etc

Usually generated by graphic editor of computer programs

-4

-2

0

2

4

-4

-2

0

2

4-10

-5

0

5

10

Example of

graphics (FIG file)


Images

2D matrix consisting of pixels

Pixel—smallest element of resolution of the image

One pixel is represented by a number of bits

Pixel depth– the number of bits available to code the pixel

Have no structural information

Two categories: scanned vs. synthesized still image

Computer

software

Capture and

A/D conversion

Digital still image

Synthesized

image

Scanned

image

Camera


Images (cont.)

Examples of images

Binary image – pixel depth 1

Gray-scale – pixel depth 8

Color image – pixel depth 24

Binary image

Gray-scale image

Example of image.ppt


Graphics vs. Image

Graphics

Revisable documents

Document format retains structural information

Semantic content is preserved in presentation

Described as objects

Images

Not revisable

Document format is unaware of any structural information

Semantic content is NOT preserved

Described as bitmaps formed of individual pixels


Video vs. Animation

Both images and graphics can be displayed as a succession

of view which create an impression of movement

Video – moving images or moving pictures

Captured or Synthesized

Consists of a series of bitmap images

Each image is called a frame

Frame rate: the speed to playback the video (frame per second)

Animation – moving graphics

Generated by computer program (animation authoring tools)

Consists of a set of objects

The movements of the objects are calculated and the view is

updated at playback


Sound

1-D time-based signal

Speech vs. non-speech sound

Speech – supports spoken language and has a semantic content

Non-speech – does not convey semantics in general

Natural vs. structured sound

Natural sound – Recorded/generated sound wave represented as

digital signal

Example: Audio in CD, WAV files

Structured sound – Synthesize sound in a symbolic way

Example: MIDI file

0 100 200 300 400 500 600 700 800 900 1000-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2


Networked Multimedia

Local vs. networked multimedia

Local: storage and presentation of multimedia information in

standalone computers

Sample applications: DVD

Networked: involve transmission and distribution of multimedia

information on the network

Sample applications: videoconferencing, web video broadcasting,

multimedia Email, etc.

Internet Video server

Image server A scenario of multimedia networking


Consideration of Networked Multimedia

Characteristics of multimedia information

Large data volume

Exercise: What is the size of a video clip of 60 minutes if the frame size is 640*480, the pixel depth is 24, and the frame rate is 24 fps?

Real-time property

Continuous display

Delay requirement of multimedia applications

Properties of current Internet

Limitation of bandwidth

Best effort network, cannot guarantee quality of multimedia applications

Heterogeneity

Different user requirements

Different user network conditions


Consideration of Networked Multimedia

Requirements of multimedia applications on the network

Delay requirement

Quality requirement

Satisfactory quality of media presentation

Synchronization requirement

Continuous requirement

Can tolerant some degree of information loss

Challenges of multimedia networking

Conflict between media size and bandwidth limit of the network

Conflict between the user requirement of multimedia application

and the best-effort network

How to meet different requirements of different users?


Technologies of Multimedia Networking

Media compression – reduce the data volume

Address the1st challenge

Image compression

Video compression

Audio compression

Multimedia transmission technology

Protocols for real-time transmission

Rate / congestion control (traffic)

Error control


Multimedia Networking Systems

Live media transmission system

Capture, compress, and transmit the media on the fly (example?)

Send stored media across the network

Media is pre-compressed and stored at the server. This system

delivers the stored media to one or multiple receivers. (example?)

Differences between the two systems

For live media delivery:

Real-time media capture, need hardware support

Real-time compression– speed is important

Compression procedure can be adjusted based on network conditions

For stored media delivery

Offline compression – better compression result is important

Compression can not be adjusted during transmission


Generic Media Streaming System

Video Encoder

Input video Compressed

Video Streaming Server

Internet

Receiver Video Decoder

Video Display

Error control, rate control can be done here to improve QoS

Error control, provide feedback to the sender

Compressed Video Video Packets

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