Multimedia- and Web-based Information Systems Lecture 3.

Multimedia- and Web-based Information Systems

Lecture 3

Multimedia: Introduction

Introduction to Multimedia

The term Multimedia Media Properties of a data stream

Multimedia from a user‘s point of view

Presentation of Information also using Audio and Animation

Information is easier conveyed Integration of Media with the Computer

allows for– Interactive Presentations– Transmission across computer networks

Multimedia and the Industry

Sectors affected by the developments in Multimedia

Telecommunications Consumer Electronics TV- and Radiostations Publishing Houses

=> Convergence of Sectors

Properties of multimedia processing

High data troughput Realtime Synchronisation

Development of the term „Multimedia“

1950s– System with more than one medium, e.g.

Presentation using an overhead projector, a tape recorder and a film projector

1960s– „Multimedia“-Computer used to control analog

devices

Development of the term „Multimedia“

End of 1980s– „Multimedia-PC“, Quicktime

End of 1990– Development of Internet applications

Areas in Multimedia-Systems

Databases Operating Systems Communication System

Computer Technology

Memory Networks

Compression

Audio Video

Areas in Multimedia-Systems

Abstractions

Documents

Applications

User Interface

Terminology

Multi [lat. much], as a Prefix Medium, mediating element, means to

reproduce Information

The term „medium“

Means for the distribution and presentation of information– Examples: Text, Figure, Image, Voice, Music

Further differentiation of the term in the MHEG-Standard (1993)– On the following two slides

Different media terms

Perception-Medium– To See, to Hear (how?)

Representation-Medium– JPEG, MPEG (Structure, Coding)

Presentation-Medium– Screen, Speakers, Keyboard (Input/Output)

Different media terms

Storage-Medium– Paper, Harddisk, CD-ROM (where from?)

Transmission-Medium– Network (on what?)

Information-Exchange-Medium– Transmitter / Storage of Information: CD, Network

(higher abstraction)

Presentation values and domains

Presentation domains– Screen, Paper (visual presentation domains)– Stereophonetics

Presentation values– Character, shock wave

Presentation dimension

Every presentation domain has presentation dimensions– Screen: 2 spatial dimensions

In Addition, Time as a dimension possible– Time as additional dimension fundamental for

multimedia systems

Classes of media

Classification using the time dimension– Discrete Media

Independent from time Examples: Text, Figures

– Continuous Media Dependent on time Examples: Sound, Motion Picture

The Term „Multimedia“

Qualitative rather than quantitative understanding

What kind of media instead of multiple media– A Combination of text and picture is not sufficient

for the term „Multimedia“

„Controversial term“

Main properties of a multimedia system

Combination of Media– Processing of discrete and continuous media

Independency– in the layout of the media in space and time

Computerized Integration– Computer as a tool

(Systems able to communicate)– Distributed Multimedia-Systems

Definition of „Multimedia“

A multimedia system is defined through the computerized, integrated creation, manipulation, presentation, storage and communication of independent information coded in at least one continuous and one discrete medium.

Usage of the term „Multimedia“

In a narrow sense– Continuous Media– Borders in Time

In a broader sense– Shared processing of multiple media

Transmission of media data

Transmission of data of discrete and continuous media

For information exchange Based on data streams

Data stream

Units (Packets) Send from source to sink Data stream is a sequence of single packets For discrete and continuous media

Asynchronous Transmission

No restrictions in time for the packets of the data stream– Example: IP

Normally not suitable for multimedia

Synchronous Transmission

Defined Maximum End-To-End Latency For multimedia this means a guarantee on

when packets will be arriving

Isochronous Transmission

Defined maximum and minimum end-to-end latency

Jitter of single packets is restricted Buffers can be calculated more exact Suitable for „Streaming“, transmission of very

large amounts of data

Data streams of continuous media

Different Properties– Time interval between packets– Amount of data / size of packets– Correlation of packets

Possibly because of compression Example: Audio- and video transmission

Strongly periodic data stream

Time interval between neighbouring packets is constant

Example: Voice in a telephone operation system

T

Weakly periodic data stream

Time interval between packets follows a function of finite period duration

Example: Animation

T

T1 T2 T3 T1 T2

Aperiodic data stream

Neither strongly nor weakly periodic

Example: Transmission of events (e.g. Mouse interactions)

T1 T2 Tn

• • •

Strongly regular

Constant amount of data of all packets

D1

Dn

t

Weakly regular

Amount of data of packets varies periodicly

D1

t

D2

D3

D1

D2

D3

T

Not regular

Amount of data is neither constant nor periodic

D1

t

D2

D3

Dn

• • •

Correlation of successive packets

Coherent data stream– Packets are transmitted one after another without

gaps

Incoherent data stream– Gaps between the data packets

t

t

Units of information

Medium consists of a sequence of single units of information

PDU: protocol data unit LDU: logical data unit Example: Logical units of a movie sequence

– Movie, Clip, Frame, Raster, Pixel