1. Multimedia- and Web-based Information Systems Lecture 3

2. Multimedia: Introduction

3. Introduction to Multimedia The term Multimedia Media Properties of a data stream

4. 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

5. Multimedia and the Industry Sectors affected by the developments in Multimedia Telecommunications Consumer Electronics TV- and Radiostations Publishing Houses => Convergence of Sectors

6. Properties of multimedia processing High data troughput Realtime Synchronisation

7. 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

8. Development of the term „Multimedia“ End of 1980s – „Multimedia-PC“, Quicktime End of 1990 – Development of Internet applications

9. Areas in Multimedia-Systems DatabasesOperating SystemsCommunication System Computer Technology MemoryNetworks Compression AudioVideo

10. Areas in Multimedia-Systems Abstractions Documents Applications User Interface

11. Terminology Multi [lat. much], as a Prefix Medium, mediating element, means to reproduce Information

12. 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

13. Different media terms Perception-Medium – To See, to Hear (how?) Representation-Medium – JPEG, MPEG (Structure, Coding) Presentation-Medium – Screen, Speakers, Keyboard (Input/Output)

14. 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)

15. Presentation values and domains Presentation domains – Screen, Paper (visual presentation domains) – Stereophonetics Presentation values – Character, shock wave

16. 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

17. 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

18. 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“

19. 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

20. 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.

21. Usage of the term „Multimedia“ In a narrow sense – Continuous Media – Borders in Time In a broader sense – Shared processing of multiple media

22. Transmission of media data Transmission of data of discrete and continuous media For information exchange Based on data streams

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

24. Asynchronous Transmission No restrictions in time for the packets of the data stream – Example: IP Normally not suitable for multimedia

25. Synchronous Transmission Defined Maximum End-To-End Latency For multimedia this means a guarantee on when packets will be arriving

26. 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

27. 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

28. Strongly periodic data stream Time interval between neighbouring packets is constant Example: Voice in a telephone operation system T

29. Weakly periodic data stream Time interval between packets follows a function of finite period duration Example: Animation T T1T1 T2T2 T3T3 T1T1 T2T2

30. Aperiodic data stream Neither strongly nor weakly periodic Example: Transmission of events (e.g. Mouse interactions) T1T1 T2T2 TnTn

31. Strongly regular Constant amount of data of all packets D1D1 DnDn t

32. Weakly regular Amount of data of packets varies periodicly D1D1 t D2D2 D3D3 D1D1 D2D2 D3D3 T

33. Not regular Amount of data is neither constant nor periodic D1D1 t D2D2 D3D3 DnDn

34. 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

35. 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