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  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 Databases Operating Systems Communication System Computer Technology Memory Networks Compression Audio Video

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

  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 T1 T2 T3 T1 T2 T

  30. Aperiodic data stream • Neither strongly nor weakly periodic • Example: Transmission of events (e.g. Mouse interactions) • • • T1 T2 Tn

  31. Strongly regular • Constant amount of data of all packets D1 Dn t

  32. Weakly regular • Amount of data of packets varies periodicly D1 D2 D3 T D1 D2 t D3

  33. Not regular • Amount of data is neither constant nor periodic D1 D2 D3 • • • t Dn

  34. Correlation of successive packets • Coherent data stream • Packets are transmitted one after another without gaps t • Incoherent data stream • Gaps between the data packets 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