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SWE 423: Multimedia Systems

SWE 423: Multimedia Systems. Chapter 2: Media and Data Streams. The Term Multimedia. Multi Prefix From Latin “Multus” meaning numerous Media Root Plural form of the Latin word “Medium”. “Medium” is a noun meaning middle or center. The Term Media.

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SWE 423: Multimedia Systems

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  1. SWE 423: Multimedia Systems Chapter 2: Media and Data Streams

  2. The Term Multimedia • Multi • Prefix • From Latin “Multus” meaning numerous • Media • Root • Plural form of the Latin word “Medium”. • “Medium” is a noun meaning middle or center.

  3. The Term Media • Media: A means to distribute and present information • Text • Graphics • Pictures • Voice • Sound • Music

  4. Attributes of Media • Perception Media • Representation Media • Presentation Media • Storage Media • Transmission Media • Information Exchange Media • Presentation Spaces and Presentation Values • Presentation Dimensions

  5. Key Properties of a Multimedia System • Discrete and continuous media • Support of one type does not constitute multimedia (according to authors) • Independent media • Unlike video, one can have more than one type. • Computer-controlled systems • Video recorder is not sufficient • Integration

  6. Characterizing Data Streams • Distributed networked multimedia systems transmit continuous and discrete data • Data transmission characteristics: • Asynchronous • Synchronous • Isochronous

  7. Asynchronous Transmission • The sender and the receiver do not need to coordinate before data can be transmitted. • Two independent clocks (one at the sender and the other at the receiver) determine the start of each bit (bit synchronization)

  8. Synchronous Transmission • The beginning of transmission may only take place at well-defined times, matching a clocking signal that runs the synchronism with that of the receiver.

  9. Isochronous Transmission • The time interval separating any two corresponding transitions is equal to the unit interval or to a multiple of the unit interval. • Transmission rate “guaranteed” and jitter is minimized. • Significant instants of two or more sequential signals have a constant phase relationship.

  10. Characterizing Continuous Data Streams • This is in relation to audio and video transmission • Strongly and Weakly Periodic Data Streams • Variation of the data volume of consecutive information units. • Interrelationship of consecutive packets.

  11. Strongly Periodic Data Stream • Constant time interval • Minimum jitter • e.g. PCM encoded voice in telephone systems

  12. Weakly Periodic Data Stream • Duration of time intervals between neighboring packets is a function with finite period duration. • Time intervals between neighboring packets is not constant.

  13. Non-Periodic Data Streams • Other possibilities • e.g. mouse movement on white boards of the screen in video conferences

  14. Variation of the Data Volume of Consecutive Information Units. Periodically Regular e.g. MPEG Strongly Regular e.g. uncompressed audio/video

  15. Variation of the Data Volume of Consecutive Information Units. Irregular e.g. JPEG

  16. Connection between consecutive packets: Interrelated • No gaps in between • Maximal throughput and use of resources • e.g. ISDN channel transmitting audio

  17. Connection between consecutive packets: Non-Interrelated • Gaps between some packets • e.g. DVI-PLV encoded streams over FDDI

  18. Comparison

  19. Information Units • Logical Data Units • E.g. Video Data • Clips • Scenes • Images • Regions • Pixels

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