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Multimedia Information

Multimedia Information

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Multimedia Information

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  1. Multimedia Information Internet Multimedia - Lecture 3 Internet multimedia - Lecture 3

  2. Information quality and reliability • A reliable communication implies reliable information but.. • Other factors influence its quality e.g. • Timeliness of the delivered information • Speed or frequency of the information provision • Completeness of the information • Selectivity of the information • Relevance or specificity of the information Internet multimedia - Lecture 3

  3. Information • What is information? • How is it • derived? • communicated? • used? • Any event produces information • much of this is now stored as • text, image, audio, video and in databases Internet multimedia - Lecture 3

  4. Information • Users of information often have many choices but some restrictions • bandwidth • access equipment • physical proximity • cost considerations etc. • Is the information of the right type? • will it provide what is required? Internet multimedia - Lecture 3

  5. Horse Race example Towcester - Going Soft 4.10 Hartford Handicap Chase 3m 1f £3,849 (5 declared) 1 1-1F13 Kilmington (29) J Gifford 9-11-10……………………..………..P Hide 2 -32443 Texan Baby (BEL) (7) N Twiston-Davies 9-11-5………..C Llewellyn 3 PP3UP Ballydougan (10) (CD) R Matthew 10-10-8……...………...S Curran * 4 5-24P3 Gold Pigeon (9) (D) B Rothwell 9-10-0……….………Mr S Durack (5) 5 1F4022 Steeple Jack (43) K Bishop 11-10-0……………………….....R Greene Betting: 6-4 Texan Baby, 7-4 Kilmington, 4-1 Steeple Jack, 8-1 Gold Pigeon, 25-1 Ballydougan Internet multimedia - Lecture 3

  6. More horse race information • A typical result would be: TOWCESTER 4:10 (3m 1f): 1, Ballydougan, S Curran (16-1) ; 2,Kilmington, (15-8 Fav); 3, Texan Baby(BEL), (5-2). 5 ran. 22, dist. (R Matthew) Tote: £20.40; £3.30, £1.10. Dual Forecast: £20.00. CSF; £43.30. • Full interpretation requires contextual information Internet multimedia - Lecture 3

  7. Information structure • Example horse race information • Only the basic information is presented • There is only an indication of 6 previous runs • No information of what events were attempted • No indication of previous opposition • No information on preferred • distance, going, race type, course etc. • Little evidence in the result of what happened except the outcome • More information from a video recording or more detailed comments Internet multimedia - Lecture 3

  8. Channel considerations • Video information needs a high bandwidth channel (e.g. satellite broadcast of horse race) • Audio could be used over lower bandwidth channel but some information is lost • Picture/text can be used in newspapers and • Text only on Teletext and computer stored information • Databases are used to store information for later retrieval • Indexed on • horse name, race time/date, jockey, trainer etc. • Multimedia would aid in the dissemination of this information - appropriate info for user’s access device Internet multimedia - Lecture 3

  9. Information structure • Raw data contains information • This information will contain structure If more data is available then.. more information should be able to be extracted (some data may be no use - e.g. blank video screen) • Some information structures are better related to one medium than others • Information can usually be extracted to suit most media • E.g. A video can be processed to give • still images, audio extract, text synopsis • All result in loss of information Internet multimedia - Lecture 3

  10. Information structure in computers Internet multimedia - Lecture 3

  11. Structure • The levels may each have a different encoding and structure • This may impose restrictions on • information storage and retrieval or • performance • Good quality systems should not restrict the information requirements • Example • Distributed storage of WWW pages restricts access time • Coding restricts date information - Y2K problem? Internet multimedia - Lecture 3

  12. Encoding • Most appropriate encoding determined by • structure of the information • user’s need and intended use as an example - consider different maps - each scale has a different level of detail but could all be generated from the same GIS • available channels • Available channel will determine the scope of the information that can be communicated • limits to quality, response time, usability etc. • User’s needs example - Horse race information • gambler needs only the result • trainer may need video or more detailed text/audio Internet multimedia - Lecture 3

  13. Complexity Video Image High quality sound sound Speech quality Structured information Text Size of object Encoded information objects Internet multimedia - Lecture 3

  14. Text • ASCII uses 7-bits per character • Efficient storage and transmission • uses a limited symbol set (26+26 + punctuation) • Only applies to English • Other versions can be used for other symbol sets • New encoding of text based on Unicode • a 16-bit system that encompasses all language symbols Internet multimedia - Lecture 3

  15. ASCII Internet multimedia - Lecture 3

  16. Structured information • Structured information can be very efficient • Structure imparts meaning • this is easier than with free text • example - 29 WV1 1LL could be used to retrieve an address • There can be problems • querying databases can produce masses of data unless the query is specified to exact limits • Example A driver database could be queried for a John Smith in Wolverhampton but would produce a large response if the Wolverhampton is missed out of the specification of the query. Internet multimedia - Lecture 3

  17. Audio • Audio information has many different standards • Some of the differences are due to differing requirements of systems • Two common standards • CD-quality stereo audio and mono speech quality A. CD uses 44.1 kHz sampling, 2 x 16 bit channels = 44 100 x 16 x 2 = 1 411 200 bps B. Mono speech uses 8 kHz sampling on 1 x 8-bit channel = 8000 x 8 x 1 = 64 000 bps (ISDN rate!) Internet multimedia - Lecture 3

  18. Image • Two main types of image • bit-mapped or graphic images • bit-mapped are generally pictures • graphic images are generally line drawings or graphic designs • Each has different storage and transmission requirements Internet multimedia - Lecture 3

  19. Image 2 • Diverse set of standards • JPEG is commonly used and a robust, open, international standard • others are GIF, TIFF, TGA, etc….. Internet multimedia - Lecture 3

  20. Video • The most complex of multimedia types • Transmission and storage requirements determined by • Frame rate (15-30 is common) • Size of display (can be changed to suit transmission rate) • Resolution used (can be determined by display) • Colour depth (depends on requirements 8-24 bit) • Typical figures Video conferencing quality 15 fps, 160 x 120 pixel window, 16 colours = 15 x 160 x 120 x 4 = 1 152 000 bps (about 1Mbps) Internet multimedia - Lecture 3

  21. Mixed information types -Multimedia? • When various media types combined into single coherent object • Examples - text, database, stills, animation, graphic, video, audio • Communication links use channels which can be shared by different media types • Recent advances in computer/communications has significantly expanded possibilities for multimedia use • Multimedia not unique to computers - e.g. children’s story tapes/books Internet multimedia - Lecture 3

  22. Multimedia examples: • Sound + Video • advs: familiar concept, effective • disadvs: familiarisation = contempt , …TV/cinema, passive etc. • digitisation: various transfer + synchronisation methods • Sound + Image • e.g. slide show + audio commentary/music • advs: portable, flexible, simple • disadvs: needs preplanning, lacks movement • digitisation: straightforwardtransfer + synchronisation not critical Internet multimedia - Lecture 3

  23. Multimedia - more examples • Hardcopy Image + Text • e.g. picture album, brochure • advs: familiar, simple, portable • disadvs: lacks movement, content inflexible, copying (?) • digitisation: design important • Sound + Text • e.g. language learning pack • advs: easy to use, familiar • disadvs: selected replays difficult, lacks visuals • digitisation: more effective links+flexibility, easily added visuals Internet multimedia - Lecture 3

  24. Selection of media • The examples given indicate the diversity available • Long history of traditional uses of mixed media types • Some mixtures and styles of mixing are more recent • Digitisation tends to present more options, but opens up more complex design issues (HCI) • Availability of information in a particular form often means inclusion but…… • Selection and design should reflect delivery purpose and user preferences/needs Internet multimedia - Lecture 3

  25. Linkage between Media Types • Traditional links between media types used in an application tend to be retained in digitised formats • Use of single device (computer) often simplifies linking and synchronisation • Two forms of links • different types present for ‘automatic’ viewing • e.g. text with an inserted picture (in-line link) • explicit optional link from text to a musical soundtrack • external hyperlink Internet multimedia - Lecture 3

  26. Synchronisation • Not particularly problematic - except for some cases of audio/video transmission • Even ‘off-the-shelf’ broadcast packages have difficulties with attaining ‘lip-synch’ quality • Audio can by ‘synched’ to the beginning of frames but constraints relating to channel capacity and hardware/ software affect performance • Audio and image/text synchronisation is much easier • image change(s) at specific point(s) in audio track Internet multimedia - Lecture 3

  27. Multimedia Issues • Vary depending on application • Core issues: • access • how achieved • how regulated • cost restrictions • equipment constraints • awareness ? • Bandwidth conflicts ? • Timeliness • Confidentiality • Socialising Internet multimedia - Lecture 3

  28. Another core issue - content • Content control: • regulatory control (law and professional code of conduct) • code of practice (self-imposed/conditions of access) • IRC/Chat Forums can reach over international boundaries • Local rules (e.g. Video conferencing/Closed Group forum, discussion board) • Parental control packages Internet multimedia - Lecture 3

  29. Interface requirements • Computer/Internet based Multimedia is ‘open’ to many platforms and environments via standards • Standards can be open, proprietary, or from other sources • Some inconsistency • e.g Media player, RealPlayer, QuickTime • Min requirements can specify • Screen size • Colour depth – no. of bits • Sound sample processing - sampling rate – sample size • Video resolution, frame rate • Video capture/audio standard etc., • Internet connection/network Internet multimedia - Lecture 3

  30. Usage implications (computer based) • Technical capability to achieve planned service needs to be considered • E.g video links need to have appropriate bandwidth and machine/peripheral availability • Cater for average and ‘peak’ activities • Specialist technical support • Testing and training • Costing Internet multimedia - Lecture 3

  31. Standards • Many available • Streaming • Audio • Video • International standards • JPEG, MPEG, SMIL Internet multimedia - Lecture 3

  32. Summary • Information has inherent structure • Structure can • be used to simplify storage or transmission requirements (results) • reduce usefulness (Y2K) • Different information types have different transmission requirements • Information types should be used to suit user needs channel available, information need, other requirements. Internet multimedia - Lecture 3

  33. Summary • Mixed media is not new • Educational use for decades • Computers make it more useable • Easier to construct and maintain • Streaming allows most mixed media to be delivered easily over the Internet • Broadband allows greater use of video Internet multimedia - Lecture 3