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Multimedia Information. Internet Multimedia - Lecture 3. 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

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multimedia information

Multimedia Information

Internet Multimedia - Lecture 3

Internet multimedia - Lecture 3

information quality and reliability
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

  • 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

  • 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

horse race example
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

more horse race information
More horse race information
  • A typical result would be:


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

information structure
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

channel considerations
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

information structure1
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

information structure in computers
Information structure in computers

Internet multimedia - Lecture 3

  • 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

  • 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

encoded information objects




High quality sound


Speech quality

Structured information


Size of object

Encoded information objects

Internet multimedia - Lecture 3

  • 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


Internet multimedia - Lecture 3

structured information
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

  • 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

  • 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

image 2
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

  • 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

mixed information types multimedia
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

multimedia examples
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

multimedia more examples
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

selection of media
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

linkage between media types
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

  • 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

multimedia issues
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

another core issue content
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

interface requirements
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

usage implications computer based
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

  • Many available
    • Streaming
    • Audio
    • Video
  • International standards

Internet multimedia - Lecture 3

  • 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

  • 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