Transcript Chapter 9 Hypertext

Chapter 13
Combining Media
Key Points
► There
are two models for combining
elements of different media types: pagebased and synchronization-based.
► Hypermedia is a page-based model that
generalizes hypertext to include other media
types. The World Wide Web is an
example of a hypermedia system.
Key Points
► Helper
applications are used by Web browsers
to display media types they cannot handle
themselves. Plug-ins are used to extend the
range of types that can be displayed within the
browser environment.
► The object element is provided for embedding
arbitrary media in HTML 4 documents, but img
and embed are more commonly used.
► An image map is an image containing `hot' areas,
which are associated with URLs. The map element
performs the association.
Key Points
► Multimedia
can be organized in time using a
timeline, as in Director.
► SMIL (Synchronized Multimedia
Integration Language) is a tag-based
language, derived from XML, for specifying
the temporal structure of a presentation.
► SMIL's synchronization elements include
par for specifying media elements to be
displayed in parallel, and seq for sequences.
Key Points
► Elements
within a par element can be
synchronized with each other using event values.
► Hard synchronization or soft synchronization
can be applied when media are independently
subject to unpredictable delays.
► HTML+Time is a proposal to merge SMIL's
synchronization features with HTML.
► The Web Accessibility Initiative guidelines
should be followed to ensure that multimedia on
the Web is accessible to the widest possible range
of people.
Introduction
► There
are two models currently in use for
combining elements of different media types
 Paged-based
 Synchronization-based
Paged-based
► Paged-based
 In a two-dimensional arrangement that resembles the
way text and images are laid out in books and
magazines.
 Time-based elements, such as video clips and sound,
are embedded in the page as if they were images,
occupying a fixed area; controls may be provided to
start and stop playback.
 Linking mechanism
► Linked
paged-based multimedia productions are known as
hypermedia.
► World Wide Web
Synchronization-based
► Makes
time the central organizing principle
► Presented as a sequence, like a slide show
► Transitions, such as dissolves and wipes,
may be used to go from one element in the
sequence to the next.
► Parallelism
 Several video clips may be shown at the same
time, perhaps overlaid against a s6tatic image,
or a sound track may play during an animation.
Interactive
► Scripting:
author to write simple programs
► Page-based multimedia
 Temporal organization can be added
► Synchronization
 linking
presentation
HTML and Hypermedia
► Link:
href attribute
► Helper applications
► Plug-in
► OBJECT: HTML 4.0, preferred way
► IMG: previous version
► Netscape: EMBED
OBJECT
► OBJECT
has content.
 The content is displayed only user agent is
unable to display the object.
 P. 422, movie clip
 Support arbitrary media
 PARAM, name and vale, p.423
►Controller
= false, autoplay=true, loop=true
Links
►A
element with a href attribute
► Image map: an image containing ‘hot’ areas
 Shape: rect, circle, poly
 P. 424
Synchronization-based presentations
► Pure
hypermedia: no temporal structure
► Timelines for authoring
► Slide show packages
 Transitions: wipes, dissolves, ripples, page turns
► Timeline-based
multimedia
 More complex
►Macromedia Director
 Cast, Cast members, Score
 Sprites can be animated using key frames.
 Sprite properties can be animated.
SMIL
► Synchronized
Multimedia Integration
Language
► Text-based language, no special authoring
tool
► SMIL 1.0, 1998
► RealPlayer G2, QuickTime 4.1
► Defined XML DTD
SMIL
►
Layout elements
 Absolute positioning
 SMIL basic layout language
►
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►
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►
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Region attribute
<par>, <seq>, p.428
Clock value, h:m:s.ms
Indefinite, dur
Figs. 13.3-4
Id(element-id)(time-value), p.431
Repeat
SMIL
► Soft
sync, hard sync
 13.5-8
► SWITCH
 P.435
 Test attribute: system-bitrate
► Uni-directional
link, p. 436
► Anchor = A element in HTML
 source or destination of hyperlink
 P.440
HTML +TIME
► HTML,
SMILL cannot be truly integrated
► HTML+TIME
 Timed Interactive Multimedia Extensions
► Slide
shows: adding sync to HTML
► Extending HTML: goes against current trend
► Temporal stylesheet
Accessibility
► Poor
eyesight
► Hard of hearing
 Transcripts of speech and song lyrics can be
provided
► Textual
form for a non-visual user agent
► Not all authoring tools and formats provide
much help, but HTML 4 has features
designed to assist in making Web pages
accessible to everybody.
Accessibility
► alt
► If
a longer description of an image is
required, the longdesc attribute can be set
to its URL.
►
<IMG SRC=“flower1.jpeg” usemap=“#image-map-1”
alt=“Flower image map”
longdesc=“flowermap.html”>
 A text-based set of links to the same destinations as those offered
by the image map
►
SMIL shares some of features in HTML
 All media elements support alt and longdesc attributes.