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DigiCULT
.
Info
46
requires a few lines of mark-up. No spe-
cialised tools are required to author SMIL;
it can be written in a text editor and many
free tutorials have been published on the
Web making it accessible to new users.To
play SMIL presentations, your browser
must be SMIL compatible several free
SMIL browsers exist (e.g. X-Smiles
(http://www.x-smiles.org/), GriNS
(http://www.oratrix.com/GRiNS//),
HPAS (http://www.research.compaq.
com/SRC/HPAS/), and SOJA
(http://www.helio.org/products/)) and
most of the more common browsers now
support the language.
S
MIL's flexibility means that SMIL pre-
sentations can be as varied as Web
pages. A simple example of a multimedia
presentation could be a slide show: a pic-
ture is displayed with an audio commentary
(in parallel); once the first commentary is
finished, the presentation moves on to the
second picture and commentary (in
sequence). Another example might be a
musical analysis application: `Peter and the
Wolf ' plays as an audio file while text and
images appear at set points in the piece to
identify each animal and to describe the
story.The possibilities of cultural heritage
applications of synchronised multimedia are
huge and SMIL offers a simple, flexible and
accessible way to achieve them.
M
ore information and SMIL
resources can be found at the
Synchronised Multimedia homepage,
http://www.w3.org/AudioVideo/, at the
dedicated Web page JustSMIL http://smw
.internet.com/smil/, and the upcoming
DigiCULT Technology Watch Report 2, chap-
ter on the XML family of specifications,
due for publication early in 2004.To see
the potential of SMIL in action, although
not in a cultural heritage context, look at
http://www.people.hbs.edu/lbouthillier/
smil/, or for an easy tutorial, try http://
www.helio.org/products/smil/tutorial/
toc.html.
are defined as sequential or parallel. If con-
tained within a pair of <seq> </seq> tags,
the tags will produce a display as follows:
prelude.jpg is shown for 6 seconds in the
image window, then there will be a second
of blankness, followed by the video
columns.mov looping three times in the
video window. However, if the tags are
contained within <par> </par> tags, the
image will be displayed as before, but after
1 second the video will also start. Five sec-
onds later the image will disappear, and the
video will stop when it has completed
three repetitions.The <par> and <seq>
tags can be nested, thereby facilitating any
complex synchronisation of media, as long
as the individual tags are placed within the
correct combination of parallel and
sequence tags.
47
S
MIL allows interactive control of multi-
media by supporting the definition of
buttons such as Play, Stop, FastForward and
so on, and includes features of HTML such
as linking to separate files.This means that a
user can interrupt a presentation in order
to follow an interesting link and then
resume the display when finished browsing.
Recent versions of SMIL have included
more elaborate control mechanisms such as
slow motion or a random starting point.
HOW CAN SMIL BE USED?
S
MIL can be further compared to
HTML in that it was designed specifi-
cally to be easy to use a simple presenta-
tion can be authored in a few lines of
SMIL just as a simple HTML page only
show ImageA at the same time as playing
AudioB) or sequential (e.g. play VideoC
then show TextD). Synchronisation can be
further controlled (again using methods
familiar from HTML) by defining times as
relative or absolute. An example of using
relative and absolute temporal definitions
could be: show ImageE three seconds after
VideoF starts playing (absolute), stop
showing ImageE when VideoF finishes
(relative). As parallel and sequential display
is defined by tags, these two temporal dis-
play types can be nested to create very
complex multimedia displays.
A SMIL EXAMPLE:
M
ultimedia definition in SMIL can be
extremely simple; only a very few
tags are required to display most media.
Two typical pieces of SMIL code pertain-
ing to one media file each are shown
below.The first tag displays an image in a
previously specified area, image_window.
The image is shown for 6 seconds.The
second tag plays a video in a different area
of the screen defined by the region play-
back_window.The video has an intrinsic
length, therefore the duration tag can be
omitted. However, the begin time specified
causes the video to wait 1 second before
beginning playback.The video will repeat
three times.This file is given an id number
that can be referenced by later tags and
used to specify behaviour such as `start v2
playing 10 seconds after v1 has finished'.
E
xactly how these two files are dis-
played depends on whether the tags
Daisy
Abbott,
2002
47 Example taken from Daisy Abbott, Documentary Previsualisation: Multimedia Presentation Languages (September 2002).
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