Re: MHEG

> What are the differences between SMIL and the MHEG standard?

There are two important differences: SMIL is easier to author and SMIL
is more adaptive.  This doesn't necessarily make SMIL better; it makes SMIL and
MHEG appropriate for different things.  SMIL makes things easier for
the author, and MHEG (may) make things easier for the presenter.

MHEG is a final-form presentation format.  It's only variant that
remains at all active (but significantly so, as part of DAVIC) is
MHEG-5.  MHEG-5 is important because it is a bare-bones, easily
processed format, making it appropriate for settop boxes and other
small systems.  MHEG-5 is timer event based and offers no reuse of
timing or spatial layout information, making it cumbersome to author.
MHEG-5 is also very specific about what goes in the final
presentation, stating exactly what media objects are to be used where.

SMIL, like HTML, was designed to be easy to author (for smaller
documents) with text editors, and uses an XML(SGML)-based markup
format like HTML's.  Its hierarchically timing structure makes setting
initial timing relationships easy and reusable.  It also offers
synchronization constructs for more complex timing.  Its alternate
construct allows the author to specify alternatives for media objects
or document portions from which the presenting system can choose the
one that is most appropriate.  Its separation of layout from document
structure allows alternatives to be specified for the document's style
of appearance.  It is also intended to be easy to process.  SMIL is
also intended to be easy to process and write implementations for.  It
remains to be see how much easier or harder SMIL is to process for
presentation than MHEG-5, but SMIL does have more complex constructs
and requires the presentation system to make more decisions.

The SMIL Working draft is at http://www.w3.org/TR/WD-smil.html.  Links
for more MHEG and MHEG-5 information are available at
http://www.cwi.nl/~lloyd/Hypermedia/.

Lloyd

--
Lloyd Rutledge                                         vox: +31 20 592 41 27
CWI (Centrum voor Wiskunde en Informatica)             fax: +31 20 592 41 99
Kruislaan 413,  NL-1098 SJ Amsterdam, The Netherlands  net: lloyd@cwi.nl
P.O. Box 94079, NL-1090 GB Amsterdam, The Netherlands  http://www.cwi.nl/~lloyd

Received on Wednesday, 10 December 1997 04:15:19 UTC