Questions about the SMIL Time Model

The Opera project of INRIA is working on the implementation of a SMIL
import functionnality from its multimedia authoring environment, namely
Madeus. 
It means that our goal is to read SMIL documents using the existing
Madeus player. 

The temporal body of a SMIl document is our main interest. 
We have a first version of this import functionnality 
which takes only basic tree temporal structures of seq and par with
some delay offset.
We are now working on the integration of "event-value" operand in a
begin or end attribute. We find very difficult to understand the
semantic rules with the four kinds of events (expected,
desired,implicit, and effective). 

More precisely, applying the  different rules to a simple example (see
below), we get a cyclic system of equations, whereas the example seems
to be intuitively correct.

The example: 
A,B and C are three video. Their respective intrinsic durations are:
4,6,8

<smil>
...
<body>
<par endsync = "last">
   <video id=  "A">
   <video id = "B"  end = id(A)(End)>
   <video id = "C">
</par>
</body>
</smil>

Intuitively, it seems to us that the execution of such an example would
give:

t = 0 A,B and C begin to be played.
t = 4 A ends and B is interrupted
t = 8 C ends

If we applyed the different rules, we get at the end:

Abreviations used:
 IE (resp. ID) means Implicit End (resp. implicit Duration)
 EfE (resp. EfD) means Effective End (resp. Effective Duration),
 DE (resp. DD) means Desired End (resp. Desired Duration).

EfE(par node) = max(DD(A),DD(B),DD(C))
DD(A) = 4
DD(B) = EfE(A)
DD(C) = 8

EfE(A) = EfE(par node)

There is a cycle between EfE(par node) and EfE(A).

Could someone help us to understand where we are wrong ?

Thanks in advance,

Muriel Jourdan

-- 
__________________________________________________
            Muriel.Jourdan@imag.fr
Tel : 76.61.53.58            Fax : 76.61.52.07
        Unite de Recherche INRIA Rhone-Alpes,
     projet OPERA ( http://opera.inrialpes.fr/OPERA/ )
          ZIRST, 655 avenue de l'Europe,
       38330 MONTBONNOT SAINT MARTIN, FRANCE

Received on Wednesday, 15 July 1998 03:30:00 UTC