Fractional Repeat counts?

Hi,

SMIL 2.0 supports fractional repeat counts (ex. repeatCount = "0.75").

Consider the following example.

...
<video src="video1.mpg4" region="Region1" repeatCount="0.75" />
...

I suppose that the standard assumes that the intrinsic duration of  
"video1.mpg4"
is available beforehand for this to work correctly. But on small hand held  
embedded
devices it may be very expensive to calculate the exact intrinsic duration  
of the
streams. (especially for elementary streams as that of MPEG4, AAC).

How does the standard expect the SMIL players to deal with these  
situations in which
the intrinsic duration of the media objects is simply "unknown"?

TIA,

John