master shot ref

[Paul Over <over@nist.gov>]

Hi Georges,

I think there should be a minimum threshold on the size of
shots we accept as search and feature extraction results
because shots shorter than 3 secs or so cause problems for
our assessment software, which uses a Real version of
the videos. Also because some features require a minimum
length due to their definition or to be perceivable.

Let's postpone setting that limit for the moment and  
separate this threshold from one that might be used in 
remaking the master shot ref - even though the two are 
related.

It's hard to know what to do about the master shot ref.
I think we could live with the current one if we have
to but it's worth thinking about a revision.

As you point out, we could use the one we have. Then some
small percentage of frames are lost to us because they
belong to shots too short to even be used. More worrisome
is the fact that the false short shots may chop real 
longer shots into pieces we cannot use. But I have no idea
how often that is happening.

The best thing would be a rerun with the sensitivity knob 
turned down.  But maybe such a knob does not exist on the 
CLIPS-IMAG system or its not clear where to set it - thats
a research issue for SB detection systems. So you must do 
some merging of weak transitions. 

If you do this, I think a larger minimum threshold of say 1 sec 
should be used. This makes the reference less of a true shot 
reference and the accuracty of the evaluation a bit less. But 
the shot reference is mainly a means to common evaluation based 
on some logical segmentation and that goal is not violated if
if two shots are merged now and then. The granularity of the 
evaluation is coarser but still useful I think.

Even if there are no objections to this - I'm thinking
especially of the groups working on ASR results for
July 1 and tied to the master shot ref - I am not clear
about how you will do the merging, either the simple
or more complicated way. Can you explain?

- Paul

PS: I think the percentages you gave for the 2001 SBD
collection shots should be 10 times larger - but the
point you make with them is unchanged.
-- 
Paul Over - Retrieval Group
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