[MPlayer-dev-eng] More on inverse telecine!

[D Richard Felker III]

I've been working on a new, much better inverse telecine filter to
replace vf_detc. So far, it's working quite well, but there are a few
nasty special cases it doesn't detect well, and which vf_detc didn't
detect very well either.

The most troubling one is the following: Suppose you have a still
picture that's scrolling vertically at almost exactly 1 pixel per
(24fps) frame. Now suppose this sequence has been telecined. In the
two interlaced frames out of a five-frame sequence, the upper and
lower fields are identical due to the scrolling. According to any sane
metric I can think of for measuring interlacing, this condition is the
most non-interlaced you can get, absolutely zero interlacing. However
to a human being both these frames look really awful and are obviously
the ones that need to be fixed by merging fields across frames.

Could anyone suggest to me a decent way to detect such a condition? If
I can find a solution to this problem that's not a huge nasty hack,
I think we'll finally have really good non-beta-ish inverse telecine!
the code so far is working on all the samples uploaded to mphq, except
a few broken ones, and working mostly very well on SE:Lain, which has
proved again and again to be much more difficult to de-telecine than I
ever originally imagined!

Rich