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

[Billy Biggs]

D Richard Felker III (dalias at aerifal.cx):

> 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!

  I'm doing pulldown detection in tvtime now, so I'm back in the scene.
When you come across the titles, shouldn't you maintain the current
pulldown pattern so long as the results are consistent?  That is, I know
what I try and do is, once I've found the phase, unless I get numbers
that conflict with it, maintain the current phase.

  I'm curious about your difference metric too.  I've had some bad bad
test cases lately.  If you don't mind, I'm going to port some of your
code into tvtime and see what results I get.

  BTW, something fun:

  http://sourceforge.net/mailarchive/forum.php?thread_id=1938923&forum_id=6588

  -Billy