[MPlayer-dev-eng] New inverse-telecine filter

[Zoltan Hidvegi]

> > I've actually experimented with more complicated metrics, but it was
> > not better.  [3 1] is not that good for qpel, but better than [1 1]
> > hpel used in licomb.  And I qpel on both fields, and somehow the
> > errors tend to cancel out, that's how you get zero on all quadratic
> > curves.  I've tried 4-tap cubic interpolation, and it was worse.  I
> > think the problem is that many-tap works well for smoth changes, but
> > do badly at sharp edges.  Perhaps n-tap looks good on screen, but it
> > does not necessarily mean that it is a good metric.  I've tried many
> > metrics, testing them on known progressive sources, where they should
> > show near perfect match between the fields of a progressive frame.
> > More complicated filters were slower, and were not more accurate.
> 
> OK, I was just curious if you'd tested. BTW, your metric is less
> accurate than the [1 1] hpel used in pullup in at least one case. I
> tried adding qpel [3 1] compare to pullup, and the floating "E" at the
> end of lain-op-evil-m.avi gets mishandled for one frame, giving an
> interlaced output frame. The affinities at that point are detected as

That's with just a simple [3 1] or with my metric, which takes the
minimums?  Without the minimum qpel is more sensitive to sharp
horizontal edges, because is does less bluring than [1 1], so
horizontal edges cause more differences between fields.

> .0+.1..2..3++4. with qpel instead of .0+.1++2..3++4. with hpel. In the
> former case, pullup sees a clear duration-2 frame ahead, so it decides
> to treat the first three fields as a duration-3 frame so it doesn't
> have to merge fields, but this turns out to be incorrect.
> 
> In any case, this behavior is probably incorrect. .0+.1..2..3++4.
> should be treated as a duration-2, followed by a broken field,
> followed by another duration-2, and I'm planning to commit such a
> change, but I still find it unfortunate that your qpel method doesn't
> recognize that fields 1 and 2 clearly go together like my hpel metric
> does...
> 
> If you want to investigate, it's around frame #195 of the clip (hard
> to give exact frame numbers because of the buffering :).

This frame is in the middle of interlaced fading.  Frames 192-200 in
your evil-m sample is telecined film with hard interlaced wideo
frade-out added.  You can run tfields and see that each field is
getting dimmer.  My filter flags this as hard interlaced, but since
the fading is slow, it does not really looks combed.  You can probably
set some thresholds higher to treat it as film, but I do not think
it's incorrect to treat these as interlaced.

Zoli